Lead
A child who was talking normally just days before begins acting like a stranger. She reports hallucinations. He screams uncontrollably. A seizure occurs. Emergency evaluation finds no clear cause; the child is referred to psychiatry.
This course of events is one of the classic presentations of autoimmune encephalitis. Unlike infectious encephalitis, this condition operates through a different mechanism — and until Dalmau and colleagues described anti-NMDA receptor encephalitis in 2007 [1], many of these cases were managed as "psychiatric illness of unknown origin." Early recognition and timely immunotherapy are what determine outcome.
What Autoimmune Encephalitis Is
Autoimmune encephalitis is a non-infectious inflammation of the brain in which autoantibodies: antibodies the immune system mistakenly produces against the body's own proteins, causing self-directed tissue damage target neurons. The best-known form involves autoantibodies directed against the glutamate receptor: a protein on neuron surfaces that responds to glutamate, the main excitatory signaling chemical in the brain — specifically the NMDA: N-methyl-D-aspartate, a receptor subtype critical for learning and memory; antibody attack causes psychosis, seizures, and movement abnormalities (N-methyl-D-aspartate) receptor — giving rise to "anti-NMDA receptor encephalitis."
In a UK study of encephalitis etiology, anti-NMDA receptor encephalitis accounted for approximately 4% of all encephalitis cases — the most common identifiable cause of autoimmune encephalitis — a proportion comparable to some infectious forms [3].
In children and adolescents, anti-NMDA receptor encephalitis has been characterized in detail by Florance and colleagues [4]. There is a female predominance, though less pronounced than in adults. In adult women, association with ovarian teratoma is clinically important; in children, this association is much less frequent.
Clinical Picture — How the Illness Unfolds
The typical progression of autoimmune encephalitis, particularly the anti-NMDA receptor form, has recognizable stages [1,2]:
Prodrome (days to two weeks): Non-specific symptoms resembling a viral illness — fever, headache, vomiting. Diagnosis at this stage is difficult.
Psychiatric phase: Rapid behavioral change, hallucinations (visual and auditory), delusional speech, insomnia, intense anxiety. At this point, the presentation is easily mistaken for a primary psychiatric condition.
Motor and consciousness phase: Involuntary movements (mouth opening and closing, hand rubbing and similar stereotypies), seizures, autonomic instability (fluctuating temperature, blood pressure, and heart rate), and declining level of consciousness.
The involvement of multiple systems simultaneously or in rapid sequence, and the speed of progression, are the distinguishing features from infectious encephalitis and functional psychiatric illness.
Diagnosis — Why It Gets Missed
The most common reason autoimmune encephalitis is diagnosed late is that psychiatric symptoms come first. Rapid behavioral change, hallucinations, and intense emotional volatility frequently result in referral to psychiatry before a neurological workup is completed.
The diagnostic workup combines several modalities: cerebrospinal fluid: the clear liquid that surrounds and cushions the brain and spinal cord; sampled by lumbar puncture to detect signs of inflammation or infection analysis (elevated cell count and protein), MRI (signal abnormality in limbic structures: brain regions involved in emotion, memory, and behavior, frequently inflamed in autoimmune encephalitis), EEG: electroencephalogram; a recording of the brain's electrical activity used to detect seizure patterns and encephalitis-specific waveforms (abnormal patterns, including the characteristic delta brush pattern), and antibody testing (anti-NMDA receptor antibodies in cerebrospinal fluid, among others) [2].
Antibody results take time. When the clinical picture is strongly suggestive, immunotherapy is often started before results are available. Data indicate that delay from diagnosis to treatment initiation affects outcome [2].
Treatment and Prognosis
First-line immunotherapy includes corticosteroid pulse therapy, intravenous immunoglobulin (IVIg: a preparation of pooled human antibodies given by infusion to modulate abnormal immune responses), and plasmapheresis: a procedure that removes plasma from the blood to clear out harmful autoantibodies, then returns the blood cells. When response is inadequate, second-line agents — rituximab and others — are added.
In children with anti-NMDA receptor encephalitis treated with appropriate immunotherapy, approximately 75–80% achieve partial to full recovery [4]. Recovery, however, often takes months to more than a year.
Relapse occurs in approximately 12–15% of cases, with higher risk in those treated with corticosteroids alone [2]. Long-term follow-up remains necessary after recovery.
What Parents Should Know
Autoimmune encephalitis is rare, but the characteristic of "rapid multi-system change" is a flag for seeking evaluation without delay. The following warrant prompt assessment by a neurologist or pediatric neurologist if they appear within days to weeks:
- Psychiatric symptoms (hallucinations, delusions, rapid personality change) occurring alongside or immediately followed by motor symptoms
- Repeated seizures
- Fluctuating level of consciousness
- Combined temperature and pulse irregularities
A timeline — "when did each symptom first appear, and in what order did they progress" — is critical information for a neurologist constructing a diagnosis. In the middle of a crisis, recording is often impossible. Whatever can be reconstructed afterward, even partially, is worth preserving. Autoimmune encephalitis is one of those conditions where a log can directly influence diagnosis.
Summary
Autoimmune encephalitis is a non-infectious brain inflammation in which antibodies attack neuronal receptors. The combination of acute-onset psychiatric and motor symptoms is the diagnostic key, and most patients recover with early immunotherapy. Rather than accepting "unexplained psychiatric illness" as a conclusion, seeking consultation with a neurologist or pediatric neurologist is the appropriate response when this picture presents.
References
- Dalmau J, Tüzün E, Wu HY, et al. Paraneoplastic anti-N-methyl-D-aspartate receptor encephalitis associated with ovarian teratoma. Ann Neurol. 2007;61(1):25–36. doi:10.1002/ana.21050. PMID: 17262855.
- Dalmau J, Lancaster E, Martinez-Hernandez E, Rosenfeld MR, Balice-Gordon R. Clinical experience and laboratory investigations in patients with anti-NMDAR encephalitis. Lancet Neurol. 2011;10(1):63–74. doi:10.1016/S1474-4422(10)70253-2. PMID: 21163445.
- Granerod J, Ambrose HE, Davies NW, et al. Causes of encephalitis and differences in their clinical presentations in England. Lancet Infect Dis. 2010;10(12):835–844. doi:10.1016/S1473-3099(10)70222-X. PMID: 21030279.
- Florance NR, Davis RL, Lam C, et al. Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis in children and adolescents. Ann Neurol. 2009;66(1):11–18. doi:10.1002/ana.21756. PMID: 19670433.
- Japanese Society of Neurology; Japanese Society of Neurological Therapeutics; Japanese Society of Neurological Infectious Diseases. Diagnostic Guidelines for Autoimmune Encephalitis and Limbic Encephalitis (2017 edition).
- Lancaster E. The diagnosis and treatment of autoimmune encephalitis. J Clin Neurol. 2016;12(1):1–13. doi:10.3988/jcn.2016.12.1.1. PMID: 26754777.