Cubital Tunnel Syndrome: A neuropathy of the ulnar nerve causing symptoms of tingling, numbness and shooting pain along the medial aspect of the forearm, also including the medial half of the fourth digit and the fifth digit, usually caused by compression or irritation of the nerve at the elbow.

Ulnar Nerve Anatomy: C8 and T1 nerve roots join and give rise to the medial cord of the brachial plexus. Ulnar nerve originates as a branch of the medial cord. The ulnar nerve then travels down the arm along with the brachial artery towards the elbow joint. At the midpoint of the arm, the nerve enters the posterior compartment by piercing the intermuscular septum(arcade of Struthers). It then traverses along the medial aspect of the triceps to enter the cubital tunnel. At this point, the ulnar nerve travels between the olecranon and the medial epicondyle and beneath the Osborne ligament. Once the nerve exits the cubital tunnel, it passes under the aponeurotic head of flexor carpi ulnaris to enter the forearm. The cubital tunnel region is where the ulnar nerve is most likely to be compressed due to its location and anatomy. However, the nerve can also get compressed at the arcade of Struthers or by the aponeurotic head of flexor carpi ulnaris resulting in symptoms of ulnar neuropathy. The ulnar nerve innervates the medial side of the forearm, ulnar side of the palm, the little finger and ulnar half of the ring finger. It supplies motor branches to flexor carpi ulnaris, flexor profundus of the little and ring fingers, hypothenar muscles, adductor pollicis brevis, all of the interossei and the third and fourth lumbricals. It is noteworthy that the ulnar nerve gives no motor or sensory branches above the elbow.

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 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 the nerve damage as the nerve passes posterior to the medial epicondyle.

Pathophysiology

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

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. 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 the distribution of the ulnar nerve but the diagnostic value of these tests are poor. In some cases, the ulnar nerve may be subluxating 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.

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.

Treatment / Management

Pathological findings should undergo careful evaluation when deciding on treatment options. Patients can often benefit from non-surgical interventions; therefore 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.

• 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.

• Simple analgesia such as NSAIDs will also help with the pain.

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. Studies have shown no benefit of one over the other in terms of clinical outcomes.

Prognosis

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

Complications

• One in eight patients may find that their symptoms recur after surgical decompression. Insufficient decompression has been the most frequent cause for 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 lead to a painful neuroma

Postoperative and Rehabilitation Care

Patients are generally allowed a full range of motion of the elbow following surgical intervention. Normally post-operative physical therapy is not necessary unless there is significant muscle weakness. Patients can return to light work in 3 to 4 weeks.

Deterrence and Patient Education

Patient education about the etiology and pathophysiology is of great importance if the aim is to manage the patient with conservative means as slow improvement of symptoms can put people off from conservative management.

If using non-steroidal anti-inflammatory medications, then education about the use of NSAIDs and gastric protection is a necessary discussion to have with patients. Gastric protection is obtainable by using proton pump inhibitors (PPIs). It is also suggested to take NSAIDs with or after food.

Pearls and Other Issues

Ulnar nerve neuropathy can be due to multiple etiologies. Differential diagnosis should be kept in mind while evaluating patients with ulnar neuropathy. Thorough knowledge of the motor and sensory distribution of the ulnar nerve is critical in evaluating patients with ulnar neuropathy and to identify the site of pathology.

Enhancing Healthcare Team Outcomes

An interprofessional team including a nurse, physical therapist, and clinician input can enhance recovery. Physiotherapy can provide significant help if muscle weakness is present. Discussion with the pharmacist can help patients to understand the use and side-effects of analgesic medications. The surgeon should discuss the surgical approach and the potential risks/benefits of the procedure. The nurse should assist in follow up care and monitoring for complications.