Question

Injury R upper extremity in 29 y/o M, difficulty holding pencil in R hand. Reflexes intact, weakness of opponens R thumb and adduction of 4th and 5th digits. Decreased sensation R 4th and 5th digits extending into palm of hand and ending at crease of wrist. Cause:

Answer 1

The symptoms suggest that there is damage to the ulnar nerve near the wrist or hand due to the weakness and sensory deficits localized to the areas innervated by this nerve.

Step-by-step explanation:

The symptoms described, including weakness of the opponens of the right thumb, adduction weakness of the 4th and 5th digits, and decreased sensation in the same area, are indicative of ulnar nerve damage at the wrist or hand.

This nerve innervates the muscles responsible for the movements and sensations that are deficient. The etiology may be a result of direct trauma/compression to the ulnar nerve or a fracture near the elbow or wrist where the ulnar nerve runs. It is important to also consider potential causes such as a Colles fracture (distal radius fracture) which commonly occurs after a fall onto an outstretched hand, as indicated by the provided information, although this typically affects the radial nerve rather than the ulnar nerve.

Conversely, a carpal tunnel syndrome primarily affects the median nerve and would not typically result in symptoms primarily involving the ulnar nerve distribution.