Psychiatry and Neurology
Psychiatry and neurology are examined together and reward two skills: localisation in neurology and the time course in psychiatry. Ask always: acute or chronic, focal or diffuse, fluctuating or stable.
Core rules
- Delirium versus dementia: delirium is acute, fluctuating, with impaired attention. Look for infection, anticholinergics, benzodiazepines, withdrawal, electrolytes, pain, urinary retention, and constipation.
- Depression: at least 2 weeks of low mood or anhedonia plus five symptoms; ask directly about suicide.
- Schizophrenia: psychotic symptoms persisting months with functional decline; antipsychotics. Distinguish neuroleptic malignant syndrome (rigidity, hyperthermia, raised CK - dantrolene, bromocriptine) from serotonin syndrome (clonus, hyperreflexia, autonomic instability).
- Stroke: time of onset is decisive - intravenous thrombolysis within 4.5 h, thrombectomy in selected patients up to 6 h and beyond with imaging selection. Check glucose and exclude haemorrhage before lysis.
- Localisation: upper motor neuron signs include hyperreflexia and Babinski; lower motor neuron signs include atrophy and fasciculation; crossed findings point to the brainstem.
- Status epilepticus: benzodiazepine first, then levetiracetam, fosphenytoin, or valproate.
Worked example
A 76-year-old admitted with pneumonia becomes confused at night, reports seeing insects, has fluctuating attention, and is tremulous. Reasoning: hyperactive delirium, not dementia or schizophrenia. Search for hypoxia, sepsis, retention, constipation, and causative drugs; treat the cause, avoid restraints, and use low-dose antipsychotics briefly only for distressing symptoms.
Traps
- Missing Wernicke encephalopathy (ophthalmoplegia, ataxia, confusion) in a malnourished patient - give thiamine before glucose.
- Diagnosing dementia from one cognitive test in a depressed or poorly educated patient.
- Labelling catatonia as psychosis without considering a benzodiazepine trial.