optic nerve and neuro

Question 1

Which 3 of the following extraocular muscles are supplied by the MEDIAL muscular branch of the ophthalmic artery? (Select 3)

Correct answer Medial rectus

Superior oblique

Inferior rectus

Inferior oblique

Lateral rectus

Answer 1

Medial rectus

Inferior rectus
Inferior oblique
The medial muscular branch of the ophthalmic artery supplies the medial rectus, inferior rectus, and the inferior oblique extra-ocular muscles, while the lateral muscular branch supplies the superior rectus, superior oblique, lateral rectus, and levator palpebrae superioris.

Question 2

What is the correct order of the optic nerve meninges progressing from most external to most internal?

Dura mater, pia mater, arachnoid

Dura mater, arachnoid, pia mater

Arachnoid, dura mater, pia mater

Arachnoid, pia mater, dura mater

Answer 2

Dura mater, arachnoid, pia mater

Explanation - The correct order of the optic nerve meninges is the same as those found on the brain which makes sense since they are extensions of each other. The dura mater is the most external layer and is composed of very dense connective tissue. Next is the arachnoid follows next whose connective tissue is less ordered than the dura mater. The most internal of the meninges is the pia mater which is adhered to the nerve.

Question 3

The FIRST synapse in the visual pathway occurs in which of the following layers of the retina?

Ganglion cell layer

Outer nuclear layer

Inner nuclear layer

Inner plexiform layer

Outer plexiform layer

Photoreceptor layer

Answer 3

Outer plexiform layer
The first synapse of the visual system occurs in the outer plexiform layer (OPL) of the retina. It is here that the cone pedicles and rod spherules are synaptic upon the dendrites of various bipolar cells. Additionally, projections from horizontal cells also make contact with rods, cones, and bipolar cells in the outer plexiform layers.

Question 4

Which of the following cranial nerves is affected in a patient diagnosed with Bell’s palsy?

Third cranial nerve

Ninth cranial nerve

Eleventh cranial nerve

Seventh cranial nerve

Eighth cranial nerve

Fifth cranial nerve

Answer 4

Seventh cranial nerve

Bell’s palsy is an idiopathic isolated peripheral palsy of the ipsilateral seventh cranial nerve (facial nerve). It is thought that inflammation of the nerve results in compression of the fibers where it exits the skull within its bony canal, thereby blocking the transmission of neural signals.

Question 5

Which of the following nerves does NOT travel within the lateral wall of the cavernous sinus but rather passes through the middle of the sinus alongside the internal carotid artery?

Maxillary branch of trigeminal nerve

Ophthalmic branch of trigeminal nerve

Abducens nerve

Oculomotor nerve

Trochlear nerve

Answer 5

Abducens nerve
Unlike the oculomotor, trochlear, and ophthalmic and maxillary branches of the trigeminal nerve, the abducens nerve (CN VI) does not run within the lateral wall of the cavernous sinus. Rather, it courses through the body of the sinus alongside the internal carotid artery.

Question 6

Double-ring sign is an observable feature associated with which of the following congenital optic nerve anomalies?

Buried optic disc drusen

Morning glory syndrome

Optic disc dysplasia
Optic nerve hypoplasia

Optic disc coloboma

Megalopapilla

Answer 6

Optic nerve hypoplasia

Patients with optic nerve hypoplasia present with several characteristic funduscopic features that comprise its diagnosis. Classically, the optic disc is small, has a greyish appearance, and is surrounded by a mottled, yellow, hypo-pigmented peripapillary border that encircles the disc, forming a halo. This halo is also bordered by a darker pigmented ring, which leads to the name “double ring sign.” The outer ring represents what would have been the margin of the disc had it been of normal size.

Question 7

Damage to pupillary fibers connecting which of the following structures results in light-near dissociation?

Retina to pretectal nucleus

Ciliary ganglion to iris sphincter

Edinger-Westphal nucleus to ciliary ganglion

Pretectal nucleus to Edinger-Westphal nucleus

Answer 7

Pretectal nucleus to Edinger-Westphal nucleus
The pupillary light reflex begins with the retinal photoreceptors and is composed of four neurons, ending at the iris sphincter. The first neuron connects each retina with both pretectal nuclei that reside in the midbrain in the area of the superior colliculi. Fibers running from the nasal retina decussate at the optic chiasm and pass along the opposite optic tract, reaching the contralateral pretectal nucleus.

Contrastingly, impulses originating at the temporal retina are conducted by fibers that traverse the ipsilateral optic tract, terminating at the ipsilateral pretectal nucleus. The second neuron in this pupillary light reflex connects each pretectal nucleus to both the ipsilateral and contralateral Edinger-Westphal nuclei. It is because of these connections that a light stimulus presented to one eye will evoke a bilateral and symmetrical pupillary constriction. Damage to these neurons (also known as intercalated neurons) is responsible for light near dissociation that is commonly associated with neurosyphilis. The next neuron in this pathway connects the Edinger-Westphal nucleus to the ipsilateral ciliary ganglion, while the final neuron leaves the ciliary ganglion and terminates at the iris sphincter muscle.

