Cubital Tunnel Syndrome

Etiology

Multiple etiologies can result in ulnar nerve compression at the cubital tunnel and cause symptoms such as tingling along the medial aspect of the forearm, the little finger, and the medial aspect of the ring finger.

• Pressure on the ulnar nerve is a common cause of symptoms. The ulnar nerve is quite superficial at the point of the medial epicondyle; this is why people may experience the feeling of shooting pain and electric shock in the forearm if they accidentally hit their elbow on a hard surface.
• Stretching the ulnar nerve can also result in similar symptoms. The ulnar nerve lies behind the medial epicondyle. During flexion of the elbow joint, the ulnar nerve gets stretched because of this anatomical position. Repetitive elbow flexion and extension can cause further damage and irritation to the ulnar nerve. Some individuals sleep with elbows bent which can stretch the ulnar nerve for an extended period during sleep, which is an identified cause of irritation to the ulnar nerve.
• Injuries to the elbow joint (fractures, dislocations, swelling, effusions) can cause anatomical damage which will cause symptoms because of compression/irritation of the ulnar nerve.

A study of 117 patients identified that direct pressure on the nerve because of habits while sitting, or secondary to occupational activities is a significant cause of nerve damage as the nerve passes posterior to the medial epicondyle.[1]

Epidemiology

Ulnar nerve neuropathy is the second most common compression neuropathy of the arm, following carpal tunnel syndrome. A study of 91 patients identified that close to 60% of these patients had anatomical changes in the cubital tunnel that caused the ulnar nerve neuropathy, of which nearly 20% of patients had a subluxation of the ulnar nerve. Other causes identified in this study were osteophytes in almost 7% of patients and luxation of the ulnar nerve in nearly 10% of patients. Post-traumatic lesions also can cause symptoms in about 3.3% of patients.[2]

Pathophysiology

The exact pathophysiology of cubital tunnel syndrome is unknown. There has been some association with smoking.[3] Males are more often affected than females and the left side is more often affected.[4]

History and Physical

The presenting complaint is typically one of "pins and needles" in the forearm and the hand. On further questioning of the precise nature of the patient's complaint, the tingling sensation usually is present along the little finger and medial half of the ring finger. The symptoms are generally aggravated with elbow flexion. These symptoms may be present transiently initially then gradually get worse. On examination, findings may include a reduced or complete loss of sensation on the palmar and dorsal sides of the little finger and the medial part of the ring finger in advanced cases.[5][6] Tinel's sign may be positive along the cubital tunnel. Provocative tests like sustained elbow flexion for one minute or compression of the ulnar nerve at the cubital tunnel region may also be positive, causing paresthesia along with the distribution of the ulnar nerve, but the diagnostic value of these tests are poor.[7] In some cases, the ulnar nerve may be subluxated over the medial epicondyle with elbow flexion.

Motor symptoms are less common and usually manifest in severe cases of ulnar neuropathy. Patients may complain of weakness in the hand and frequent dropping of objects. On examination, findings could range from mild weakness of the interosseous muscles to severe atrophy of the hand intrinsics and weakness of the handgrip. Froment's sign can be positive, indicating weakness of adductor pollicis, which is supplied by the ulnar nerve. Ulnar claw hand is unlikely in cubital tunnel syndrome because the flexor digitorum profundus to the ring and little fingers also is denervated.

Evaluation

Thorough knowledge of the motor and sensory distribution of the ulnar nerve is critical in evaluating patients with ulnar neuropathy. Diagnosis can be made clinically, and nerve conduction studies are often used to mainly confirm the diagnosis. In some patients, however, nerve conduction may be normal in the early stages of symptoms; therefore, interpretation of nerve conduction studies should always be in a clinical context.

X-ray of the elbow joint can be done to exclude bony pathologies such as osteophytes and old fractures which may cause compression of the nerve.[8]

Both ultrasonic scanning (USS) and magnetic resonance imaging (MRI) have sensitivity and specificity over 80% in diagnosis. MRI and USS are also helpful to identify other causes of compression, which may not be picked up on plain radiograph films such as soft tissue swelling and lesions such as neuroma, ganglions, aneurysms, etc.[9]

Treatment / Management

Pathological findings should undergo careful evaluation when deciding on treatment options. Patients can often benefit from non-surgical interventions; therefore, the clinician should evaluate and determine an end goal with the patient for treatment before deciding on the route of treatment.

Non-surgical Treatment

• If the symptoms are purely the result of mechanical factors such as leaning over the desk at work with weight on the elbows or sleeping with bent elbows, then correcting these postures that provoke ulnar neuropathy can be the mainstay of treatment.
• In an Italian study, Padua et al. followed up 24 patients who had willingly declined surgery after the initial diagnosis. About half of these patients reported improvement in their symptoms during their follow-up appointments. Their further nerve conduction studies also showed an improvement, which further supports the evidence that patients with mild symptoms can be managed without surgical interventions.[10]
• Splinting at night time to keep the elbows straight has been suggested in published papers as an initial management option in patients with mild symptoms.[6]
• Simple analgesia such as NSAIDs will also help with the pain.
(B2)

Surgical Treatment

Patients with severe signs and symptoms such as atrophy of interossei and handgrip strength weakness might not improve with conservative management. Also, patients who have failed conservative treatment for 6 months would require surgical intervention to improve their symptoms. Surgical management involves decompression of the nerve throughout the entire cubital tunnel. Some surgeons release the pressure in the cubital tunnel region, while others prefer free mobilization of the ulnar nerve. 

Various methods of surgical treatment have been discussed and performed. Some of the well-accepted surgical procedures for the treatment of cubital tunnel syndrome are 1) in-situ decompression; 2) endoscopic decompression; 3) decompression followed by subsequent subcutaneous transposition, intramuscular transposition, or submuscular transposition and 4) medial epicondylectomy along with in-situ decompression.[6] Studies have shown no benefit of one over the other in terms of clinical outcomes.[11](A1)

Differential Diagnosis

• Lesions in the Guyon (ulnar) canal
• Cervical spondylosis
• Brachial plexus injuries
• Thoracic outlet syndrome
• Syringomyelia
• Pancoast tumors
• Motor neuron disease
• Carpal tunnel syndrome
• Polyneuropathy

Prognosis

About half the patients achieve an improvement in their symptoms with conservative management.[5]

Complications

• One in eight patients may find that their symptoms recur after surgical decompression.[12] Insufficient decompression has been the most frequent cause of revision surgery.
• Recovery may be slow and incomplete.
• Symptoms may worsen before they improve.
• Injury to the medial antebrachial cutaneous nerve of the forearm is a common complication with cubital tunnel release and can be painful.[13]