Test your medicine knowledge with the MKSAP challenge, in partnership with the American College of Physicians.

A 54-year-old man is seen for follow-up evaluation of a tremor in his upper extremities that has been present since age 20 years. The tremor was mild for many years and did not interfere with his work but has become more prominent in recent years. He has difficulty writing and using utensils during meals. He has no associated slowness, stiffness, or change in gait. The patient started a trial of propranolol, which provided better control of the tremor, but after a few months, the tremor again worsened. He has subsequently been taking clonazepam without significant relief of symptoms. Alcohol, which the patient uses infrequently, temporarily diminishes the tremor. He also has kidney stones and glaucoma. His father and two sisters have a similar tremor.

On physical examination, vital signs are normal. A persistent large-amplitude tremor of the upper extremities is noted when the patient holds his arms in an outstretched position and during finger-to-nose testing. The tremor is bilateral and absent at rest. Tandem gait cannot be performed, but gait is otherwise normal.

Which of the following is the most appropriate next step in treating this patient’s tremor?

A: Botulinum toxin
B: Deep brain stimulation
C: Levodopa
D: Primidone
E: Topiramate

MKSAP Answer and Critique

The correct answer is D: Primidone.

This patient should begin a trial of primidone for his worsening essential tremor. His long history of a bilateral action tremor, family history of tremor, and ethanol responsiveness are consistent with familial essential tremor. Although the severity of this type of tremor remains stable over a lifetime in most patients, a few experience tremor progression that can become disabling. Primidone and propranolol are FDA-approved first-line treatments of essential tremor. Because propranolol has already been administered without lasting relief, a trial of primidone is warranted.

Botulinum toxin injections can be effective in patients with essential tremor of the voice and head, but its benefit is more limited in the limbs because of the adverse effect of weakness. In this patient, primidone should be initiated first.

In patients with severe medication-refractory essential tremor, deep brain stimulation (DBS) of the thalamus is most likely to maximize tremor control. However, this option should be reserved for those who have not responded to medical therapy or have a marked disabling tremor. In this subset of patients, DBS has the potential to provide significant tremor control beyond that offered by the best medical therapy. DBS is premature for this patient who has not yet had a trial of primidone.

This patient does not have features of Parkinson disease, such as a tremor at rest. Therefore, levodopa therapy is not indicated.

Topiramate is a second-line treatment of essential tremor but is contraindicated in a patient with a history of kidney stones and glaucoma.

Key Point

• In patients with essential tremor, propranolol and primidone are FDA approved first-line therapies.

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