Susac syndrome (SS) is a rare autoimmune disease that typically affects 20-40-year-old females. The syndrome was first described by John O. Susac in 1979 [1] and since then it has been recognized more often as the diagnostic tools improve, although the real incidence is unknown. The underlying pathophysiology is microangiopathy with occlusion of small vessels in the brain, retina, and cochlea, giving the classic clinical triad with CNSdysfunction, visual disturbance, and hearing loss.
This disease has also been called “small infarctions of cochlear, retinal and encephalic tissue” (SICRET) and “microangiopathy with retinopathy, encephalopathy, and deafness” (RED‑M) which contributes to the underdiagnosis and some confusion in the literature [2],[3).
The CNS dysfunction results from acute or subacute encephalopathy and usually present as psychiatric features of personality change and bizarre behavior. Other forms of neurologic involvement include impaired cognition and memory, ataxia, dysarthria, vertigo, and corticospinal tract dysfunction.
The visual loss occurs due to branch retinal arteriolar occlusions (BRAO). The diagnosis of such occlusions can be done by retinal fluorescein angiography. Segmental loss of vision in one or both eyes and visual scintillating scotoma are typical visual complaints [4].
The hearing loss is sensorineural, usually on low-frequency with impaired discrimination and can be uni or bilateral. It may be associated with tinnitus, vertigo, nausea, vomiting, nystagmus and unsteady gait [5].
The disease is frequently misdiagnosed as multiple sclerosis, migraine, lupus erythematosus, encephalitis, Menière disease, thromboembolic stroke, and even schizophrenia [6],[7].
The etiology and pathogenesis of this microangiopathy remain unknown: no procoagulant state or definite connective tissue disease has been consistently documented. An auto-immune based mechanism triggered by previous infections is thought to be the best explanation.
There is no an entirely specific feature of Susac syndrome, but the presence of brain MR alterations, ophthalmologic angiography, and audiogram can help in the diagnosis. A high level of suspicion is necessary as the majority of patients do not present with the complete triad. As a matter of fact, the triad may only be complete after several years or never be complete at all leading to partial forms of the syndrome [7].
Rapid diagnosis is fundamental for early initiation of therapy on a disease that affects so profoundly the quality of life of such young patients. The radiologist can help in the diagnosis when the SS is suspected and better orientate the further investigation.
MR image is the modality of choice. The main finding includes T2 and T2 FLAIR focal hyperintensities in the white matter mainly at corpus callosum (genu, body, and splenium), centrum semiovale, internal capsule, periventricular white matter, brain stem, cerebellum, cerebral and cerebellar peduncles, basal ganglia, and thalamus [8]. Acute or subacute lesions can present with contrast enhancement as small foci or in the form of leptomeningeal enhancement. Brain atrophy can also be present.
The disease usually has an active fluctuating monophasic self-limited course, lasting from months to years, with varying functional outcomes and residual disabilities [4].
Treatment with corticosteroids is usually recommended with variable response. Other immunosuppressors as cyclophosphamide can also be used, and, in severe cases, intravenous immunoglobulin can be useful.
Early recognition and appropriate therapy of this syndrome may reduce the permanent sequelae that are seen with this disease.
