Teaching NeuroImages: Diffusion tensor tractography of cortico-ponto-cerebellar pathways in Rasmussen encephalitis.

A 34-year-old man developed since age 18 years epilepsia partialis continua followed over the years by progressive ataxic hemiparesis involving the left side (figure 1). Structural cerebral abnormalities, mitochondrial diseases, and known autoimmune disorders were excluded. Cerebral MRI showed progressive right cerebral and crossed left cerebellar hemiatrophy (figure 2, A and B). Tractography of cortico-ponto-cerebellar (CPC) pathways (figure 2, C and D) demonstrated marked involvement of the right tract, suggesting that a dying-back mechanism of efferent CPC fibers may cause crossed cerebellar atrophy. We infer that crossed cerebellar atrophy is a distinctive feature of long-term Rasmussen encephalitis evolution.