Autoimmune encephalitis is a relatively recently recognized clinical unit. Dia gnosis is based on clinical manifestations of the disease, and can be further confirmed by positivity of specific anti-neuronal antibodies.
In spite of the fact that there are new types of antibodies discovered almost every year, there are still patients who manifest with clinical signs of autoimmune encephalitis, and yet do not test positive on anti-neuronal antibody assay testing. The reasons for this can be as follows: 1) specific antibodies for these cases might not have been discovered yet; 2) methods used for their detection are not sensitive enough; or 3) humoral immunity does not play a major role in the autoimmune response in a particular case.
The absence of anti-neuronal antibodies to confirm the dia gnosis of autoimmune encephalitis complicates clinical dia gnosis. Recognition and early identification of the group of patients with negativity of anti-neuronal antibodies is crucial, because prompt initiation of immunotherapy is associated with a better outcome.