Which maneuver assesses ulnar nerve function?

Which maneuver assesses ulnar nerve function?

• A. Extending wrist; Sensory: dorsum of hand
• B. Opposing thumb; Sensory: palm
• C. Abduct/Spread fingers against resistance; Sensory: little finger
• D. Flexing thumb; Sensory: tip of index finger

Answer: (C)

The key idea is that the ulnar nerve controls the intrinsic hand muscles that move the fingers together and apart—the interossei. Asking a patient to abduct (spread) or adduct their fingers against resistance directly tests those interossei muscles. If these movements are weak, it suggests ulnar nerve dysfunction; the accompanying sensation to the little finger further supports this distribution since the little finger is a classic area served by the ulnar nerve. By contrast, opposing the thumb primarily tests the median nerve because the thenar muscles responsible for thumb opposition are median-innervated; flexing the thumb also involves median nerve function, as does sensation at the tip of the index finger. Extending the wrist tests the radial nerve and its dorsal hand sensation.

The key idea is that the ulnar nerve controls the intrinsic hand muscles that move the fingers together and apart—the interossei. Asking a patient to abduct (spread) or adduct their fingers against resistance directly tests those interossei muscles. If these movements are weak, it suggests ulnar nerve dysfunction; the accompanying sensation to the little finger further supports this distribution since the little finger is a classic area served by the ulnar nerve.

By contrast, opposing the thumb primarily tests the median nerve because the thenar muscles responsible for thumb opposition are median-innervated; flexing the thumb also involves median nerve function, as does sensation at the tip of the index finger. Extending the wrist tests the radial nerve and its dorsal hand sensation.