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.

Introduction

The ulnar nerve has several potential compression sites along its course. Although the elbow is the most common site of compression, the ulnar nerve is also susceptible to injury at the wrist, forearm, and upper arm. Prevention of compression and early diagnosis/treatment is important for its prognosis because the treatment outcome is usually disappointing once the nerve has axonal damage.

The C8 and T1 nerve roots merge to form the lower trunk of the brachial plexus which continues as the medial cord to give rise to the ulnar nerve. The ulnar nerve then courses along the upper arm medial to the brachial artery, in proximity to the median nerve. Just above the elbow, the ulnar nerve courses posteriorly to pass through the retroepicondylar groove between the medial epicondyle and olecranon process. It then passes underneath the humeroulnar aponeurotic arcade (HUA), which is a dense aponeurosis between the tendon attachments of the flexor carpi ulnaris (FCU). The area beneath the HUA is also called the cubital tunnel. The nerve then passes through the belly of the FCU muscle and out through the deep flexor-pronator aponeurosis. At the forearm, it innervates the FCU and the flexor digitorum profundus (FDP). At the mid to distal forearm, the palmar ulnar cutaneous branch (PUC) splits from the ulnar nerve and enters the hand ventral to the Guyon canal and gives sensory innervation to the skin at the hypothenar area. Distal to the bifurcation of the PUC, the dorsal ulnar cutaneous (DUC) branch separates from the main trunk, curves around the ulna, and provides sensory innervation to the dorsum of the skin of the medial hand, medial half of the fourth digit, and fifth digit.

The main trunk of the ulnar nerve enters through the Guyon’s canal at the level of the distal wrist crease. The proximal wall of Guyon’s canal is formed by the pisiform bone and the distal wall by the hook of the hamate. The roof is formed by the palmaris brevis muscle, and the floor is formed by the combination of the transverse carpal ligament, the hamate, and the triquetrum bone. A thick band is formed at the outlet (pisohamate hiatus) connecting the hook of the hamate to the pisiform bone. In the canal, the nerve separates into the superficial sensory branch and the deep palmar motor branch. The superficial sensory branch provides sensory innervation to the palmar aspects of the medial half of the fourth digit and the fifth digit. Before the nerve exits through the pisohamate hiatus, the motor fibers branch off from the deep palmar motor branch to innervate the hypothenar muscles (abductor digiti minimi, flexor digiti minimi, opponens digiti minimi, and palmaris brevis). The deep palmar branch gives motor innervation to the adductor pollicis, the deep head of the flexor pollicis brevis, the third and fourth lumbricals, and the three palmar and four dorsal interossei muscles.

Etiology

The second most common upper extremity entrapment neuropathy is ulnar neuropathy at the elbow (UNE). At the elbow, the ulnar nerve lacks protective cover in the ulnar groove. This causes its susceptibility to external compression. Repetitive elbow flexion and extension, arthritic changes, and valgus deformities at the elbow increase its vulnerability to injury. In some individuals, the ulnar nerve may be subluxed out of the retroepicondylar groove medially over the medial epicondyle during elbow flexion. In a study investigating patients with UNE, the pressures recorded between the ulnar nerve and overlying arcade increased up to above 200 mm Hg in elbow flexion or during isometric contraction of the flexor carpi ulnaris muscle. In contrast, the pressure was less than 19 at elbow extension.

Repetitive movement that exerts pressure on the ulnar wrist and hypothenar eminence predisposes the ulnar nerve to develop neuropathy. Wrist fractures and compressive mass lesions may also cause ulnar neuropathy at the wrist (UNW).

Epidemiology

There are limited studies of incidence and prevalence rates for ulnar neuropathy. In a study in the general population in Italy, incidence was 20.9%, with males affected more than females. In a population-based survey in Egypt, crude prevalence rates showed that ulnar neuropathy at the elbow was the second most common type of entrapment.

Pathophysiology

Neurapraxia of the ulnar nerve is often seen with mild injury. However, moderate-to-severe injuries of the nerve will present as axonotmesis, or in severe cases, neurotmesis.

