MRI findings of crossed cerebellar diaschisis in a case of Rasmussen’s encephalitis

Abstract

We report the case of an 11-year-old girl with a medical history significant for Rasmussen’s encephalitis (RE), manifesting with intractable complex partial seizures, who developed severe brain hemiatrophy and MRI evidence of contralateral cerebellar atrophy due to crossed cerebellar diaschisis (CCD). The patient was born full term and had a normal childhood until seizures started at the age of six. Neurological examination disclosed only a slight right hemiparesis. Clinically, seizures lasted between 1 and 3 min and were accompanied by focal twitches of the right arm and foot. EEG revealed intermittent electroclinical seizures with left temporal onset spreading throughout the left hemisphere, followed by rhythmic sharp and slow waves over the right hemisphere. Brain MRI showed high T2-signal intensity in patchy areas of the cortex of the left hemisphere (Fig. 1a–c). Brain biopsy disclosed findings compatible with Rasmussen’s encephalitis (Fig. 2). Several therapeutic treatments, including seizure medicines (valproic acid, phenytoin carbamazepine, lorazepam), immunotherapy with IVIg, and vagus nerve stimulation, were unsuccessful in managing the progression of the disease or controlling seizures. There was no change in seizure frequency despite all therapies. Follow-up brain MRI at the age of 11 (Fig. 1d–f) demonstrated interval increase of atrophy of the left sylvian region, the left temporal lobe and the left occipital lobe. Striking interval atrophy of the right cerebellum, consistent with CCD, was also evident. The patient subsequently underwent left functional hemispherectomy achieving mild reduction of seizures. Rasmussen’s encephalitis is a rare hemispheric inflammatory disease of the brain generally manifesting with intractable seizures, cognitive decline and progressive neurological deficits. Normally this disorder affects children while an adult onset of the disease is less frequent and associated with a less aggressive course [1, 2]. Crossed cerebellar diaschisis is a condition in which cerebellar hypometabolism is noted in association with injuries to the contralateral cerebral hemisphere. It is ascribed to functional cerebellar disconnection from the cerebral cortex of the contralateral hemisphere. Interruption of the cerebro-pontine-cerebellar pathway is thought to be the most likely mechanism of this remote transneuronal metabolic depression [3]. CCD is frequent in patients with hemispheric strokes, and it is usually shown with nuclear medicine techniques while it is more rarely demonstrated on MRI [4, 5]. SPECT findings of CCD have been described in patients with RE whereas its correlate on MRI has been seldom reported [6–10]. A. Cianfoni M. L. Bradshaw Neuroradiology Section, Radiology Department, Medical University of South Carolina (MUSC), Charleston, SC, USA