Anterior Interosseous Syndrome

Median nerve

Anterior Interosseous Syndrome is an entrapment neuropathy of the anterior interosseous nerve - a branch of the Median nerve. This nerve branches off from the median nerve, just above the inner elbow.

It travels down the forearm and supplies the Flexor Digitorum Profundus, Flexor Pollicis Longus and Pronator Quadratus muscles.

Symptoms

    • Difficulty moving or weakness in the index and middle fingers.
    • Difficulty bending the last joint of the thumb, as well as the index and middle fingers.
    • Pain in the upper forearm, sometimes even as high as the elbow.
    • When pinching with the index finger and thumb, normally a circle is formed. when the AI nerve is compressed, the final joints in the thumb and index fingers are straight rather than bent.

Causes

This nerve can be compressed within the forearm by a number of structures, or for a number of reasons. For example:

  • An enlarged biceps tendon bursa.

Treatment

  • Initial conservative treatment of rest, splinting and anti-inflammatory medications.
  • Corticosteroid or nerve block injections may be used.
  • Surgery to release the nerve is sometimes used if conservative treatment fails.