Anterior interosseous syndrome
| Anterior interosseous syndrome | |
|---|---|
| Other names | Kiloh-Nevin syndrome I |
| Specialty | Neurology, hand surgery  |
Anterior interosseous syndrome is an idiopathic neuropathy of the anterior interosseous nerve (AIN), a distal motor and sensory branch of the median nerve. It is characterized by weakness of the pincer movement of the thumb and index finger, the flexor pollicis longus and the part of the flexor digitorum profundus innervated by the AIN specifically. There may be distal forearm and wrist pain (the terminal, sensory branch of the AIN innervates the bones of the carpal tunnel).
Most cases of AIN syndrome are now thought to be due to a transient neuritis. Other possibilities include compression of the AIN in the forearm. Trauma to the median nerve or around the proximal median nerve can cause AIN palsy.
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 concluded that there is no difference in outcome in surgically versus nonsurgically treated patients. The role of surgery in AIN syndrome remains controversial. Indications for considering surgery include a known space-occupying lesion that is compressing the nerve (a mass) or fascial compression, and persistent symptoms beyond 1 year.
Symptoms and signs
The findings are weakness in bending (flexion) the tips of the thumb and index finger.[1]
Clinical signs
In a pure lesion of the anterior interosseous nerve there is weakness of the long flexor muscle of the thumb (Flexor pollicis longus) and the deep flexor muscle of the index finger (Flexor digitorum profundus). Weakness of the flexor digitorum profundus to the long finger varies because it is connected to the ulnar nerve innervated ring and small finger flexor digitorum profundus.
Causes
Anterior interosseous nerve syndrome refers to idiopathic neuropathy. Palsies due to trauma such as pediatric supracondylar fractures or laceration from a penetrating injury are not considered anterior interosseous nerve syndrome.[2][3]
The etiology of idiopathic anterior interosseous nerve syndrome is speculative. Some posit fibrous bands or arcuate (curved) ligaments may compress the anterior interosseous nerve.[4][5]
The syndrome is often mistaken for index finger and/or thumb tendon laceration or rupture.[6]
Although there is still controversy among upper extremity surgeons, AIN syndrome is now regarded as an idiopathic neuropathy, possibly a neuritis (inflammation of the nerve) in most cases; this is also referred to as Parsonage–Turner syndrome. Although the exact etiology is unknown, it is hypothesized that this is associated with an immune-mediated response that can follow surgery or other illnesses, such as pneumonia or severe viral illness.
Anatomy
The anterior interosseous nerve is a branch of the median nerve that passes distally, anteriorly along the interosseous membrane and provides motor branches to the flexor pollicis longus, flexor digitorum profundus to index and middle finger as well as pronator quadratus, and supplies sensory feedback from the wrist bones.[7]
Diagnosis
Electrophysiologic testing can measure anterior interosseous neuropathy. Electromyography (EMG) measures abnormalities in the flexor pollicis longus, flexor digitorum profundus to the index and long fingers and the pronator quadratus muscles.[6][8]
Anterior interosseous nerve syndrome is straightforward to diagnose on examination. Elecrodiagnostic measurements and imaging such as MRI and ultrasound imaging are not necessary for diagnosis or treatment and their role is unclear.[9][10]
If asked to make the "OK" sign, patients will make a triangle sign instead. This 'pinch-test' exposes the weakness of the flexor pollicis longus muscle and the flexor digitorum profundus I leading to weakness of the flexion of the distal phalanges of the thumb and index finger. This results in impairment of the pincer movement and the patient will have difficulty picking up a small item, such as a coin, from a flat surface.[3][11]
Treatment
Most AIN neuropathy resolves over time without specific treatment, which is the preferred initial approach. The condition is not painful and there are no known disease-modifying treatments. Recovery often begins within the first several months and may continue up to one to two years after onset.[12] In a prospective multicenter study of spontaneous AIN palsy, about 80% of nonoperatively treated limbs achieved good recovery, and all limbs showing any improvement within six months went on to recover well.[13]
Surgery is generally reserved for neuropathy that does not improve after several months of conservative treatment, or where a specific compressive lesion is identified. Options include surgical exploration, neurolysis, and decompression, with good outcomes in selected patients.[12] Interfascicular neurolysis has been advised for cases showing no recovery by six months after onset.[13]
History
The syndrome was first described by Parsonage and Turner in 1948[14] and further defined as isolated lesion of the anterior interosseous nerve by Leslie Gordon Kiloh and Samuel Nevin in 1952.[15]
See also
References
- ↑ Sood, M. K.; Burke, F. D. (1997). "Anterior interosseous nerve palsy. A review of 16 cases". The Journal of Hand Surgery (European Volume). 22 (1): 64–68. doi:10.1016/s0266-7681(97)80020-4. PMID 9061529.
