(From Lawton AW: Retrochiasmal pathways, higher cortical function, and nonorganic visual loss. In: Yanoff M, Duker JS (eds) Ophthalmology, 2nd edn. St Louis, Mosby, 2004.)

(From Bajandas FJ, Kline LB: Neuro-Ophthalmology Review Manual. Thorofare, NJ, Slack, 1988.)

Figure 4-7 Pathways for vertical gaze. Upgaze pathways originate in the rostral interstitial nucleus of the medial longitudinal fasciculus and project dorsally to innervate the oculomotor and trochlear nerves, traveling through the posterior commissure. Lesions to both axon bundles are necessary to produce upgaze paralysis (lesions B or C). Upgaze paralysis is a feature of the dorsal midbrain syndrome as a result of the lesion’s effect on the posterior commissure (lesion A). Downgaze pathways also originate in the rostral interstitial nucleus of the medial longitudinal fasciculus but probably travel more ventrally. Bilateral lesions also are needed to affect downgaze and usually are located dorsomedial to the red nucleus.

(From Donahue SP, Lavin PJM: Disorders of supranuclear control of ocular motility. In: Yanoff M, Duker JS (eds) Ophthalmology. London, Mosby, 1999.)

Physiology

Testing

Color vision tests

Ishihara pseudoisochromatic or Hardy-Rand-Ritter plates; Farnsworth tests

Congenital defects: usually red / green

Acquired macular disease: may diminish blue / yellow in early stages (blue cones concentrated in perifoveal ring)

Fovea has mostly red / green cones, so red / green defects are detected in optic nerve diseases. Perception of red object indicates gross macular function

Photostress recovery test

determine best-corrected vision, shine bright light into eye for 10 seconds, record time for vision to recover within 1 line of best-corrected vision; test each eye separately; invalid for eyes with vision worse than 20/80

Optic nerve disease: normal recovery time (<60 seconds)

Macular disease: prolonged time (>90 seconds)

Contrast sensitivity

Pelli-Robson chart; Regan contrast sensitivity chart; VectorVision chart

Visually evoked cortical potentials / responses (VEP, VER)

measure macular visual function, integrity of primary and secondary visual cortex, and continuity of optic nerve and tract radiations; fovea has large area in occipital cortex, close to recording electrodes; smaller area representing more peripheral retina lies deep within calcarine fissure (Figure 4-8)

Can measure vision in preverbal infants

Flash VER: strobe light

Pattern VER: checkerboard pattern or bar grating (amacrine and ganglion cell layer of retina)

P100 wave: positive deflection at 100 ms; amplitude is height from peak to trough, latency is time from onset of flash to peak of wave

Toxic or compressive optic neuropathies: reduction of amplitude more pronounced than prolongation of latency

Demyelination: latency is prolonged; amplitude may be only mildly reduced

Figure 4-8 Normal visual evoked cortical response.

(Reprinted with permission from Slamovits TL: Basic and clinical science course. Section 12: Retina and Vitreous. San Francisco, American Academy of Ophthalmology, 1993.)

Amsler grid

tests central 10° of the visual field (held at 35 cm); 10 cm × 10 cm grid composed of 5-mm squares; primarily used to evaluate foveal pathology

Optokinetic nystagmus (OKN)

presence suggests visual input is present; slow phase is noted in direction of moving stimulus

Parieto-occipital area controls slow pursuit, frontal lobe controls saccades

Pathway in visual association area terminates in ipsilateral pontine gaze center, resulting in pursuit movements to the same side (i.e. right visual association area controls pursuit to the right)

Can use to diagnose functional visual loss

Normal (symmetric) OKN response: occipital lobe, temporal lobe, LGB, or optic tract lesions do not interfere with pursuit

Deficient pursuit movements to side of lesion (asymmetric OKN): parietal lobe lesion

Cogan’s dictum (for homonomous hemianopia): asymmetric OKN indicates parietal lobe lesion; symmetric OKN indicates occipital lobe lesion

