Susac syndrome is a rare autoimmune condition that affects small blood vessels in the brain, retina and cochlea. It is characterized by a clinical triad of encephalopathy, sensorineural Hearing Loss and visual loss. Most cases occur in middle-aged women, and its cause is still unknown.

The diagnose is a correlation between clinic and complementary exams such as audiometry, retinal angiofluoresceinography and magnetic resonance imaging (MRI). 

A 12-year-old female presented with mental confusion, irritability, behavior and psychiatric disorders, aphasia, walking and global movement disfunction with three months of evolution. Neurological exam showed ataxic gait, deep tendon hyperreflexia in lower members, tetraparesis, and Babinski sign on right side.

MRI evidenced hypersignal nodular lesions located in the corpus callosum, periventricular white matter, and middle cerebellar peduncles, measuring 3 to 7 mm, characterizing “Snowballs”. And also signs of restriction to water molecules diffusion proven by apparent diffusion coefficient (ADC) map.

Audiometry test demonstrated bilateral severe sensorineural hearing loss, and the retinal angiofluoresceinography revealed multiple retinal arteriolar obstructions. The patient was treated with pulses of intra-venous methylprednisolone, cycles of human immunoglobulin and cyclophosphamide.

After 6 cycles of cyclophosphamide treatment, the patient's neurological examination showed normal gait, lucidity, time and space orientation, stable talking and mood, no neurological focal signs, preserved deep tendon reflexes and lower limb strength, negative Babinski sign bilaterally. 

Susac syndrome leads to microvascular occlusions and ischemia in the brain, retina and cochlea, associated with endothelial proliferation, basement membrane and tunica adventitia thickening with internal elastic lamina loss.

It is in this context that MRI may assist in the diagnosis, combined with other exams and the patient's clinical condition.