Question 8

Which of the following vessels provides the majority of the blood supply to the optic nerve head?

Anterior ciliary arteries

Central retinal artery

Short posterior ciliary arteries

Long posterior ciliary arteries

Answer 8

Short posterior ciliary arteries

The ophthalmic artery provides the majority of the supply of blood to both the inner retina and the optic nerve.

• The central retinal artery (CRA) branch of the ophthalmic artery enters the optic nerve approximately 12mm behind the globe
• In the retina, the retinal ganglion cell bodies and the nerve fiber layer are primarily supplied by capillary branches of the central retinal artery that emerge from the optic nerve head
• As the CRA courses over the optic disc, it provides partial perfusion to some of the superficial optic disc; however, it provides minimal perfusion to the optic nerve itself, through which it courses
• Branches of the medial and lateral short posterior ciliary arteries (SPCAs) also originate from the ophthalmic artery
• These provide the majority of the blood supply to the optic nerve head as well as the choroid
• Most notably, anastomoses of the SPCAs create the Circle of Zinn-Haller, which provides significant perfusion to the optic nerve head

Question 9

Which of the following medications has been identified as a risk factor for the development of non-arteritic anterior ischemic optic neuropathy (NAION)?

Omeprazole

Celecoxib

Atenolol

Simvastatin

Sildenafil

Hydrochlorothiazide

Answer 9

Sildenafil

• Non-arteritic anterior ischemic optic neuropathy is an ocular condition that typically presents as a sudden, painless loss of vision that is thought to be triggered by inadequate perfusion of the optic nerve head. This eventually leads to infarction, causing swelling and compression of the tissue, ischemia, and further infarction. Unlike an arteritic anterior ischemic optic neuropathy, there typically aren’t any warning signs of the impending condition, but there have been associated risk factors identified of which clinicians should be aware. These predisposing factors include a small optic disc with a small or crowded cup (known as a “disc at risk”). In these cases, if the disc begins to swell, the fibers have no place to go except to further compress on nearby axons, which leads to further swelling. Nocturnal (or nighttime) hypotension is also thought to be a risk factor due to the fact that many cases of NAION occur upon wakening or shortly thereafter. Several studies have also found a connection between sleep apnea and cases of NAION.

When it comes to medication correlations, there have been several reported cases of NAION occurring in men after taking sildenafil citrate (Viagra®). The exact mechanism is unclear; however, it is believed that because the drug is involved in modulating blood vessel diameter, it is also then likely to have an effect on perfusion to the optic nerve tissue

Question 10

Evaluation of the pupillary reflex assesses the integrity of which cranial nerve?

Cranial nerve IX

Cranial nerve II

Cranial nerve VI

Cranial nerve IV

Answer 10

Cranial nerve II

The neurological integrity of cranial nerve II is assessed via the pupillary reflexes. The afferent pathway (the pathway from the eye to the brain) is evaluated by having the patient focus on a distant target under moderate lighting conditions. A bright controlled light source (transilluminator) is then directed from below the patient’s line of sight into the pupil. A normal pupil will quickly constrict and then slowly increase in size until it is mid-dilated followed by hippus. The procedure is then repeated on the other eye. The light source is then alternated quickly back and forth between the pupils to evaluate the consensual response. Damage to the afferent pathway will cause an afferent pupil defect or light-near dissociation. Light-near dissociation occurs when the pupil response to a near stimulus is greater than the pupil reaction to light. Pupillary reflexes also test the efferent pathway (from the brain to the eye), which is controlled, in part, by cranial nerve III and the oculo-sympathetic pathway. If there is cranial nerve III damage, the pupillary response to bright light will be decreased, but the consensual response will remain unaffected or there will be a change in the pupil size of one eye (as long as the damage is unilateral or asymmetrical).

Question 11

Which of the following ocular conditions will NEVER produce a relative afferent pupillary defect in the ipsilateral eye?

Optic nerve glioma

Total retinal detachment

Central retinal artery occlusion

Mature cataract

Optic neuritis

Answer 11

Mature cataract
A relative afferent pupillary defect (RAPD) occurs in patients who have a history of an incomplete optic nerve lesion (a complete lesion would result in an absolute afferent pupillary defect), or the presence of severe retinal disease. The clinical features of a relative afferent pupillary defect include a pupil that responds weakly to light stimulation in the diseased eye and briskly to light stimulation in the normal eye. The results are exaggerated during the swinging flashlight test, in which both eyes will constrict when the normal eye is presented with a light stimulus, and both eyes will slowly dilate when the diseased eye is presented with the same amount of light. This anomalous result of dilation of the pupils in response to light occurs because the normal dilation that occurs when the light is withdrawn from the normal eye is more pronounced than the constriction that is produced by stimulating the abnormal eye.

There are several conditions that may cause an afferent pupillary defect. These include severe retinal diseases, or macular scarring, severe asymmetric glaucoma, an optic nerve glioma or meningioma, central retinal artery occlusion or ischemic central retinal vein occlusion, optic neuritis, or any lesion that occurs along any segment of the optic nerve, usually prior to the chiasm. A dense cataract will never cause a relative afferent pupillary defect in the same eye, and should, therefore, never be used to explain the presence of an RAPD.