Reversal of OKN response: 60% of patients with congenital motor nystagmus

Dorsal midbrain syndrome: downward moving OKN drum causes convergence–retraction nystagmus

Congenital ocular motor apraxia: loss of voluntary horizontal gaze (vertical gaze intact); abnormal OKN (fast phase absent); maintained tonic deviation; requires neuroimaging

Potential acuity meter (PAM)

projects image of letter chart onto retina to test macular potential in patients with media opacities

Purkinje vascular phenomena and blue field entopic test

visualization of retinal vasculature; indicates gross retinal function

Visual Field (VF) Defects (Figure 4-9)

Types

Blind spot: physiologic due to ON; 15° temporal to fixation and slightly below horizontal midline

Baring of blind spot: glaucoma, normal patients

Cecocentral scotoma: involves blind spot and macula (within 25° of fixation); can occur in any condition that produces a central scotoma, dominant optic atrophy, Leber’s optic atrophy, toxic / nutritional optic neuropathy, optic pit with serous retinal detachment, optic neuritis

Central scotoma: unilateral (optic neuritis, compressive lesion of ON, retinal lesion [macular edema, disciform scar]); bilateral (toxic optic neuropathy, nutritional deficiency, macular lesions)

Arcuate scotoma: glaucoma, optic neuritis, anterior ischemic optic neuropathy (AION), branch retinal artery occlusion (BRAO), branch vein occlusion (BVO), ON drusen

Altitudinal defect: damage to upper or lower pole of optic disc; optic neuritis, AION, hemiretinal artery or vein occlusion

Spiraling of VF: suggests malingering / functional visual loss

Pseudobitemporal hemianopia (slope and cross-vertical meridian): uncorrected refractive error, tilted optic disc, enlarged blind spot (papilledema), large central or cecocentral scotoma, sector retinitis pigmentosa (nasal quadrant), overhanging lid, coloboma

Binasal defect: most nasal defects due to arcuate scotomas (glaucoma); also, pressure on temporal aspect of ON and anterior angle of chiasm, aneurysm, pituitary adenoma, infarct

Constricted field (ring scotoma): retinitis pigmentosa, advanced glaucoma, thyroid-related ophthalmopathy, ON drusen, vitamin A deficiency, occipital stroke, panretinal photocoagulation, functional visual loss

Neurologic defect: bilateral and respects vertical midline

Figure 4-9 VF defects.

Localizing VF defects

Nerve fiber layer: arcuate, papillomacular, temporal wedge

Chiasm: bitemporal hemianopia (junctional scotoma if involving Willebrand’s knee)

Optic tract: incongruous homonymous hemianopia

Temporal lobe (Meyer’s loop): ‘pie-in-the-sky’ (denser superiorly, spares central)

Parietal lobe: denser inferiorly

Occipital lobe: congruous; ±macular sparing

Neurologic VF defects

Congruity of VF defect (retrochiasmal lesions): the more congruous the defect, the more posterior is the lesion

Superior field: anterior retinal ganglion cells → lateral portion of optic tract → temporal lobe (Meyer’s loop) → inferior bank of calcarine fissure

Vision not reduced by unilateral lesion posterior to the chiasm (20/20 acuity with macula-splitting hemianopia)

Chiasm: pituitary tumor, pituitary apoplexy, craniopharyngioma, meningioma, ON glioma, aneurysm, trauma, infection, metastatic tumor, MS, sarcoid

ANTERIOR CHIASMAL SYNDROME: lesion at junction of ON and chiasm; involves fibers in Willebrand’s knee (contralateral nasal retinal loop); causes junctional scotoma (central scotoma in 1 eye and superotemporal defect in the other)

BODY OF CHIASM: bitemporal hemianopia; vision may be preserved

POSTERIOR CHIASM: bitemporal hemianopia; primarily involves crossing macular fibers

