Anterior Interosseous Syndrome

Anterior Interosseous Syndrome

Jarrod Yamanaka, MD


  • The anterior interosseous nerve (AIN) is a motor branch of the median nerve that innervates the pronator quadratus, flexor pollicis longus, and flexor digitorum profundus serving the index finger.

  • Anterior interosseous syndrome (AIS) is a “catch-all” term for neuropathies that result in paralysis of these muscles secondary to several causes.

  • Overall AIS is a rare condition with a paucity of research (1).


The most frequent causes of AIS are direct traumatic nerve damage and external compression. Insidious onset of the condition thought to be a transient neuritis (1):

  • Traumatic causes:

    • Penetrating trauma

    • Blunt injury

    • Traction injury

    • Chronic vibration (cyclists)

    • Fracture

    • Surgery

    • Venipuncture

    • Injection

    • Cast pressure

  • External compression:

    • Bulky, tendinous origin of the deep head of the pronator teres

    • Soft tissue mass such as lipoma, ganglion, or tumor

    • Accessory muscle

    • Fibrous band originating from the superficial flexor

    • Vascular abnormality

Mar 14, 2020 | Posted by in SPORT MEDICINE | Comments Off on Anterior Interosseous Syndrome
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