The Older Man Who Keeps Falling and Forgetting

Differential:

• Alzheimer's disease - insidious progressive episodic memory loss, disorientation, functional decline, global atrophy on MRI. Plausible and probably the leading diagnosis.
• Vascular cognitive impairment - white-matter hyperintensities, vascular risk factors; less likely to be pure Alzheimer's but may coexist.
• Medication-related cognitive impairment - oxybutynin is a strongly anticholinergic drug started 6 months ago; anticholinergic burden is a well-recognised reversible contributor to confusion and falls in older adults.
• Normal-pressure hydrocephalus - gait disturbance and falls; MRI shows atrophy rather than ventriculomegaly, which argues against it, but gait should be characterised (magnetic, wide-based).
• Depression / pseudodementia - bereaved 2 years ago, lives alone; mood should be assessed.
• Lewy body dementia / Parkinson's disease dementia - slow gait, falls; ask about visual hallucinations, REM sleep behaviour disorder, fluctuation, parkinsonism.
• Metabolic causes - B12 210 pg/mL is low-normal; methylmalonic acid or homocysteine would clarify true deficiency.
• Subdural haematoma - on aspirin with falls; MRI makes this unlikely but the falls need a cause.

Contributory/reversible factors to address:

1. Stop oxybutynin and review the anticholinergic burden; consider an alternative for urinary urgency.
2. Postural hypotension (138/80 lying to 104/70 standing) - review amlodipine, hydration, and falls risk; this likely explains the falls.
3. B12 - check methylmalonic acid/homocysteine and treat if deficient.
4. Depression and grief - screen formally.
5. Sensory, hearing and vision - check and correct.
6. Alcohol - quantify.

Exam point: the classic trap is to accept Alzheimer's at the first visit while missing anticholinergic medication and postural hypotension, both of which are treatable and both of which explain the falls.

Memory clinic referral - yes, with a clear purpose. The value is not to 'confirm Alzheimer's' for its own sake but to:

• Establish a baseline for cognitive and functional status, so future change can be measured.
• Optimise reversible contributors (medication, B12, mood, vascular risk).
• Access support - cognitive stimulation, occupational therapy, carer support, and legal/financial planning while he still has capacity.
• Consider symptomatic treatment (an acetylcholinesterase inhibitor) if a diagnosis of Alzheimer's is confirmed; benefit is modest but real, and decisions about starting and stopping should be explicit.
• Advance care planning - discuss wishes, lasting power of attorney, and future care needs early.

Driving - this is a safety and legal question, not a courtesy.

• Cognitive impairment and falls raise fitness-to-drive concerns. Assess with a structured approach: history of near-misses, getting lost, family observations, and formal cognitive assessment.
• Advise him and the family that he should not drive pending assessment, and explain the legal duty (in most jurisdictions) to inform the licensing authority of a diagnosis likely to affect driving. Document the advice.
• Refer for a driving assessment (on-road or simulator) where available. Do not simply tell the family to 'hide the keys' without a plan.
• Reassess if cognition or medication changes.

Exam point: the answer must combine clinical reasoning (is the referral useful?) with legal/professional obligation (driving fitness and disclosure), and must not collude with the family's wish to avoid telling him.

Likely cause: cholinergic excess (donepezil toxicity), possibly precipitated by the recent oxybutynin change, dehydration from vomiting, or drug interaction.

Features of cholinergic toxicity: nausea, vomiting, diarrhoea, bradycardia, hypersalivation, sweating, lacrimation, miosis, bronchospasm, and in severe cases weakness and confusion. Bradycardia of 48 with vomiting and worsening confusion fits.

Management:

1. Stop donepezil immediately.
2. Assess and treat dehydration - IV fluids, check electrolytes and renal function; vomiting plus bradycardia is high-risk in an older adult.
3. ECG - look for bradyarrhythmia or heart block; review other rate-slowing drugs (beta-blockers, digoxin, calcium-channel blockers).
4. Review interactions - anticholinergics and cholinergics together are a particular hazard; also check for other causes of vomiting (infection, obstruction, new medication).
5. Reassess cognition after recovery; consider restarting at a lower dose only if the benefit clearly outweighed the adverse effect, with slow titration.
6. Document and communicate with the family and carer about warning signs.

Exam point: a new deterioration after starting a cholinesterase inhibitor should prompt consideration of cholinergic adverse effects before assuming disease progression.