Anterior interosseous syndrome

Anterior interosseous syndrome
Classification and external resources
ICD-10	G56.0, G56.1
ICD-9	354.0, 354.1

Anterior interosseous syndrome or Kiloh-Nevin syndrome I is a medical condition in which damage to the anterior interosseous nerve, 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 Kiloh-Nevin syndrome are due to compression of the nerve as a result of trauma at the elbow, often associated with haemorrhage into the deep musculature.

Surgical decompression is effective at relieving symptoms and preventing ongoing nerve damage.

Contents 1 History 2 Anatomy 3 Symptoms 4 Clinical signs 5 Causes 6 Diagnosis 7 Treatment 8 References

History

The syndrome was first described by Parsonage and Turner in 1948⁠^[1] and further defined as isolated lesion of the anterior interosseous nerve by Leslie Gordon Kiloh and Samuel Nevin in 1952.^[2]

Anatomy

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, index and middle finger.

Symptoms

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.^[3]
⁠ The characteristic impairment of the pincer movement of the thumb and index finger is most striking.

Clinical signs

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.^[4][5]

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.⁠⁠⁠^[6][7]

There is little sensory deficit since the anterior interosseous nerve has no cutaneous branch.

Causes

Injuries of the forearm with compression of the nerve is the most common cause: examples include supracondylar fractures, often associated with haemorrhage into the deep musculature; injury secondary to open reduction of a forearm fracture; or dislocation of the elbow.⁠⁠^[8][9]

Direct trauma from a penetrating injury such as a stab wound is a common cause in less civilised countries.

Fibrous bands or arcuate ligaments may entrap the median as well as the anterior interosseous nerves, in which case a patient may experience numbness as well as pain.⁠⁠^[3][10]

Rheumatoid disease and gouty arthritis may be a predisposing factor in anterior interosseous nerve entrapment.

Very similar syndromes can be caused by more proximal lesions, such as brachial plexus neuritis.⁠^[11]

Anterior interosseous nerve entrapment or compression injury remains a difficult clinical diagnosis because it is mainly a motor nerve and the syndrome is often mistaken for finger ligamentous injury.⁠^[12]

Diagnosis

Electrophysiologic testing is an essential part of the evaluation of Anterior interosseous nerve syndromes. Nerve conduction studies may be normal or show pronator quadratus latency.⁠⁠^[13] Electromyography (EMG) is generally most useful and will reveal abnormalities in the flexor pollicis longus, flexor digitorum profundus I and II and pronator quadratus muscles.⁠⁠^[4][14]

The role or MRI and ultrasound imaging in the diagnosis of Kiloh-Nevin syndrome is unclear.⁠^[15][16]

Treatment

Surgical decompression can give excellent results if the clinical picture and the EMG suggest a compression neuropathy.^[17][18][19] In brachial plexus neuritis, conservative management may be more appropriate.^[11] Spontaneous recovery has been reported, but is said to be delayed and incomplete.^[20][21]

There is a role for physiotherapy and this should be directed specifically towards the pattern of pain and symptoms. Soft tissue massage, stretches and exercises to directly mobilise the nerve tissue may be used.⁠^[22]

References

Nervous system pathology, PNS, somatic (G50–G64, 350–357)   Nerve, nerve root, plexus Cranial nerve disease V (Trigeminal neuralgia, Anesthesia dolorosa) · VII (Facial nerve paralysis, Bell's palsy, Melkersson–Rosenthal syndrome, Parry–Romberg syndrome, Central seven) · XI (Accessory nerve disorder) Radiculopathy, plexopathy brachial plexus (Brachial plexus lesion, Thoracic outlet syndrome) · Phantom limb Mono- neuropathy Upper limb median nerve (Carpal tunnel syndrome, Ape hand deformity) ulnar nerve (Ulnar nerve entrapment, Froment's sign, Guyon's canal syndrome, Ulnar claw) radial nerve (Radial neuropathy, Wrist drop, Cheiralgia paresthetica) long thoracic nerve (Winged scapula) Lower limb lateral cutaneous nerve of thigh (Meralgia paraesthetica) tibial nerve (Tarsal tunnel syndrome) plantar nerve (Morton's neuroma) superior gluteal nerve (Trendelenburg's sign) sciatic nerve (Piriformis syndrome) General Causalgia · Mononeuritis multiplex · Neuropathy (Neuralgia/Neuritis) · Nerve compression syndrome   Polyneuropathies/Polyradiculoneuropathy HMSN Charcot–Marie–Tooth disease · Dejerine–Sottas disease · Refsum's disease · Hereditary spastic paraplegia Autoimmune/demyelinating Guillain–Barré syndrome · Chronic inflammatory demyelinating polyneuropathy Other Alcoholic polyneuropathy M: PNS anat(h/r/t/c/b/l/s/a)/phys(r)/devp/prot/nttr/nttm/ntrp noco/auto/cong/tumr, sysi/epon, injr proc, drug(N1B)