A physician notes weakness of a patient's thumb in extension, although rotation, flexion, abduction, adduction, and opposition are normal. Which of the following nerves is most likely involved?: (A) Median and radial, (B) Median and ulnar, (C) Median only, (D) Radial only
Answer is D. All three of the nerves listed innervate muscles that supply the thumb. Extension is provided by the extensors pollicis longus and brevis, which are innervated by the radial nerve. Ref: Maheshwari 6e pg 63,65.