Adult–onset Rasmussen encephalitis with high anti N–methyl–D aspartate type glutamate receptor subunit antibody titer in serum and cerebrospinal fluid : Effects of high–dose intravenous methylprednisolone pulse therapy implemented eleven years after onset

Abstract

Refractory epilepsy, right hemiplegia, and impaired fluency of expression had progressed over a period of 10 years in a 48–year–old male who had initially been diagnosed with secondary generalized seizures and aphasia. He was also unable to walk without support and levels of anti–N–methyl–D–aspartate type glutamate receptor subunit antibody were elevated in serum and cerebrospinal fluid. T2–weighted and fluid attenuated inversion recovery brain imaging showed hyperintensity on paraventricular white matter and EEG revealed a sharp wave with a front pole focus in the left cerebral cortex, where atrophy was more prominent. The brain MRI findings were worse at ten years than at two years after onset. He was diagnosed with Rasmussen's encephalitis based on the Bien diagnostic criteria and underwent high–dose intravenous methylprednisolone pulse (IVMP) therapy. Thereafter, he was able to walk without support for over 100 meters and the secondary generalized seizures and aphasia were improved. Rasmussen's encephalitis tends to progress more slowly in cases of adult onset than in childhood onset. The frequency of epilepsy increases and motor and cognitive decline progresses within months without immediate immunomodulation therapy. However, the frequency of epilepsy, gait disturbance, and aphasia was improved in our patient despite IVMP therapy being implemented eleven years after onset. Slowly progressive, refractory epilepsy of adult onset should be carefully assessed because immunomodulation therapy could be effective even if Rasmussen's encephalitis is diagnosed late.