Neurocognitive, neuropsychiatric and consultation-liaison psychiatry
This domain rewards a systematic approach to the confused inpatient and to psychiatric presentations of medical illness and medication effects.
Core rules
- Delirium: acute onset, fluctuating course, inattention, disorganized thinking or altered consciousness. Use the CAM algorithm. Identify the cause (infection, medication, metabolic, withdrawal, hypoxia, retention, pain) and treat it; low-dose haloperidol is used for distressing agitation, but benzodiazepines are reserved for alcohol or benzodiazepine withdrawal and for some cases of Lewy body disease and Parkinson disease.
- Dementia profiles: Alzheimer disease (amnestic onset, medial temporal atrophy), vascular (stepwise, executive and gait involvement), Lewy body (fluctuating cognition, formed visual hallucinations, parkinsonism, severe neuroleptic sensitivity), frontotemporal (personality and language variants, younger onset), Huntington (caudate atrophy, CAG repeats), prion disease (myoclonus, periodic sharp waves).
- Serotonin syndrome versus NMS: serotonin syndrome gives clonus, hyperreflexia, mydriasis and agitation with a rapid onset after serotonergic agents; NMS gives lead-pipe rigidity, bradyreflexia and marked CK elevation over days after dopamine blockade and is treated with bromocriptine or dantrolene.
- Capacity is decision-specific and assessed by four abilities: communicate a choice, understand the information, appreciate the situation, and reason about options. Capacity is a clinical judgement; competence is a legal determination.
- Medication causes to remember: SSRIs and SIADH/hyponatremia, interferon and depression, corticosteroids and mania, isoniazid and psychosis, beta-blockers and depression.
Worked example
A 78-year-old hospitalized woman on oxybutynin and ciprofloxacin becomes acutely confused and inattentive at night while her baseline cognition was intact. Fluctuation plus inattention and acute onset equal delirium; the work-up targets urinary retention, infection and the anticholinergic burden, and antipsychotics are avoided in suspected Lewy body disease.
Traps
Calling delirium dementia; assuming haloperidol is safe in Lewy body disease; diagnosing depression as the cause of weight loss and forgetting hyperthyroidism or malignancy; equating capacity with compliance.