Question 12

Which of the following conditions has been associated with an intact pupillary light response and absent near response?

Diabetes

There is no clinical condition in which this exists

Neurosyphilis

Myotonic dystrophy

Adie’s tonic pupil

Aberrant regeneration of the third nerve

Answer 12

There is no clinical condition in which this exists
The near reflex is activated when a person changes gaze from a distant to a near object. It is comprised of a triad of accommodation, convergence, and pupil miosis. Vision is not required for this response, and there is no clinical condition in which the pupillary light reflex is intact and the near response is absent. However, there are several conditions that are associated with dissociation of light and near responses in which the light reflex is either absent or sluggish and the near response is normal. Although the final pathways for both responses are identical, the center for the near reflex is controlled by a supranuclear influence.

Question 13

Which of the following optic nerve conditions results from an increase in intracranial pressure?

Papillitis

Papilledema

Optic neuritis

Ischemic optic neuropathy

Answer 13

Papilledema
Papilledema is defined as passive swelling of the optic disc caused by increased intracranial pressure, usually as a result of intracranial tumors or malignant hypertension. The condition is almost always bilateral, and vision is usually normal unless there is associated edema or exudates in the macular area.

Optic neuritis is inflammation of the optic nerve that can occur at any location as it courses from the eye. It is typically caused by swelling and destruction of the myelin sheath that surrounds the nerve.

Papillitis is a specific type of optic neuritis in which there is an inflammation of the optic nerve head. This condition is almost always unilateral, and because the optic nerve is inflamed, it is commonly associated with vision loss.

Ischemic optic neuropathy is caused by obstruction of blood flow to the optic nerve, resulting in the loss of structure or function of a portion of the nerve. It is classified as either arteritic or non-arteritic, according to the location of the nerve that is affected. Patients with this condition will often present with acute loss of visual acuity and an altitudinal visual field defect.

Question 14

Which of the following BEST describes the rotation of the eyeball during Bell’s phenomenon?

Upward and outward

Downward and outward

Upward and inward

Downward and inward

Answer 14

Upward and outward
Bell’s phenomenon is a reflex coordinated between the facial nerve and the oculomotor nuclei in which the eyeball is rotated upward and outward upon closure of the eyelids. The reflexive movement occurs as a protective mechanism that repositions the cornea up under the eyelid and, therefore, away from potential danger. The neurological pathway of this phenomenon is not completely understood. It is also not present in about 10% of otherwise healthy individuals; thus, its absence cannot be relied upon as a cause or cited as a sign of disease.

Question 15

Which of the following pupillary fibers is damaged in patients presenting with an Adie’s tonic pupil?

Post-ganglionic parasympathetic

Pre-ganglionic parasympathetic

Pre-ganglionic sympathetic

Post-ganglionic sympathetic

Answer 15

Post-ganglionic parasympathetic
An Adie’s tonic pupil is usually an idiopathic, benign form of internal ophthalmoplegia that occurs as a result of damage and subsequent denervation of the postganglionic parasympathetic pupillomotor fibers. These fibers originate from the ciliary ganglion (which is located within the muscle cone, just behind the globe), and travel forward to eventually supply the pupil sphincter.

Around 90% of patients presenting with an Adie’s pupil are women, typically between the ages of 20 and 40. The condition is unilateral in 80% of cases; however, involvement of the fellow eye may develop later. Initially, anisocoria is present, in which the abnormal eye is dilated and reacts poorly to light and accommodates poorly. Slit-lamp evaluation will commonly show an iris that exhibits segmental contraction in response to light (vermiform movement). Later, the affected pupil will become miotic (“little old Adie’s”).

Question 16

Which of the following sequences describes the correct order of the oculosympathetic pathway as the neurons descend from the brain?

Hypothalamus–> ciliospinal center of Budge–> superior cervical ganglion–> ophthalmic division of trigeminal nerve

Pretectal nucleus–> superior cervical ganglion–> ciliospinal center of Budge–> ophthalmic division of trigeminal nerve

Pretectal nucleus–> ciliospinal center of Budge–> superior cervical ganglion–> ophthalmic division of trigeminal nerve

Hypothalamus–> superior cervical ganglion–> ciliospinal center of Budge–> ophthalmic division of trigeminal nerve

Answer 16

Hypothalamus–> ciliospinal center of Budge–> superior cervical ganglion–> ophthalmic division of trigeminal nerve

The oculosympathetic pathway contains three neurons as it courses from the brain to structures of the eye. The first neuron (central neuron) in this pathway begins at the posterior region of the hypothalamus. It descends down the brainstem to synapse at the ipsilateral ciliospinal center of Budge, which lies between C8 and T2 of the spinal cord. The second neuron (pre-ganglionic neuron) traverses a long course from the ciliospinal center to the superior cervical ganglion in the neck region. During its path, it is closely related to the apical area of the lung where it can be damaged by a Pancoast tumor, or in some cases, during surgery on the neck. The final neuron in the oculosympathetic pathway (post-ganglionic neuron) ascends with the internal carotid artery where it eventually enters the cavernous sinus and joins with the ophthalmic division of the trigeminal nerve. From here, the sympathetic fibers reach the pupil dilator and ciliary body by means of the long ciliary nerves and nasociliary nerves.

