Partial anterior interosseous nerve palsy: isolated neuropraxia of the branch to flexor pollicis longus.

Anterior interosseous nerve palsy is rare. Isolated neuropraxia of its branch to the flexor pollicis longus is even rarer. We present a case of a 24-year-old man who presented with weakness of his left thumb flexion after sustaining closed fracture of the proximal third of his left radius. On exploration, the anterior interosseous nerve and its branches was found to be intact as was the flexor pollicis longus. Electrophysiological studies demonstrated acute left anterior interosseous nerve neuropathy. Electromyography showed discrete motor unit at the flexor pollicis longus. Two months later the patient had full recovery of the flexor pollicis longus. We would like to highlight this rare occurrence and present a detailed history of this case to increase awareness amongst clinicians regarding this condition.