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Susac Syndrome

KEY FACTS

TERMINOLOGY

• Microangiopathy of brain, retina, and cochlea

IMAGING

• T2 hyperintense corpus callosum lesions in patient with

clinical triad

○ Encephalopathy, bilateral hearing loss, and branch retinal

artery occlusions

• Multifocal T2 hyperintensities similar to MS

○ More often round, midcallosal rather than callososeptal

location

• May involve brainstem, basal ganglia, thalamus, subcortical

white matter, centrum semiovale

• Lesions may show acute diffusion restriction

• Variable enhancement of lesions and leptomeninges

TOP DIFFERENTIAL DIAGNOSES

• Multiple sclerosis

• Acute disseminated encephalomyelitis (ADEM)

• Systemic lupus erythematosus

• Vasculitis

PATHOLOGY

• Microinfarctions in cerebral cortex that are generally not

seen on imaging

• No demyelination seen on pathology

CLINICAL ISSUES

• 20-40 year old (F > > M)

• Sudden visual loss, deafness; headache, variable

encephalopathy

• Usually self-limited (2-4 years), but may lead to permanent

deafness or blindness

DIAGNOSTIC CHECKLIST

• Most patients do not exhibit entire triad (up to 97% at time

of presentation)

• Complete triad seen after 2 weeks or after 2 years

(Left) Axial FLAIR MR shows

multiple hyperintensities ſt in

corpus callosum of this 27-

year-old woman with Susac

syndrome who presented with

headache and confusion. The

classic clinical triad includes

encephalopathy, bilateral

hearing loss, and branch

retinal artery occlusions.

(Right) Postcontrast sagittal

FLAIR in the same patient

shows classic involvement ſt

of corpus callosum body with

hyperintense lesions. Note

leptomeningeal enhancement

﬇, which may be seen in up

to 50% of patients.

(Left) Axial DWI trace shows

multiple hyperintense lesions

﬇, many of which had

corresponding low ADC values

representing true diffusion

restriction. Acute lesions may

mimic vasculitis. (Right)

Funduscopic examination

shows multiple retinal artery

branch occlusions and

irregularities ﬈, classic for

Susac syndrome. Susac

syndrome is often mistaken

for multiple sclerosis on

imaging studies. Its etiology is

uncertain but most likely

represents an autoimmune

microangiopathy, not a

demyelinating disorder.

Brain: Pathology-Based Diagnoses: Malformations,

Trauma, and Stroke

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