How to Diagnose Anterior Interosseous Nerve Syndrome

The interosseous nerve branches off of the median nerve about 6 cm below the elbow and runs along the interosseous membrane. It supplies motor function to the flexor policis longus, pronator quadratus muscles and part of the flexor digitorum profundus. Anterior interosseous nerve syndrome occurs when this nerve becomes entrapped or compressed against other anatomical structures. The following steps will show how to diagnose anterior interosseous nerve syndrome.

Instructions

• 1

  Obtain the presenting symptoms. This commonly includes general pain in the proximal forearm and weakness of the flexor digitorum profundus and flexor policis longus of the index finger.

• 2

  Reproduce the symptoms with the aid of a hand therapist. Once a nerve compression is suspected, the patient will typically perform a series of arm and hand maneuvers to determine the specific nerve being affected. Other tests also should be performed to determine any losses in sensation or strength.

• 3

  Instruct the patient to form a circle with his thumb and forefinger. The inability to hyperextend the distal interphalangeal joint of the index finger and thumb is characteristic of anterior interosseous nerve syndrome.

• 4

  Perform electrodiagnostic studies such as electromyograms and nerve conduction studies as the standard diagnostic technique for neuropathic conditions. These tests are highly operator-dependent but nevertheless useful for isolating the compression site.

• 5

  Determine the cause of anterior interosseous nerve syndrome. Like most types of nerve compression, anterior interosseous nerve syndrome has a wide range of compression sources including abnormal arterial branches, accessory muscles, a deep head of the pronator teres, tendinous bands and fractures.