Autoimmune Encephalitis

Autoimmune encephalitis (AIE) is an immune-mediated condition that induces brain inflammation and is one of the most common causes of non-infectious encephalitis. In the past decade, AIE has become an emerging addition to the differential diagnosis when a classical infection cannot explain focal neurological symptoms. While the exact mechanism of AIE is unknown, current literature suggests that autoimmune antibodies target synaptic proteins, leading to widespread inflammation. AIE commonly presents as a new onset of memory loss, psychosis, altered mental status, or seizures, with the presentation taking place over a few weeks to three months. AIE involves several parts of the nervous system, including the limbic system, the spinal cord, and/or the entire neuraxis. AIE can be confirmed by multiple modalities, including laboratory testing (antibody detection), neuroimaging, and electrophysiological studies (electroencephalogram). Although classical paraneoplastic encephalitis is commonly associated with cancer, AIE may or may not be related. Therefore, once the diagnosis is established, patients should undergo cancer screening due to a high degree of association with underlying malignancy. Although these tests can be time-consuming, clinicians should consider initiating treatment early in the course if their clinical suspicion is high, as they are often treatment-responsive and have significantly improved outcomes. The most commonly studied subtype of AIE is anti-N-methyl-D-aspartate receptor encephalitis, so the management approach is primarily based on that. This review describes the current state of knowledge on various types of autoimmune encephalitis and educates readers with a concise, up-to-date summary.