Question 17

The ophthalmic portion (V1) of cranial nerve V (the trigeminal nerve) possesses three main sub-divisions. Which of the following is a subdivision of V1?

Maxillary division

Mandibular division
Frontal division

Supratrochlear division

Answer 17

Frontal division
Cranial nerves and their respective divisions can be very confusing and are best understood and remembered with diagrams and mnemonics.

The trigeminal nerve has three main divisions: ophthalmic (V1), maxillary (V2), mandibular (V3).

The ophthalmic division (V1) has three sub-divisions (think NFL) which are the nasociliary, frontal and lacrimal.

The frontal division of the V1 branch possesses two sub-divisions: the supraorbital and the supratrochlear divisions. The frontal division is the most commonly affected in herpes zoster ophthalmicus.

The nasociliary division has four sub-divisions (think LINE): long ciliary, infratrochlear, nasal, and the posterior ethmoid.

Question 18

Which 2 of the following pupil anomalies would cause anisocoria that is more prevalent in bright lighting? (Select 2)

Horner’s syndrome

Argyll Robertson pupil

Physiologic anisocoria
Acute Adie’s tonic pupil

Marcus Gunn pupil

Oculomotor palsy

Answer 18

Acute Adie’s tonic pupil
Oculomotor palsy
When investigating the etiology of a pupil abnormality, it is important to first determine which pupil is affected; this is accomplished by measuring pupil diameter sizes in both bright and dim light. Cases in which anisocoria is more prevalent in bright lighting suggests that the abnormal pupil is the larger pupil, as it will not constrict in the presence of light. Anisocoria that is more obvious in dim lighting suggests that the smaller pupil is abnormal because it does not dilate at the same rate as the normal pupil.
ossible causes of an abnormal dilated pupil in which anisocoria is greater in bright light:
- Adie’s tonic pupil: pupil is irregular, reacts minimally to a light stimulus and slowly to a near target demand; over time, an Adie’s pupil may become miotic
- Cranial nerve III (oculomotor palsy): will present with associated ptosis and extraocular muscle palsies
- Pharmacologically dilated pupil: typically has a history of getting some type of pharmacologic agent in the eye; reaction to light depends on when the offending agent came in contact with the eye
- Iris sphincter damage (trauma): usually associated with a torn pupil margin, or iris transillumination defects

Question 19

A 9-year old patient presents with a unilateral ptosis of the left eyelid that improves in position when he widely opens his jaw. This condition, known as Marcus-Gunn jaw winking, is the result of aberrant connections between which 2 of the following cranial nerves? (Select 2)

Cranial nerve IV

Cranial nerve II

Cranial nerve VI

Cranial nerve VII

Cranial nerve III

Cranial nerve V

Answer 19

Cranial nerve III
Cranial nerve V
Marcus-Gunn jaw winking is a phenomenon that is thought to occur as a result of an abnormal connection between cranial nerve V and cranial nerve III. Branches from the motor root of the trigeminal nerve that are meant for the ipsilateral pterygoid muscle aberrantly connect with the ipsilateral levator muscle instead. This allows for an elevation effect of the upper eyelid when jaw movements are initiated. This type of aberrant innervation may occur in up to 5% of patients presenting with a congenital ptosis; it tends to lessen in severity with age. This condition should not be confused with aberrant regeneration of cranial nerve VII; it is an isolated neurologic finding and does not require further work-up. Furthermore, Marcus-Gunn jaw winking is typically monitored indefinitely unless there is cosmetic concern and/or surgical intervention is desired.

Question 20

Which of the following is LEAST likely to result in the observation of an afferent pupillary defect?

Severe, bilateral, asymmetrical macular degeneration

A patient with a dense corneal scar in one eye and glaucomatous damage in the contralateral eye

Asymmetric, bilateral, glaucomatous damage with 20/20 acuity in both eyes

A dense unilateral cataract

Answer 20

A dense unilateral cataract
The afferent pathway (the pathway from the eye to the brain) is evaluated by having the patient focus on a distant target under moderate lighting conditions. A bright controlled light source (transilluminator) is then directed from below the patient’s line of sight into the pupil. A normal pupil will quickly constrict and then slowly increase in size until it is mid-dilated, followed by hippus. This procedure is then repeated on the other eye. The light source is then alternated quickly back and forth between the pupils to evaluate the consensual response. Damage to the afferent pathway will cause an afferent pupil defect or light-near dissociation. Light-near dissociation occurs when the pupil response to a near stimulus is greater than the pupil reaction to light.

Afferent pupillary defects are observed if there is retinal or optic nerve damage. However, the damage between the eyes must be asymmetrical in order for an APD to be observed. Even a small amount of nerve damage may cause an APD, whereas a much larger degree of retinal damage is required to produce an APD. As long as the light source used is adequate, a dense cataract or a corneal scar should (in theory) not cause an APD.

