A 60-year-old man develops a tremor in his fingers. The tremor is most pronounced when he reaches for his coffee cup or points to an object. Which of the following components of the motor system is most likely to be involved?
Basal ganglia
Cerebellar hemisphere
Cerebellar vermis
Frontal eye field
Motor nucleus of the thalamus
Correct answer
Cerebellar hemisphere
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correct answer: B
The tremor described in the question stem is an intention tremor since it is most obvious as the patient’s hand moves closer to his target (i.e. his coffee cup), and is not present while at rest. Intention tremors are common in essential tremor, intoxication, multiple sclerosis. They are a sign of cerebellar dysfunction. The cerebellum is split into the vermis and hemispheres. The cerebellar hemisphere (B) regulates the coordination of the ipsilateral extremities and therefore would be involved in an intention tremor. The cerebellar vermis © regulates the trunk and midline structures and its dysfunction would cause ataxia (balance problems).
Basal ganglia (A) involvement would cause rest tremor like those seen in Parkinson’s. Frontal eye field (D) would cause vision problems but not a tremor.
Motor nucleus of the thalamus (E) would most likely cause strength deficits, but not a tremor.