Chapter 1

Question 1

1.Which of the following represents the actions of the superior oblique muscle?

Answer 1

d.

Question 2

2.Which of the following represents the actions of the inferior rectus muscle?

Answer 2

b.

Question 3

3.Which of the following muscles is not innervated by the oculomotor nerve?

Answer 3

c. There are six muscles controlling movements for each eye: superioroblique, inferior oblique, superior rectus, inferior rectus, medialrectus, and lateral rectus. Each muscle has a primary action andasecondary action (except the medial rectus and lateral rectus,which work only in the horizontal plane). The secondary action ofthe “superior” muscles is intorsion, whereas that of the “inferior”muscles is extorsion. The primary and secondary actions,respectively, of each muscle are described below: • Superior oblique: Depression/intorsion • Inferior oblique: Elevation/extorsion • Superior rectus: Elevation/intorsion • Inferior rectus: Depression/extorsion • Medial rectus: Adduction • Lateral rectus: Abduction All extraocular muscles are innervated by the oculomotor nerve except for two: the superior oblique (innervated by the trochlearnerve) and the lateral rectus (innervated by the abducens nerve). Wilson-Pauwels L, Akesson EJ, Stewart PA, et al. Cranial Nerves inHealth and Disease. 2nd ed. Ontario: B.C. Decker Inc.; 2002.

Question 4

4.A 58-year-old man presents with a left-sided headache and neck pain that occurred during weight lifting. He was concerned because he felt like his left eye was “droopy.” On examination, you confirm that he has slight ptosis of the left eye. What is the cause of this finding?

Answer 4

c.

Question 5

5.Which of the following is not a known association with this disorder?

Answer 5

a.

Question 6

6.During your examination, you attempt to better localize the extent of the lesion. Which of the following findings would suggest that the lesion is proximal to the carotid bifurcation?

Answer 6

b. There are several muscles with varied innervation involved in theresting state of the eyelids, and lesion location will cause differentseverities of clinical signs. The upper and lower eyelids open andclose due to facial nerve innervation of the orbicularis oculi. Thelevator palpebrae superioris helps with opening of the upper eyelidand is innervated by the oculomotor nerve. Müller’s muscle arisesfrom the undersurface of the levator palpebrae superioris, and hassympathetic innervation, contributing to 1 to 2 mm of upper eyelid69 elevation. The sympathetics also innervate the superior andinferior tarsal muscles that contribute to slight upper eyelidelevation and lower eyelid depression, respectively. Due to the sympathetic innervation of the eyelid muscles, slight overelevationof the eyelid may be seen in high sympathetic states (such as fear), and subtle ptosis may be seen in low sympathetic states (such asfatigue). In normal patients, the upper eyelid should cover the superior 1 to 1.5 mm of the limbus (junction of the sclera with the cornea), and the lower eyelid should lie at the inferior limbus. This patient has a left-sided Horner’s syndrome due to reducedsympathetic innervation to the left eye. This patient likely hasaleft internal carotid dissection that has affected the sympatheticfibers running along it. Horner’s syndrome is characterized by: 1. Ptosis of the upper eyelid (due to impaired superior tarsal andMüller’s muscles, which normally contribute to upper eyelidelevation). 2. Slight elevation of the lower eyelid (due to impaired inferiortarsal muscle function, which normally contributes to lowereyelid depression). 3. Pupillary miosis (impaired pupillodilator function). 4. Facial anhidrosis (if dissection or other lesion extendsproximal to the region of the carotid bifurcation, because sweating fibers travel primarily with the ECA and would notbe involved in an ICA dissection). 5. Enophthalmos (appearance of enophthalmos from decrease inpalpebral fissure). Beard C. Müller’s superior tarsal muscle: anatomy, physiology, andclinical significance. Ann Plast Surg. 1985;14: 324–333. Biousse V, Touboul PJ, D’Anglejan-Chatillon J, et al. Ophthalmologic manifestations of internal carotid artery dissection. Am J Ophthalmol. 1998;126(4):565–577.

Question 7

7.You are consulted on a 76-year-old man who is referred for right eyelid ptosis and right pupillary constriction. He also mentions that when he exerts himself, he notices that the right side of his face does not seem to sweat like the left side. Using this information, which of the following would not be a probable cause for these symptoms?

Answer 7

e.

Question 8

8.Which of the following is true regarding the sympathetic pathway to the orbit and face?

Answer 8

b.

Question 9

9.You are determined to further try to localize the lesion. After placing 4% cocaine eye drops in his eyes, you notice that the left eye dilates further, whereas the right eye remains unchanged. Which of the following can be definitively concluded on the basis of this finding?

Answer 9

b.

Question 10

10.You next use 1% hydroxyamphetamine eye drops to help you localize the lesion further. After instillation, both pupils dilate. Which of the following can be definitively concluded on the basis of this finding?

Answer 10

e. This patient has a classic Horner’s syndrome. The sympatheticpathway to the eye is a three-neuron pathway. Horner’s syndrome can result from a lesion anywhere along this pathway. The first-order neurons (central neurons) originate in the posteriorhypothalamus and descend through the brainstem to the firstsynapse, located in the lower cervical and upper thoracic spinalcord (levels C8 to T2). This spinal segment is called the ciliospinalcenter of Budge. The second-order neurons (preganglionic neurons) exit the spinal cord, travel near the apex of the lung, under the subclavian artery, and ascend the neck and synapse in the superiorcervical ganglion, near the bifurcation of the carotid artery at thelevel of the angle of the mandible. The third-order neurons(postganglionic neurons) travel with the carotid artery. Thevasomotor and sweat fibers branch off at the superior cervicalganglion near the level of the carotid bifurcation and travel to theface with the ECA. The oculosympathetic fibers continue with the ICA, through the cavernous sinus to the orbit, where they thentravel with the ophthalmic (V1) division of the trigeminal nerve totheir destinations. These pathways are illustrated in Figure 1.6 . Figure 1.6 Sympathetic innervation to the eye. ECA; ICA. Illustration byJoseph Kanasz, BFA. Reprinted with permission, Cleveland Clinic Centerfor Medical Art & Photography © 2015. All rights reserved. Shown also in color plates . Differentiation between causes of Horner’s syndrome can be difficult and depends on the location along the pathway. Ingeneral, a lesion to the first-order neurons (central neurons) will be associated to brainstem or other focal neurologic findings fromacentral lesion. A second-order (preganglionic) lesion is oftenassociated with lesions of the neck, mediastinum, or lung apex.Athird-order (postganglionic) lesion is often associated with pain orheadache, caused by conditions such as a skull base tumor, orcarotid dissection. Cocaine 4% or 10% eye drops are sometimesused for confirmation of a Horner’s syndrome. Cocaine blocks thereuptake of norepinephrine released at the neuromuscular junctionof the iris dilator muscle, allowing more local availability ofnorepinephrine. Following instillation of cocaine, the sympathetically denervated eye will not respond and the anisocoriawill become more pronounced. (The Horner’s pupil will not72 change, but the unaffected pupil will become more dilated.)Therefore, in this patient, this test will only confirm the sympathetic denervation and the presence of a Horner’s syndrome,but will not further localize it. Hydroxyamphetamine 1% eye dropswill differentiate between a lesion affecting the first- or second-order neurons from a third-order neuron. There is nopharmacologic test to distinguish between a first-and second-orderlesion. Hydroxyamphetamine causes release of storednorepinephrine in the third-order neurons. Following instillation, ifthe Horner’s pupil dilates, the lesion is either involving the first-orsecond-order neurons. If the Horner’s pupil does not dilate, there isa third-order neuron lesion. This correlates with the finding ofanhidrosis on the right face in this patient, consistent with a first-or second-order neuron lesion. Kardon R. Anatomy and physiology of the autonomic nervous system. In: Miller NR, Newman NJ, Biousse V, et al., eds. Walsh and HoytClinical Neuro-ophthalmology. 6th ed. Baltimore, MD: Williams&Wilkins; 2005; 649–712. Kardon RH, Denison CE, Brown CK, et al. Critical evaluation of thecocaine test in the diagnosis of Horner’s syndrome. Arch Ophthalmol. 1990;108:384–387. Maloney WF, Younge BR, Moyer NJ. Evaluation of the causes andaccuracy of pharmacologic localization in Horner’s syndrome. AmJOphthalmol. 1980;90:394–402.

Question 11

11.A 61-year-old woman with a history of diabetes, hyperlipidemia, and hypertension presents to the emergency department with double vision that she woke up with this morning. On examination, you find that she has a complete left oculomotor nerve palsy with intact pupillary function. Which of the following is the most likely cause of her examination findings?

Answer 11

c.

Question 12

12.Which of the following is true regarding the oculomotor nuclear complex?

Answer 12

c.

Question 13

13.Which of the following is true regarding the course of the oculoparasympathetic innervation of the eye?

Answer 13

b.

Question 14

14.Which of the following is true regarding the pupillary light response and oculoparasympathetic pathways?

