Autoimmune encephalomyelitis

Recent discoveries of several autoantibodies produced in patients with autoimmune encephalomyelitis have contributed largely to categorize new clinical entities in this field, and also provided a deep understanding of the background of neurological symptoms in these disorders together with new insights in the basic neuroscience. Most of these recently identified autoantibodies bind to the neuronal or glial cell surface synaptic receptors. They alter synaptic functions and develop characteristic clinical features depending on each target antigen. Among them, N‐methyl‐D‐aspartate receptor (NMDAR) is the most frequent antibody, causing NMDAR encephalitis syndrome, which has various characteristic clinical features including acute psychosis, memory disturbance, seizures, dyskinetic abnormal movements, conscious disturbance and respiratory dysfunction mainly in young women with ovarian teratoma. The next most frequently detected antibody is anti‐leucine‐rich glioma‐inactivated 1(LGI1) antibody, formerly designated as voltage‐gated potassium channel antibody. The anti‐LGI1 antibodies are detected in older patients of both sex and show symptoms related to the limbic system without having associated tumors. Patients with these cell‐surface antibodies show neurological symptoms closely related to the function of target synapse/channel antigens, which also bring new insights in signal transduction research. The triggers to develop specific antibody production and inducing encephalopathy are not known yet; however, they tend to respond to antigen‐removal treatment even if they have tumors. Thus, it is important to diagnose autoantibody production and initiate therapy as early as possible.