332NEUROLOGIC

Most patients have psychiatric overlay and may improve with psychotherapy, hypnosis, and biofeedback. No improvement proven with anticholinergics, baclofen, Librium, or lithium (one third of patients obtain some relief with placebo).

Meige’s syndrome: accounts for 12% of dystonias; characterized by blepharospasm plus lower face involvement (oromandibular dystonia). May also have torticollis or upper arm involvement. Related to essential blepharospasm.

Hemifacial spasm: accounts for 26% of dystonias; unilateral, involving an entire side of the face. Usually presents in a middle-aged patient; females affected 2:1. Persists in sleep, and 95% are caused by a vascular tortuosity compression of CN VII at the brainstem. Compression of facial nerve axons (usually from the anterior and posterior inferior cerebellar arteries) causes ephaptic transmission (a ‘‘hotwire’’ false synapse between adjacent axons). Symptoms begin with twitches follwed by sustained spasm, and all branches of CN VII are involved. If new onset, rule out tumor (5% incidence, usually brainstem glioma). Treat with Botox injections or neurosurgery ( Jannetta procedure to decompress the nerve root at the CPA; 84–97% successful).

Gaze Abnormalities

HORIZONAL GAZE ABNORMALITIES Brainstem or supranuclear disorders that cause gaze deficiency. See also Chapter 9.

Congenital ocular motor apraxia: deficient voluntary horizontal eye movements in infancy, causing the child to thrust the head toward the desired direction of gaze; improves with age and is usually benign. If acquired (Balint’s syndrome), is often from bilateral cerebral disease with deficient saccades and pursuits.

Internuclear ophthalmoplegia (INO): the ipsilateral eye shows abnormal adduction with contralateral nystagmus in the abducting eye. Caused by lesion in the MLF interfering with interneurons that normally connect the ipsilateral CN III (adduction deficit) to the contralateral PPRF/CN VI nucleus (abducting nystagmus). Usually from MS; in older patients is usually of vascular origin.

Wall-eyed bilateral INO (WEBINO): lesions in both MLF tracts, causing a bilateral INO and thus bilateral adduction

deficits; pathognomonic for demyelinating disease (MS).

‘‘One-and-a-half ’’ syndrome or paralytic pontine exotropia: caused by an ipsilateral gaze palsy and a contralateral INO, allowing the unopposed contralateral PPRF to drive one eye away from the midline.

Pontine conjugate gaze palsy: ipsilateral gaze palsy from PPRF or CN VI nucleus damage.

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Ocular neuromyotonia: unilateral spasm of a single EOM (usually CN III excitability), causing transient diplopia, especially with sustained eccentric gaze. Rare, associated with previous radiation therapy; may treat with Tegretol 200 mg bid–tid.

Spasticity of conjugate gaze: lesion of the temporal or parietal lobes, causing gaze up and away from the lesion (Cogan’s sign).

VERTICAL GAZE ABNORMALITIES Upgaze palsies are usually from more dorsal lesions (Parkinson’s disease, Parinaud’s syndrome, etc.), and downgaze palsies are usually from midbrain lesions (e.g., progressive supranuclear palsy). See also Chapter 9.

Ocular tilt reaction: sustained or paroxysmal cyclovertical deviation with head tilt, often associated with skew deviation. Pathologic head tilt has a contralateral hypertropia (HT) and torsion toward the tilt (normally would be away from the tilt). Caused by an imbalance in otolithic inputs (sustained movement or tonic stimulus).

Oculogyric crisis: tonic vertical supranuclear deviation; caused by postencephalitis, Parkinson’s disease, or phenothiazines (mnemonic: ‘‘the three P’s’’).

Parinaud’s dorsal midbrain syndrome: a lesion in the posterior commissure (mnemonic ‘‘CLUES’’): convergence-retraction nystagmus (accentuated by a downgoing OKN drum), light-near dissociation, upgaze paralysis, eyelid retraction (Collier’s sign), and skew deviation. Etiology by age: hydrocephalus from aqueductal stenosis is the leading cause in children, but also consider pinealomas; trauma, or AVM in young adults, stroke in older patients.