Answer 14

d. Based on the clinical findings, this patient most likely hasadiabetic cranial nerve palsy involving the oculomotor nerve.Acomplete pupil-sparing oculomotor nerve palsy without otherneurologic findings is most often caused by ischemia to the oculomotor nerve. This is frequently associated with diabetes, especially in the setting of other vascular risk factors. The pupil73 sparing in diabetic oculomotor nerve palsies is explained on thebasis of the anatomy of the nerve itself. The pupillomotor fiberstravel along the peripheral aspects of the oculomotor nerve,whereas the somatic fibers to the muscles innervated by the oculomotor nerve travel centrally. The terminal branches of the arterial supply to the nerve are most affected by microvascularchanges from diabetes and other risk factors as the vessels decrease in diameter from the periphery of the nerve to the central regions.Therefore, the supply to the periphery of the nerve (where thepupillomotor fibers reside) is spared, whereas the central fibers are affected. Compressive lesions (such as posterior communicating artery aneurysms) typically affect the peripheral pupillomotorfibers, leading to pupil dilatation with poor response to light(although rarely there may be some pupil sparing). At the level of the superior colliculus in the dorsal midbrain,there are paired and separate oculomotor subnuclei for the inferiorrectus, medial rectus, and inferior oblique—all providing ipsilateralinnervation. The superior rectus subnucleus is also paired butprovides contralateral innervation. It is rare for these subnuclei tobe affected in isolation from central lesions without also affectingnearby subnuclei and nuclei. The paired midline Edinger–Westphal subnuclei providesparasympathetic innervation to the iris sphincters and ciliarymuscles. There is also a midline subnucleus providing innervationto both levator palpebrae superioris muscles. Therefore, a lesion tothis single midline nucleus can cause bilateral ptosis, but it wouldbe rare to affect only this nucleus without affecting nearbystructures, and other clinical findings are expected to be present. The optic pathways are illustrated in Figure 1.7 . Afferentneurons beginning in retinal ganglion cells (carrying signals fromlight stimulation) travel through the optic nerve to the opticchiasm where decussation occurs. Nasal retinal fibers (carrying information from temporal fields) decussate at the chiasm andtravel in the contralateral optic tract. Temporal retinal fibers(carrying information from nasal fields) travel ipsilaterally in the optic tract. In the optic tracts, some neurons project to the ipsilateral lateral geniculate body (for vision) and a few leave the optic tract, ipsilaterally enter the brachium of the superior74 colliculus, and synapse in the ipsilateral pretectal nuclei (forpupillary response). Therefore, each pretectal nucleus receiveslight input from the contralateral visual hemifield. From eachpretectal nucleus, the afferent signals travel via interneurons, connecting ipsilaterally and contralaterally in the Edinger–Westphal nuclei, respectively, completing the afferent arm. Fromthe Edinger–Westphal nucleus, efferent preganglionicparasympathetic fibers travel concurrently through the bilateraloculomotor nerves to the ciliary ganglia, which innervate the irissphincter muscles and the ciliary muscles, resulting in pupillaryconstriction and ciliary muscle activation that leads to accommodation (for near vision) with increased curvature of thelens. Figure 1.7 Pupillary light reflex. Periaqueductal gray (PAG). Illustration byJoseph Kanasz, BFA. Reprinted with permission, Cleveland Clinic Centerfor Medical Art & Photography © 2015. All rights reserved. Shown also in color plates . Myasthenia gravis would present more often with bilateralfatigable ptosis. Neoplastic infiltration would be a slower process. Brainstem infarct would have additional neurologic features. Brazis PW, Masdeu JC, Biller J. Localization in Clinical Neurology. 6th75 ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2011. Leigh RJ, Zee DS. The Neurology of Eye Movements. 3rd ed. NewYork, NY: Oxford University Press; 2006. Sanders S, Kawasaki A, Purvin VA. Patterns of extra-ocular muscleweakness in vasculopathic pupil-sparing, incomplete, third nervepalsies. J Neuroophthalmol. 2001;21:256–259. Wilson-Pauwels L, Akesson EJ, Stewart PA, et al. Cranial Nerves inHealth and Disease. 2nd ed. Ontario: BC Decker Inc; 2002.

Question 15

15.A 9-year-old girl presented to your office with complaints of diplopia. This began after she had a bad fall off her bicycle, hitting her head. On the basis of the directions of gaze noted on your examination, and shown in Figure 1.1 , what nerve is involved?

Answer 15

b.

Question 16

16.In this type of nerve lesion, which of the following corrective head positions would be expected to lessen the severity of diplopia?

Answer 16

d.

Question 17

17.Which of the following is true regarding the course and innervation of this nerve?

Answer 17

c. This patient has a left trochlear nerve palsy (cranial nerve IV). Thisnerve is the only cranial nerve that exits dorsally from thebrainstem. Of note, the trochlear nerve fibers decussate just beforethey exit dorsally at the level of the inferior colliculi of themidbrain. Therefore, motor neurons from each trochlear nucleusinnervate the contralateral superior oblique muscle. After exiting,the trochlear nerve curves ventrally around the cerebral peduncle and passes between the posterior cerebral and superior cerebellararteries, lateral to the oculomotor nerve. Although it is the smallestnerve, the trochlear nerve has the longest intracranial course dueto this dorsal exit, making it more prone to injury, as seen in thispatient. The trochlear nerve innervates the superior obliquemuscle, which allows for depression and intorsion of the eye, especially when the eye is adducted. Patients with trochlear nerve palsies may complain of verticaldiplopia and/or tilting of objects (torsional diplopia). Because ofloss of intorsion and depression from the superior oblique muscle,the affected eye is usually extorted and elevated due to unopposedaction of its antagonist, the inferior oblique. Objects viewed inprimary position or downgaze may appear double (classically,when going down a flight of stairs). Symptoms of diplopia oftenimprove with head tilting to the contralateral side of the lesion, and the patient adapts to this primary head position to avoid the diplopia. In this patient, vertical and torsional diplopia due to herleft trochlear nerve palsy improve with the head tilted toward theright and with the head slightly flexed (chin downward). Thisoccurs because the left eye is in a slightly extorted and elevatedposition in primary gaze due to the lesion. On tilting right, theright eye must intort, and when it matches the same degree thatthe left eye is extorted, the diplopia improves. Brazis PW, Masdeu JC, Biller J. Localization in Clinical Neurology. 6thed. Philadelphia, PA: Lippincott Williams & Wilkins; 2011. Wilson-Pauwels L, Akesson EJ, Stewart PA, et al. Cranial Nerves inHealth and Disease. 2nd ed. Ontario: BC Decker Inc; 2002.

Question 18

18.A 68-year-old woman with diabetes, hypertension, and hyperlipidemia presents to your office for diplopia. Her extraocular motor examination is seen in Figure 1.2 . On pupillary examination, you note that her right pupil is dilated and nonreactive. Which of the following nerves is affected?

Answer 18

a.

Question 19

19.Which of the following would be the least likely cause of this patient’s findings?

Answer 19

d. This patient has a right oculomotor nerve palsy (cranial nerve III) in the classic “down and out” position. Aneurysms involving all the choices except the posteroinferior cerebellar artery (PICA) couldpotentially cause a complete oculomotor nerve palsy with pupillaryinvolvement, the most common being the PComm aneurysm. Whena patient presents with an acute oculomotor nerve palsy secondaryto an aneurysm, it most likely represents an acute change of the aneurysm (growth or even possibly rupture), and therefore investigations should be made emergently to detect the aneurysmand treat it promptly. The oculomotor nerve and nucleus are discussed in questions 11to 14. Briefly to review, the oculomotor nerve supplies the levatorpalpebrae superioris muscles of the eyelid (single central nucleuscontrols both sides) and four extraocular muscles: medial rectus(ipsilateral nucleus), superior rectus (contralateral nucleus), inferior rectus (ipsilateral nucleus), and inferior oblique (ipsilateralnucleus). The actions of these muscles are discussed in questions 1to 3, and paresis of the levator palpebrae superioris leads to ptosis. In the setting of an oculomotor palsy, the unopposed actions of thenonparetic muscles innervated by the trochlear and abducens nervelead to the “down and out” position in primary gaze (as shown inFig. 1.2 ). The oculomotor nerve also carries the parasympathetic77 fibers from the Edinger–Westphal nucleus that supply the ciliarymuscle and the iris sphincter as detailed in questions 11 to 14.After exiting the brainstem and entering the subarachnoid space,the oculomotor nerve passes between the posterior cerebral andsuperior cerebellar arteries (near the basilar tip), in proximity tothe posterior communicating artery, as well as the uncus of thetemporal lobe. Therefore, aneurysms in any of these arteries couldpotentially cause a compressive lesion of the oculomotor nerve.Uncal herniation also is a classic cause of third nerve palsy, although the patient is often comatose by the time this wouldoccur. As compression occurs, the parasympathetic fibers are oftenfirst involved given their peripheral distribution in the nerve, asdiscussed in questions 11 to 14. Brazis PW, Masdeu JC, Biller J. Localization in Clinical Neurology. 6thed. Philadelphia, PA: Lippincott Williams & Wilkins; 2011. Wilson-Pauwels L, Akesson EJ, Stewart PA, et al. Cranial Nerves inHealth and Disease. 2nd ed. Ontario: BC Decker Inc; 2002.

Question 20

20.A 42-year-old woman with a history of multiple sclerosis presents with a complaint of recent onset of diplopia, especially when she looks to the right. On examination, you find that on right lateral gaze she has impaired adduction of the left eye and nystagmus of the abducted right eye. Where do you suspect this lesion is localized?

