318 NEUROLOGIC

syndrome, uveitis, branch retinal artery occlusion (BRAO), CRVO, or focal retinochoroiditis. Confirm diagnosis with serum indirect fluorescence Ab. Consider treatment with oral ciprofloxacin, rifampin (89% success), or Septra (58% success) for 6 weeks.

Neoplastic Disease

CARCINOMATOUS OPTIC NEUROPATHY Acute devastating decreased VA from infiltrative malignancy (usually lymphoma or leukemia), often with normal fundus and imaging. Diagnose with lumbar puncture.

CNS ASTROCYTOMA Classified as grade I, II, III (anaplastic astrocytomas), or IV (glioblastoma multiforme characterized by necrosis and very poor life prognosis). Rarely may arise from the optic nerve astrocytes; more commonly, CNS tumor causes mass effect that may cause papilledema. Patients may need palliative ON sheath decompression to preserve visual function.

CRANIOPHARYNGIOMA (SUPRASELLAR) Arises from remnants of Rathke’s pouch near the pituitary and often compresses the chiasm, causing a bitemporal hemianopsia; often calcified; almost always occurs in childhood.

FOSTER KENNEDY SYNDROME Frontal lobe tumor causes one pale disk (direct pressure on optic nerve) and one swollen disk (increased ICP). Clinical appearance may be similar to bilateral nonsimultaneous AION.

MELANOCYTOMA Darkly pigmented magnocellular nevus that is benign. See Chapter 7.

NEUROFIBROMA Endoneural fibroma that arises from nerve fibers.

ON GLIOMA Occurence in childhood has a good prognosis and is considered a hamartoma; 50% of patients with ON gliomas have NF1 (15% of NF1 patients have ON glioma). Arising in adulthood, it has a poor prognosis and usually is glioblastoma multiforme. See Chapter 2.

ON SHEATH MENINGIOMA Tumor that arises from the ON meningeal sheath, causing progressive optic atrophy and loss of vision with optociliary shunt vessels. Good prognosis in adults, poor prognosis in children. ‘‘Railroad track’’ sign on CT. Pathology shows proliferation of benign meningiothelial cells in whorls with calcified psammoma bodies. Treatment is controversial. See Chapter 2.

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SCHWANNOMA Neurilemmal (nerve sheath) tumor arising in cranial peripheral nerve (usually superior location in the orbit).

Metabolic and Degenerative Disease

ALZHEIMER’S DISEASE Better VA is associated with decreased hallucinations, and visual function is strongly related to cognitive function. Thus, give patients a good refraction, and do cataract surgery if appropriate.

Visual variant of Alzheimer’s disease (VVAD): slowly progressive reading difficulty with a Balint-like picture.

NUTRITIONAL, TOBACCO, OR ALCOHOL OPTIC NEUROPATHY Optic nerve degeneration may be seen with alcohol, drug or tobacco abuse, poor nutrition, or malabsorption syndrome. VF shows bilateral cecocentral scotomas or ‘‘biscuit cut’’ VF. Also check for pernicious anemia.

Coffee and doughnut maculopathy: inner retinal layer defect with ring scotoma, good VA. Variant of macular neuroretinopathy.

Systemic and Vascular Disease

ARTERITIC ISCHEMIC OPTIC NEUROPATHY, GIANT CELL OR TEMPORAL ARTERITIS Inflammatory infiltration of medium-size arteries by lymphocytes, monocytes, or giant cells, causing closure of the artery and resulting in ischemic optic neuropathy or retinal infarction and potentially blindness. If arteritis causes AION, patients may present with a swollen disk with focal arteriolar narrowing at the rim and altitudinal VF loss. Also consider the diagnosis in patients with PION, CRAO, choroidal infarction (FA shows a vertical watershed zone through the disk, delineating choroidal vasculature), ocular ischemic syndrome, cranial nerve ischemia, or muscle ischemia causing diplopia.