LATERAL COMPRESSION (very rare): binasal hemianopia (more commonly caused by bilateral ON or retinal lesions)

Optic tract: posterior sellar or suprasellar lesions; homonymous hemianopia, contralateral RAPD

Retro-LGB lesions: 90% of isolated homonymous hemianopias due to stroke

Optic radiations:

TEMPORAL LOBE (Meyer’s loop): ‘pie-in-the-sky’ (superior homonymous hemianopia), formed visual hallucinations, seizures

PARIETAL LOBE: inferior homonymous hemianopia, hemiparesis, visual perception difficulty, agnosia, apraxia, OKN asymmetry

GERSTMANN’S SYNDROME: lesion of dominant parietal lobe; acalculia, agraphia, finger agnosia, left–right confusion, associated with inferior homonymous hemianopia if optic radiation involved

Occipital lobe:

HOMONYMOUS HEMIANOPIA WITH MACULAR SPARING: suggests infarct in area supplied by posterior cerebral artery; macular region receives dual supply from both middle cerebral artery and posterior cerebral artery

BILATERAL CONGRUOUS CENTRAL ISLANDS WITH VERTICAL STEP: equivalent to homonymous hemianopia with macular sparing; vertical step does not occur in retinal or optic nerve lesions

CHECKERBOARD FIELD: bilateral incomplete homonymous hemianopias, superior on 1 side and inferior on opposite side (left upper and right lower homonymous quadrant defects)

BILATERAL HOMONYMOUS ALTITUDINAL DEFECTS: infarction or trauma to both occipital lobes, above or below calcarine fissure

MONOCULAR TEMPORAL CRESCENT DEFECT: anterior occipital infarct; far temporal field is seen by only 1 eye

Cortical blindness: bilateral occipital lobe destruction; pupillary response intact, blindsight (rudimentary visual capacity), unformed visual hallucinations, Riddoch phenomenon (perceive moving targets but not stationary ones); may deny blindness (Anton’s syndrome)

Eye Movements under Supranuclear Control

Horizontal gaze center (Figures 4-10,4-11)

Saccades: contralateral frontal eye fields (frontal lobe) → superior colliculus → pontine paramedian reticular formation (PPRF) → horizontal gaze center (CN 6 nucleus) → ipsilateral lateral rectus l (LR) and contralateral medial rectus (MR) (via MLF)

Smooth pursuit: ipsilateral parieto-occipital lobe → superior colliculus (SC) → PPRF → horizontal gaze center → ipsilateral LR and contralateral MR (via MLF)

Figure 4-10 FEM (voluntary), SEM (pursuit), and SEM (vestibular). Pathways all converge on PPRF for horizontal eye movements. VN, vestibular nuclei.

(From Bajandas FJ, Kline LB: Neuro-Ophthalmology Review Manual. Thorofare, NJ, Slack, 1988.)

Figure 4-11 Composite reminder of the course and lateralization of the 3 conjugate horizontal eye movement pathways.

(From Bajandas FJ, Kline LB: Neuro-ophthalmology Review Manual. Thorofare, NJ, Slack, 1988, p 55.)

Saccadic system

generates fast eye movements (FEM) (refixation); 300-700°/s

Tests: refixation, rotation, calorics, and optokinetic nystagmus (fast saccadic return phase)

Abnormalities: progressive external ophthalmoplegia, myasthenia gravis, Wilson’s disease, Huntington’s disease, ataxia-telangiectasia, spinocerebellar degeneration, progressive supranuclear palsy, olivopontocerebellar atrophy, Whipple’s disease, Gaucher’s disease, MS, Pelizaeus-Merzbacher disease

Ocular motor apraxia: failure to initiate a saccade

Smooth pursuit system

slow eye movements (SEM); following movements; ipsilateral parieto-occipital junction (horizontal); interstitial nucleus of Cajal (vertical)

Tests: Doll’s head, rotation, OKN (pursuit movement)