Answer 20

b.

Question 21

21.Your patient returns 2 weeks later with complaints of diplopia in all directions of gaze. On examination, you find that she now has exotropia of both eyes on primary gaze and no voluntary horizontal adduction. Where do you localize her findings to?

Answer 21

e.

Question 22

22.Three months after treatment with pulse corticosteroid therapy and return of normal extraocular function, your patient presents to you again with new ocular complaints. On examination, you find that she has no horizontal movements of the right eye and only has abduction of the left eye associated with nystagmus. Where do you localize her current findings to?

Answer 22

d. In question 20, this patient has a left internuclear ophthalmoplegia(INO) resulting from a left MLF lesion. INO is characterized byimpaired adduction of the affected side and nystagmus of the abducting contralateral eye (the normal side). The pathways mediating horizontal eye movements are illustrated in Figure 1.8 . The PPRF is also known as the conjugate gaze center for horizontal eye movements. The PPRF receivescontralateral cortical input. Normally, on horizontal eye movementinitiated by the contralateral premotor frontal cortex, the PPRFactivates the ipsilateral abducens nerve nucleus and, thus, the ipsilateral lateral rectus muscle. From the activated ipsilateralabducens nerve nucleus, fibers cross the midline, enter the contralateral MLF, and activate the contralateral medial rectussubnucleus of the oculomotor complex and, thus, the contralateral78 medial rectus muscle. The end result is a finely coordinated gaze deviation to one side, with abduction of one eye and adduction ofthe other. An INO results from a lesion in the MLF, ipsilateral to the impaired adducting eye, as it runs through the pons or midbraintegmentum. Patients may complain of horizontal diplopia onlateral gaze, which is not usually present in primary gaze. The classic findings include impaired adduction on lateral gaze (the side of the affected MLF), with nystagmus in the contralateralabducting eye. Slowing of the adducting eye may be a sign ofapartial INO, as can be detected on optokinetic nystagmus testing. Figure 1.8 Pathways of horizontal gaze. MLF, medial longitudinalfasciculus; PPRF, paramedian pontine reticular formation. Illustration byJoseph Kanasz, BFA. Reprinted with permission, Cleveland Clinic Centerfor Medical Art & Photography © 2015. All rights reserved. Shown also in color plates . There are some important variations of INO. A bilateral INO, dueto bilateral MLF lesions, will cause exotropia of both eyes and isknown as “wall-eyed bilateral INO” (WEBINO), as depicted inquestion 20. A lesion to both the ipsilateral abducens nucleus or79 PPRF and ipsilateral MLF results in loss of all horizontal eyemovements on that side, and abduction of the contralateral eye isthe only lateral eye movement retained (which is also typicallyassociated with abduction nystagmus). This finding is known as the “one-and-a-half syndrome” and is described in question 20. Brazis PW, Masdeu JC, Biller J. Localization in Clinical Neurology. 6thed. Philadelphia, PA: Lippincott Williams & Wilkins; 2011. Frohman EM, Frohman TC, Zee DS, et al. The neuro-ophthalmology ofmultiple sclerosis. Lancet Neurol. 2005;4: 111–121.

Question 23

23.Which of the following cranial nerves would most likely be affected in a patient presenting to your office with papilledema, headache, and significant obstructive hydrocephalus?

Answer 23

c. The abducens nerve (cranial nerve VI) is prone to a stretching injury, especially as it passes over the petrous ridge, and is themost likely nerve to be involved with elevated intracranialpressure. An abducens nerve palsy due to elevated intracranialpressure is often bilateral and is termed a “false localizing sign”because this long cranial nerve could be affected anywhere along its path, and does not necessarily reflect a specific central lesion.The action of the abducens nerve is purely abduction of the eye due to its innervation of the lateral rectus muscle. Patel SV, Mutyala S, Leske DA, et al. Incidence, associations, andevaluation of sixth nerve palsy using a population-based method. Ophthalmology. 2004;111:369–375.

Question 24

24.A 34-year-old woman with diabetes presents to your office complaining of mild left eye ache and an increased left pupil size that she noticed in the mirror yesterday. On examination, you find that her right pupil reacts normally to light, but her left pupil is nonreactive to direct and consensual light, or to accommodation. What do you suspect as the likely cause?

Answer 24

d.

Question 25

25.In the chronic stage of this disease process, which of the following pupillary findings are most often seen?

Answer 25

e. This patient has an idiopathic tonic (Adie’s) pupil. It is thought toresult from a lesion in the postganglionic parasympathetic pathwayto either the ciliary ganglion or the short ciliary nerves and is mostoften attributed to viral etiology, although evidence is lacking.Acutely, there is unilateral mydriasis and the pupil does notconstrict to light or accommodation because the iris sphincter andciliary muscle are paralyzed. Sectoral palsy of part of the irissphincter may be involved, and is considered the earliest and most80 specific feature. Patients often complain of photophobia, visualblurring, and ache in the orbit. Within a few days to weeks, denervation supersensitivity to cholinergic agonists develops andthis is most often tested with low-concentration pilocarpine 0.125%, in which the tonic pupil will constrict but the normal pupilis unaffected by the low concentration. Eventually, slow, sustainedconstriction to accommodation and slow redilation after nearconstriction occur, and the baseline pupil decreases slightly in size (in ambient light), whereas the other features remain. In general,the chronic stage is characterized by the pupillary light reflexrarely improving, whereas the accommodation reflex doesimprove, although it often remains slower (tonic). This is termed“light-near dissociation.” It is sometimes associated withdiminished or absent deep tendon reflexes and this is referred to as“Holmes–Adie syndrome,” or Adie’s syndrome. Argyll Robertson pupils are classically associated withneurosyphilis. They are characterized by bilateral irregular miosiswith little to no constriction to light, but constriction to accommodation without a tonic response as opposed to Adie’spupil. Optic neuritis would be associated with a relative afferentpupil defect. An aneurysm would likely have more oculomotorinvolvement (although not necessarily). Diabetic oculomotorneuropathy is classically associated with pupil sparing, althoughthe appearance of Argyll Robertson pupils can occur as well. Brazis PW, Masdeu JC, Biller J. Localization in Clinical Neurology. 6thed. Philadelphia, PA: Lippincott Williams & Wilkins; 2011. Loewenfeld IE, Thompson HS. Mechanism of tonic pupil. Ann Neurol. 1981;10(3):275–276. Thompson HS, Kardon RH. The Argyll Roberson pupil.JNeuroophthalmol. 2006;26(2):134–138.

Question 26

26.A 29-year-old woman with a history of hypertension presents with complaints of right eye pain on eye movement, impaired and blurry vision, and the feeling that some colors “do not look right.” On the “swinging light test,” when light is shone in her left eye, both pupils constrict normally. Then, when the light is quickly moved to the right eye, both pupils dilate slightly and the amount of constriction is much less as compared to when the light was shone in the left eye. Her visual acuity is impaired in the right eye, as is red color perception. Which of the following is the most likely cause of this finding?

Answer 26

e.

Question 27

27.Her fundoscopic examination of the right eye is shown in Figure 1.3 . What diagnosis do you suspect?

Answer 27

d.

Question 28

28.A brain MRI with contrast confirms your suspicion. Which of the following would be the most appropriate next course of treatment?

