Rasmussen's encephalitis: Imaging spectrum on simultaneous FDG-PET and MRI imaging correlation

Rasmussen encephalitis (RE) is a rare, chronic, idiopathic, progressive, inflammatory, neurodegenerative disease process and typically seen in pediatric cohort. Although primarily a disease affecting children, adult cases with RE have also been reported. It manifests as drug refractory epilepsia partialis continua (EPC). Immunomodulation, although delays progression of disease, seldom influences outcome. Imaging is crucial for early diagnosis, and monitoring disease progression. Magnetic resonance imaging (MRI) is mainstay of imaging with nuclear imaging being a complimentary tool for diagnosing RE. Typical imaging features of RE on MRI are hemispherical atrophy, caudate nucleus atrophy, ex vacuo dilatation of the ventricular system and sulci. We review 5 cases of RE who fulfilled diagnostic criteria proposed by Bien et al. in 2005. One patient had typical imaging pattern of RE while other four patients had atypical imaging features of RE on PET-MRI.