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