Answer 28

b. This finding is called relative afferent pupillary defect (RAPD), also known as a Marcus Gunn pupil, and is most commonly caused byalesion anywhere from the optic nerve to the optic chiasm. Innormal eyes, the reaction of the pupils of both eyes are linked, anda bright light shone into one eye leads to an equal constriction ofboth pupils. When the light source is taken away, the pupils ofboth eyes enlarge equally. This is called the consensual light reflex. The “swinging light test” is used to detect a RAPD by finding differences between both eyes in how they respond to a light shone in each eye individually. This is done by shining the light in thefirst eye for 3 seconds. In a normal response, the pupil of the eyebeing illuminated reacts briskly and constricts fully to the light, asdoes the pupil of the other eye (consensual reflex). Then, the lightshould be moved quickly to shine in the other eye for 3 seconds. Changes in the pupil should be noted, whether the pupil being illuminated stays the same size, constricts further, or gets bigger. In the absence of a RAPD, both pupils should again constrict to thelight shone in the opposite eye as well. When the light is shone into an eye with a RAPD, the pupils of both eyes will constrict, butnot completely. This is explained by a defect in the afferentpathway in this eye. When the light is then moved to stimulate thenormal eye, both pupils will constrict further since the afferentpathway of this eye is not impaired. Then, when the light is movedback to shine into the abnormal eye again, both pupils will getlarger due to the afferent defect in the pathway of that eye. In general, retrochiasmal lesions do not cause a pure RAPD. However, a RAPD combined with contralateral hemianopiasecondary to an optic tract lesion may occur infrequently. Retinallesions, refractive errors, amblyopia, and disease of the lens, cornea, and retina generally do not cause RAPD, although rarely, severe macular disease has been associated with RAPD. Thepathway of the pupillary light reflex is discussed in detail inquestions 11 to 14. RAPD is frequently seen in optic neuritis.Alesion to the lateral geniculate body would cause a homonymoushemianopia. This structure is involved in vision and not inpupillary responses. This patient’s fundoscopic examination reveals optic nerve edema consistent with optic neuritis. Optic neuritis develops overhours to days and is associated with symptoms of reduced color82 perception (especially red, called red desaturation), reduced visualacuity (especially central vision), visual loss, eye pain, andphotopsias. Only one-third of patients have papillitis withhyperemia and swelling of the disc, blurring of disc margins, anddistended veins. The rest of cases have only retrobulbarinvolvement, and therefore, have a normal fundoscopicexamination. The Optic Neuritis Treatment Trial (ONTT) randomized patientsto one of three groups: oral prednisone for 14 days with a 4-daytaper versus intravenous methylprednisolone followed by oralprednisone for 11 days with a 4-day taper versus oral placebo for14 days. The intravenous methylprednisolone group showed fastervisual recovery, but at 1 year, visual outcomes were similar. The intravenous methylprednisolone group also had a reduced risk ofconversion to multiple sclerosis (MS) within the first 2 yearscompared with the other groups. At 5 years, there were no differences in the rates of multiple sclerosis between treatmentgroups though. Interestingly, only the oral prednisone group wasfound to have a higher 2-year risk of recurrent optic neuritiscompared to both the intravenous methylprednisolone and placebo groups. At 10 years, the risk of recurrent optic neuritis was stillhigher in the oral prednisone group when compared with the intravenous methylprednisolone group, but not the placebo groups. Papilledema is not present in this fundoscopic examination. Anearly finding in papilledema is loss of spontaneous venouspulsations, although the absence of spontaneous venous pulsationscan also be a normal variant. Disc margin splinter hemorrhagesmay be seen early also. Eventually, the disc becomes elevated, the cup is lost, and disc margins become indistinct. Blood vesselsappear buried as they course the disc. Engorgement of retinal veinslead to a hyperemic disc. As the edema progresses, the optic nervehead appears enlarged and may be associated with flamehemorrhages and cotton wool spots, as a result of nerve fiberinfarction. Anterior ischemic optic neuropathy (AION) is discussedin question 29. In giant cell arteritis (GCA), the optic disc is more often pallid, rather than hyperemic. Beck RW, Cleary PA, Anderson MM Jr, et al. A randomized, controlled trial of corticosteroids in the treatment of acute optic neuritis. The Optic Neuritis Study Group. N Engl J Med. 1992;326:581–588. Broadway DC. How to test for a relative afferent pupillary defect(RAPD). Community Eye Health. 2012;25(79–80): 58–59. The Optic Neuritis Study Group. The 5-year risk of MS after optic neuritis. Experience of the optic neuritis treatment trial. Neurology. 1997;49:1404–1413.

Question 29

29.A 52-year-old man with diabetes, hypertension, and hyperlipidemia presents with severe painless visual blurring and “cloudiness” in the left eye which he woke up with this morning. The fundoscopic examination findings of the left eye are shown in Figure 1.4 . What diagnosis do you suspect?

Answer 29

e. This patient has anterior ischemic optic neuropathy (AION). AIONis considered to be the most common optic nerve disorder inpatients older than age 50. It can also affect the retrobulbar opticnerve in isolation, in which case it is termed posterior ischemicoptic neuropathy (diagnosis of exclusion). Patients often have riskfactors for cardiovascular and cerebrovascular diseases, such asdiabetes and hypertension. AION is a result of ischemic insult tothe optic nerve head. Clinically, it presents with acute, unilateral,usually painless visual loss, although 10% of patients may havepain that can be confused with optic neuritis. Fundoscopicexamination shows optic disc edema (unless retrobulbar),hyperemia with splinter hemorrhages, and crowded and cuplessdisc. The painless vision loss is one key feature in differentiatingAION from optic neuritis, which is often associated with painfuleye movements. Optic neuritis is discussed in question 26 to 28. Inaddition, optic neuritis presents more often in younger (especiallyfemale) patients and may be associated with disc edema (but notalways), but without splinter hemorrhages. In contrast to giant cellarteritis (GCA), the optic disc edema in AION is more oftenhyperemic rather than pallid, as would be more common in GCA.Papilledema is not present in this fundoscopic examination and isdiscussed in questions 26 to 28. Hayreh SS, Zimmerman MB. Nonarteritic anterior ischemic optic neuropathy: natural history of visual outcome. Ophthalmology. 2008;115:298–305. Rucker JC, Biousse V, Newman NJ. Ischemic optic neuropathies. CurrOpin Neurol. 2004;17:27–35.

Question 30

30.A 64-year-old man presents with a right homonymous hemianopia. Which of the following is the most likely localization for this finding?

Answer 30

d.

Question 31

31.A 57-year-old woman presents with a left upper quadrantanopsia. Which of the following would be the most likely localization?

Answer 31

a. The visual pathways are illustrated in Figure 1.9 . A righthomonymous hemianopia could be caused by a left lateralgeniculate body lesion, and a left upper quadrantanopsia could be caused by a lesion to the right lower bank of the calcarine cortex.Ahomonymous hemianopia is caused by lesions of theretrochiasmal visual pathways that consist of the optic tract, lateralgeniculate nucleus, optic radiations, and the cerebral visual(calcarine, occipital) cortex. At the optic chiasm, the retinalganglion afferents from the temporal retina (nasal visual field) continue in the ipsilateral lateral optic chiasm and pass into the ipsilateral optic tract, whereas the retinal ganglion afferents fromthe nasal retina (temporal visual field) decussate in the opticchiasm and continue into the contralateral optic tract. Therefore,beyond the optic chiasm, each optic tract contains crossed anduncrossed nerve fibers relaying visual information from the contralateral visual field. The optic tracts continue to the lateralgeniculate body. Beyond the lateral geniculate body, the opticradiations continue carrying the visual information from the contralateral visual field to the primary visual cortex in the occipital lobe. The superior fibers of the optic radiations carryinformation from the inferior visual field as they pass through theparietal lobe. The inferior fibers of the optic radiations carryinformation from the superior visual field as they pass through thetemporal lobe, forming Meyer’s loop. When this visual informationreaches the visual cortex, the upper bank of the calcarine cortexreceives projections representing the inferior visual field, whereasthe lower bank of the calcarine cortex receives informationrepresenting the superior visual field. Figure 1.9 Visual pathways. Illustration by Joseph Kanasz, BFA. Reprintedwith permission, Cleveland Clinic Center for Medical Art & Photography©2015. All rights reserved. Shown also in color plates . Brazis PW, Masdeu JC, Biller J. Localization in Clinical Neurology. 6thed. Philadelphia, PA: Lippincott Williams & Wilkins; 2011.

Question 32

32.A 67-year-old woman with a chronic neurologic disease describes a long progressive loss of vision in the left eye greater than the right eye over the past 15 years. Her fundoscopic examination of the left eye is seen in Figure 1.5, and she has a relative afferent pupillary defect in the same eye. What do you suspect as the cause of this finding?

Answer 32

d. The fundoscopic examination reveals optic nerve atrophy, consistent with a long-standing history of multiple sclerosis. The other choices are described in questions 26 to 28 and 29. Signs ofchronic optic neuritis include persistent visual loss, colordesaturation (especially red), and possibly a persistent relative afferent pupillary defect. In optic atrophy the disc appearsshrunken and pale, especially in the temporal half, and this pallorextends beyond the margins of the disc. Daroff RB, Fenichel GM, Jankovic J, et al. Bradley’s Neurology inClinical Practice. 6th ed. Philadelphia, PA: Elsevier; 2012. Ropper AH, Samuels MA, Klein JP. Adams and Victor’s Principles ofNeurology. 10th ed. New York, NY: McGraw-Hill; 2014.

Question 33

33.A 56-year-old man with uncontrolled diabetes presents with 1 week of fever, double vision, and visual blurring. He has proptosis bilaterally, bilateral abduction weakness, visual acuity 20/50 in the right eye and 20/100 in the left, and facial numbness in V2 on the right side. You suspect the following diagnosis:

Answer 33

c. This patient has mucormycosis involving the cavernous sinus andposterior orbits. This can occur in poorly controlled diabetes. Itcauses proptosis, visual blurring, and unilateral or bilateralcavernous sinus syndrome (combination of III, IV, V1, V2, and VI cranial nerve involvement), and visual acuity may also be impaired. The contents of the cavernous sinus are illustrated inFigure 1.10 . A chronic meningitis would not cause proptosis.Amidbrain infarction could cause third and fourth nerve palsies, butwould not cause facial numbness or visual blurring. A third nervepalsy would not present in this fashion. Idiopathic cranialpolyneuropathy is a diagnosis of exclusion and would not causeproptosis. Figure 1.10 Cavernous sinus. Illustration by Ross Papalardo, BFA. Reprinted with permission, Cleveland Clinic Center for Medical Art&Photography © 2015. All rights reserved. Shown also in color plates . Daroff RB, Fenichel GM, Jankovic J, et al. Bradley’s Neurology inClinical Practice. 6th ed. Philadelphia, PA: Elsevier; 2012. Ropper AH, Samuels MA, Klein JP. Adams and Victor’s Principles ofNeurology. 10th ed. New York, NY: McGraw-Hill; 2014.

