Less Common Compressive Neuropathies

Overview

The most common nerve compression problems of the upper limb are carpal tunnel syndrome (median nerve at the wrist) and cubital tunnel syndrome (ulnar nerve at the elbow). Those conditions have their own pages. This page covers a handful of less common syndromes that can look similar but arise from different places — and need different treatments.

If you have been treated for carpal tunnel or cubital tunnel and your symptoms did not improve, one of these syndromes may be the reason.

Pronator syndrome (median nerve at the elbow)

Compression of the median nerve as it passes under the pronator teres muscle in the forearm. Unlike carpal tunnel syndrome, the symptoms involve the forearm as well as the hand.

• Symptoms: forearm aching, a "fullness" feeling in the forearm, numbness in the thumb and index finger, weakness of thumb-to-index pinch. Unlike carpal tunnel, there is usually no night-time waking with numbness.
• Exam: tenderness in the forearm over the pronator muscle, symptoms reproduced by resisted forearm pronation or by resisted finger flexion.
• Tests: EMG / nerve conduction studies can be normal even when the diagnosis is correct, because the compression is often intermittent.
• Treatment: activity modification, physical therapy, and splinting first. Surgical release of the pronator teres and related structures is considered when symptoms persist.

Anterior interosseous nerve (AIN) syndrome

Compression of a pure motor branch of the median nerve that supplies the muscles that bend the tip of the thumb and the tip of the index finger.

• Symptoms: inability to make the "OK" sign because the thumb and index fingertips cannot bend to touch each other. There is no numbness because the AIN carries no sensory fibers.
• Differential: spontaneous AIN palsy (so-called Parsonage-Turner syndrome) is an inflammatory condition that can look identical. Distinguishing between compression and inflammation changes the treatment.
• Tests: EMG, MRI of the shoulder and arm. A careful history often reveals a preceding viral illness or vaccination in Parsonage-Turner.
• Treatment: Parsonage-Turner is treated conservatively and usually recovers over 6 to 18 months. True compression of the AIN by a mass or tight tissue band is treated with surgical release.

Posterior interosseous nerve (PIN) syndrome

Compression of a pure motor branch of the radial nerve as it passes through the supinator muscle in the forearm. It supplies the muscles that straighten the fingers and thumb.

• Symptoms: progressive inability to straighten the fingers and thumb at the big knuckles. The wrist can still be extended because the main radial nerve branches to the wrist extensors before the PIN takes off. Patients often say "my fingers droop."
• Differential: a ruptured extensor tendon (particularly in rheumatoid arthritis) can look identical. The tenodesis test (passively bending and extending the wrist) helps distinguish the two.
• Tests: EMG, MRI to look for a mass or lipoma in the supinator area.
• Treatment: observation if the cause is unclear and sudden (possible inflammatory process). Surgical decompression is indicated when there is a space-occupying lesion or when recovery is not happening on its own.

Wartenberg's syndrome (superficial radial nerve)

Compression or irritation of the superficial radial nerve on the back of the wrist and thumb. The most common cause is a tight watchband, handcuffs, or a tight splint.

• Symptoms: burning pain, tingling, and numbness on the back of the thumb and the web space between the thumb and index finger. No weakness.
• Differential: de Quervain's tenosynovitis can produce pain in the same area and is much more common.
• Exam: a Tinel sign (tingling reproduced by tapping over the nerve) on the back of the forearm just above the wrist.
• Treatment: remove the offending source of pressure (watchband, tight bracelet, splint), brace the forearm in a neutral position, avoid forceful pronation. Nerve-pain medications (gabapentin, topical lidocaine) can help. Surgical decompression is reserved for refractory cases.

How these are diagnosed

• Exam. The distribution of numbness, the pattern of weakness, the specific tenderness, and provocative tests each point toward a specific syndrome.
• EMG / nerve conduction studies. Useful but not always positive in these syndromes, particularly pronator and Wartenberg's.
• Ultrasound or MRI. Can identify a compressing mass, thickened fibrous bands, or nerve swelling.

Treatment options

Non-surgical treatment

• Activity modification and ergonomic changes
• Bracing in a neutral position
• Physical therapy with nerve gliding exercises
• Anti-inflammatories
• Nerve-pain medications for burning or tingling
• Targeted corticosteroid injections in selected cases

Surgical treatment

Surgical decompression releases the specific tissue that is compressing the nerve — the pronator teres in pronator syndrome, the arcade of Frohse in PIN syndrome, tight fascia in AIN compression, or the brachioradialis tendon in Wartenberg's. These are outpatient procedures. Nerve recovery after decompression typically takes weeks to months, and is more complete the earlier the compression is released.

What to expect at your visit

Dr. Barrera will take a detailed history, examine the arm systematically, and order EMG or imaging when indicated. Because these syndromes are less common than carpal or cubital tunnel, the evaluation is often also focused on ruling out mimics — a disc problem in the neck, an inflammatory neuropathy like Parsonage-Turner, or a tendon rupture.

Related

Carpal tunnel syndrome · Cubital tunnel syndrome · Nerve injury

Questions?

Call your office location for non-urgent questions:

• NYU Langone Laurelton · 646-501-4950
• NYU Orthopedic, Woodside · 929-429-3222
• NYU Orthopedic, Richmond Hill · 718-206-6923
• Jamaica Hospital Ambulatory Care Center (ACC) · 718-301-0720

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