Abnormalities: demyelination (young patients), microvascular disease (older patients)

Vergence system

maintains foveal fixation on approaching object; controlled by frontal and occipital lobes, and possibly midbrain

Types: voluntary, accommodative, fusional

Test: look from distance to near

Position maintenance system (vestibulo-ocular reflex [VOR])

maintains specific gaze position during head movements

Teleologically oldest eye movement system; also fastest (shortest latency)

Semicircular canals → CN 8 → vestibular nucleus → contralateral horizontal gaze center → EOMs

Test: calorics; rotation

Abnormalities cause oscillopsia

Nonoptic reflex systems

integrate eye movements with body movements

Normal caloric and Doll’s head responses when nuclear and internuclear connections are intact

Calorics: irrigate water into ears and observe induced eye movements; mnemonic COWS (cold opposite, warm same) refers to direction of fast phase of nystagmus in awake patient (jerk nystagmus); in comatose patient, get tonic deviation in opposite direction of mnemonic (sustained slow phase movement only (Figure 4-12))

Bilateral cold water irrigation produces nystagmus with fast phase upward in awake patient and downward tonic deviation in comatose patient; opposite effects with warm water

PATHWAY: vestibular nuclei → contralateral CN 6 nuclei → ipsilateral LR and contralateral MR (via MLF); no connection to the PPRF

Doll’s head (oculocephalic reflex): turn head and observe direction of eye movements; vestibular system moves eyes; use when patient cannot voluntarily move eyes

Eyes should have tonic movement in direction opposite head rotation

INTACT DOLL’S HEAD: supranuclear lesion (cranial nerve pathways to muscles are intact) (i.e. progressive supranuclear palsy)

ABNORMAL DOLL’S HEAD: lesion is infranuclear paresis or restrictive disease (perform forced ductions)

Bell’s phenomenon: upward turning of eyes with forced closure of eyelids

INTACT BELL’S PHENOMENON: supranuclear lesion

Figure 4-12 Vestibulo-ocular reflex demonstrating right beating nystagmus. Right COWS = cold opposite, warm same. (Calorics should be performed with head back 60°.)

(From Bajandas FJ, Kline LB: Neuro-Ophthalmology Review Manual. Thorofare, NJ, Slack, 1988.)

Diplopia

Types

Comitant: amount of deviation same in all fields of gaze

Incomitant: amount of deviation varies in different fields of gaze

Etiology

Monocular: high astigmatism, chalazion or lid mass, corneal abnormality, iris atrophy, polycoria, cataract, subluxed crystalline lens, decentered IOL, posterior capsular opacity, retinal pathology, functional

Binocular: neuropathic (cranial nerve palsies, MS), myopathic (thyroid-related ophthalmopathy, orbital pseudotumor), neuromuscular junction (MG)

Differential diagnosis (DDx)

Supranuclear (due to inadequate convergence): skew deviation, progressive supranuclear palsy, Parkinson’s disease, Huntington’s disease, dorsal midbrain syndrome

Intermittent: MG, MS, migraine, thyroid-related ophthalmopathy, convergence spasm, decompensated phoria, convergence-retraction nystagmus, ocular myotonia

Vertical: MG, MS, thyroid-related, orbital disease (tumor, trauma, inflammation), CN 3 or CN 4 palsy, Brown’s syndrome, skew deviation

Aberrant regeneration: Duane’s syndrome, Marcus Gunn jaw-winking syndrome

Restrictive syndromes

IOP elevation >4 mmHg when eyes directed into restricted field (thyroid, trauma, inflammatory orbital disease, neoplastic process)

Eye Movement Disorders

Central Disorders (Supranuclear) (Figure 4-13)

Often no symptoms or complaints

Figure 4-13 Supranuclear control of eye movements. The pontine horizontal gaze center (blue) and the vertical gaze center in the midbrain (yellow) receive input from the frontal eye fields to initiate saccades, and from the parietal occipital temporal junction to control pursuit. These gaze centers control ocular motility by synapsing upon the ocular motor nerve nuclei (III, IV, and VI).

