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Anti-NMDA receptorA glutamate receptor in the brain involved in learning and memory, and a target of drugs like ketamine and memantine.Read more → encephalitis matters because it is a reversible autoimmune brain disease that can look exactly like a primary psychotic illness at first. NMDA (N-methyl-D-aspartate) receptors are a type of glutamate receptor important for memory and cognition, and in this condition antibodies attack these receptors directly. For example, imagine a previously well young woman who develops rapid-onset psychosis (a mental state with delusionsA fixed false belief, held with total conviction, that is not shared by the person's culture and is not changed by evidence against it.Read more → and hallucinationsSeeing, hearing, or otherwise sensing things that are not really there.Read more →) and catatoniaA syndrome of abnormal movement and behaviour, ranging from being frozen and unresponsive to being excessively agitated.Read more → (a syndrome of abnormal movement and unresponsiveness). If she then develops seizures and abnormal orofacial (mouth and face) movements over days, this pattern should trigger urgent screening for an ovarian teratoma (a type of ovarian tumour) and antibody testing. In practice, recognising this pattern early changes management completely, from antipsychotics alone to immunotherapy and tumour removal.

Anti-NMDA receptorA glutamate receptor in the brain involved in learning and memory, and a target of drugs like ketamine and memantine.Read more → encephalitis is caused by antibodies (immune proteins) against the NMDA receptor, a glutamate receptor central to learning and memory. It is most common in young women, often associated with an ovarian teratoma, a tumour that can trigger the immune response. The illness typically starts with a viral-like prodrome (an early phase before typical symptoms). It then progresses to prominent psychiatric symptoms, psychosis and catatoniaA syndrome of abnormal movement and behaviour, ranging from being frozen and unresponsive to being excessively agitated.Read more →, which can initially be mistaken for a primary psychiatric disorder such as schizophreniaA long-term mental illness involving episodes of psychosis such as hallucinations and delusions.Read more →. Over days to weeks, it typically progresses further to seizures, orofacial dyskinesias (abnormal repetitive mouth and face movements), and autonomic instability (unstable blood pressure, heart rate, and temperature). Take a psychiatry inpatient with a working diagnosis of first-episode psychosis who then develops seizures and unstable blood pressure. This evolution should prompt urgent neurological work-up rather than simply escalating the antipsychotic dose. Diagnosis relies on CSFCerebrospinal fluid, the fluid that cushions the brain and spinal cord.Read more → (cerebrospinal fluid) antibody testing, MRI (magnetic resonance imaging), and EEG (electroencephalogramA recording of the brain's electrical activity, usually shortened to EEG.Read more →). Treatment combines immunotherapy, such as steroids, intravenous immunoglobulin, or plasma exchange, with removal of any underlying tumour.

• An electroencephalogramA recording of the brain's electrical activity, usually shortened to EEG.Read more → in a woman with suspected autoimmune encephalitis shows a distinctive rhythmic slow pattern with superimposed fast activity. What is this pattern called?
• Two weeks into her illness, a woman with confirmed autoimmune encephalitis develops swinging blood pressure, cardiac arrhythmia and irregular breathing. Which complication does this…
• A woman admitted with a first episode of psychosis is being assessed for an organic cause. Which feature should most raise suspicion of an autoimmune rather than primary psychiatric cause?
• A man recovers from herpes simplex encephalitis, then deteriorates weeks later with new psychiatric symptoms and abnormal movements. Which development best explains this second…

• Anti-NMDA receptor encephalitis, progresses to seizures, dyskinesias, and autonomic instability, unlike a primary psychotic disorder such as schizophreniaA long-term mental illness involving episodes of psychosis such as hallucinations and delusions.Read more → which does not.
• Ovarian teratoma, a common trigger in young women, whereas older patients or men more often have no identified tumour.
• CSF antibody testing, confirms the diagnosis, rather than relying on clinical psychiatric assessment alone.
• Immunotherapy plus tumour removal, the definitive treatment, unlike antipsychotics alone which do not address the underlying autoimmune process.

• That reaction produces sustained muscle spasm rather than these signs.
• Liver failure is not a recognised consequence of the usual immunotherapy.
• Those waves suggest a metabolic encephalopathyA general term for brain dysfunction, often causing confusion, that has a physical cause.Read more → such as liver failure.
• That pattern occurs under deep anaesthesia or after severe brain injury.
• That chaotic pattern occurs in infantile spasms.

• Localise the clue to the relevant anatomical level, cell type, pathway or molecular process.
• Map that structure or process to its normal function.
• Predict the deficit or clinical sign produced when it is disrupted.
• Reject options that belong to a neighbouring structure, pathway or level of explanation.