Clinical diagnosis; thus, treat patients if there is a high index of suspicion. Consider the diagnosis in anyone with transient visual loss over age 55, catastrophic vision loss especially if patients have constitutional symptoms such as polymyalgia rheumatica (PMR), jaw claudication (pain with chewing; do not confuse with temporomandibular joint pain, which is worse at rest and usually seen in younger females with bruxism and stress), fever, or unexplained weight loss.

Diagnostic tests: usually increased Westergren sedimentation rate (usually > 50) and C-reactive protein (higher sensitivity than ESR) and often positive TAB, which may be positive even on steroids up to 6 months.

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320NEUROLOGIC

Normal sedimentation rate for men is less than their age divided by 2; for women, their age plus 10 divided by 2.

Temporal artery biopsy is 100% specific, 85 to 91% sensitive. If the first temporal artery biopsy is negative, then only 3 to 5% will be positive with second biopsy. One clinical scoring method recommends doing a temporal artery biopsy if 6 points are present: 2 points for age >65, headache, ION, jaw claudication, scalp tenderness, or diabetes; and 1 point for fever, weight loss, or muscle weakness.

Treat with prompt intravenous steroids for 5 days with 10-day taper, then long-term oral steroids to keep ESR <20. Fellow eye becomes involved in one third of cases (75% if untreated).

CAROTID ARTERY DISSECTION Fifty-two percent of cases have eye findings, usually painful Horner’s syndrome (44%) or transient visual loss (28%); needs prompt investigation.

CEREBROVASCULAR ACCIDENT (CVA) Thrombotic (far more common) or embolic vascular disease that leads to ischemic (far more common) or hemorrhagic stroke. See Lesion Localization under Signs and Symptoms.

DURAL SINUS THROMBOSIS Decreased CNS venous outflow causes increased intracranial pressure and possibly papilledema that mimics pseudotumor cerebri (PTC). Diagnose with MRI (delta sign from enhanced sinus wall) plus magnetic resonance venography (MRV) (54% have normal CT). Treat with steroids, and rule out hypercoagulable state.

MALIGNANT HYPERTENSION May cause bilateral ON swelling and exudatve RD. See Chapter 7.

MIGRAINE HEADACHE Classic if it has preceding aura, often with scintillating scotoma associated with throbbing headache. Complex migraine if accompanied by neurologic deficits or TIA. Purely ocular variant has scotomata without headache. All cases carry a 3.5 times increased risk of ischemic stroke (same incidence whether simple or classic migraine). Twenty-eight percent of NTG patients have migraines, possible common vascular etiology.

NONARTERITIC ANTERIOR ISCHEMIC OPTIC NEUROPATHY (NAION) Unilateral, painless, swollen disk with VA ranging from 20/20 to NLP, altitudinal VF loss, and presence of APD; on exam, disk shows sectoral edema (‘‘proud flesh’’ appearance) and focal arteriolar narrowing at the rim. Usually from atherosclerotic plaque occlusion of a posterior ciliary artery; often occurs upon awakening in the morning. Age >50 years old; occurs in the fellow eye in 15 to 40% of cases. Normal VEP and MRI, and FA shows

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delayed disk filling. May have pseudo–Foster Kennedy syndrome, with one pale disk from old AION and the other disk swollen with acute AION.

Risk factors: hypertension, hyperlipidemia, disk at risk (small C:D, tighter aperture for vessels to traverse), nocturnal hypotension (also is risk for NTG and POAG). Also consider hypercoagulable state if no vasculopathic history, and rule out hyperhomocystinemia or antiphospholipid Ab (lupus anticoagulant, anticardiolipin Ab).

Rule out arteritic causes/GCA as appropriate for the patient. Treat with aspirin (protective). NAION is not predictive of coronary artery or carotid disease, stroke, or myocardial infarction. Vision may improve up to 2 years or remain unchanged. L-dopa is not effective.

