Pathophysiology and Clinical Presentation

Antibodies in autoimmune encephalitis can target intracellular antigens or antigens on neuronal surface/synaptic space. Among those, antibodies which target intracellular antigens are usually associated with paraneoplastic syndromes and a poor prognosis. Antibodies to intracellular antigens include anti-Hu (also known as antineuronal nuclear antibody, type 1, ANNA-1), anti-Ma2 (also called anti-Ta), collapsin-responsive mediator protein-3, protein-4, and protein-5 (CRMP3-5), anti- amphiphysin, anti-Yo, anti-Ri, adenylate kinase 5, and BR serine/threonine kinase (BRSK2) antibodies. Table 8.1 summarizes the antibodies to intracellular antigens and their clinical presentation.

Antibodies to neuronal surface/synaptic antigens can also be associated with cancer; however, they are more responsive to immunotherapy. Antibodies to neuronal surface/synaptic antigens are often related to limbic encephalitis. In this group, anti-N-methyl-D-aspartate (NMDA) receptor encephalitis and anti-leucine-rich glioma-inactivated 1 (LGI1) comprise 85% of patients [1]. Anti-NMDA receptor encephalitis has become one of the most frequently recognized autoimmune encephalitides since its discovery. The disease is more frequent among women (80%) and adults younger than 45 years old [39]. Almost half of the patients initially present with a headache and a viral-like process, followed by psychiatric manifestations, altered mental status, in addition to language and memory dysfunction [15, 40]. Seizure is frequent among pediatric patients [39]. More than two-third of the patients suffer from seizures [39]. Table 8.2 summarizes the antibodies to intracellular antigens, their associated syndromes.

More than half of patients with autoimmune encephalitis present with symptoms of limbic encephalopathy including memory deficits, altered mental status, seizures, and neuropsychiatric syndrome. Refractory seizures and status epilepticus have also been reported [59, 60, 68]. Other common features of autoimmune encephalitis include headache, tremor, language difficulties, ataxia, and sleep disorders.

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