314 NEUROLOGIC

Homonymous VF defects that respect the midline: lesions posterior to the chiasm. VF defects become more congruous with more posterior lesions; patients typically have normal VA.

Ninety percent of isolated homonymous hemianopias are caused by stroke.

Cogan’s dictum (especially relevant prior to CT scanning): evaluate a homonymous hemianopsia with the OKN drum. If normal response, then visual field defect is likely from an occipital stroke; if OKN is abnormal, then be concerned about an occipital tumor (pressure forward on the parietal lobe causing the inaiblity to pursue ipsilaterally).

Incongrous homonymous hemianopia with or without central scotoma: optic tract

Homonymous superior quandrantanopia (‘‘pie in the sky’’): lesion affecting inferior fibers of the optic radiations in the temporal lobe as they sweep around the ventricles (Meyer’s loop).

Homonymous inferior quandrantanopia (‘‘pie on the floor’’): optic radiations in the parietal lobe (often have OKN asymmetry).

Highly congruous homonymous quadrantanopia: posterior occipital lobe.

Homonymous hemianopia with macular sparing: occipital lobe (posterior cerebral artery stroke, but the occipital lobe tip that represents the macula receives a dual vascular supply from the middle cerebral artery). Other VF patterns associated with occipital lobe lesions include bilateral homonymous altitudinal defects, bilateral homonymous hemianopia with bilateral macular sparing (keyhole field), checkerboard field, and temporal crescent.

Monocular contralateral temporal defect: anterior occipital lobe

alized ophthalmoplegia and ptosis with no pupil abnormalities. See Chapter 2.

Myotonic dystrophy: autosomal dominant disorder characterized by abnormal systemic muscle function, including CPEO; also associated with polychromatic lenticular deposits and frontal balding.

Oculopharyngeal dystrophy: CPEO plus difficulty swallowing, usually seen in French-Canadians.

Kearns-Sayre syndrome: CPEO with cardiac conduction defects, pigmentary retinopathy. Mitochondrial DNA defect with ‘‘ragged red fibers’’ seen on pathology.

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MEGALOPAPILLA Disc size >2.1 mm; bilateral with increased cup:disk ratio, increased blind spot with normal VA.

MORNING GLORY ANOMALY Unilateral, sporadic, large excavated disk (central ‘‘coloboma’’) with a central core of glial tissue; retinal vessels exit from the borders of the defect, and disk is pigmented inferiorly. Defects involve the disk and retina, thus, may have retinal folds, and 30% of patients have RD. Associated with transphenoidal basal encephalocele (look at the hard palate).

MYELINATED NFL Ganglion cell axon myelination from oligodendrites proceeds from the LGN toward the disk; usually stops at the lamina cribosa, but may extend onto the retina as white, feathery radiating fibers. Usually asymptomatic, but if large, may cause VF defect and in the macula may cause decreased VA.

ON ATROPHY Often acquired but may be genetic; also, may be either primary or secondary (genetic causes: Kjer’s, Behr’s, and Leber’s atrophies). Primary or secondary genetic ON atrophy causes usually present with bilateral ON pallor with arteriolar attenuation; most have normal ERG (exception is recessive optic atrophy with cone dystrophy).

Kjer’s dominant optic atrophy, juvenile optic atrophy: insidious onset of moderately decreased VA (20/20–200) seen in preschool children. Typically has temporal disk pallor, temporal peripheral retinal changes (may have a pseudobitemporal hemianopsia), acquired tritan anomaly (blue-yellow color defects as with glaucoma), and no nystagmus. VF shows a cecocentral scotoma or enlarged blind spot. Examine the patient’s parents. Atrophy is autosomal dominant with high penetrance and variable expressivity disorder of the ganglion cell. Usually from chromosome 3 defect in the OPA1 gene that interacts with mitochondrial DNA (possibly similar mechanism to Leber’s atrophy).

Behr’s recessive congential optic atrophy: rare autosomal recessive disorder with severe vision loss and normal ERG. Technically, only called Behr’s if optic atrophy is associated with mental retardation, cerebella ataxia, hypertonia, and spasticity.

Leber’s optic atrophy: progressive optic atrophy seen in young males with decreased VA, often to 20/200 (but patient will usually not go blind). The fellow eye is involved within 3 months. Exam shows triad of circumpapillary telangiectasias, pseudopapilledema (disk edema), with absence of fluorescein disk staining. The acute phase is characterized by the hyperemic disk with tortuous telangiectatic vessels that do not leak on FA; rapidly progresses to late phase with a pale disk. VF shows central or cecocentral scotoma. Typically, only mild APD is present (pupillovisual dissociation with selective sparing of pupillary control axons, and vision loss is often symmetric).

