Anterior interosseous syndrome
| Anterior interosseous syndrome | |
|---|---|
| Classification and external resources | |
| Specialty | neurology |
| ICD-10 | G56.0, G56.1 |
| ICD-9-CM | 354.0, 354.1 |
Anterior interosseous syndrome or Kiloh-Nevin syndrome I is a medical condition in which damage to the anterior interosseous nerve (AIN), a motor branch of the median nerve, causes pain in the forearm and a characteristic weakness of the pincer movement of the thumb and index finger.
Most cases of AIN syndrome are due to a transient neuritis, although compression of the AIN can happen. Trauma to the median nerve have also been reported as a cause of AIN syndrome.
Although there is still controversy among upper extremity surgeons, AIN syndrome is now regarded as a neuritis (inflammation of the nerve) in most cases; this is similar to Parsonage–Turner syndrome. Although the exact etiology is unknown, there is evidence that it is caused by an immune mediated response.
Studies are limited, and no randomized controlled trials have been performed regarding the treatment of AIN syndrome. While the natural history of AIN syndrome is not fully understood, studies following patients who have been treated without surgery show that symptoms can resolve starting as late as one year after onset. Other retrospective studies have shown that there is no difference in outcome in surgically versus nonsurgically treated patients. Surgical decompression is rarely indicated in AIN syndrome. Indications for considering surgery include a known space-occupying lesion that is compressing the nerve (a mass) and persistent symptoms beyond 1 year of conservative treatment.
The syndrome was first described by Parsonage and Turner in 1948 and further defined as isolated lesion of the anterior interosseous nerve by Leslie Gordon Kiloh and Samuel Nevin in 1952.
The anterior interosseous nerve is a motor branch of the median nerve, which arises just below the elbow. It passes distally in the anterior interosseous membrane and innervates the long flexor muscles of the thumb (FPL), index and middle finger (FDP).
Most patients experience poorly localised pain in the forearm. The pain is sometimes referred into the cubital fossa and elbow pain has been reported as being a primary complaint.
The characteristic impairment of the pincer movement of the thumb and index finger is most striking.
In a pure lesion of the anterior interosseous nerve there may be weakness of the long flexor muscle of the thumb (Flexor pollicis longus), the deep flexor muscles of the index and middle fingers (Flexor digitorum profundus I & II), and the pronator quadratus muscle.
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