Autoimmune Encephalitis: When the Brain Is Attacked by the Immune System

Autoimmune encephalitis (AE) — inflammation of the brain caused by antibodies against neuronal surface proteins — was only characterised and systematically described from 2007 onwards, but has rapidly become one of the most important causes of new-onset encephalopathy, especially in young people. The antibodies impair neuronal function and cause the clinical syndrome. The most common and paradigmatic form is anti-NMDA receptor encephalitis, but dozens of antibody-specific variants exist. AE is frequently misdiagnosed as psychiatric illness for weeks to months — a dangerous delay that worsens outcomes.

Anti-NMDA Receptor Encephalitis — Stages of Presentation

This condition disproportionately affects young women (but also men and children). The clinical course progresses through characteristic stages: Prodrome (1–2 weeks): Flu-like illness — headache, fever, fatigue. Psychiatric phase (2–4 weeks): Anxiety, agitation, paranoia, hallucinations (visual and auditory), behavioural change, insomnia. Patients are referred to psychiatry and treated with antipsychotics — which have minimal effect. Neurological phase: Seizures; abnormal involuntary movements (orofacial dyskinesias — chewing, grinding movements; limb choreiform movements); speech disorganisation and then mutism; autonomic instability (heart rate and BP fluctuations); progressive loss of consciousness. This is an ICU emergency.

Red Flags That Should Prompt AE Testing

New-onset psychiatric symptoms in a previously well young person with no psychiatric history; rapid deterioration over weeks; fever with psychiatric symptoms; seizures alongside psychiatric symptoms; orofacial dyskinesias; treatment-resistant psychiatric presentation; CSF pleocytosis (white cells — unusual in primary psychiatric illness).

Treatment

First-line: IV methylprednisolone + IV immunoglobulin (IVIG) or plasma exchange. Remove underlying tumour if present (30% of anti-NMDA encephalitis in adult women is associated with ovarian teratoma — removal is part of treatment). Second-line for non-responders: rituximab, cyclophosphamide. Prognosis is good with early treatment — most patients make substantial recovery. Delayed diagnosis worsens outcomes. Sri Anand CNC, Chanda Nagar, Hyderabad. Call +91 90633 66983.