(From Lavin PJM, Donahue SP: Disorders of supranuclear control of ocular motility. In: Yanoff M, Duker JS (eds) Ophthalmology, 2nd edn. St Louis, Mosby, 2004.)

Horizontal Gaze Palsies

Congenital

Must distinguish between supranuclear and infranuclear causes; often abnormality of CN 6 or interneurons; vertical movements usually unaffected

Möbius’ Syndrome

Horizontal gaze palsy with CN 6, 7, 8, and 9 palsies (facial diplegia, deafness, abnormal digits)

Ocular Motor Apraxia

Saccadic palsy; impairment of voluntary horizontal eye movements with preservation of reflex movements; male > female; congenital or acquired (Balint’s syndrome); extensive bilateral cerebral disease involving supranuclear pathways (usually bilateral frontoparietal); usually benign and resolves in congenital disease

Associations

Gaucher’s disease, spinocerebellar degeneration, MR, ataxia-telangiectasia, Wilson’s disease, hypoplasia of corpus callosum, hydrocephalus; rarely cerebellar mass lesion (perform magnetic resonance imaging [MRI])

Findings

Head thrusting: patient must move head to look at objects; head thrust toward desired direction of gaze results in contralateral slow eye movement so patient must overshoot target; lessens with age; may resolve by age 20; patient may also blink to break fixation

Abnormal OKN: fast phase absent

Abnormal vestibular nystagmus: fast phase absent

Normal pursuits

Normal vertical saccades

Acquired

Frontoparietal lesion (stroke, trauma, or infection)

tonic deviation of eyes to side of lesion (contralateral area 8 unopposed); seizure will move eyes away from lesion

Doll’s head testing and calorics

can turn eyes contralateral to lesion (intact vestibular pathway)

Parieto-occipital lesion

ipsilateral pursuit palsy (cogwheel pursuit)

Parkinson’s disease

reduced blinking, reduced saccades, reduced glabellar reflex suppression, blepharospasm, oculogyric crisis

Huntington’s chorea

Metabolic disorders: hyperglycemia, Wernicke’s encephalopathy, Wilson’s disease

Drug-induced

tricyclic antidepressants, phenytoin, phenothiazines

Pseudogaze palsies

myasthenia gravis, chronic progressive external ophthalmoplegia (CPEO), Duane’s syndrome

Internuclear ophthalmoplegia (INO) (Figure 4-14)

lesion of MLF; inability to adduct ipsilateral eye with nystagmus of fellow eye; may have skew deviation, vertical diplopia, and gaze-evoked, upbeat nystagmus; rule out myasthenia gravis

Unilateral: ischemia (older), demyelination (young patients), tumor, infection (meningitis, encephalitis), trauma, compression

Bilateral (involves both MLF near junction with the 3rd nerve nucleus in midbrain): demyelination / MS (most common), trauma, ischemia, infection, Chiari malformation, toxicity (amitriptyline, ethanol, benzodiazepine)

Types:

ANTERIOR (midbrain): preserved convergence

POSTERIOR (pons): impaired convergence (WEBINO = wall-eyed bilateral INO)

Figure 4-14 1. Right internuclear ophthalmoplegia (INO) 2. Bilateral INO.

(From Bajandas FJ, Kline LB: Neuro-Ophthalmology Review Manual. Thorofare, NJ, Slack, 1988.)

One-and-a-half syndrome (Fisher syndrome) (Figure 4-15)

lesion of CN 6 nucleus and ipsilateral MLF; causes ipsilateral gaze palsy and INO; only movement is abduction of contralateral eye (with nystagmus); supranuclear lesion therefore convergence intact; called paralytic pontine exotropia when patient appears exotropic; patients with recovery from syndrome may develop oculopalatal myoclonus

Etiology: stroke (most common), MS, basilar artery occlusion, pontine metastases

Figure 4-15 Right acute syndrome (paralytic pontine exotropia).

