Psychotic disorder due to another medical condition — structured clinical viva

Frame. This is not routine cannabis-FEP. Subacute psychosis plus speech change and possible faciobrachial dystonic seizure–like events push organic / autoimmune encephalitis to the top while keeping metabolic, infectious, and primary differentials open.^[1][4]

Assessment spine. Risk, MSE with examples, attention (delirium screen), full neurologic bedside, collateral, capacity for MRI/LP, local MHA principles if detention needed (no invented section numbers), medication/substance timeline.^[5]

Work-up. Tier 1 labs + ECG immediately. Escalate MRI, EEG, LP (after imaging if ICP risk), paired serum–CSF cell-based neuronal antibodies. Do not stop at normal MRI if AE still likely. Pollak autoimmune-psychosis and Graus AE frameworks guide urgency of immunotherapy discussion with neurology — detail of first-line IVIG/steroids/PLEX lives in the AE topic, but you must own recognition and hand-off.^[2][3][4]

Symptomatic psychiatry. Low-dose antipsychotic if risk requires (e.g. olanzapine 2.5–5 mg oral) with monitoring; avoid aggressive D2 blockade if catatonia/NMS risk; benzos if catatonic features. Treat medical driver as primary.^[5]

Communication. Explain to family: "symptoms may be driven by a treatable brain inflammatory or other medical process; we will investigate urgently; medicine and psychiatry work together."^[2]