A 63-year-old man is brought to the office by his daughter due to recurrent falls. According to his daughter, the patient has lost his balance and fallen several times over the past 6 months. He has not sustained serious injuries. She has also noticed some "shaking" of his right hand that is most apparent at rest. The patient has lived alone since his wife died 5 years ago and still shops, cooks, and cleans independently. Blood pressure is 141/68 mm Hg and pulse is 72/min. Neurologic examination shows mild rigidity of the limb muscles that is most prominent on the right side with a slow, shuffling gait. The patient is prescribed medication for his symptoms but returns to the office 4 weeks later reporting "disturbing visions of strangers creeping around corners of his apartment." On examination, he is alert and scores 27/30 on the Montreal Cognitive Assessment (normal: ≥26). Which of the following is the most likely explanation for this patient's new symptoms?

Question

A 63-year-old man is brought to the office by his daughter due to recurrent falls.  According to his daughter, the patient has lost his balance and fallen several times over the past 6 months.  He has not sustained serious injuries.  She has also noticed some "shaking" of his right hand that is most apparent at rest.  The patient has lived alone since his wife died 5 years ago and still shops, cooks, and cleans independently.  Blood pressure is 141/68 mm Hg and pulse is 72/min.  Neurologic examination shows mild rigidity of the limb muscles that is most prominent on the right side with a slow, shuffling gait.  The patient is prescribed medication for his symptoms but returns to the office 4 weeks later reporting "disturbing visions of strangers creeping around corners of his apartment."  On examination, he is alert and scores 27/30 on the Montreal Cognitive Assessment (normal: ≥26).  Which of the following is the most likely explanation for this patient's new symptoms?

Quizplus · Accepted Answer

This patient's tremor, rigidity, bradykinesia (ie, slowed gait), and unsteadiness with falls are consistent with a diagnosis of Parkinson disease (PD). Asymmetric motor symptoms are common, especially in early PD. The patient's subsequent hallucinations after starting a medication for PD are most likely caused by a dopamine agonist (eg, pramipexole), which is a class of medication frequently used in adult patients age <65 with PD. Levodopa, a dopamine precursor, is another common initial treatment for PD and may also be associated with hallucinations; this adverse effect is less common with levodopa than with dopamine agonists. Treating hallucinations and other psychotic symptoms (eg, delusions) in PD is challenging because their etiology is often multifactorial (ie, hallucinations can occur in PD even without medication) and because adjusting medication regimens can be difficult. Treatment of hallucinations in PD often begins with an initial trial adjustment of a medication regimen (eg, switching pramipexole to levodopa), but regimen changes and dose reduction are often limited due to resurgent motor symptoms. When hallucinations persist despite initial efforts, a low-dose antipsychotic may be tried. The most frequent antipsychotics used in PD are low-potency, second-generation antipsychotics (eg, quetiapine, pimavanserin). (Choices A and E) Catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO) type B inhibitors are used in PD but have less risk of inducing hallucinations compared to dopamine agonists. COMT inhibitors (eg, entacapone) may be given with levodopa to promote more stable and sustained levodopa levels. Selective MAO-B inhibitors (eg, selegiline) may be used in patients with very mild PD symptoms. (Choices B and D) A diagnosis of dementia requires marked cognitive impairment that impairs activities of daily living (eg, shopping, cooking). This patient scores within the normal range on cognitive testing and does not demonstrate functional impairment. Dementia with Lewy bodies may be diagnosed when a patient with dementia meets 2 of the following 4 criteria: visual hallucinations, parkinsonism, REM sleep behavior disorder, and fluctuating cognitive function. The hallmark feature of frontotemporal dementia is early change in personality (eg, disinhibition, apathy). Educational objective: Medications used in the treatment of Parkinson disease may cause hallucinations. Dopamine agonists and, to a lesser extent, levodopa are associated with this adverse effect. References: Adverse effects produced by different drugs used in the treatment of Parkinson's disease: a mixed treatment comparison. (http://www.ncbi.nlm.nih.gov/pubmed/28872217) The psychosis spectrum in Parkinson disease. (http://www.ncbi.nlm.nih.gov/pubmed/28106066)

A 63-Year-Old Man Is Brought to the Office by His