A 36-year-old woman is evaluated in the clinic due to left hand clumsiness. The patient works as an office secretary and has been having difficulty typing. Six months ago, she had an episode of vertigo and difficulty walking that improved after several weeks. The patient also has a history of bipolar disorder and takes valproic acid. On physical examination, she is asked to close her eyes and stretch out her arms with the palms facing up. Several seconds later, her left arm involuntarily drifts downward and the palm turns toward the floor. Which of the following best explains the findings observed in this patient?

Question

A 36-year-old woman is evaluated in the clinic due to left hand clumsiness.  The patient works as an office secretary and has been having difficulty typing.  Six months ago, she had an episode of vertigo and difficulty walking that improved after several weeks.  The patient also has a history of bipolar disorder and takes valproic acid.  On physical examination, she is asked to close her eyes and stretch out her arms with the palms facing up.  Several seconds later, her left arm involuntarily drifts downward and the palm turns toward the floor.  Which of the following best explains the findings observed in this patient?

Quizplus · Accepted Answer

11ec25c8_d5b5_7b4c_bc81_47ab46285dc7_MD0003_00 This young woman with neurologic deficits disseminated in space and time (eg, hand clumsiness, ataxia, vertigo) most likely has multiple sclerosis, an inflammatory demyelinating disorder characterized by white matter lesions in the central nervous system. Pronator drift is a physical examination finding that is relatively sensitive and specific for upper motor neuron or pyramidal/corticospinal tract disease. The pronator drift test is particularly useful in patients with subtle deficits as it can accentuate pyramidal motor weakness. It is performed by having the patient outstretch the arms with the palms up and eyes closed (so that only proprioception is used to maintain arm position). Upper motor neuron lesions cause more weakness in the supinator muscles compared to the pronator muscles of the upper limb. As a result, the affected arm drifts downward and the palm turns (pronates) toward the floor. pyramidal/corticospinal tract (Choice A) Basal ganglia dysfunction typically results in extrapyramidal signs, such as resting tremor, rigidity, bradykinesia, and choreiform movements. Pronator drift is not typically observed. (Choice B) Cerebellar dysfunction usually causes ataxia, intention tremor, and impaired rapid alternating movements. Cerebellar lesions result in an upward drift (rather than the downward drift seen in pyramidal tract lesions) due to hypotonia. Other pyramidal tract signs (eg, focal weakness, spasticity, hyperreflexia, Babinski sign) are not observed. (Choice C) Drug-induced hyperammonemia can be observed in patients using valproic acid and usually presents with encephalopathy (eg, confusion, lethargy) and neuromuscular findings (eg, bradykinesia, asterixis). Focal weakness and pronator drift are not characteristic. (Choice D) Proprioception is evaluated by passively moving the distal phalange of a digit up and down and having patients identify the direction of movement with their eyes closed. It is also assessed with the Romberg test in which patients are observed for unsteadiness as they stand with their feet together, arms to the sides, and eyes closed. Patients with impaired proprioception (eg, vitamin B₁₂ deficiency, tabes dorsalis) have difficulty determining joint position and may lose balance during Romberg testing. Romberg test Educational objective: Pronator drift is a relatively sensitive and specific sign for upper motor neuron or pyramidal tract disease affecting the upper extremities. It is performed by having the patient outstretch the arms with the palms up and eyes closed. In patients with pyramidal lesions, the affected arm drifts downward and the palm turns (pronates) toward the floor. References: Images in clinical medicine. Pronator drift. (http://www.ncbi.nlm.nih.gov/pubmed/24131195) Detection of focal cerebral hemisphere lesions using the neurological examination. (http://www.ncbi.nlm.nih.gov/pubmed/15774443)

A 36-Year-Old Woman Is Evaluated in the Clinic Due to Left