Disorders• 2 SECTIONNerve Optic Congenital

Optic Disc Hypoplasia

Key Facts

•Small optic disc (and nerve) owing to reduced number of axons

•Degree of visual deficit variable

•Subtle hypoplasia may be hard to detect on ophthalmoscopy (characteristic double-ring sign present in <50% of cases)

•Forebrain anomalies more likely if optic disc hypoplasia is bilateral

•Superior segmental hypoplasia variant associated with maternal diabetes

Clinical Findings

•Small diameter disc substance usually accompanied by peripapillary atrophy

•outer margin of disc and outer margin of peripapillary atrophy may be slightly pigmented, giving rise to double-ring sign

•If hypoplasia is minimal and there is no double-ring sign, may be difficult to recognize ophthalmoscopically (compare area occupied by vessels with diameter of disc)

Ancillary Testing

•Brain imaging may show forebrain anomalies, including absence of septum pellucidum and hypoplasia of corpus callosum (de Morsier syndrome)

•T1 MRI posterior pituitary bright spot may be absent or displaced upward into tuber cinereum

• If so, growth and adrenocorticotropic hormones may be deficient

•Monitor growth and development and assess hormone levels

Differential Diagnosis

• Small but normal optic disc

Treatment

• Directed at associated brain anomalies and hormone deficiencies

Prognosis

• Visual dysfunction stable and very difficult to assess in infancy

Fig. 2.10 Bilateral severe optic disc hypoplasia in an infant with multiple midline cerebral defects.

Disorders Chiasm• 3 SECTIONor Nerve Optic Acquired

Typical Optic Neuritis

Key Facts

•Acute or subacute monocular visual loss caused by primary demyelination of the optic nerve

•Isolated idiopathic condition or part of multiple sclerosis (MS)

•Afferent pupil defect often the only objective finding

•>75% of patients show enhancement of affected optic nerve on T1 fat-suppressed MRI

•Spontaneous near total recovery of visual function within 6 months in >85%

•No treatment improves on long-term spontaneous recovery of visual function

Clinical Findings

•Acute or subacute visual loss often accompanied by ipsilateral periocular pain exacerbated by eye movement

•Reduced visual acuity or nerve fiber bundle visual field defects in affected eye

•Afferent pupil defect in affected eye (unless fellow eye has equivalent optic nerve damage)

•Optic disc appears normal (60%) or only mildly swollen

•May have symptoms, signs, or previous diagnosis of MS

•No other clinical manifestations except those attributable to MS

Ancillary Testing

•MRI: enhancement of affected optic nerve in >75%, cerebral white matter signal abnormalities typical of MS in 50% (high-risk MRI)

•Visual evoked potentials: prolonged latencies in affected (and sometimes fellow) eye

•Lumbar puncture: elevated immunoglobulins and/or oligoclonal bands in 25%

Fig. 3.1 Optic neuritis, right eye. Mild optic disc swelling and hyperemia are evident. Caution: many patients with typical optic neuritis show no abnormalities on fundus examination!

Disorders Chiasm• 3 SECTIONor Nerve Optic Acquired

Typical Optic Neuritis (Continued)

Differential Diagnosis

•Atypical optic neuritis

•Ischemic optic neuropathy

•Compressive optic neuropathy

•Infiltrative (neoplastic) optic neuropathy

•Leber hereditary optic neuropathy

•Paraneoplastic optic neuropathy

Treatment

•Patients with high-risk MRI: intravenous methylprednisolone 1 g/day for 3 days followed by prednisone 1 mg/kg for 11 days, administered within 1 week of onset, significantly reduces likelihood of developing MS during next 2 years but not thereafter

•In patients with high-risk MRI, treatment with interferon beta or glatiramer acetate reduces accumulation of MRI signal abnormalities and clinical relapses but there is no solid evidence that this regimen improves long-term disability from MS

•In patients with MRI white matter signal abnormalities (high-risk MRI), intravenous and oral methylprednisolone regimen reduces chances of developing MS during next 2 years but does not alter long-term chances of developing MS

Prognosis

•Spontaneous near total recovery of vision in >85% within 6 months

•30% get recurrent optic neuritis in previously affected or fellow eye within 5 years

•40% of patients develop MS within 10 years

•Abnormal white matter signal on MRI at onset of first-attack optic neuritis triples likelihood of developing MS