Which clinical finding would favor pronator teres syndrome over anterior interosseous nerve entrapment?

Which clinical finding would favor pronator teres syndrome over anterior interosseous nerve entrapment?

• A. Paresthesias in the hand
• B. Pure motor deficit without sensory loss
• C. Weakness in fine motor tasks
• D. Thenar atrophy

Answer: (C)

The key distinction is sensory involvement versus pure motor loss. Pronator teres syndrome compresses the median nerve trunk near the elbow, so both motor and sensory fibers can be affected. That often presents with paresthesias or numbness in the median nerve distribution of the hand. Anterior interosseous nerve entrapment, on the other hand, is a motor-only problem because the anterior interosseous nerve supplies deep forearm muscles (like flexor pollicis longus and the flexors to the index/middle), with no sensory loss. Therefore, a finding of paresthesias in the hand would favor pronator teres syndrome, while a pure motor deficit without sensory loss would favor anterior interosseous nerve entrapment. Weakness in fine motor tasks and thenar atrophy are more characteristic of motor involvement limited to specific forearm or intrinsic hand muscles, respectively, and would align more with motor-only lesions or other median nerve pathology rather than distinguishing PT syndrome from AIN entrapment based on sensory symptoms.

The key distinction is sensory involvement versus pure motor loss. Pronator teres syndrome compresses the median nerve trunk near the elbow, so both motor and sensory fibers can be affected. That often presents with paresthesias or numbness in the median nerve distribution of the hand. Anterior interosseous nerve entrapment, on the other hand, is a motor-only problem because the anterior interosseous nerve supplies deep forearm muscles (like flexor pollicis longus and the flexors to the index/middle), with no sensory loss. Therefore, a finding of paresthesias in the hand would favor pronator teres syndrome, while a pure motor deficit without sensory loss would favor anterior interosseous nerve entrapment. Weakness in fine motor tasks and thenar atrophy are more characteristic of motor involvement limited to specific forearm or intrinsic hand muscles, respectively, and would align more with motor-only lesions or other median nerve pathology rather than distinguishing PT syndrome from AIN entrapment based on sensory symptoms.