(From Bajandas FJ, Kline LB: Neuro-Ophthalmology Review Manual. Thorofare, NJ, Slack, 1988.)

Vertical Gaze Abnormalities

Progressive Supranuclear Palsy (Steele-Richardson-Olszewski Syndrome)

Progressive vertical (early) and horizontal (late) gaze palsy (downward gaze usually affected first); no Bell’s phenomenon; doll’s head maneuver gives full range of movement (ROM), indicating supranuclear nature of disorder; eventually frozen globe to all stimuli, spasm of fixation, decreased blink rate, blepharitis, blepharospasm; occasionally, apraxia of eye opening; also, axial rigidity, dysarthria, and dementia

Skew Deviation

Vertical misalignment of visual axes due to imbalance of prenuclear inputs; comitant or incomitant

Vertical tropia, hyperdeviation usually increases on ipsilateral downgaze, no cyclodeviation; hypodeviated eye usually ipsilateral to lesion, except when associated with INO in which hyperdeviated eye is ipsilateral; may occur with other brain stem symptoms or cerebellar disease; MRI of posterior fossa recommended

Etiology

brain stem infarct, MS, increased intracranial pressure (ICP), pseudotumor cerebri, vestibulo-ocular imbalance, cerebellar disease; vertebral–basilar insufficiency may cause transient skew deviation

Treatment

often transient and requires observation only; chronic deviations may be treated with prism spectacles or surgery

Whipple’s Disease

Oculomasticatory myorhythmia (vertical eye movements and facial activity similar to myoclonus)

Olivopontocerebellar Atrophy

Hereditary or sporadic; onset early adulthood; unsteady gait, slurred speech, dementia, optic atrophy, retinal degeneration

Eye movements progressively slow in all directions, finally complete external ophthalmoplegia

Kernicterus

Progressive loss of eye movements

Also, metabolic diseases (maple syrup disease, Wernicke’s encephalopathy), drug-induced

Nystagmus

Rhythmic involuntary oscillations of the eyes due to disorder of SEM system. Direction named after fast phase (brain’s attempt to correct problem), even though abnormality is noted with slow phase

Childhood Nystagmus

Most commonly, congenital, latent, sensory, and spasmus nutans (see Ch. 5, Pediatrics / Strabismus)

Physiologic Nystagmus

Several forms of nystagmus, including end-gaze, optokinetic, caloric, and rotational

Acquired Nystagmus

Pattern helps localize pathology, may have oscillopsia

Bruns’

Combination of gaze-paretic nystagmus when looking toward lesion (fast phase toward the lesion), and vestibular imbalance nystagmus when looking away from lesion (fast phase away from lesion) (i.e., with right-sided lesion: high-amplitude, low-frequency, right-beating nystagmus on right gaze; low-amplitude, high-frequency, left-beating nystagmus on left gaze)

Gaze-paretic component is of high amplitude and low frequency (because of impairment of horizontal gaze mechanism on side of lesion)

Vestibular component is of low amplitude and high frequency, with fast phase away from damaged vestibular nuclei on side of lesion

Due to cerebellopontine angle mass (usually acoustic neuroma or meningioma)

Convergence-Retraction

Cocontraction of lateral recti produces convergence movement (abnormal saccades) on attempted upgaze

Due to periaqueductal gray matter or dorsal midbrain lesion (Parinaud’s syndrome, pinealoma, trauma, brain stem arteriovenous malformation [AVM], MS)

Dissociated

Asymmetric between the 2 eyes (different direction, amplitude, frequency, etc); always pathologic

Due to posterior fossa disease, MS

Downbeat

Eyes drift upward with corrective saccade downward; worsens in downgaze, improves in upgaze; oscillopsia

