Susac Syndrome

Susac syndrome is a rare autoimmune endotheliopathy affecting small vessels in the brain, retina and inner ear, causing the clinical triad of encephalopathy, branch retinal artery occlusions and sensorineural hearing loss.

• Mostly women aged 20 to 40; incidence about 0.024 per 100,000.

• Pathology: microinfarcts from precapillary arteriolar occlusion, with anti-endothelial cell antibodies; complement and T cell mediated.

• Triad complete in only a minority at onset; develops over months.

• Self-limited in 2 to 4 years in many but with residual deficits; relapses occur.

• Encephalopathy: headache (often migraine-like), confusion, memory loss, personality change, psychosis, focal deficits, seizures, ataxia.

• Visual scotomata or field loss from branch retinal artery occlusions (often painless, bilateral).

• Hearing loss (low frequency), tinnitus, vertigo, nausea.

• Skin changes (livedo) are uncommon.

• Brain MRI: multiple small T2/FLAIR hyperintense lesions in the corpus callosum ("snowball" lesions in the central fibres, spokes), deep grey matter and leptomeningeal enhancement.

• Fluorescein angiography: branch retinal artery occlusions, arterial wall hyperfluorescence (focal).

• Audiometry: low to mid frequency sensorineural loss.

• CSF: raised protein, mild pleocytosis.

• Exclude multiple sclerosis, ADEM, CNS vasculitis, antiphospholipid syndrome, CADASIL, MELAS, Cogan syndrome, infection, lupus, thrombotic microangiopathy.

• Early aggressive immunosuppression:

• Pulse methylprednisolone 1 g IV daily for 3 to 5 days, then prednisolone 1 mg/kg tapered over many months.

• IVIG 2 g/kg over 2 to 5 days (monthly for 6 months or more) often combined.

• Cyclophosphamide 500 to 1000 mg/m2 monthly, mycophenolate mofetil 1 to 1.5 g twice daily, or rituximab 1 g on days 1 and 15 as steroid-sparing agents; azathioprine for maintenance.

• Aspirin 75 to 100 mg daily and consideration of anticoagulation in microvascular occlusion.

• Intratympanic steroids for hearing; cochlear implant for profound loss.

• Calcium channel blockers (nimodipine) in retinal arteriolar disease have been used.

• Regular follow up: MRI, fluorescein angiography, audiometry every 3 to 6 months; relapse after treatment withdrawal is possible.

• Neurorehabilitation and psychiatric support.