Question 21

Which 2 of the following signs and symptoms can aid in differentiating between a microvascular and compressive third cranial nerve palsy? (Select 2)

Third nerve palsies due to compressive lesions will always have an affect on pupil size

The presence of pain is more common in aneurysmal third nerve palsies

Third nerve palsies associated with microvascular disease commonly spontaneously resolve within 3 months

Microvascular third nerve palsies do not typically involve the pupil

Aberrant regeneration typically result from microvascular third nerve palsies

Answer 21

Third nerve palsies associated with microvascular disease commonly spontaneously resolve within 3 months

Correct answer Microvascular third nerve palsies do not typically involve the pupil

Explanation - There are several signs and symptoms that clinicians utilize in order to aid in differentiating between microvascular and compressive third nerve palsies. Some of these are summarized below:

• Third nerve palsies associated with microvascular disease commonly spare the pupil due to the superficial location of pupillary fibers as they travel in the nerve
• Third nerve palsies associated with compressive lesions commonly involve the pupil due to compression of the superficial pupil fibers
• It is important to note that this is only a general principle; there are several cases in which compressive lesions do not affect the pupil initially but may eventually if the lesion continues to grow (also, some diabetic palsies have been shown to cause pupil dilation)
• Third nerve palsies due to microvascular lesions will typically resolve within a period of three months (if a suspected microvascular lesion does not resolve within this time, imaging must be completed)
• Aberrant regeneration will only occur following acute traumatic or compressive third nerve palsies (but never after a microvascular palsy) due to the fact that the endoneural nerve sheaths remain intact in vascular pathology
• The presence of pain is common in both diabetic and aneurysmal third nerve palsies; therefore, it cannot be used to differentiate the two

Question 22

Which of the following is the correct order of structures through which the pupillary fiber pathway passes?

Optic nerve -> optic chiasm -> optic tract -> Lateral geniculate nucleus in the thalamus

Optic nerve -> optic chiasm -> brachium of the superior colliculus -> pretectal region of the midbrain -> Edinger-Westphal nucleus

Optic nerve-> optic chiasm -> Lateral geniculate nucleus in the thalamus-> Edinger-Westphal nucleus

Optic nerve -> optic chiasm -> optic tract -> pretectal region of the midbrain -> Lateral geniculate nucleus in the thalamus
.

Answer 22

Optic nerve -> optic chiasm -> brachium of the superior colliculus -> pretectal region of the midbrain -> Edinger-Westphal nucleus
explanation - The pupillary fibers exit the eye through the optic nerve and pass through the optic chiasm, where they then exit the optic tract and enter into the brachium of the superior colliculus and synapse onto cells in the pretectal area of the midbrain. The pathway then continues and stimulates intercalated neurons, which in turn stimulate cells in the Edinger-Westphal nucleus. The axons of the pupillary pathway never enter the lateral geniculate nucleus.

Question 23

Which area of the retina naturally corresponds with a sensitivity of 0 decibels on visual field testing?

The inferior arcade

The optic nerve head

The superior arcade

The macula

The papillomacular bundle

Answer 23

The optic nerve head
The optic nerve head, also known as the blind spot, will demonstrate a sensitivity of 0 decibels, because this area of the eye does not contain any visual receptors, and therefore does not possess any viable vision. The area of the retina with the highest decibel level (hence the highest sensitivity) as seen with visual field testing is the fovea. The sensitivity to stimuli decreases with increasing distance from the fovea.

Question 24

Which space in the meninges of the optic nerve is continuous with the space between the brain meninges such that an increase in cerebrospinal fluid pressure may cause the appearance of papilledema?

The subpial space

Subarachnoid space

The subdural space

Dural sinuses

Answer 24

Subarachnoid space
he subarachnoid space of the optic nerve is continuous with that of the brain. The subarachnoid space exists between the arachnoid and the pia mater and ends at the lamina cribrosa where it folds back on itself and terminates in a cul-de-sac. This space is filled with cerebrospinal fluid (CSF) and therefore should anything cause an increase in CSF pressure, this can translate down to the nerve and manifest as papilledema.

The dural sinuses are venous channels that carry blood from the brain to the heart, not cerebrospinal fluid.

The dura is generally firmly attached to the skull or bones and the arachnoid is connected to the dura. In the event of injury, trauma or sickness the dura and arachnoid may become separated resulting in a space called the subdural space.

In a healthy individual there should not exist a space underneath the pia mater. The pia mater is an extremely thin membrane that adheres very closely to the brain, spinal cord and optic nerve such that it follows the sulci and gyri of the brain’s surface.

Question 25

Which 2 of the following muscles are innervated by the superior division of the third cranial nerve? (Select 2)

Levator palpebrae superioris

Medial rectus

Superior oblique

Sphincter pupillae

Superior rectus

Mueller’s muscle

Answer 25

Levator palpebrae superioris
Superior rectus
he superior division of the third cranial nerve innervates the levator palpebrae superioris and the superior rectus muscles.

