A 76-year-old retired architect is brought to the clinic by his son. Over the past 8 month… — USMLE Step 2 CK

A 76-year-old retired architect is brought to the clinic by his son. Over the past $8$ months, the patient has experienced a progressive decline in his cognitive abilities. His son notes that the patient's alertness fluctuates significantly from day to day; he sometimes stares blankly for several minutes during conversations. The patient also frequently reports seeing unfamiliar children playing in his living room, though he is not distressed by their presence. His medical history includes major depressive disorder, for which he has taken fluoxetine for $5$ years. Vital signs are within normal limits. Neurological examination reveals a resting tremor in the left hand, symmetric rigidity, and a slow, shuffling gait. The Montreal Cognitive Assessment (MoCA) score is $19/30$ . Laboratory studies show:

Thyroid-stimulating hormone (TSH): $2.4 \text{ \mu U/mL}$ (normal: $0.4-4.0 \text{ \mu U/mL}$ )
Free thyroxine (T4): $1.3 \text{ ng/dL}$ (normal: $0.9-2.4 \text{ ng/dL}$ )

The son is overwhelmed by the recent changes and demands that his father be admitted to a locked psychiatric facility immediately. However, the patient's previously executed advance directive designates his wife as the healthcare proxy and expresses a clear preference for home-based care.

Which of the following is the most appropriate next step in the management of this patient?

Initiate rivastigmine therapyAnswer
B
Add selegiline to the current medication regimen
C
Authorize psychiatric admission at the son's request
D
Initiate levothyroxine supplementation
E
Initiate haloperidol for schizophreniform disorder

Answer

The most appropriate next step is to initiate rivastigmine therapy.

This patient's clinical presentation—progressive cognitive decline, marked fluctuations in alertness, well-formed visual hallucinations, and spontaneous parkinsonism—is highly characteristic of major neurocognitive disorder with Lewy bodies (LBD). Cholinesterase inhibitors, such as rivastigmine, donepezil, or galantamine, are the first-line pharmacological treatment to manage the cognitive and behavioral symptoms of LBD. They effectively improve hallucinations, stabilize fluctuating cognition, and carry a lower risk of exacerbating motor symptoms compared to antipsychotics.

Step-by-Step Solution

Analyze the clinical presentation and timeline.

The patient has an 8-month history of progressive cognitive decline, marked fluctuations in alertness, well-formed visual hallucinations, and spontaneous parkinsonism (resting tremor, rigidity, shuffling gait).

Identifying the classic clinical triad establishes the diagnosis of Major Neurocognitive Disorder with Lewy bodies (LBD).

Evaluate the laboratory results and ethical context.

TSH and free T4 are within normal limits, ruling out primary hypothyroidism. The patient has a valid advance directive naming his wife as proxy and preferring home care, superseding the son's demands.

Ruling out reversible causes (like thyroid dysfunction) and respecting ethical guidelines are mandatory before initiating new therapies.

Determine the optimal pharmacological management for the confirmed diagnosis.

Rivastigmine, a central acetylcholinesterase inhibitor, is selected.

Cholinesterase inhibitors are the first-line evidence-based treatment for the cognitive and behavioral symptoms (including hallucinations) of LBD. Antipsychotics must be avoided due to severe neuroleptic sensitivity.

Key Concept

Major neurocognitive disorder with Lewy bodies (LBD) presents with fluctuating cognition, visual hallucinations, and parkinsonism; cholinesterase inhibitors are the preferred initial treatment for cognitive and neuropsychiatric symptoms.

Estimated Time:1m 30s

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