- ↑ Penkert, G.; Schwandt, D. (1980). "[A case of anterior interosseus nerve lesion (Kiloh-Nevin syndrome)]". Handchirurgie. 12 (1–2): 19–21. ISSN 0046-6794. PMID 7250795.
- 1 2 van der Wurff, Peter; Hagmeyer, Ruud H. M.; Rijnders, Willem (1984). "Case Study: Isolated Anterior Interosseous Nerve Paralysis: The Kiloh-Nevin Syndrome". Journal of Orthopaedic & Sports Physical Therapy. 6 (3): 178–180. doi:10.2519/jospt.1984.6.3.178. ISSN 0190-6011. PMID 18806369.
- ↑ Rask, M. R. (1979). "Anterior interosseous nerve entrapment: (Kiloh-Nevin syndrome) report of seven cases". Clinical Orthopaedics and Related Research (142): 176–181. doi:10.1097/00003086-197907000-00029. ISSN 0009-921X. PMID 498633.
- ↑ Knight, C. R.; Kozub, P. (July 1979). "Anterior interosseous syndrome". Annals of Plastic Surgery. 3 (1): 72–76. doi:10.1097/00000637-197907000-00011. ISSN 0148-7043. PMID 543635.
- 1 2 Rosenberg, J. N. (March 1990). "Anterior interosseous/median nerve latency ratio". Archives of Physical Medicine and Rehabilitation. 71 (3): 228–230. ISSN 0003-9993. PMID 2317141.
- ↑ Wertheimer, Alex; Kiel, John (2023-07-24), "Anatomy, Shoulder and Upper Limb, Forearm Anterior Interosseous Nerve", StatPearls [Internet], StatPearls Publishing, PMID 30335313, retrieved 2026-06-26
- ↑ Gessini, L.; Bove, L.; Jandolo, B.; Landucci, C.; Pietrangeli, A. (1980). "[Anterior interosseus nerve syndrome (Kiloh-Nevin) (author's transl)]". Rivista di Patologia Nervosa e Mentale. 101 (1): 1–11. ISSN 0035-6433. PMID 7244544.
- ↑ Roggenland, D.; Heyer, C. M.; Vorgerd, M.; Nicolas, V. (June 2008). "[Nervus interosseus anterior syndrome (Kiloh-Nevin syndrome)--diagnosis with MRI]". RoFo: Fortschritte Auf dem Gebiete der Rontgenstrahlen und der Nuklearmedizin. 180 (6): 561–562. doi:10.1055/s-2008-1027210. ISSN 1438-9029. PMID 18584776.
- ↑ Martinoli, Carlo; Bianchi, Stefano; Pugliese, Francesca; Bacigalupo, Lorenzo; Gauglio, Cristina; Valle, Maura; Derchi, Lorenzo E. (November 2004). "Sonography of entrapment neuropathies in the upper limb (wrist excluded)". Journal of Clinical Ultrasound. 32 (9): 438–450. doi:10.1002/jcu.20067. ISSN 0091-2751. PMID 15558622.
- ↑ Spinner, M. (April 1969). "The functional attitude of the hand afflicted with an anterior interosseous nerve paralysis". Bulletin of the Hospital for Joint Diseases. 30 (1): 21–22. PMID 5348010.
- 1 2 Akhondi, Hossein; Lui, Forshing; Varacallo, Matthew A. (2026), "Anterior Interosseous Syndrome", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID 30247831, retrieved 2026-07-18
- 1 2 Ochi, Kensuke; Tajiri, Yasuhito; Kurimoto, Shigeru; Kitamura, Yo; Tsuruta, Toshiyuki; Ikegami, Shota; Ikeda, Kazuo; Satake, Hiroshi; Nishiwaki, Masao; Hara, Yuki; Kato, Naoki; Shinomiya, Rikuo; Osada, Ryusuke; Tazaki, Kenichi; Okazaki, Masato (July 2025). "Clinical characteristics and results after conservative treatment or interfascicular neurolysis of 100 limbs with spontaneous anterior interosseous nerve palsy: A prospective Japanese multicenter study". Journal of Orthopaedic Science. 30 (4): 605–613. doi:10.1016/j.jos.2024.10.009. PMID 39578131.
- ↑ Parsonage, M. J.; Turner, J. W. A. (1948-06-26). "Neuralgic amyotrophy; the shoulder-girdle syndrome". Lancet. 1 (6513): 973–978. doi:10.1016/s0140-6736(48)90611-4. ISSN 0140-6736. PMID 18866299.
- ↑ Kiloh, L. G.; Nevin, S. (1952-04-19). "Isolated neuritis of the anterior interosseous nerve". British Medical Journal. 1 (4763): 850–851. doi:10.1136/bmj.1.4763.850. ISSN 0007-1447. PMC 2023229. PMID 14916168.