Due to lesion that affects pathways responsible for downgaze; cervicomedullary junction lesion (Arnold-Chiari malformation, tumor, syrinx: 33%), spinocerebellar degeneration, intoxication, lithium, paraneoplastic cerebellar degeneration, 50% with no identifiable cause

Gaze-Evoked

Nystagmus in direction of gaze, absent in primary position, fast phase toward lesion (cerebellar)

Due to extra-axial mass compressing brain stem (acoustic neuroma, cerebellar hemisphere tumor), intoxication (alcohol or anticonvulsant medications)

If asymmetric, must obtain neuroimaging

Periodic Alternating Nystagmus (PAN)

Changes horizontal direction; jerks right 90 seconds, 5- to 10-second pause, jerks left 90 seconds, repeats; remains horizontal in vertical gaze; usually acquired

Due to disease of vestibulocerebellar system (albinism, cranio-cervico junction lesion [Arnold-Chiari malformation], MS, syphilis, tumor, vascular, dilantin, spinocerebellar degeneration)

Treatment

baclofen; surgery (large recession of all 4 recti muscles)

Seesaw

Vertical and torsional nystagmus with 1 eye rising and intorting while fellow eye falls and excyclotorts, then reverses

Due to suprasellar lesions, CVA, or trauma, or is congenital (craniopharyngioma)

MRI

rule out large parasellar tumors expanding into third ventricle

Upbeat

Eyes drift downward with corrective saccade upward

Due to medullary lesions, midline cerebellar (vermis) lesions, medulloblastoma, cerebellar degeneration, MS

Vestibular

Horizontal, rotary, jerk nystagmus in primary gaze; same in all fields of gaze; slow component is linear; remains horizontal in vertical gaze

Due to vestibular disease, infection (labrynthitis), Ménière’s disease, vascular, trauma, toxicity

Peripheral vestibular disease

fast phase toward good side; slow phase toward lesion; associated with tinnitus, vertigo, deafness; fixation inhibits vertigo and nystagmus; direction of Romberg fall changes with head turning

Voluntary

Unsustainable for longer than 30 seconds; associated with hysteria and malingering

Other Eye Movement Disorders

Ocular Bobbing

Intermittent conjugate rapid downward eye movements followed by slow return to primary position

Often secondary to hemorrhage; patient usually comatose

Ocular Dipping

Opposite of ocular bobbing; intermittent rapid upward eye movements followed by slow return to primary position

Ocular Myoclonus

Vertical pendular nystagmus associated with synchronous palatal (uvula) beating

Due to bilateral pseudohypertrophy of inferior olives in medulla, lesion in myoclonic triangle (red nucleus, ipsilateral inferior olive, contralateral dentate nucleus)

Opsoclonus (Saccadomania)

Rapid, chaotic eye movements in all directions; persists in sleep

Associated with dancing hands and feet

Abnormality of pause cells (normally suppress burst cells of PPRF)

Due to remote, paraneoplastic effect on cerebellum from metastatic neuroblastoma (check urine vanillylmandelic acid [VMA]), occasionally with encephalitis

Waveform

no slow phase; repetitive, random; no intersaccadic interval

Oscillopsia

Illusion of movement in the seen world

Usually occurs in SO myokymia and acquired nystagmus; rarely in congenital nystagmus

Due to vestibulo-ocular reflex abnormality

Cranial Nerve Palsies (FIGURE 4-16)

Oculomotor Nerve (CN 3) Palsy

Anatomy

nucleus in rostral midbrain; fascicle travels ventrally through midbrain, traversing red nucleus and corticospinal tract in cerebral peduncle; nerve enters subarachnoid space, passes between posterior cerebral and superior cerebellar arteries, then courses lateral to posterior communicating artery and enters lateral wall of cavernous sinus; receives sympathetics from internal carotid plexus; passes through superior orbital fissure and divides into superior (supplies SR and levator) and inferior (supplies IR, MR, IO, iris sphincter, and ciliary muscle) divisions.