Question 34

34.A 58-year-old woman with a history of hypertension, diabetes, and hyperlipidemia presents to the emergency department for left “facial droop.” She woke this morning and noticed unilateral facial paralysis on the left, which was not present the prior night. She also reports hyperacusis in the left ear and says food tastes different. There have been no other new symptoms over the last year of any kind. On examination, you notice left facial droop and inability to close the left eye. She is unable to wrinkle the left side of her forehead. What is the most likely diagnosis?

Answer 34

d.

Question 35

35.What is the most appropriate diagnostic and/or management strategy at this time?

Answer 35

e.

Question 36

36.What initial treatment do you recommend at this time for this patient?

Answer 36

a. This patient most likely has Bell’s palsy. No testing is necessary atthis time and steroids should be initiated. “Bell’s palsy” is the termoften used for an acute peripheral facial nerve palsy of unknowncause. It is frequently seen in the third trimester of pregnancy or inthe first postpartum week and is also seen in patients withdiabetes, however, it can affect any patient. A herpes simplex–mediated viral inflammatory mechanism has been proposed asacontroversial etiology. Other common viruses have also beenassociated with Bell’s palsy, including varicella-zoster virus as inRamsay Hunt syndrome. Ischemia of the facial nerve has also beensuggested, especially in patients with diabetes. Patients with Bell’s palsy typically present with relatively abruptonset of unilateral facial paralysis, which often includes difficultyclosing the eye, drooping eyebrow, mouth droop with loss ofnasolabial fold, loss of taste sensation on the anterior two-thirds ofthe tongue (in distribution of facial nerve), decreased tearing, andhyperacusis. Patients may complain of discomfort behind or aroundthe ear prior to symptom onset. There may also be a history ofrecent upper respiratory infection. It is important to differentiatebetween a peripheral and central (upper motor neuron) lesion. Sparing of the forehead muscles suggests a central lesion because of bilateral cortical supply to the facial subnuclei innervating theforehead, as opposed to unilateral cortical supply to the facialsubnucleus innervating the lower face (below the eye). However,alesion to the facial nerve nucleus itself in the pons can lead to complete facial paralysis (of both the upper and lower face). Bell’spalsy should classically involve only the facial nerve, althoughadditional cranial nerve involvement has been infrequentlyreported, including the trigeminal, glossopharyngeal, andhypoglossal nerves. Some studies have reported ipsilateral facialsensory impairment suggesting trigeminal neuropathy, althoughthis sensation has often been attributed to abnormal perception onthe basis of “droopy” facial muscles. Diagnostic studies are not necessary in all patients with Bell’spalsy. Those with a typical history and examination consistent withBell’s palsy do not need further studies initially. Imaging should be considered if there is slow progression beyond 3 weeks, if thephysical signs are atypical, or if there is no improvement at688 months. If imaging is pursued, an MRI with and withoutgadolinium is optimal. Electrodiagnostic studies may be consideredin patients with clinically complete lesions for prognostic purposesif they do not improve. If the history suggests an alternate etiology, evaluation should be targeted as such. A pontine strokewould be unlikely to affect only the facial nerve nucleus withoutaffecting surrounding structures; hemiparesis contralateral to thefacial nerve palsy would suggest involvement of corticospinalstructures, as in Millard–Gubler syndrome (see, Chapter 2 ), andipsilateral impairment of eye abduction would suggest involvementof the ipsilateral cranial nerve VI nucleus, as in Foville’s syndrome (see Chapter 2 ). These additional focal symptoms should promptinvestigation for pontine infarct. This patient did not have a historyor symptoms consistent with Lyme disease or multiple sclerosis.Multiple sclerosis would be highly suspected in a young patientwith bilateral Bell’s palsy, although Lyme disease and sarcoidosiswould also be in the differential. A cholesteatoma would presentwith a much slower onset. Treatment of Bell’s palsy has been controversial regarding steroid and antiviral therapy. For patients with new onset Bell’spalsy, steroids can be very effective and should be offered to increase the probability of recovery of facial nerve function (2Class I studies, Level A). The addition of antiviral agents does notsignificantly increase the probability of facial functional recovery,but a modest benefit cannot be excluded. Due to the possibility ofamodest benefit, patients might be offered antivirals (in addition to steroids) (Level C), particularly in more severe cases of facialparalysis or those with possible zoster sine herpete. Artificial tears and eye patches should also be used for eyeprotection when needed. Nerve stimulation and surgicaldecompression are not routinely recommended on the basis ofcurrent evidence. Prognosis of Bell’s palsy depends on severity of the lesion, and ingeneral, clinically incomplete lesions tend to recover better thancomplete lesions. In addition, the prognosis is favorable if somerecovery is seen within the first 21 days of onset. Daroff RB, Fenichel GM, Jankovic J, et al. Bradley’s Neurology inClinical Practice. 6th ed. Philadelphia, PA: Elsevier; 2012. Engstrom M, Berg T, Stjernquist-Desatnik A, et al. Prednisolone andvalaciclovir in Bell’s palsy: a randomised, double-blind, placebo-controlled, multicentre trial. Lancet Neurol. 2008;7:993–1000. Grogan PM, Gronseth GS. Practice parameter: Steroids, acyclovir, andsurgery for Bell’s palsy (an evidence-based review): report of theQuality Standards Subcommittee of the American Academy ofNeurology. Neurology. 2001;56:830–836. Gronseth GS, Paduga R; American Academy of Neurology. Evidence-based guideline update: steroids and antivirals for Bell palsy: report ofthe Guideline Development Subcommittee of the American Academyof Neurology. Neurology. 2012;79:2209–2213. Sullivan FM, Swan IR, Donnan PT, et al. Early treatment withprednisolone or acyclovir in Bell’s palsy. N Engl J Med. 2007;357:1598–1607.

Question 37

37.Which of the following cranial nerves does not have a synapse in the thalamus before terminating in the cortex?

Answer 37

c. The olfactory nerve is the only nerve listed that does not haveasynapse in the thalamus prior to traveling to the cortex. Afferentsfor all sensory modalities, except for the olfactory nerve, haveasynapse in the thalamus prior to terminating in the cortex. Fromthe olfactory bulb, secondary neurons project directly to the olfactory cortex and then have direct connections to the limbicarea. The limbic area plays a role in memory formation and thisexplains why some smells provoke specific emotions andmemories. The olfactory cortex has connections with autonomicand visceral centers, including the hypothalamus, thalamus, andamygdala. This may explain why some smells can cause changes ingut motility, nausea, and vomiting. The facial nerve has autonomicfibers descending from the thalamus to the superior salivatorynucleus. It also has sensory afferents for taste that travel to theventral posteromedial (VPM) nucleus of the thalamus andsubsequently to the cortex. Wilson-Pauwels L, Akesson EJ, Stewart PA, et al. Cranial Nerves inHealth and Disease. 2nd ed. Ontario: BC Decker Inc; 2002.

Question 38

38.A 43-year-old man with a history of right-sided Bell’s palsy the prior year, who made a good recovery, comes to you complaining of excessive tearing of the right eye, mainly when he is eating. What do you attribute this to?

Answer 38

e. This phenomenon is called “crocodile tears,” and results whenmisdirected regenerating facial nerve axons originally supplyingthe submandibular and sublingual salivary glands, innervate thelacrimal gland through the greater petrosal nerve. This anomalousinnervation results in abnormal unilateral lacrimation when eating. In addition, some axons from the motor neurons to the labialmuscles involved in smiling may regenerate and misdirect to the orbicularis oculi, which results in closure of the eye on smiling.This phenomenon is termed synkinesis. The reverse may also occurand result in twitching of the mouth on blinking. Wilson-Pauwels L, Akesson EJ, Stewart PA, et al. Cranial Nerves inHealth and Disease. 2nd ed. Ontario: BC Decker Inc; 2002.

Question 39

39.A 45-year-old woman with mild hypertension presents to the emergency department with complaints of severe vertigo, unsteadiness, nausea, and vomiting. These symptoms began this morning and she has had several exacerbations since then, each lasting about a minute or so, especially on neck extension. Her examination is normal with exception of nystagmus and nausea brought on by certain head movements. You are trying to decide if her vertigo is central or peripheral in origin. What would be the next step in evaluation of this patient?

Answer 39

c.

Question 40

40.Which of the following is most suggestive of central vertigo?

Answer 40

b.

Question 41

41.Which of the following is incorrect regarding nystagmus from a peripheral etiology?

Answer 41

a.

Question 42

42.What is the pathophysiology for the disease process you suspect in this patient?

Answer 42

d.

Question 43

43.What would be the best initial treatment at this time for this patient?