The inferior division innervates the medial rectus, inferior rectus, and inferior oblique muscles. The branch that leads to the inferior oblique also contains preganglionic parasympathetic pupillary fibers from the Edinger-Westphal subnucleus, which innervate the pupillary sphincter and ciliary muscle.

Question 26

Which of the following are the MOST common causes of a pupil sparing and pupil involving third nerve palsy, respectively?

Compressive lesions, microvascular disease

Demyelinating disease, microvascular disease

Compressive lesions, demyelinating disease

Microvascular disease, compressive lesions

Microvascular disease, demyelinating disease

Demyelinating disease, compressive lesions

Answer 26

Microvascular disease, compressive lesions

The parasympathetic pupillary fibers, along with the surface of the oculomotor nerve, derive their blood supply from the surrounding blood vessels of the pia mater. Conversely, the main trunk of the third nerve is supplied by the vasa nervorum, which courses internally in the nerve. Due to the location of pupillary fibers and the difference in blood supply to the superficial and internal fibers of the oculomotor nerve, certain features that present in cases of third nerve palsies can help differentiate a “surgical” from a “medical” lesion.

Surgical lesions (aneurysms, trauma, uncal herniation) characteristically involve the pupil due to compression of the superficially coursing pupillary fibers and pial blood vessels. These cases are known as “pupil involving third nerve palsies.” Medical lesions (hypertension, diabetes) commonly spare the pupil because these conditions typically involve the vasa nervorum, leading to ischemia of the internal fibers of the oculomotor nerve while sparing the superficial pupillary fibers. This condition is also known as a “pupil-sparing third nerve palsy.”

It is important to note that these principles are not infallible. There are some cases in which pupil involvement is associated with diabetes, and compressive lesions may not initially cause pupil involvement.

Question 27

Damage to the left trochlear nucleus will affect which of the following muscles?

The right superior rectus

The left medial rectus

The left superior oblique
The right superior oblique

The left superior rectus

Answer 27

The right superior oblique
Fibers of the trochlear nerve decussate, and therefore innervate, the CONTRALATERAL superior oblique muscle. The superior oblique is responsible for incyclotorsion, depression, and abduction. Cranial nerve (CN) IV is unique in that it travels the longest intracranial course when compared to all of the other cranial nerves. The trochlear nerve is also the smallest cranial nerve, and because this nerve is so thin it is prone to damage. A CN IV palsy will cause a hypertropia of the eye on the affected side and the patient will report vertical diplopia that is worse in downgaze and at near.

Question 28

The optic nerve is vital for transmission of visual information to the brain. Where does the optic nerve terminate?

At the visual cortex

At the lateral geniculate nucleus

At the optic chiasm

At the optic disc

Answer 28

At the optic chiasm
The optic nerve is approximately 50 mm in length and originates at the optic disc which is visible upon examination of the eye with an ophthalmoscope. The optic nerve extends from the globe and terminates at the optic chiasm. At the optic chiasm the nasal fibers cross over contralaterally whereas the temporal fibers remain ipsilateral. The chiasm then gives way to the optic tract which courses to the visual cortex.

Question 29

In general, at which location in the eye do axons of the nerve fiber layer become myelinated?

Juxtafoveally

Posterior to the lamina cribrosa

At the equator

Anterior to the lamina cribrosa

Answer 29

Posterior to the lamina cribrosa
Axons of the nerve fiber layer generally become myelinated just after they pass posteriorly through the lamina cribrosa. Occasionally, oligodendrites will enter the eye during ebryogenesis causing myelination of the nerve fiber layer. This will appear as a white nerve fiber layer with feathery margins usually extending from the optic disc. In general, axons within the retina should not be myelinated. Myelination of the nerve fiber layer can be associated with amblyopia, strabismus, nystagmus, optic neuritis, neovascularization of the retina and myopia. However, in most cases, individuals that display this condition are asymptomatic.

Question 30

You are performing a slit-lamp examination on your 37 year-old male patient. He is having difficulty keeping his eyes open due to the bright light. This is an example of which of the following reflexes?

Facial

Pupil

Menace

Dazzle

Corneal

Answer 30

Dazzle
Explanation - The dazzle reflex is a subcortical reflex that results in bilateral narrowing of the palpebral fissures when the retina is stimulated with a very bright light. This acts to cut down the amount of incident light that reaches the retina. In this type of reflex, the afferent arm originates in the retina, with collateral fibers passing to the oculomotor nuclei. An interesting point to note is that the dazzle reflex is still intact in patients suffering from cortical blindness.

The menace reflex also results in bilateral reflexive closure of the eyelids but occurs in response to an object that rapidly approaches the eye. Corneal irritation from dust or other debris in the eye will cause reflexive blinking as well; this is known as the blink or corneal reflex.

Question 31

The trigeminal nerve has three main divisions. Which of the following corresponds to division 1 of the trigeminal nerve (V1)?

Ophthalmic division

Long ciliary

Supraorbital

Posterior ethmoid

Infratrochlear

Answer 31

Ophthalmic division
ranial nerves and their respective divisions can be very confusing and are best understood and remembered with diagrams and mnemonics.