Figure 4-16 Cranial nerve pathways.

(Copyright Peter K. Kaiser, MD.)

Only 1 subnucleus (midline location) supplies both levator palpebrae superioris; fibers from superior rectus (SR) subnucleus supply contralateral SR; Edinger-Westphal nucleus supplies both pupils (Figure 4-18)

Figure 4-18 Anatomy of the 3rd nerve nucleus. The 3rd nerve nucleus consists of a single, central, caudally located nucleus for the levator palpebrae, paired bilateral subnuclei with crossed projections that innervate the superior recti, and paired bilateral subnuclei with uncrossed projections that innervate the medial recti, inferior recti, and inferior oblique muscles. Parasympathetic input to the ciliary body and iris sphincter arises from the Edinger-Westphal nucleus.

(Redrawn from Warwick R: Representation of the extraocular muscles in the oculomotor nuclei of the monkey. J Comp Neurol 98:449–503,1953.)

Findings

ptosis, hypotropia, exotropia; may involve pupil (fixed and dilated); may cause pain

7 syndromes (Figure 4-17)

Nuclear CN 3 palsy (Figure 4-17,

): extremely rare; contralateral SR paresis and bilateral ptosis; pupil involvement is both or neither

Fascicle syndromes (see Figure 4-17,

): ischemic, infiltrative (tumor), or inflammatory (rare)

NOTHNAGEL’S SYNDROME: lesion of fascicle and superior cerebellar peduncle that causes ipsilateral CN 3 paresis and cerebellar ataxia

BENEDIKT’S SYNDROME: lesion of fascicle and red nucleus that causes ipsilateral CN 3 paresis, contralateral hemitremor (resting and intentional), and contralateral decreased sensation

WEBER’S SYNDROME: lesion of fascicle and pyramidal tract that causes ipsilateral CN 3 paresis and contralateral hemiparesis

CLAUDE’S SYNDROME: combination of Nothnagel’s and Benedikt’s syndromes

Uncal herniation (see Figure 4-17,

): supratentorial mass may cause uncal herniation compressing CN 3

Posterior communicating artery (PCom or PCA) aneurysm (see Figure 4-17,

): most common nontraumatic, isolated, pupil involving CN 3 palsy; aneurysm at junction of PCom and carotid artery compresses nerve, particularly external parasympathetic pupillomotor fibers; usually painful

Cavernous sinus syndrome (see Figure 4-17,

): associated with multiple CN palsies (3, 4, V₁, 6) and Horner’s; CN 3 palsy often partial and pupil sparing; may lead to aberrant regeneration

Orbital syndrome (see Figure 4-17,

): tumor, trauma, pseudotumor, or cellulitis; associated with multiple CN palsies (3, 4, V₁, 6), proptosis, chemosis, injection; ON can appear normal, swollen, or atrophic

After passing through the superior orbital fissure, CN 3 splits into superior and inferior divisions; therefore, CN 3 palsies distal to this point may be complete or partial

Pupil-sparing isolated CN 3 palsy (see Figure 4-17,

): small-caliber parasympathetic pupillomotor fibers travel in outer layers of nerve closer to blood supply (but more susceptible to damage by compression); fibers at core of nerve are compromised by ischemia; may explain pupil sparing in 80% of ischemic CN 3 palsies and pupil involved in 95% of compressive CN 3 palsies (trauma, tumor, aneurysm)

ETIOLOGY:

ADULTS: vasculopathic / ischemic (diabetes mellitus [DM], hypertension [HTN]), trauma, giant cell arteritis (CGA), occasionally tumor, aneurysm (very rare)

CHILDREN: congenital, trauma, tumor, aneurysm, migraine

14% of PCom aneurysms initially spare pupil

20% of diabetic CN 3 palsies involve pupil

Microvascular CN 3 palsies usually resolve in 3 to 4 months

Myasthenia gravis may mimic CN 3 palsy