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Autoimmune encephalitis
Autoimmune encephalitis presents as subacute decline (under 3 months) in memory, behaviour and consciousness with seizures — and it is treatable: start immunotherapy early, even before antibody results, and search for a tumour.
Why it matters in the exam
The classic scenario is a young woman with new psychiatric symptoms (anxiety, psychosis, insomnia), followed by seizures, involuntary mouth and face movements, autonomic instability and falling consciousness — anti-NMDA receptor encephalitis, sometimes with an ovarian teratoma. A second scenario is an older man with brief, frequent seizures of the face and arm on the same side and hyponatraemia — LGI1 antibodies. The tests check antibody testing in CSF and serum, the search for a tumour (pelvic ultrasound or MRI for teratoma), and stepwise treatment. Distractors: diagnosing a primary psychiatric disorder and giving high-dose antipsychotics (susceptibility to neuroleptic malignant syndrome), or waiting for antibodies before treatment. MRI may be normal, especially in anti-NMDA receptor encephalitis, so a normal MRI does not exclude the diagnosis. Recovery is slow and takes months, but most patients treated early return to good function.
Key points
- Autoimmune encephalitis: subacute decline in memory, behaviour and consciousness, with seizures.
- NMDA antibodies: a young woman, psychiatric symptoms then seizures and mouth movements — look for a teratoma.
- LGI1 antibodies: an older man, brief dystonic seizures of face and arm, hyponatraemia.
- First line: steroids, IVIG or plasma exchange, early and before results.
- Second line: rituximab or cyclophosphamide.
Summary table
| Syndrome | Clues | Work-up and treatment |
|---|---|---|
| NMDA receptor antibodies | Young women and children; psychiatric symptoms, then seizures, mouth and face movements, autonomic instability, reduced consciousness | CSF antibodies are more sensitive than serum; search for and remove an ovarian teratoma |
| LGI1 antibodies | Older men; brief dystonic seizures of face and arm; hyponatraemia; memory impairment | MRI with medial temporal involvement; good response to immunotherapy |
| Classic paraneoplastic antibodies | Hu (small-cell lung cancer), Ma2 (testicular tumour) | Poor response to treatment; treat the tumour |
| First-line treatment | Methylprednisolone 1 g intravenously daily for 5 days, IVIG or plasma exchange | Start early, before antibody results |
| Second-line treatment | Rituximab or cyclophosphamide when there is no improvement within about two weeks | Early treatment improves outcome and reduces relapse |
A free exam question
באיזה מהמצבים הבאים נצפה תהליך של Wallerian degeneration ? (the question as examined, in Hebrew)
- א. Anti-Hu sensory neuronopathy
- ב. Motor neuron disease
- ג. Multifocal motor neuropathy
- ד. Section of dorsal spinal root
In the full version for subscribers
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Sources
- A Clinical Approach to Diagnosis of Autoimmune Encephalitis (Graus et al., Lancet Neurology), 2016 — Diagnostic criteria
- Autoimmune Encephalitis: Treatment Consensus (Abboud et al., J Neurol Neurosurg Psychiatry), 2021 — First- and second-line immunotherapy
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.