Diffusion-weighted imaging of encephalopathy related to idiopathic hypereosinophilic syndrome

Abstract

Encephalopathy related to idiopathic hypereosinophilic syndrome (HES encephalopathy) is a rare (but well-documented) syndrome. Magnetic resonance imaging (MRI) findings of HES encephalopathy, particularly diffusion-weighted images (DWI) findings, have not been reported. We report a case of HES encephalopathy in a 79-year-old male presenting with a focal neurological deficit and cognitive function disorders. Eosinophil number was >20,000/mm 3. Initial DWI revealed multiple high-signal lesions that were clearer than on T2-weighted images. After corticosteroid therapy, symptoms improved and MRI-identified lesions decreased. This is the first report demonstrating DWI findings of HES encephalopathy. We suggest that lesions identified on MRI may be related to a combination of demyelination, inflammation and/or even small-vessel infarction due to local intimal lesions and clotting, secondary to eosinophilic toxicity. Investigation using DWI should therefore be done in patients with HES encephalopathy even if T2-weighted images are normal.