A 28-year-old woman comes to the office due to right hand tremors for the past several weeks. The patient has difficulty performing daily activities and feels embarrassed in social gatherings. She has a history of the remitting-relapsing form of multiple sclerosis. There is no family history of tremors. On physical examination, no abnormal hand movement is observed at rest. When the patient is instructed to touch an object on the table, a coarse tremor is observed that gradually increases as the hand moves closer to its target. Dysfunction of which of the following structures is the most likely cause of this patient's tremor?

Question

A 28-year-old woman comes to the office due to right hand tremors for the past several weeks.  The patient has difficulty performing daily activities and feels embarrassed in social gatherings.  She has a history of the remitting-relapsing form of multiple sclerosis.  There is no family history of tremors.  On physical examination, no abnormal hand movement is observed at rest.  When the patient is instructed to touch an object on the table, a coarse tremor is observed that gradually increases as the hand moves closer to its target.  Dysfunction of which of the following structures is the most likely cause of this patient's tremor?

Quizplus · Accepted Answer

11ec160b_35cb_4d5a_9249_df76bb7c6bb1_MD0001_00 This patient has developed a large-amplitude (ie, coarse) tremor that worsens as the hand approaches the target, suggesting a cerebellar tremor. Cerebellar tremor can result from multiple pathologies that affect the cerebellum, most commonly multiple sclerosis, as in this patient. Other common causes include stroke, fragile X syndrome, and cerebellar degeneration. Tremors due to cerebellar lesions are classically low frequency (ie, "slow," <5 Hz) and high amplitude (ie, coarse) because they involve the proximal, as well as the distal, muscles. The tremor classically increases in amplitude as an action approaches a target (ie, intention tremor). It is often accompanied by other cerebellar signs, including ataxia, dysmetria, and/or impaired rapidly alternating movements. (Choice A) Parkinson disease occurs due to loss of dopaminergic neurons in the basal ganglia (substantia nigra). In contrast to this patient, patients with Parkinson disease classically have a resting tremor that improves with intentional movement. In addition, tremor would be accompanied by rigidity (increased resistance to passive movements), bradykinesia (slowing of voluntary movements), and gait disturbances. (Choice C) The motor cortex controls voluntary muscle activity. Damage to this area causes a combination of spastic paralysis, clasp-knife rigidity, hyperreflexia, and pathologic reflexes but does not typically cause a rhythmic tremor. (Choice D) The premotor frontal cortex is responsible for the selection of movements in response to internal and external cues. A lesion affecting this part of the brain can result in abnormal posturing or repetitive movements but not an action tremor. (Choice E) Lesions affecting the thalamus typically result in contralateral hemiplegia or contralateral hemisensory loss rather than tremor. Educational objective: Cerebellar tremors are classically low frequency (<5 Hz) and high amplitude and increase as an action approaches a target. They are often accompanied by other cerebellar signs, including ataxia, dysmetria, and impaired rapidly alternating movements.

A 28-Year-Old Woman Comes to the Office Due to Right