Rasmussen encephalitis and related conditions

Rasmussen encephalitis Definition and epidemiology of Rasmussen encephalitis In 1958, Theodore Rasmussen and co-workers at the Montreal Neurological Institute reported three patients suffering from severe focal seizures, accompanied by progressive hemiparesis and cognitive decline, in association with pathologic features of chronic encephalitis (Rasmussen et al. 1958). In the following years, most researchers and clinicians have adopted the term Rasmussen encephalitis (RE) for this condition characterized by chronic encephalitis and epilepsy (Andermann 1991). More recently, important new insights have added to our understanding of the pathophysiology, the diagnosis, and the management of this condition. Rasmussen encephalitis is a rare, sporadic disease with no evidence for a genetic component (Andermann 1991). So far, no geographic, seasonal, or clustering effect has been detected; moreover there is no apparent increase in pre-existent febrile convulsions or immediately preceding viral illnesses (Antel and Rasmussen 1996). Pathology The histopathological properties of RE are non-specific and are suggestive of chronic multifocal encephalitis (Robitaille 1991). The affected hemisphere shows microglial nodules with or without neuronophagia, perivascular cuffs of small lymphocytes and monocytes, and gliosis, with destructive changes appearing first as laminar necrosis and later spongy degeneration. Four stages of the condition have been delineated that correspond to disease duration (Robitaille 1991).