The trigeminal nerve has three main divisions: ophthalmic (V1), maxillary (V2), mandibular (V3).

The ophthalmic division (V1) has three sub-divisions (think NFL) which are the nasociliary, frontal, and lacrimal.

The frontal division of the V1 branch possesses two sub-divisions: the supraorbital and the supratrochlear. The frontal division is the most commonly affected in herpes zoster ophthalmicus.

Question 32

A college student presents with bilateral internuclear ophthalmoplegia (INO). This finding is pathognomonic for which one of the following?

Multiple sclerosis

Bell’s palsy

Lyme disease

Pseudotumor cerebri

Answer 32

Multiple sclerosis
An internuclear ophthalmoplegia is caused by an interruption or dysfunction in the medial longitudinal fasciculus. This is a heavily myelinated tract, and the clinical disturbance is a failure of conjugate lateral gaze. When an attempt to look to the right is made, the affected eye (in this case, the left eye) cannot adduct (move in to maintain conjugate gaze) while the unaffected eye (in this case, the right eye) will usually manifest a nystagmus due to overcompensation during abduction. In young patients, either a one-sided or bilateral INO is highly suggestive of multiple sclerosis. In older patients, it may represent a vascular defect or stroke.
Lyme disease does not produce INOs but can present with facial palsy; it is said that bilateral facial palsies are pathognomonic for Lyme disease. Bell’s palsy is a paralysis of the seventh cranial nerve (CN VII). Pseudotumor cerebri is a defect in the reabsorption of cerebrospinal fluid leading to elevated intracranial pressure and the finding of papilledema. It is most commonly seen in young overweight females.

Question 33

A patient with bilateral tilted discs whose crescents are inferior and nasally displaced will typically display a defect located along which portion of the visual field test?

Superior temporal

Inferior nasal

Superior nasal

Inferior temporal

Answer 33

Superior temporal
A patient who has tilted discs will have an optic nerve that exits the eye superiorly, and may be accompanied by situs inversus, fundus ectasia, myopia, and superior temporal visual field defects that do not generally respect the midline. Sometimes the visual field defects can appear similar to those of a person who suffers from a pituitary tumor. It is important to distinguish between the two and this situation requires further evaluation.

Question 34

Visual acuity can be used to assess the function of which cranial nerve?

VI

VI

III

II

IV

Answer 34

II

Visual acuity, along with confrontational fields, pupil reflex evaluation, and the red cap desaturation test, can be utilized to assess the integrity of cranial nerve II (optic). Cranial nerves III (oculomotor), IV (trochlear), and VI (abducens) can be evaluated via extraocular motility (versions). Cranial nerve V (trigeminal) is measured via facial stimulation (forehead, nose, and jawline to assess all three divisions), corneal sensitivity, and palpation of the masseter muscles while the patient clenches their teeth.

Question 35

Which 4 of the following nerves are strictly MOTOR in function? (Select 4)

Cranial nerve I

Cranial nerve XI

Cranial nerve III

Cranial nerve IV

Cranial nerve II

Cranial nerve VI

Answer 35

XI, III, IV, VI
Cranial nerves I (olfactory), II (optic), and VIII (vestibulocochlear) are sensory in function. Cranial nerves III (oculomotor), IV (trochlear), VI (abducens), XI (spinal-accessory) and XII (hypoglossal) have exclusively motor functions. Cranial nerves V (trigeminal), VII (facial), IX (glossopharyngeal) and X (vagus) possess both motor and sensory functions. A good mnemonic is: Some Say Marry Money But My Brother Says Big Brains Marry Money (The words correspond to the cranial nerves in proper numerical order, with all ‘S’ words representing sensory function: ‘M’ words depict exclusive motor function, and ‘B’ words signify nerves with both motor and sensory function).

Question 36

Which of the following statements is TRUE in regards to pharmacologic testing in patients with a suspected Horner’s syndrome?

Cocaine and hydroxyamphetamine can be used interchangeably to differentiate between pre and post-ganglionic lesions

Hydroxyamphetamine confirms a diagnosis of Horner’s; cocaine will differentiate between pre and post-ganglionic lesions

Cocaine confirms a diagnosis of Horner’s; hydroxyamphetamine will differentiate between pre and post-ganglionic lesions

Cocaine and hydroxyamphetamine can be used interchangeably to confirm a diagnosis of Horner’s

Answer 36

Cocaine confirms a diagnosis of Horner’s; hydroxyamphetamine will differentiate between pre and post-ganglionic lesions

n patients with a suspected Horner’s syndrome, cocaine will confirm the diagnosis, while hydroxyamphetamine will differentiate a pre-ganglionic from a post-ganglionic lesion. A summary of pharmacologic testing in Horner’s is summarized below.

