We present a case which was partial median nerve lesion at supracondylar level of humerus that mimicks anterior interosseous syndrome clinically. The lesion was caused by blunt trauma of right arm due to traffic accident 6 months before the examination. It is characterized by weakness of muscles innervated by the anterior interosseous nerve branch of the median nerve as well as other more proximal median nerve innervated muscles, namely, the pronator teres, flexor carpi radialis and flexor digitorum sublimis. But other median nerve innervated distal hand muscles were not involved. Sensibility was intact, Electrodiagnostic study revealed fibrillation potentials and positive sharp waves at rest and absent of reduced recruitment patterns in muscles above mentioned. Routine sensory and motor conduction velocity of upper extremities was within normal limits, except a half amplitude of compound muscle action potential of anterior interosseous nerve picked up at pronator quadratus compared to left side.

We hypothesized neurotopographically this partial median nerve lesion is at supracondylar level, especially posterior portion of the nerve trunk, which contains the bundles to from the anterior interosseous nerve and branches of superficial flexor muscle group at elbow level, It will be discussed along with internal topographic illustrations.