Autoimmune and Paraneoplastic Encephalitis: A Review for the Intensivist

Abstract

Autoimmune encephalitis are rare conditions that can be triggered by a cancer. Two groups of encephalitis differ depending on the type of autoantibodies that are associated with it. In the presence of onconeuronal antibodies, which are usually directed against an intracellular antigen, a cancer is frequently found and there is a diffuse neuronal loss compromising the functional prognosis. Conversely, when autoantibodies are directed against a synaptic protein, cancers are less frequent and the symptoms are related to a reversible synaptic dysfunction that is mediated by the autoantibodies.

The clinical picture differs depending on the target of the associated antibody. Autoimmune encephalitis most often presents a subacute central nervous system impairment predominantly involving limbic structures and leading to behavioral or psychiatric disorders, amnesia and temporo-mesial seizures. Extra-limbic signs, especially autonomic symptoms and movement disorders, may be seen as well. Impairment of consciousness, central hypoventilation due to autonomic impairment and status epilepticus can be seen at the onset of the disease.

Temporo-limbic hyperintensities on brain MRI and signs of inflammation in the lumbar puncture are suggestive, but their absence does not eliminate the diagnosis. The search for a possible underlying cancer is urgent and must be guided by the antibodies found.

The management of autoimmune encephalitis must be guided by the antibodies found in patients, focusing on the search for an underlying cancer and immunosuppression.