Progressive supranuclear palsy (PSP), Steele-Richardson-Olszewski syndrome: unrelenting neurodegenerative disease characterized by midbrain and basal ganglia gliosis. Patients are unable to look up (‘‘dirty tie’’ syndrome) and have progressive dementia and a poor life prognosis. May be a primary disorder or associated with

Whipple’s disease with vitritis and malabsorption; treat with tetracycline.

Neimann Pick variant in teenagers characterized by downgaze deficit, ataxia, and foam cells.

Skew deviation: cyclovertical deviation that does not isolate to a single muscle. Arises from vertical misalignment of visual axis by disturbance of prenuclear inputs. Usually from brainstem pathology (e.g., trauma, stroke, MS). Often associated with peripheral vestibulopathy and vestibular midbrain lesions (may also have INO), and often has other signs of neurologic dysfunction (e.g., nystagmus).

Diagnose with the ‘‘four-step test’’ : the standard three-step test looking at the deviation in primary gaze, side gaze, and with head tilt, plus checking for torsion (e.g., double Maddox rod or look at the fundus).

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334NEUROLOGIC

The hypertropic eye is intorted, unlike CN IV palsy, in which the HT eye either has no torsional component or up to 7 pD of excyclotorsion. The lower eye is usually on the side of the brainstem lesion, and the head tilt is usually toward the lesion (ipsilateral).

Wallenberg’s syndrome, lateral medullary infarction: skew deviation with lateropulsion of saccades associated with ipsilateral decreased facial pain and temperature sensation, ipsilateral Horner’s sydrome, ipsilateral limb ataxia (descending corticospinal tracts affected), and contralateral decreased trunk pain and temperature sensation. Usually from ipsilateral vertebral artery infarction or dissection.

Treat with prisms, patching, and waiting.

Nystagmus

GENERAL

The word nystagmus derives from the Greek nystagmos, meaning ‘‘drowsiness,’’ to describe head bobbing in drunken sailors. It indicates an involuntary rhythmic beating of the eyes. If acquired, the patient may complain of oscillopsia; otherwise, the nystagmus may just cause decreased VA. It is usually most prominent in primary gaze. Alexander’s law states that nystagmus worsens when looking toward the fast phase. May exhibit a glissade, or a residual drift to focus.

Evaluation: note if it is jerk or pendular nystagmus (if jerk, then note the direction of fast beating); note whether it is horizontal, vertical, circular, elliptical, or torsional; and note if it is conjugate or disconjugate. May help to draw a nine-square noting the presence and direction of nystagmus in each field of gaze (the length of arrow indicates its amplitude: fine, medium, or coarse).

Etiology: many causes (see below), but the leading cause overall is drug side effect.

Unipolar causes of nystagmus (horizontal in any plane): congenital nystagmus, periodic alternating nystagmus (PAN), and peripheral vestibular nystagmus.

AFFERENT OR SENSORY NYSTAGMUS Pendular nystagmus that develops at least 10 weeks after birth when VA is worse than 20/200. Caused by (mnemonic: ‘‘seven A’s’’): albinism, aniridia, achromatopsia, atrophic optic neuropathy if it occurs within 3 months, anterior segment disease (cornea, cataract, coloboma), amaurosis of Leber’s, and all others (cone dystrophy, CSNB, Che´diak-Higashi syndrome, juvenile X-linked retinoschisis).

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NYSTAGMUS 335

CEREBELLAR-OCULAR DYSMETRIA Characterized by ocular flutter, opsoclonus, skew deviation, gaze-evoked nystagmus, and oculopalatal myoclonus.

CONVERGENCE–RETRACTION NYSTAGMUS An attempt to quickly look up (as when viewing a downgoing OKN drum) that causes retraction convergence and horizontal muscle retraction; often associated with Parinaud’s dorsal midbrain syndrome with light-near dissociation and deficit of upgaze and convergence.

Differential diagnosis by age: congenital causes are usually from aqueductal stenosis or hydrocephalus. Patients’ age: 10 years old— consider pinealoma; 20 years—most likely trauma; 30 years—often postencephalitis; 40 years—most likely MS; 50 years old or older— often from basilar artery aneurysm or tumors.

DISSOCIATED NYSTAGMUS Asymmetric nystagmus indicating posterior fossa disease, such as abducting nystagmus, as in INO.