Answer 43

e. Aprovoking maneuver should be done to evaluate for benignparoxysmal positional vertigo (BPPV) in patients such as this witha typical history. History and examination are less consistent foracute stroke, vertebral dissection, or a slow-growing acousticschwannoma. BPPV is most commonly attributed to calcium debrisin a semicircular canal (canalithiasis) and most commonly occurs inthe posterior canal. The debris likely represents loose otoconiamade up of calcium carbonate crystals within the utricular sac thathave migrated into the semicircular canal. The Dix–Hallpikemaneuver is most commonly done for the diagnosis of thiscondition, and is performed as follows. With the patient sitting, theneck is extended and turned to one side. The patient is then rapidlybrought back to a supine position, so that the head hangs over the edge of the bed. This position is kept until 30 seconds have passedif no nystagmus occurs. The patient is then returned to a sitting position and observed for another 30 seconds for nystagmus. Thenthe maneuver is repeated with the head turned to the other side.This maneuver is most useful for diagnosing posterior canal BPPV(the most common form), and the nystagmus is usuallycharacterized by beating upward and torsionally. After it stops andthe patient is sitting again, the nystagmus may occur in the opposite direction (reversal). Besides posterior BPPV, there arethree other types of BPPV, including anterior canal, horizontalcanal, and pure torsional BPPV. Anterior canal BPPV (superiorcanal BPPV) has similar provoking factors as posterior canal BPPV,but the nystagmus is downbeat and torsional. Horizontal canalBPPV is provoked by turning the head while lying down andsometimes by turning it in the upright position, but not by getting in or out of bed or extending the neck. Therefore, the nystagmus iselicited by a lateral head turn in the supine position, rather thanwith the head extended over the edge of the bed, and ischaracterized by horizontal nystagmus beating toward the floorafter turning the affected ear down. The nystagmus lasts less than1 minute, pauses for a few seconds, and then a reversal of thenystagmus is seen. Pure torsional nystagmus may mimic a centrallesion, and results from canalithiasis, simultaneously involvingboth the anterior and posterior canals, though is less common. Thisform of BPPV tends to persist longer than other forms of BPPV. Absence of nystagmus latency would be suggestive of a centrallesion. Central nystagmus has the following characteristics:nonfatiguing, absent latency (onset of nystagmus immediately afterprovocative maneuver), not suppressed by visual fixation, durationof nystagmus is greater than 1 minute, and may occur in anydirection. Although purely torsional or vertical nystagmus isclassically central in origin, pure torsional BPPV may mimic centralnystagmus. Central vertigo is usually subjectively less severe thanperipheral vertigo, but gait impairment, falls, and unsteadiness aremuch more pronounced and other neurologic signs often coexist. Hearing changes and tinnitus are usually absent. Peripheralnystagmus is characterized by fatigability with repetition, latencytypically of 2 to 20 seconds, suppression by visual fixation, duration of nystagmus less than 1 minute, unidirectional, andusually horizontal, occasionally with a torsional component. Walking is typically preserved, although unilateral instability mayexist. Hearing changes and tinnitus are more common withperipheral lesions. A unilateral peripheral vestibular lesion, such as in BPPV, leadsto an asymmetry in vestibular activity. This results in a slow driftof the eyes away from the target in one direction (toward the affected side and away from the unaffected side), followed byafast cortical corrective movement to the opposite side (toward theunaffected side, away from the affected side). The amplitude ofnystagmus increases with gaze toward the side of the fast phase (toward the unaffected ear and away from the affected ear), andthis is known as Alexander’s law. As mentioned above, peripheralnystagmus is suppressed by visual fixation and this helpsdifferentiate it from central nystagmus. Initial treatment of BPPV is symptomatic and should begin witha particle-repositioning maneuver, consisting of a sequence of headand body repositioning with the goal of moving the debris fromthe semicircular canal back into the utricular cavity. The mostcommonly used is the Epley maneuver, or modified Epleymaneuver, although other variations exist. These specific sequencesare beyond the scope of this discussion. The Epley maneuver ismost efficacious for posterior canal repositioning, whereas anteriorand horizontal canal repositioning often require differentmaneuvers. Self-treatment exercises should be given for the patientto use at home. Postmaneuver activity restrictions, such as use ofacervical collar and maintenance of an upright head position for2days after treatment, had previously been recommended to preventreturn of particles into the semicircular canal. Recent studies have shown no significant benefit from postmaneuver activityrestrictions, or the use of meclizine. Daroff RB, Fenichel GM, Jankovic J, et al. Bradley’s Neurology inClinical Practice. 6th ed. Philadelphia, PA: Elsevier; 2012. De la Meilleure G, Dehaene I, Depondt M, et al. Benign paroxysmalpositional vertigo of the horizontal canal. J Neurol NeurosurgPsychiatry. 1996;60:68–71. Imai T, Takeda N, Uno A, et al. Three-dimensional eye rotation axisanalysis of benign paroxysmal positioning nystagmus. ORLJ93 Otorhinolaryngol Relat Spec. 2002;64:417–423. Korres S, Riga M, Balatsouras D, et al. Benign paroxysmal positionalvertigo of the anterior semicircular canal: atypical clinical findingsand possible underlying mechanisms. Int J Audiol. 2008;47:276–282. Oas JG. Benign paroxysmal positional vertigo: a clinician’s perspective. Ann NY Acad Sci. 2001;942:201–209.

Question 44

44.Regarding the vestibular sensory organs, which of the following is correct?

Answer 44

b.

Question 45

45.Which of the following is correct regarding the vestibuloocular reflex (VOR) when the head is turned to the right side in a purely horizontal plane, while the eyes are focused directly ahead on an object?

Answer 45

b.

Question 46

46.You are consulted on a comatose 79-year-old man who was found down at home for an unknown amount of time. On the basis of cold calorics, you suspect that he is not brain dead. If the cold water is infused into the left ear canal, which of the following responses would not be expected in a patient with an intact brainstem?

Answer 46

e. The vestibular sensory organs consist of the otolithic organs andsemicircular canals. The otolithic organs are the saccule and utricle, and these two organs are expansions of the membranous labyrinth.Within each of these organs there is a macula, which is a layer ofhair cells overlain by a heavy gelatinous otolithic membrane covered by calcium carbonate particles (the otoconia). Duringlinear acceleration of the head, the head moves relative to the otoconia. This results in bending of the hair cells and a subsequentchange in neuronal activation. The otolithic organs detect linearand vertical motions of the head relative to gravity. There are three semicircular canals within each vestibularapparatus on each side, oriented at right angles to each other.These are tubes of membranous labyrinth extending from eachutricle. Therefore, there are two horizontal canals, two verticallydirected anterior canals, and two vertically directed posteriorcanals. The semicircular canals contain endolymph. Each canaldilates at the base forming a sac called the ampulla. Each ampullacontains sensory hair cells, which are embedded in a gelatinous captermed the cupula, and does not contain otoconia. During headrotation, inertia causes the endolymph to lag behind and push onthe cupula. Similar to the otolithic organs, this bends the hair cellsand causes neuronal activation. The semicircular canals are more sensitive to angular motions of the head. Information regarding head movement is transmitted to the ocular motor nuclei, resulting in eye movement in an equalmagnitude and opposite direction to the head turn, allowing the eyes to remain stationary in space despite head movement. Thisphenomenon is termed the vestibuloocular reflex (VOR). Headmovement in the direction of a semicircular canal will excite thatrespective semicircular canal and the correlative extraocularmuscles. The VOR keeps the line of sight stable in space while thehead is moving (e.g., keeping your eyes focused on one objectwhile shaking your head back and forth). This occurs because eachsemicircular canal has excitatory and inhibitory projections to agonist and antagonist extraocular muscles (one per eye; the agonistic muscle is activated, whereas the antagonistic muscle isinhibited). Each semicircular canal has excitatory projections toapair of agonistic extraocular muscles (one in each eye) andinhibitory projections to a pair of antagonistic extraocular muscles(one in each eye). The medial and lateral recti adduct and abductthe eye, respectively, in a purely horizontal plane. When the headturns right, the right horizontal canal is stimulated. This leads to excitation of the right medial rectus and left lateral rectus, alongwith inhibition of the right lateral rectus and left medial rectus. Cold caloric testing is helpful to assess brainstem integrity(which helps define whether brain death is present or not) and thisis a passive way to evaluate the VOR. It should be done using coldwater at 30°C and by bringing the head of the bed to 30 degreesfrom the horizontal position in order to bring the horizontal canalsinto a more vertical plane for optimal testing. The temperature difference between the body and the infused water createsaconvective current in the endolymph of the nearby horizontalsemicircular canal. Warm and cold water would produce currentsin opposite directions and therefore a horizontal nystagmus inopposite directions. With cold water infusion, the endolymph fallswithin the semicircular canal, decreasing the rate of vestibularafferent firing and both eyes then slowly deviate toward the ipsilateral ear. Therefore, if cold water is infused into the left ear,the following will occur; excitatory signals are sent to the leftlateral rectus and right medial rectus, as well as inhibitory signalsto the left medial rectus and right lateral rectus. This results intonic deviation of the eyes to the left. In a healthy person with95 normal functioning cortex, following a latency of about 20 seconds,nystagmus appears and may persist up to 2 minutes. The fast phase of nystagmus reflects the cortical correcting response and isdirected away from the side of the cold water stimulus. If the cortical circuits are impaired (e.g., comatose state, as in thispatient), the nystagmus will be suppressed and not present, andonly the tonic deviation will be evident (with intact brainstem).The opposite of these findings should occur with warm water.Nystagmus is named in the direction of the fast phase and thus thewell-known mnemonic COWS (coldoppositewarmsame) forcaloric testing. Purves D, Augustine GA, Fitzpatrick D, et al. Neuroscience. 4th ed. Sunderland, MA: Sinauer Associates Inc; 2008. Wilson-Pauwels L, Akesson EJ, Stewart PA, et al. Cranial Nerves inHealth and Disease. 2nd ed. Ontario: BC Decker Inc; 2002.