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316NEUROLOGIC

Maternal mitochondrial DNA (mDNA) inheritance: all children carry the gene, but not all have the disease; males are far more commonly affected than females. Most common defect is the Wallace 11778 gene that codes for subunit 4 of NADH dehydrogenase. Also 14484 gene defect is found in 11% of cases, which carries a better visual prognosis.

Diagnose by finding mDNA defect in leukocytes. Usually MRI is normal OU. May be associated with heart conduction abnormalities and skeletal muscle disease (findings similar to CPEO).

No proven treatment. Genetic counseling is important; encourage patients if appropriate to stop smoking and drinking alcohol (which may cause ‘‘mitochondrial strain’’ and increase penetrance).

Secondary optic atrophy in childhood: metabolic diseases, compressive lesions (bony lesions, craniopharyngioma, ON glioma, hydrocephalus), advanced retinal disease (e.g., RP), and neonatal anoxia

Metabolic diseases: gangliosidoses, MPS, adrenoleukodystrophy (pigmentary retinopathy), spinocerebellar ataxia, Friedreich’s ataxia, and the following:

Wolfram syndrome: DIDMOAD (diabetes insipitus, diabetes mellitus, optic atrophy, deafness); autosomal recessive disorder. Ask about bedwetting from diabetes insipitus; ocular findings and deafness occur in childhood after diabetes diagnosis.

Charcot-Marie-Tooth atrophy: sensorineural polyneuropathy that may be autosomal dominant or recessive with late childhood peroneal muscle atrophy, slowly progressive motor neuropathy of legs hands, with deafness and optic atrophy.

Bone disease with ON compression: Albright’s syndrome, osteopetrosis (anemia, calcium imbalance; patients usually need bone marrow transplant), and the craniosynostoses (Cruzon’s, Apert’s, Carpenter’s).

ON COLOBOMA Failure of fetal fissure and stalk closure with disk excavation, usually inferonasal with no central glial tuft (unlike morning glory anomaly). Usually sporadic inheritance; may be unilateral or bilateral; may have other colobomas that can involve the macula with poor VA or have associated RD.

Aicardi’s syndrome: X-linked dominant (lethal in males) disorder with coloboma of the optic nerve and optic atrophy, peripapillary chorioretinal lacunae; associated with corpus callosum agenesis, infantile spasms, and mental retardation.

CHARGE association: colobomas, heart defect, atresia choanae, retarded growth, genital anomalies, ear anomalies and deafness

Systemic associations: Warburg’s syndrome, Gorlin-Goltz focal dermal hypoplasia (clefts, syndactyl, coloboma, pigmented linear skin

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streaks, X-linked), Meckel-Gruber syndrome, Lenz microphthalmia syndrome (X-linked), renal-coloboma syndrome (autosomal dominant PAX 2 mutation).

ON DRUSEN Calcific deposits within the optic nerve, most commonly seen in the inferior disk. Usually asymptomatic and benign, but 75% of patients with visible drusen have a VF defect. May cause pseudopapilledema, optociliary shunt vessels, AION, and TVO. Clinical diagnosis; may confirm with ultrasound, autofluorescence, or CT. Two percent incidence, often familial, autosomal dominant variable penetrance, usually seen in Caucasian patients. Associated with history of migraine headaches.

OPTIC NERVE HYPOPLASIA (ONH) Small 0.3–0.5 mm disk, with anomalous vessel pattern and double-ring sign (see the round edge of the disk and also the scleral ring, which it does not quite fill). May have profound vision loss, amblyopia, nystagmus, and APD. Is the most common congenital disk anomaly with sporadic inheritance; may be unilateral or bilateral. Thirteen percent of patients have anterior pituitary and CNS developmental anomalies.

Associated with maternal diabetes (classically superior sectoral ONH) or ingestion of phenytoin/LSD/alcohol/quinine. Also aniridia (may have ON or foveal hypoplasia) or CHARGE association.

De Morsier’s syndrome (septo-optic dysplasia): ONH, midline CNS anomalies (pituitary dysfunction), absence of septum pellucidum. Often presents with growth retardation.

ON PIT Unilateral, inferotemporal small disk excavation that is round or oval, white or yellow. May be considered a minimal coloboma. Forty-five percent of patients have macular serous RD usually in second or third decade (probably has a CSF-vitreous connection). If acquired, associated with NTG.

TILTED DISK Bilateral, nonhereditary, long-axis oblique insertion of the ON showing an optic disk that does not look round. May have VF defect or Fuchs’ coloboma (inferior crescent, may have bitemporal visual field defects that do not respect midline, myopic astigmatism with plus axis parallel to the axis of ectasia).

Infectious Disease

BARTONELLA HENSELAE, CAT-SCRATCH DISEASE Causes a neuroretinitis (papillitis plus a macular star); typically has good recovery, but often neuropathy or macular RPE changes persist. May not have known cat bite or scratch. Bartonella infection may also cause Parinaud’s oculoglandular

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