DOWNBEAT NYSTAGMUS Downgoing jerk nystagmus in primary gaze that becomes worse with lateral gaze (does not follow Alexander’s law). From cervicomedullary junction lesions. (Mnemonic: DoWNBEAT): degeneration, demyelinating, or drugs (lithium); Wernicke’s encephalopathy; neoplasm or paraneoplastic cerebellar degeneration (especially gynecologic and small-cell lung cancers); brainstem disease (e.g., syringomyelia); encephalitis; Arnold-Chiari malformation; trauma or toxins. Treat with baclofen or Neurontin 1200–2400 mg/day.

DRUGS Leading cause of nystagmus; often from tranquilizers, anticonvulsants, or alcohol abuse, plus others.

EFFERENT OR CONGENITAL MOTOR NYSTAGMUS Jerk or pendular horizontal nystagmus to one side of gaze; onset is within first 3 months, and nystagmus is usually benign. Dampens with eye closure, convergence (thus ET often develops), and head turn to a ‘‘null’’ zone, and disappears with sleep. Head turn and accommodation may cause nystagmus blockage. Patients do not have oscillopsia but often have LN. OKN shows reversal, and EOG demonstrates ‘‘sea waves’’ waveform. VA is relatively good, usually 20/20–70. May treat with contact lenses to decrease astigmatism, prisms to move null point straight ahead, baclofen medication, or Kestenbaum procedure. Better prognosis if OKN is responsive.

GAZE-EVOKED NYSTAGMUS The most common form of pathologic nystagmus, seen when the eye attempts to maintain an eccentric position, with the fast phase in the direction of gaze. Associated with sedatives and anticonvulsant medication and brainstem disease.

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336 NEUROLOGIC

LATENT NYSTAGMUS Jerk nystagmus that is brought on by monocular occlusion, when the fixating eye drifts to midline, then jerks to abduction and away from the occluded eye. Associated with congenital ET and dissociated vertical deviation (DVD), with onset >1 year old. EOG waveform shows a convex upstroke with straight downstroke. Patients have better VA with both eyes open, and condition rarely needs to be treated.

OCULOPALATAL NYSTAGMUS Pendular vertical nystagmus with synchronous contraction of the palate and pharynx.

OPSOCLONUS Saccadomania (eye movements all over the place), usually from hydrocephalus in children or postviral encephalitis in adults. Always consider metastatic neuroblastoma with myoclonus and cerebellar ataxia. Also known as ‘‘dancing eyes and dancing feet.’’

PERIODIC ALTERNATING NYSTAGMUS (PAN) Horizontal nystagmus that alternates directions, with a brief null point. If congenital, it is usually from cervicomedullary junction pathology (Arnold-Chiari malformation); it may also be associated with posterior fossa tumors, trauma, MS, stroke, syphilis, and spinocerebellar degeneration.

PHYSIOLOGIC NYSTAGMUS Normal nystagmus at the end point of gaze (usually >30 degrees); fatigues.

SEESAW Dissociated pendular vertical nystagmus with conjugate torsional oscillation (twists in same direction). One eye deviates up, the other down; ‘‘roll down the plank’’ appearance. May be congenital (septo-optic dysplasia, etc.) or from craniopharyngioma (rostral midbrain/third ventricle locations, frequently with temporal hemianopia) or trauma (lesions in the ‘‘myoclonic triangle’’ involving the red nucleus or inferior olive, with delay of nystagmus onset after injury from inferior olive pseudohypertrophy).

SPASMUS NUTANS Triad of monocular or dissociated shimmering, asymmetric, small-amplitude nystagmus, head bobbing, and torticollis or head tilt. Onset at age 4 to 18 months. Usually benign and disappears within 2 years of onset, but rule out chiasmatic gliomas and subacute necrotizing encephalomyopathy (optic atrophy, irritability, vomiting, and increased intracranial pressure).

VESTIBULAR NYSTAGMUS Horizontal rotary jerk nystagmus; if peripheral, is associated with definite torsional component and vertigo or tinnitus. A common cause of acquired horizontal jerk nystagmus (Table 8–3).

UPBEAT NYSTAGMUS Upgoing jerk movements in primary gaze. From lesions in the midline cerebellum or anterior vermis (medulloblastoma,

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