Question 47

47.Which of the following muscles is not innervated by the trigeminal nerve?

Answer 47

c.

Question 48

48.Which of the following muscles is not innervated by the facial nerve?

Answer 48

b.

Question 49

49.Which of the following muscles is innervated by the glossopharyngeal nerve?

Answer 49

b. The trigeminal nerve innervates the anterior belly of the digastric,whereas the posterior belly is innervated by the facial nerve. Thetensor tympani is innervated by the trigeminal nerve and not thefacial nerve. The only muscle innervated by the glossopharyngealnerve is the stylopharyngeus muscle. The muscles innervated by the trigeminal nerve are medial andlateral pterygoids, masseter, deep temporal, anterior belly of the digastric, mylohyoid, tensor veli palatini, and tensor tympani. The muscles innervated by the facial nerve are stapedius,posterior belly of the digastric, stylohyoid, frontalis, occipitalis, orbicularis oculi, corrugator supercilii, procerus, buccinator, orbicularis oris, nasalis, levator labii superioris, alaeque nasi, zygomaticus major and minor, levator anguli oris, mentalis, depressor anguli oris, depressor labii inferioris, risorius, andplatysma. Wilson-Pauwels L, Akesson EJ, Stewart PA, et al. Cranial Nerves in96 Health and Disease. 2nd ed. Ontario: BC Decker Inc; 2002.

Question 50

50.A 39-year-old woman presents to your office with left- sided facial weakness involving the entire left half of the face. Taste is impaired and sound is excessively loud in her left ear. She denies problems with dry or runny eyes. A lesion in which of the following facial nerve locations could explain these symptoms?

Answer 50

b.

Question 51

51.If this patient presented with the same symptoms, except that she only had the left facial weakness and taste impairment, without the hearing complaints mentioned above, where would you expect the lesion to be?

Answer 51

e.

Question 52

52.Which of the following is true regarding the facial nerve and its branches?

Answer 52

b.

Question 53

53.Which of the following cranial nerve nuclei supplies the parasympathetics to the head and neck?

Answer 53

a.

Question 54

54.Which of the following glands are not innervated by the facial nerve?

Answer 54

d. The facial nerve (cranial nerve VII) is a mixed nerve, containingmotor fibers to the facial muscles, parasympathetic fibers to thelacrimal, submandibular, and sublingual salivary glands, specialsensory afferent fibers for taste from the anterior two-thirds of thetongue, and somatic sensory afferents from the external auditorycanal and pinna. Lesions of the facial nerve can be localized byremembering the course of the facial nerve and where the branchesarise, keeping in mind that everything before the lesion would beunaffected and everything after the lesion would be affected.Alesion anywhere from the facial nerve nucleus to the distalbranches can cause facial weakness in a peripheral distribution. Determining which other facial nerve functions are involved iswhat helps localize the lesion. Two roots arise from the pontomedullary junction and merge toform the facial nerve. One of these roots provides motorinnervation to the facial muscles. The second root is a mixedvisceral nerve carrying parasympathetic fibers and is called thenervus intermedius. The preganglionic cell bodies of theparasympathetics are scattered in the pontine tegmentum, whichare called the superior salivatory nuclei (SSN), and their fiberstravel in the nervus intermedius. The facial nerve courses laterallythrough the cerebellopontine angle with the vestibulocochlearnerve to the internal auditory meatus leading to the facial, orfallopian, canal. The facial canal is located in the petrous part ofthe temporal bone and consists of labyrinthine, tympanic, andmastoid segments. Within the labyrinthine segment, the facialnerve bends sharply backward. At this genu, there is a swellingthat forms the geniculate ganglion. This ganglion contains nerve cell bodies of taste axons from the tongue and somatic sensory97 axons from the external ear, auditory meatus, and external surface of the tympanic membrane. The parasympathetic greater petrosal nerve arises from the geniculate ganglion and is the first branch of the facial nerve. The greater petrosal nerve leaves the geniculate ganglion anteriorly, enters the middle cranial fossa extradurally, and enters theforamen lacerum en route to the pterygopalatine (sphenopalatine) ganglion. From the pterygopalatine ganglion, postganglionic fiberstravel with branches of the maxillary portion of the trigeminalnerve (V2) to supply the lacrimal and mucosal glands of the nasaland oral cavities. After the geniculate ganglion region and the branch of the greater petrosal nerve, the facial nerve axons then pass backwardand downward toward the stylomastoid foramen. The next branchas the facial nerve passes downward is the nerve to the stapedius,prior to exit from the stylomastoid foramen. The stapedius muscle dampens the oscillations of the ossicles of the middle ear. Impairment of the stapedius nerve and muscle will causehyperacusis, in which sounds are much louder. question 50 refersto a lesion between the geniculate ganglion/greater petrosal nerve (normal lacrimation) and nerve to the stapedius (hyperacusis). After the branch of the stapedius nerve and just before the exitfrom the stylomastoid foramen, the facial nerve gives off the thirdbranch, the chorda tympani nerve. The chorda tympani nervepasses near the tympanic membrane, where it is separated from themiddle ear cavity by a mucus membrane. It continues anteriorlyand joins the lingual nerve of V3 where it carries general sensoryafferents for the anterior two-thirds of the tongue. The chordatympani contains secretomotor fibers to sublingual andsubmandibular glands, as well as visceral afferent fibers for taste.The cell bodies of the gustatory neurons lie in the geniculate ganglion and travel via the nervus intermedius back to the nucleustractus solitarius (gustatory nucleus). Therefore, the nervusintermedius carries efferents from the superior salivatory nucleusand taste afferents to the nucleus tractus solitarius. It is importantto remember that the parotid glands are innervated by the glossopharyngeal nerve, whereas all other glands in the head andface are innervated by the facial nerve. Question 51 refers toa98 lesion between the nerve to the stapedius (absent hyperacusis) andthe chorda tympani (impaired taste). The facial nerve then exits at the stylomastoid foramen, turnsanterolaterally, and travels through the parotid gland. After thefacial nerve exits the stylomastoid foramen, it gives off differentbranches to the various facial muscles. Monkhouse WS. The anatomy of the facial nerve. Ear Nose Throat J. 1990;69:677–683, 686–687. Wilson-Pauwels L, Akesson EJ, Stewart PA, et al. Cranial Nerves inHealth and Disease. 2nd ed. Ontario: BC Decker Inc; 2002.

Question 55

55.Which of the following cranial nerve nuclei is involved in the sensation of taste?

Answer 55

d.

Question 56

56.Which of the following cranial nerve nuclei receives the initial afferent signals in the baroreceptor reflex?

Answer 56

d.

Question 57

57.Which of the following cranial nerve nuclei innervates the muscles of the pharynx and larynx?

Answer 57

b. The nucleus tractus solitarius is involved with both taste andbaroreceptor reflexes. The rostral part of this nucleus is involvedwith taste and receives taste afferents from the facial nerve (anterior two-thirds of the tongue), glossopharyngeal nerve (posterior one-third of the tongue), and the vagus nerve (base oftongue, epiglottis, and pharynx). The caudal part of this nucleus isinvolved in the baroreceptor reflexes. Baroreceptors in the wall ofthe carotid sinus are stimulated by increased blood pressure andthe glossopharyngeal afferents travel to the caudal nucleus tractussolitarius. As a result, interneurons stimulate the dorsal motornucleus of the vagus nerve, leading to activation ofparasympathetic vagal efferents projecting to the heart and causing slowing of the heart rate. The nucleus ambiguus is the centralnucleus responsible for innervation of the muscles of the larynxand pharynx, innervated by the glossopharyngeal and vagus nerves(with some laryngeal muscle innervation contributed by the spinalaccessory nerve). The superior salivatory nucleus is the source of parasympatheticinnervation to the head and neck. The inferior salivatory nucleusinnervates the parotid gland via the glossopharyngeal nerve. Crossman AR, Neary D. Neuroanatomy; An Illustrated Colour Text. 2nd ed. London, UK: Churchill-Livingstone; 2000. Wilson-Pauwels L, Akesson EJ, Stewart PA, et al. Cranial Nerves inHealth and Disease. 2nd ed. Ontario: BC Decker Inc; 2002.

Question 58

58.A 67-year-old man presents with symptoms suspicious for cavernous sinus thrombosis. Which of the following nerves is not located in the cavernous sinus?

Answer 58

a.

Question 59

59.Regarding the trigeminal nerve, which of the following is correct?

Answer 59

d.

Question 60

60.Regarding the course of the trigeminal nerve from the cranium, which of the following is incorrect?

