Neurocognitive impairment in Susac syndrome: Magnetic resonance imaging and Tc-99m hexamethylpropyleneamine oxime single photon emission computed tomography correlation.

Susac syndrome is a clinical triad of branch retinal artery occlusions, sensorineural hearing loss, and encephalopathy. The characteristic central corpus callosum involvement in Susac syndrome is readily recognizable on conventional magnetic resonance imaging (MRI); however, the neurocognitive effect of these lesions is not well-understood. We present a case of Susac syndrome with typical MRI findings of central callosal lesions at diagnosis. The patient had a protracted clinical course and did not respond well to immunosuppression therapy. Follow-up brain single photon emission computed tomography with Tc-99m hexamethylpropyleneamine oxime revealed marked unilateral frontoparietal and temporal lobe hypoperfusion. Our case highlights the utility of functional neuroimaging to uncover the possible underlying white matter dysfunction, which is not otherwise detectable with conventional MRI techniques.