Anterior Interosseous Syndrome

Excerpt

The anterior interosseous nerve (AIN) is the terminal motor branch of the median nerve. It branches from the median nerve in the proximal forearm between the two heads of the pronator teres muscle to run deep along the interosseous membrane. From proximal to distal, it innervates the flexor pollicus longus (FPL), the index and long fingers of the flexor digitorum profundus (FDP), and the pronator quadratus (PQ). AIN syndrome is an isolated palsy of these three muscles. It manifests mostly as pain in the forearm accompanied frequently by a characteristic weakness of the index and thumb finger pincer movement. Many cases of AIN syndrome arise secondary to transient neuritis, although nerve compression and trauma are known etiologies as well. Different explanations have been proposed as the etiology of the disease. Controversy still exists among upper extremity surgeons about it; nevertheless, the condition is considered a neuritis in most cases.

Parsonage and Turner first described the syndrome in 1948. Leslie Gordon Kiloh and Samuel Nevin defined it as an isolated lesion of the anterior interosseous nerve in 1952. Its old name was Kiloh-Nevin syndrome. Different methods of treatment with reasonable outcomes have been reported. Both surgical and medical interventions have been addressed with different timing and variable results.