The anterior interosseous nerve syndrome is a compressive neuropathy of a motor branch of the median nerve, caused by tendinous bands (deep head of pronator teres, arcade of flexor superficialis, thickened lacertus fibrosus etc), trauma, enlarged bursae, tumors, anomalous muscles such as Gantser´s muscle or palmaris brevis.
On clinical examination, there is weakness or paralysis of the flexor pollicis longus, flexor digitorum profundus of the index finger, and the pronator quadratus muscles with a history of pain in the proximal forearm. The patients will assume a weakness of pinch or an unusual posture of pinch without sensory deficit because of loss of function of these muscles, hyperextending the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger.
We experienced two cases of anterior interosseous nerve syndrome with typical clinical manifestations, confirmed by electrodiagnostic studies.
In both cases causative anatomical structures were released through surgical exploration. A case was caused by a sharp edge of the flexor superficialis arcade, another case by the tendinous portion of deep head of pronator teres muscle and a thickened lacertus fibrosus.
Both cases revealed partial recoveries after postoperative 3 months.
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