Adult onset chronic unihemispheric vasculitis resembling Rasmussen encephalitis

Rasmussen encephalitis (RE), a chronic inflammatory unilateral brain disease, is usually associated with intractable seizures and progressive neurologic deterioration. Despite being initially observed in children, an adult form has been more recently recognized. MRI discloses progressive atrophy and signal changes through the affected hemisphere, but rarely gadolinium enhancement, which when observed requires a brain biopsy to distinguish Rasmussen encephalitis from an alternative diagnosis as unihemispheric vasculitis.

An adult patient had at the age of 35 his first generalized seizure followed by transient right hemiparesis and aphasia. Two years later, seizures relapsed with a gradually increasing frequency associated with progressive neurologic deterioration. Repeated brain imaging, revealed progressive atrophy and signal changes within the left hemisphere with gadolinium enhancement. Histopathology disclosed focal gliosis mainly in white matter and some small intraparenchymal arteries, and arterioles with perivascular and intramural chronic inflammatory cell infiltrate.

Unihemispheric chronic vasculitis may resemble adult-onset Rasmussen encephalitis, and persistent gadolinium enhancement seen on MRI lesions is helpful for the differential diagnosis between the 2 conditions.