Anterior Interosseous Syndrome: A Case Study in a Seventy-one-Year-Old Women with Multiple Nerve compressions

Background: Anterior interosseous nerve (AIN) syndrome is rare and accounts for less than 1% of all upper extremity neuropathies. AIN syndrome can be due to trauma, compression of the nerve, or neuritis.Case Information: A 71-year-old woman presented with numbness and tingling in the right thumb, index, middle and part of the ring finger. She had difficulty flexing her index finger and thumb. Nerve study demonstrated carpal tunnel syndrome, and right ulnar nerve dysfunction without motor involvement. On exam, there was thenar atrophy and tenderness over the proximal median nerve. She had a positive Tinel's and Phalen sign of the wrist; and positive Tinel's sign in the proximal border of the pronator teres and the ulnar nerve at the cubital tunnel. She had 0/5 strength in the flexor pollicis longus and flexor digitorum profundus of the index finger, and weakness with flexor digitorum superficialis flexion. She was not able to make an O sign. During surgery, an ulnar nerve decompression and carpal tunnel release were performed. During the proximal median nerve release, an anomalous intramuscular tendon near the early portion of the AIN nerve was found and divided.Conclusion: In the elbow and the forearm, the median nerve can be compressed by the lacertus fibrosus, heads of the pronator muscle, and anomalous structures such as the ligament of Struthers and Gantzer muscle. Patients will present with only motor weakness and will not be able to flex their interphalangeal joint of the thumb and distal interphalangeal joint of the index finger.