10% Cocaine

• The normal pupil will dilate, but the abnormal pupil will not
• The rationale for this is that in a normal pupil, norepinephrine is released from the post-ganglionic sympathetic nerve endings, which is eventually re-absorbed, terminating the nerve impulse
• Cocaine inhibits the re-uptake of norepinephrine, allowing it to accumulate in the synapse, and will cause dilation of the pupil
• In Horner’s syndrome, the abnormal eye will not produce any norepinephrine in the first place, so cocaine has no effect on the pupil size

1% Hydroxyamphetamine

• In a pre-ganglionic lesion, both pupils dilate
• In a post-ganglionic lesion, the abnormal pupil will not dilate
• The rationale for this is that hydroxyamphetamine will stimulate the release of norepinephrine from the post-ganglionic neurons
• If there is damage to a pre-ganglionic neuron (leaving the post-ganglionic intact), norepinephrine will be released, and dilation will occur
• If there is damage to the post-ganglionic neuron, hydroxyamphetamine will have no effect on this neuron, no norepinephrine will be released, and the pupil will not dilate

Question 37

While performing confrontational fields, your patient reports seeing all of your fingers when presented on the left and right side of her visual field exclusively; however when your fingers are presented on both sides simultaneously, the patient only reports seeing the fingers on your left hand (her right visual field). What type of lesion is consistent with these findings?

A lesion in the right occipital lobe

Correct answer A lesion in the right parietal lobe

A lesion in the right frontal lobe

A lesion in the left parietal lobe

A lesion in the left frontal lobe

Answer 37

This type of finding is consistent with a person who suffers from a right parietal lobe lesion. Remember, the right side of the brain processes info from the left side of the body and visual field. A person who has this type of lesion may also demonstrate visual neglect, meaning that they will ignore the half of their body on the opposite side of the lesion. For example a person with a right parietal lesion will apply make-up to the right side of her face but not the left side. The neglect is much more pronounced if a person is presented with stimuli to both sides of their visual field simultaneously. For this reason it is important to test confrontational fields on both sides of the visual field at the same time in order to manifest a phenomenon called visual/parietal extinction. In this phenomenon, the object presented contralateral to the lesion will not be seen by the patient because it is extinguished by the object presented on the unaffected side. This allows for easier detection of a potential lesion, and it just takes a few more seconds of chair time for the patient.

Question 38

A healthy retinal nerve fiber layer is thickest at which portion of the optic nerve head?

Nasally

Temporally

Superiorly
Inferiorly

Answer 38

Inferiorly
The nerve fiber layer is thickest at the inferior and superior regions of the nerve, respectively. The inferior and superior arcades are composed of large diameter axons with little overlap of the receptive fields, thus explaining why a field defect occurs in these regions first for early cases of glaucoma. Inferior or superior notching of the nerve is highly suspect for glaucomatous damage, and must undergo further testing in order to rule out glaucoma. The next thickest area of nerve fiber layer tissue is nasally, which is comprised of the nasal radial fibers. These axons are affected in the later stages of glaucoma, thus explaining why a temporal island of the visual field is often left remaining in advanced cases of glaucoma. Lastly, the temporal rim area is the thinnest. Temporal rim tissue is comprised of the papillomacular bundle. The fibers in this area are very small and compact, with a high degree of receptive field overlap, therefore because of the receptive field redundancy, a visual field defect correlating to this region will occur only after significant fiber loss has occurred. Due to the fact that these fibers are so small in diameter, even though they are numerous, the fibers do not occupy a lot of space in the optic nerve. The thickness of the nerve fiber layer rim tissue is best remembered as ISNT, with inferior being the thickest and temporal rim tissue being the thinnest.

Question 39

Which layer of the retina is present at the optic disc?

The external limiting membrane

The nerve fiber layer

The outer nuclear layer

The outer plexiform layer

Answer 39

The nerve fiber layer
he nerve fiber layer is the only layer of the retina that is present at the optic disc. The disc serves as the convergent point for axons of the nerve fiber layer which then form the optic nerve to convey visual information to the brain for further processing. The actual optic disc does not contain photoreceptors and thus will not generate nervous signals. This explains why this area is also known as the ‘blind spot’.

Question 40

The anterior knee of von Willebrand is composed of optic nerve fibers carrying information from which of the following quadrants of the retina?

Superior-nasal

Inferior-nasal

Inferior-temporal

Superior-temporal

Answer 40

Inferior-nasal
Explanation - The optic chiasm is formed by the union of the right and left optic nerves. It is in this area that the fibers originating from the nasal retina (temporal visual field) decussate to join the uncrossed temporal fibers (nasal visual field) and course posteriorly as the optic tracts.

The inferior nasal fibers remain low as they traverse the optic chiasm and decussate more anteriorly. Because of their location, these fibers are more vulnerable to damage from expanding pituitary lesions, leading to involvement of the superior temporal visual fields early in the disease. It is also important to note that these inferior-nasal fibers actually loop forward into the contralateral optic nerve before coursing posteriorly in the optic tract. This region is known as the anterior knee of von Willebrand.

The superior nasal fibers remain high as they traverse the optic chiasm and decussate more posteriorly. Therefore, these fibers are typically first involved in cases of lesions growing from above the optic chiasm (craniopharyngiomas), affecting the inferior temporal visual fields early in the disease progression.