Chapter 1 Flashcards
1.Which of the following represents the actions of the superior oblique muscle?
d.
2.Which of the following represents the actions of the inferior rectus muscle?
b.
3.Which of the following muscles is not innervated by the oculomotor nerve?
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.
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?
c.
5.Which of the following is not a known association with this disorder?
a.
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?
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.
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?
e.
8.Which of the following is true regarding the sympathetic pathway to the orbit and face?
b.
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?
b.
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?
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.
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?
c.
12.Which of the following is true regarding the oculomotor nuclear complex?
c.
13.Which of the following is true regarding the course of the oculoparasympathetic innervation of the eye?
b.
14.Which of the following is true regarding the pupillary light response and oculoparasympathetic pathways?
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.
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?
b.
16.In this type of nerve lesion, which of the following corrective head positions would be expected to lessen the severity of diplopia?
d.
17.Which of the following is true regarding the course and innervation of this nerve?
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.
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?
a.
19.Which of the following would be the least likely cause of this patient’s findings?
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.
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?
b.
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?
e.
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?
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.
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?
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.
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?
d.
25.In the chronic stage of this disease process, which of the following pupillary findings are most often seen?
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.
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?
e.
27.Her fundoscopic examination of the right eye is shown in Figure 1.3 . What diagnosis do you suspect?
d.
28.A brain MRI with contrast confirms your suspicion. Which of the following would be the most appropriate next course of treatment?
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.
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?
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.
