A 68-year-old man comes to the office due to balance problems over the last 2 weeks. He has had muscle stiffness and 3 near-falls recently. The patient has no musculoskeletal pain or visual problems. He has a history of bipolar disorder and anxiety and was started on valproate and risperidone for a manic episode 5 months ago. Other medical issues include hypertension that is controlled with hydrochlorothiazide. Temperature is 37.2 C (99 F) and blood pressure is 122/78 mm Hg supine and 130/80 mm Hg standing. The patient appears slightly anxious but no longer manic. There is an asymmetric resting tremor in both hands. Finger tapping is slow and irregular bilaterally. Which of the following is the most likely cause of this patient's current condition?

Question

A 68-year-old man comes to the office due to balance problems over the last 2 weeks.  He has had muscle stiffness and 3 near-falls recently.  The patient has no musculoskeletal pain or visual problems.  He has a history of bipolar disorder and anxiety and was started on valproate and risperidone for a manic episode 5 months ago.  Other medical issues include hypertension that is controlled with hydrochlorothiazide.  Temperature is 37.2 C (99 F) and blood pressure is 122/78 mm Hg supine and 130/80 mm Hg standing.  The patient appears slightly anxious but no longer manic.  There is an asymmetric resting tremor in both hands.  Finger tapping is slow and irregular bilaterally.  Which of the following is the most likely cause of this patient's current condition?

Quizplus · Accepted Answer

11ec25c8_d75d_10bc_bc81_5907bb6be382_MD0003_00 Medications that block the dopamine (D2) receptor may cause extrapyramidal symptoms (EPS). The most common offending agents include first-generation antipsychotics (eg, haloperidol), second-generation antipsychotics (eg, risperidone) to varying degrees, and antiemetics (eg, metoclopramide). This patient likely has drug-induced parkinsonism as he developed bradykinesia (eg, slow finger tapping), rigidity, and resting tremor (may be asymmetric or symmetric) after starting risperidone. EPS also include acute dystonia, which is characterized by the sudden onset of sustained muscle contractions resulting in twisting and abnormal postures (eg, torticollis) rather than the classic parkinsonian resting tremor found in this patient (Choice A). Akathisia, another type of EPS, presents with subjective restlessness and an inability to stay still, as opposed to rigidity and bradykinesia (Choice B). Tardive dyskinesia is also less likely as it typically occurs after prolonged (>6 months) antipsychotic exposure and is characterized by dyskinetic movements that typically involve the mouth/face/trunk (eg, lip smacking, grimacing, choreoathetoid movements) (Choice H). (Choice C) Cerebellar stroke is less likely as this patient's blood pressure is well controlled and he lacks other atherosclerotic risk factors (eg, diabetes, hyperlipidemia, smoking). The onset of symptoms following treatment with risperidone makes drug-induced parkinsonism more likely. (Choice D) Charcot-Marie-Tooth disease is a hereditary peripheral neuropathy that most commonly presents with lower extremity weakness, foot drop, and, in some cases at a later stage, tremor. (Choice F) Essential tremor typically presents with an action (as opposed to resting) tremor that worsens with fine motor activity. Tremor is typically the only abnormal neurologic finding. (Choice G) Neuroleptic malignant syndrome is characterized by lead-pipe rigidity; this patient's lack of mental status changes, high fever, and autonomic instability makes it unlikely. Educational objective: Medications that block the dopamine (D2) receptor (eg, antipsychotics, metoclopramide) may cause extrapyramidal symptoms, including acute dystonia, parkinsonism, akathisia, and tardive dyskinesia. Drug-induced parkinsonism typically presents with bradykinesia, rigidity, and tremor. References: Incidence and time trends of drug-induced parkinsonism: a 30-year population-based study. (http://www.ncbi.nlm.nih.gov/pubmed/27779780) Drug-induced parkinsonism. (http://www.ncbi.nlm.nih.gov/pubmed/23540800)

A 68-Year-Old Man Comes to the Office Due to Balance