Ischemic Optic Neuropathy Decompression Trial (IONDT): a multicenter, randomized controlled trial (1992–1994), which showed that optic nerve sheath decompression (ONSD) is not effective for NAION. Patients stratified into observation versus surgical groups. Forty percent of observation patients improved versus one third of surgery patients; thus, study terminated early. ONSD patients had higher risk of losing three or more lines of VA (24% surgery vs. 12% of patients that were observed).

PAPILLOPHLEBITIS Unilateral ON swelling with good VA. May be early CRVO, usually in young patients; typically resolves.

POSTERIOR ISCHEMIC OPTIC NEUROPATHY (PION) Similar to AION, but because it occurs more posteriorly in the nerve, no disk swelling or other nerve abnormalities are seen. Work-up similar to AION.

VERTEBRAL BASILAR INSUFFICIENCY (VBI) Basilar artery disease causes brainstem ischemia and may manifest with imbalance, emesis, ataxia, and skew deviation. Check brainstem magnetic resonance angiography (MRA).

Physical Disease

RADIATION OPTIC NEUROPATHY Causes necrosis of the ON and chiasm, usually within 9 to 12 months of treatment (but may be up to 20 years).

TOXIC OPTIC NEURITIS OR NEUROPATHY Usually central scotoma because central small ON fibers from the macula depend on central retinal artery for their blood supply, in contrast to the larger peripheral nerve fibers, which rely more on diffusion from the CSF. Thus, small ON fibers benefit from the blood–brain barrier and are spared until later from toxic/metabolic stress.

Ethambutol: dose related and reversible. Diagnose by VER; related to zinc chelation.

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322 NEUROLOGIC

Methanol: contaminant of ethanol and its breakdown product, formic acid, is toxic to retinal ganglion cells and the NFL. Usually causes blurred or decreased VA within 18 hours of ingestion with systemic acidosis, early ON hyperemia and retinal edema, and late optic atrophy. VA either recovers within 6 days or is usually lost permanently. Treat with ethyl alcohol and hemodialysis.

Amiodarone: associated with ischemic optic neuropathy (chemical structure is similar to chloroquine).

TRAUMATIC OPTIC NEUROPATHY (TON) Always consider as cause of vision loss in head trauma patients until proven otherwise. Patients usually have no ophthalmoscopic signs, but have immediate decreased VA with positive APD and dyschromatopsia.

Mechanism: usually trauma causes indirect injury to the posterior nerve.

Direct: rare; from impact of penetrating orbital object compression from ON sheath hemorrhage with CRAO or CRVO, impingement by foreign body, or shearing of nerve fibers.

Indirect, anterior: rare; usually from sudden traumatic rotation of the globe (may have CRAO or avulsion of ON head).

Indirect, posterior: most common mechanism; typically caused by a blow to the forehead or midface, with force trasmitted posterior along the ON, where it is tethered at the orbital apex and in the optic canal, causing contusion of nerve or shearing of short penetrating blood vessels from deceleration forces. In children, the leading cause is bike accidents (often from not wearing a helmet; most have no loss of consciousness).

Clinical diagnosis when other causes of vision loss have been ruled out. CT is usually unremarkable, but rule out optic canal fracture with 1 mm cuts through the canal (canal fracture is not prognostic and may be protective by decompressing closed space).

Treatment: controversial whether to treat or not. Fifteen to 33% of patients improve spontaneously with observation alone; however, steroids may help as an antioxidant effect and to maintain perfusion. Steroids usually given 30 mg/kg load, then 5.4 mg/kg/hour IV infusion for 24 hours or 15 mg/kg every 6 hours for 72 hours. Rarely canal decompression is needed.

International Optic Neuropathy Trauma Study (multicenter, nonrandomized comparative interventional study with concurrent treatment groups) concluded that there is no standard of care and that patients should be treated on an individual basis. Study patients were stratified to receive megadose steroids or steroids plus optic canal decompression. The trial was stopped due to small numbers and turned into a case series. Of the 127 patients with TON, 9 received no treatment, 85 received steroids, and 33 had surgery. Trends showed that the timing of treatment made no

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