Which test involves extending the arms forward with palms up, keeping them out with eyes closed, and briskly tapping the arms downward to assess subtle drift?

• A. Romberg test
• B. Pronator drift
• C. Babinski sign
• D. Tandem gait

Answer: (B)

This test checks for subtle upper motor neuron weakness by looking for a drift and pronation of the forearm when the arms are extended. Have the patient hold both arms straight out with palms facing up and eyes closed. A normal person maintains the position, but if there’s mild corticospinal tract weakness on one side, the arm will begin to drift downward and pronate after you tap the wrists. The tapping disrupts the steady hold and reveals the involuntary drift that isn’t obvious with a regular strength exam. The presence of this pronator drift points to a central motor pathway issue, often from a mild UMN lesion such as a small stroke or other corticospinal tract involvement.

This is different from the Romberg test, which evaluates proprioception and vestibular function by having a person stand with feet together and eyes closed. It’s also different from the Babinski sign, which looks at the plantar reflex, and from tandem gait, which tests balance and coordination.