Cubital Tunnel Syndrome

Synonym: ulnar neuritis

See related record Ulnar Nerve Disorders.

The ulnar nerve arises from the medial brachial plexus and innervates the muscles of both the forearm and parts of the hand. It also carries sensory neurones supplying the skin of the back of the forearm, the palm and the fourth and little fingers. Most damage to the ulnar nerve occurs at the elbow where it passes through the cubital tunnel.¹ The ulnar nerve may also be damaged:

• At the wrist: due to pressure in Guyon's canal from a deep ganglion, tumour or laceration.
• In the hand: due to compression of the deep motor branch against the pisiform and hamate, such as with prolonged pressure over the outer palm, e.g. motorcyclists and using vibrating drills.

• The elbow is the most common site of compression of the ulnar nerve.
• Cubital tunnel syndrome is the second most common compressive neuropathy (after carpal tunnel syndrome).
• Cubital tunnel syndrome affects men more often than women.

• Causes of cubital tunnel syndrome include:
  • 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
  • Direct compression, e.g. habitual leaning on elbows
  • Repetitive elbow flexion and extension, heavy manual work, frequently playing guitar
• 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
  • Venepuncture
  • Severe haematoma

• Ulnar nerve palsy causes wasting and weakness of the small muscles of the hand and partial clawing of the ring and little finger.
• The extent of the deformity and disability depends on the site of the lesion.
• Patients often have 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.
• 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.
• Severe prolonged compression may present with intrinsic muscle wasting and clawing or abduction of the little finger.

Signs

• 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.
• 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.
• Tinel sign:
  • Tapping over the cubital tunnel causes pain, tingling or shock-like sensation down the arm into the fingers.
  • A positive Tinel sign finding is typically present in cubital tunnel syndrome. However the Tinel sign may be positive in asymptomatic people.
• The elbow flexion test:
  • Is the most diagnostic test for cubital tunnel syndrome.
  • The patient flexes the elbow past 90 degrees, supinating the forearm, and extending the wrist.
  • Result is if discomfort is reproduced or paraesthesia occurs within 60 seconds.
  • The addition of shoulder abduction may enhance the sensitivity of the test.
• Froment's sign:
  • The patient holds a piece of paper between the thumb and the side of the adjacent index finger as the paper is pulled away.
  • A patient with an ulnar nerve palsy will flex the thumb at the interphalangeal joint to try to keep hold of the paper.

• Other sites of ulnar nerve lesion, e.g. the Guyon canal at the wrist. Causes of ulnar nerve lesions at the wrist include compression by tumour or ganglion, blunt trauma, fractures.
• Other causes of neurological dysfunction along the C8-T1 distribution, e.g. cervical spondylosis with cervical radiculopathy, brachial plexus damage, thoracic outlet syndrome, syringomyelia, Pancoast tumour (apical lung cancer).
• Carpal tunnel syndrome.
• Polyneuropathy, e.g. diabetes, renal disease, multiple myeloma, amyloidosis, chronic alcoholism, malnutrition, leprosy.

Relevant blood tests regarding other causes of neuropathy, e.g. fasting glucose for diabetes.
• Elbow x-rays: evidence of arthritis, trauma.
• Other x-rays: e.g. chest x-ray for Pancoast tumour, neck x-ray for evidence cervical spondylosis.
• Nerve conduction studies will confirm the site of the lesion.³
• Ultrasound of cubital tunnel: there is a correlation between the stage of ulnar nerve palsy and the diameter of the major axis.⁴
• MRI scan is sensitive and specific for diagnosis of ulnar nerve lesions at the elbow.⁵

Management includes physiotherapy, splinting, non-steroidal anti-inflammatory drugs, surgical transposition of the nerve, and surgical decompression for cubital tunnel syndrome. The treatment depends on the site and severity of the lesion:

• Avoidance of aggravating factors such as full elbow flexion and pressure on the elbow may be sufficient in mild cases.
• Decompression of the nerve may be necessary in more severe cases.
• It may be necessary to transfer the nerve to the front of the medial epicondyle.
• Recovery may be slow and incomplete; often the symptoms are temporarily exacerbated.

• Prolonged compromise to the nerve can lead to complete loss of function.
• More pronounced ulnar nerve thickening at the time of the diagnosis is associated with poor outcome at follow-up, especially in conservatively treated cases.⁶
• Conduction study signs of demyelination on testing usually indicate a favourable outcome.⁶