Clinical, immunological and therapeutic aspects of autoimmune encephalitis

Autoimmune encephalitis is a heterogeneous group of disorders probably resulting from a reaction of the immune system against antigens of the central nervous system. Historically, the autoimmune hypothesis was based on the neuropathological discovery of an immune cellular infiltrate in the brain parenchyma and around the cerebral blood vessels, resembling a form of viral encephalitis without any detectable viral antigens. These syndromes can be divided into forms with prevalent grey matter involvement, forms with prevalent white matter damage and forms in which the target of the immune process is the vessels. In this paper, we review recent knowledge about the syndromes belonging to the first group. This group encompasses syndromes in which there is neuronal loss and antibodies directed against antigens expressed in the neurons (anti-neuronal antibodies) are frequently detected in the sera or cerebrospinal fluid. These antibodies are not necessarily the cause of neurological impairment but are important markers for these syndromes. It is essential to acquire knowledge on these disorders since they are an important cause of rapidly progressive cognitive decline and behavioural problems which may remain underrecognized, but often improve with immunomodulatory therapies.