Cubital tunnel syndrome

Synonym: ulnar neuritis, ulnar neuropathy at the elbow

See the related separate article Ulnar nerve disorders.

What is cubital tunnel syndrome? ¹

Cubital tunnel syndrome arises from compression of the ulnar nerve. The ulnar nerve arises from the medial brachial plexus and innervates the muscles of the forearm and parts of the hand. ² It also carries sensory neurons supplying the skin of the back of the forearm, the palm and the ring and little fingers. Ulnar symptoms can arise from compression of the ulnar nerve at any point along its course, from the cervical nerve roots as they exit the spinal cord, the brachial plexus, the thoracic outlet, or further down the upper extremity in the arm, elbow, forearm, or wrist.³⁴ Cubital tunnel syndrome (CuTS) is defined as compression of the ulnar nerve at the elbow in the cubital tunnel. ²

• There are very few good studies looking at cubital tunnel syndrome.

• Cubital tunnel syndrome is the second most common peripheral nerve compression and the commonest cause of ulnar nerve compression. ²

• It is thought that it affects up to 5.9% of the population, compared with carpal tunnel syndrome which affects approximately 6.8%. ²

• It is more common in those with a lower level of education, thought to be related to the fact that cubital tunnel syndrome is more likely to occur in those with more physical jobs. ²

• 74% of documented cubital tunnel syndrome in the United States occurs in White people compared with 22% in Black and 3% in Hispanic.²

Symptoms and signs are due to pressure and/or traction causing irritation of the ulnar nerve at the elbow:

• Constricting fascial bands.

• Compromise under general anaesthetic.

• Subluxation of the ulnar nerve over the medial epicondyle.

• Cubitus valgus.

• Bony spurs.

• Joint deformity in osteoarthritis or rheumatoid arthritis: osteoarthritic or rheumatoid narrowing of the ulnar groove and constriction of the ulnar nerve as it passes behind the medial epicondyle.

• Associated with medial epicondylitis ('golfer's elbow').

• Tumours.

• Ganglia.

Other causes of ulnar nerve lesions at the elbow include:

• Fractures: friction of the ulnar nerve due to cubitus valgus (a possible sequel to childhood supracondylar fractures - 'tardy ulnar palsy') can cause fibrosis of the ulnar nerve and ulnar neuropathy.

• Elbow dislocation.

• Severe haematoma.

Risk factors for cubital tunnel syndrome include:²

• Smoking.

• Repetitive elbow pressure.

• Possibly male gender.

• Possibly increased BMI.

• Patients often have intermittent numbness and tingling along the little finger and ulnar half of the ring finger, often associated with a weakness of grip and particularly when the patient rests on, or flexes, the elbow.²

• Ulnar nerve palsy causes wasting and weakness of the small muscles of the hand and partial clawing of the ring and little finger.⁵

• Muscle wasting tends to be a later presentation in CuTS. ²

• Patients may experience pain and tenderness at the level of the cubital tunnel. The severity of pain is very variable and the distribution of pain may spread proximally and/or distally.

• Symptoms may be intermittent at first and then become more constant.

• Patients with chronic ulnar neuropathy may complain of loss of grip and pinch strength and loss of fine dexterity.

• Patients may also complain that their little finger gets caught when putting their hand in their pocket. This is due to slightly greater abduction as a result of loss of the adductor effect from interosseous muscle (Wartenberg's sign).

• Severe prolonged compression may present with intrinsic muscle wasting and clawing or abduction of the little finger.

Signs of cubital tunnel syndrome

• Examination may be normal in recent-onset, mild ulnar nerve palsy or show marked neurological abnormalities in prolonged severe ulnar nerve compression.

• Inspection for claw hand (hyperextension at the metacarpophalangeal joints and flexion of the interphalangeal joints; mainly little finger and ring finger) and wasting of the small muscles of the hand and hypothenar eminence. Adduction of the little finger may be impossible.

• Loss of sensation over the palmar and dorsal aspect of the little finger and the medial half of the ring finger.

• Palpate the cubital tunnel region to exclude mass lesions.

There is a positive Tinel sign over the cubital tunnel. Froment's sign is noted due to weakness of adductor pollicis muscle. Positive flexion sign at the elbow can also be seen. However flexion and Tinel signs have been noted to be falsely positive in up to 24% of cases.

• Tinel's sign to detect an irritated nerve:

• Tapping over the cubital tunnel causes pain, tingling, or shock-like sensation down the arm into the fingers.

• A positive Tinel's sign finding is typically present in cubital tunnel syndrome. However, Tinel's sign may be positive in asymptomatic people.

• Elbow flexion test:

  • Is a specific diagnostic test for cubital tunnel syndrome.

  • The patient flexes the elbow past 90°, supinating the forearm and extending the wrist for three minutes.

  • The result is positive if discomfort is reproduced or paraesthesia occurs or worsens within 60 seconds.

• Froment's sign:

  • The patient holds a piece of paper between both thumbs and the sides of the adjacent index fingers as the paper is pulled away.

  • A patient with an ulnar nerve palsy cannot activate the adductor pollicis. As a result, they will flex the affected thumb at the interphalangeal joint to try to keep hold of the paper.

• Other sites of ulnar nerve lesion - eg, Guyon's canal at the wrist. Causes of ulnar nerve lesions at the wrist include compression by tumour or ganglion, blunt trauma, fractures.

• Acute pressure-related nerve palsy after lying or leaning on the elbow.

• Other causes of neurological dysfunction along the C8-T1 distribution - eg, cervical spondylosis with cervical radiculopathy, brachial plexus damage, thoracic outlet syndrome, syringomyelia, Pancoast's tumour (apical lung cancer), and motor neurone disease.

• Carpal tunnel syndrome.

• Polyneuropathy - eg, diabetes, renal disease, multiple myeloma, amyloidosis, chronic alcoholism, malnutrition, leprosy.

• Nerve conduction studies are usually performed to confirm a clinical diagnosis though there can be false negative results.

• Ultrasound of the cubital tunnel has been shown to be of benefit in diagnosing the cause and site of ulnar neuropathy at the elbow. There is also a correlation between the stage of ulnar nerve palsy and the diameter of the major axis.⁵

• Both CT and MRI scan have been shown to be of benefit in diagnosis of ulnar nerve lesions at the elbow. ⁵

Conservative treatment

Conservative management includes physiotherapy, splinting, and analgesia.

There is no clear evidence for the method of physiotherapy used, although physiotherapy does appear to confer benefit. ⁶

Two prospective studies have shown benefit from elbow splinting with improvement in both symptoms and in ulnar nerve conduction at 1 month and at 6 months. There was no additional benefit from steroid injections. 88% of patients who underwent splinting, were still able to be managed non-surgically at 1 year. Symptoms and grip strength were improved at 1 year with 82% showing complete resolution of their nerve conduction studies. ²

However another study showed that there was no difference in improvement between night splinting, nerve gliding exercises and a control group. All groups showed similar improvements in symptoms and grip strength. ²

Surgical management

Surgical management is recommended where there are severe deficits or where the condition is refractory to conservative management. There are two usual surgical techniques: surgical transposition of the nerve or in situ decompression.

A recent large study demonstrated an 87% improvement rate from surgery with a 3% risk of complications and 2% risk of recurrence. In situ decompression showed the highest success rate and the lowest risks of complications and recurrence. ⁵

Another recent study showed evidence of increased risk of complications from endoscopic decompression but with lower rates of post-operative chronic pain. All surgical techniques showed benefit. ⁷

• Between 50 and 88% of people get better with conservative, non-surgical treatment.

• The outcome for those requiring surgery is also good with 88% responding well to surgery.