Answer 60

d. The trigeminal nerve carries sensory information from the face, and supplies the sensory and motor innervation to the muscles ofmastication. The nerve emerges from the pons in the midlateralsurface. The trigeminal ganglion (gasserian or semilunar ganglion) is a sensory ganglion localized in the floor of the middle cranialfossa within a depression known as Meckel’s or trigeminal cave.Three primary divisions emerge from the gasserian ganglion (notthe sphenopalatine ganglion, which is discussed below): the ophthalmic (V1), maxillary (V2), and mandibular (V3). The ophthalmic division (V1) leaves the gasserian ganglion andexits the cranium through the cavernous sinus and the superiororbital fissure en route to the orbit. It branches into the tentorial,frontal, lacrimal, and nasociliary nerves. It mediates the afferentlimb of the corneal reflex while the efferent limb is provided bythe facial nerve. The V1 division supplies sensation to the skin ofthe nose, upper eyelid, forehead, and scalp (as far back aslambdoidal suture); upper half of cornea, conjunctiva, and iris,mucus membranes of frontal, sphenoidal, and ethmoidal sinuses,upper nasal cavity and septum, and lacrimal canals; and dura materof the anterior cranial fossa, falx cerebri, and tentorium cerebelli. The maxillary division (V2) leaves the gasserian ganglion,travels through the cavernous sinus, exits the cranium through theforamen rotundum, enters the sphenopalatine fossa, and thenenters the orbit through the inferior orbital fissure. Branchesinclude the zygomatic, infraorbital, superior alveolar, and palatinenerves. The V2 division supplies sensation to the lower eyelid,lateral nose, upper lip and cheek, lower half of cornea, conjunctiva, and iris; mucus membranes of maxillary sinus, lower nasal cavity,hard and soft palates, and upper gum; teeth of the upper jaw; and100 dura mater of the middle cranial fossa. The mandibular division (V3) leaves the gasserian ganglion, exitsthe cranium through the foramen ovale, travels in the infratemporal fossa, and branches into the buccal, lingual, inferioralveolar, and auriculotemporal nerves. The V3 division does nottravel through the cavernous sinus and is therefore spared incavernous sinus thrombosis. Besides the muscles of mastication, V3supplies sensation to skin of the lower lip, lower jaw, chin,tympanic membrane, auditory meatus, upper ear; mucusmembranes of floor of the mouth, lower gums, anterior two-thirdsof the tongue (not taste, which is facial nerve), and teeth of lowerjaw; and dura mater of the posterior cranial fossa (although mostof posterior fossa innervation arises from upper cervical nerves). The cavernous sinus contains the ICA (siphon), postganglionicsympathetic fibers, and cranial nerve VI on the medial wall(adjacent to the sphenoid sinus), whereas cranial nerves III, IV, V1, and V2 are found along the lateral wall. The cavernous sinusreceives blood from the middle cerebral vein and drains into thejugular vein (via the inferior petrosal sinus) and into the transverse sinus (via the superior petrosal sinus). The two cavernous sinusesare connected by intercavernous sinuses that lie anterior andposterior to the hypophysis forming a venous circle around it. The sphenopalatine ganglion (pterygopalatine ganglion) isaparasympathetic ganglion found in the pterygopalatine fossa. It isthe largest of four parasympathetic ganglia of the head and neck, along with the submandibular ganglion, otic ganglion, and ciliaryganglion. The sphenopalatine ganglion is associated with thebranches of the trigeminal nerve. It supplies the lacrimal glands,paranasal sinuses, glands of the mucosa of the nasal cavity andpharynx, the gingiva, and the mucus membrane and glands of thehard palate. Brazis PW, Masdeu JC, Biller J. Localization in Clinical Neurology. 6thed. Philadelphia, PA: Lippincott Williams & Wilkins; 2011. Crossman AR, Neary D. Neuroanatomy; An Illustrated Colour Text. 2nd ed. London, UK: Churchill-Livingstone; 2000. Wilson-Pauwels L, Akesson EJ, Stewart PA, et al. Cranial Nerves inHealth and Disease. 2nd ed. Ontario: BC Decker Inc; 2002.

Question 61

61.Which of the following is true regarding the hypoglossal nerve (cranial nerve XII)?

Answer 61

e. Most of the corticobulbar projections to the hypoglossal nuclei arebilateral, although there is one exception. The cortical neurons thatdrive the genioglossus muscles project only to the contralateralhypoglossal nucleus. There is one genioglossus muscle on each side of the tongue and they pull the tongue anterior and medial.Therefore, if tongue deviation is due to an upper motor neuronlesion affecting the genioglossus projections, tongue deviation willbe contralateral. A lower motor neuron lesion causes ipsilateraltongue deviation. The hypoglossal nerve provides innervation to all intrinsictongue muscles and three (genioglossus, styloglossus, andhyoglossus) of the four extrinsic tongue muscles, with the fourth(palatoglossus) being innervated by the vagus nerve. Wilson-Pauwels L, Akesson EJ, Stewart PA, et al. Cranial Nerves inHealth and Disease. 2nd ed. Ontario: BC Decker Inc; 2002.

Question 62

62.Which of the following is incorrect regarding the accessory nerve?

Answer 62

b. Activation of the accessory nerve causes ipsilateral head tilt andcontralateral head rotation. The accessory nerve innervates the sternocleidomastoid and the trapezius muscle on each side. The action of each sternocleidomastoid (SCM) is to pull the mastoidprocess toward the clavicle, resulting in contralateral head rotationand turning of chin to the contralateral side (ipsilateral head tilt). Each SCM is innervated by the ipsilateral motor cortex, whereaseach trapezius is innervated by the contralateral motor cortex. Wilson-Pauwels L, Akesson EJ, Stewart PA, et al. Cranial Nerves inHealth and Disease. 2nd ed. Ontario: BC Decker Inc; 2002.

Question 63

63.A 68-year-old man with an extensive history of smoking ishospitalized for aspiration pneumonia. You are consulted for evaluation of generalized weakness. Besides generalized weakness, you notice that he has a poor gag reflex as well as a slightly lowered left soft palate with mild deviation of the uvula to the right. Which of the following is correct?

Answer 63

e. The gag reflex is mediated by the nucleus ambiguus. The afferentlimb is by the glossopharyngeal nerve and the efferent limb is bythe vagus nerve. The vagus nerve exits the cranium through the jugular foramen102 with the glossopharyngeal and spinal accessory nerves. Throughfibers originating from the nucleus ambiguus, the vagus innervatespalatal, pharyngeal, and laryngeal muscles. A vagus nerve lesionwill cause impaired swallowing (likely the cause of this patient’saspiration pneumonia), hoarse voice, and flattening and lowering of the palate, which causes the uvula to point toward the contralateral side. The vagus supplies parasympathetic innervation to the heart,lungs, gastrointestinal (GI) tract, and trachea. Parasympatheticneurons of the vagus are located in the dorsal motor nucleus of thevagus (which supplies the GI tract, liver, pancreas, and respiratorytract) and medial part of the nucleus ambiguus (which supplies the cardiac plexus). The vagus nerve also supplies sensation to the base of the tongue, epiglottis, and pharynx. Wilson-Pauwels L, Akesson EJ, Stewart PA, et al. Cranial Nerves inHealth and Disease. 2nd ed. Ontario: BC Decker Inc; 2002.

Question 64

64.The maxillary branch of the trigeminal nerve (CN V2) passes through which of the following skull foramina?

Answer 64

b.

Question 65

65.The internal carotid artery passes over which of the following skull foramina?

Answer 65

c.

Question 66

66.Which of the following structures does not pass through the superior orbital fissure?

Answer 66

d.

Question 67

67.The oculomotor nerve (CN III) passes through which of the following skull foramina?

Answer 67

e.

Question 68

68.The ophthalmic branch of trigeminal nerve (CN V1) passes through which of the skull foramina?

Answer 68

c.

Question 69

69.Which of the following structures passes through the foramen spinosum?

Answer 69

d.

Question 70

70.Which of the following structures passes through the foramen ovale?

Answer 70

b.

Question 71

71.The glossopharyngeal nerve (CN IX) passes through which of the following skull foramina?

Answer 71

a.

Question 72

72.The vagus nerve (CN X) passes through which of the following skull foramina?

Answer 72

c.

Question 73

73.Which of the following structures passes through the internal acoustic meatus?

Answer 73

e. The anatomy of the cranial nerves, major intracranial vascularstructures, and the foramen through which these structures pass isimportant in localizing neurologic findings. The olfactory nervebundles pass through the cribriform plate foramina. Cranial nerve II (optic nerve) passes through the optic canal along with the ophthalmic artery. Cranial nerves III (oculomotor nerve), IV(trochlear nerve), V1 (trigeminal nerve, 1st division; ophthalmic103 nerve), and VI (abducens nerve) all pass through the superiororbital fissure. Cranial nerve V2 (trigeminal nerve, 2nd division;maxillary nerve) passes through the foramen rotundum. Cranialnerve V3 (trigeminal nerve, 3rd division; mandibular nerve) passesthrough the foramen ovale.An easy way to remember the sequence ofwhich foramen each of the three trigeminal nerve branches pass is theterm “StandingRoomOnly” (Superior orbital fissure, foramenRotundum, foramenOvale) for V1, V2, V3, respectively.The middlemeningeal artery passes through the foramen spinosum, and the internal carotid artery passes in close relationship with the foramenlacerum. The internal carotid artery passes through the carotidcanal and runs along the superior surface of the foramen lacerumbut does not travel through it. Cranial nerves VII (facial nerve) and VIII (vestibulocochlearnerve) pass through the internal acoustic meatus. Cranial nerves IX(glossopharyngeal nerve), X (vagus nerve), and XI (spinalaccessory nerve) pass through the jugular foramen. Cranial nerveXII (hypoglossal nerve) passes through the hypoglossal canal. Themedulla oblongata, vertebral arteries, and meninges pass throughthe foramen magnum. See Figure 1.11 for the skull foramina andtheir contents.