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 dis- eases, and known autoimmune disorders were excluded. 1 Cerebral MRI showed progressive right cerebral and crossed left cerebellar hemiatrophy (figure 2, A and B). Tractography of cortico-ponto-cerebellar (CPC) path- ways 2 (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 atro- phy is a distinctive feature of long-term Rasmussen encephalitis evolution.