History and Physical

Symptoms of ulnar neuropathy at the elbow usually start slowly unless it is associated with trauma. The patient may have numbness and paresthesia, radiating distally to the ulnar aspect of the hand, the fifth digit and the ulnar aspect of the fourth digit. It is usually associated with elbow flexion, particularly at night. Unless it is associated with an acute injury to the elbow, pain is not a dominant feature; however, some patients may complain of pain due to overuse of the forearm flexors such as the FCU.

Sensory symptoms involving the fifth digit and medial half of the fourth digit may indicate an ulnar neuropathy at the wrist. However, similar findings can be seen in ulnar neuropathy at the elbow. It is suggested that the fibers destined for the FCU, PUC, and DUC lie in individual fascicles at the elbow in a deep dorsolateral position, rendering them less susceptible to damage.This renders them less susceptible to injury in UNE, and may cause difficulty in distinguishing UNE from ulnar neuropathy at the wrist. However, if there is an involvement of the entire ring finger or in contrast, total sparing, the diagnosis of cervical radiculopathy or brachial plexopathy should be taken into account.

When the disease gets worse, the symptom may progress to constant numbness and paresthesia and weakness of the innervated muscles. Weakness may start from clumsiness and loss of hand dexterity. This may then progress to a decrease in handgrip and pinch strength (Froment sign). In more severe cases, there may be atrophy of the hand intrinsic muscles and clawing of the fourth and the fifth digits, classically known as claw hand.

Ulnar neuropathy at the wrist and hand can range from pure sensory to pure motor deficits. The most common type of ulnar neuropathies at the wrist is compression of the deep palmar branch. Ulnar neuropathies of the wrist and hand are divided into 3 types. Type I is a lesion of the ulnar nerve just proximal to or within the Guyon canal involving deep and the superficial branches; this causes mixed motor and sensory deficits and subsequent weakness of all the ulnar hand muscles. Type II is a lesion involving the deep branch which causes a pure motor deficit with a varied pattern of weakness based on the compression site. Type III lesion is limited to the superficial branch, causing purely sensory deficits to the palmar aspect of the medial half of the fourth digit and the fifth digit. The sensory loss in type I and type III lesions spares the dorsal aspect of the hand and fingers and the hypothenar eminence due to the more proximal innervations from the DUC and the PUC, respectively.

Evaluation

Diagnosis traditionally relies on clinical history, physical examination, and electrodiagnostic studies. It has been suggested that combination of electromyography (EMG) and nerve conduction velocity (NCV) tests can improve diagnostic accuracy by mapping out the location of pathological compression of the ulnar nerve, which would provide a relatively early diagnosis in patients who have symptoms suggestive of ulnar nerve lesions.

Ultrasound (US) has also been suggested as a screening and follow-up imaging modality in patients with ulnar neuropathy at the elbow, as US can detect the morphologic changes and the extent of the ulnar nerve lesion at the elbow. A recent meta-analysis showed that in healthy participants, the ulnar nerve cross-sectional area at various locations at the elbow rarely exceeds 10 mm, and this can be considered a cutoff point for diagnosing ulnar nerve entrapment at the elbow region. Another study suggested that by measuring ulnar nerve cross-sectional area with MRI or US at 1-cm proximal to the medial epicondyle, patients with and without UNE could be discriminated by using a cutoff threshold of 11.0 mm. It is also suggested that the ulnar nerve-swelling ratio can be a complementary tool for diagnosing ulnar neuropathy at the elbow, and other potential sonologic indicators include presence of intra-neural vascularity, increased flattening ratio, and enlarged intra-neural hypoechoic fraction, although further research is needed.

Treatment / Management

There are 2 main conservative treatments: reducing the frequency of external compression on the nerve and flexion of the elbow joint. This is expected to decrease the stress placed on the ulnar nerve. The use of elbow splints, elbow pads or sleeves, and physical therapy have been suggested. For patients with mild to moderate symptoms, conservative treatment can be administered. It was shown that in patients with mild symptoms, conservative treatments are proven to be beneficial in about 90% of the patients; however, only 38% of the patients with moderate symptoms respond well a non-operative method.

Injection procedures have also been proposed for the treatment of ulnar neuropathy at the elbow. However, studies with ultrasound-guided corticosteroid injections at the elbow have shown controversial results.

Surgical treatment becomes a consideration for patients with persistent symptoms, with accompanying sensory changes and muscle atrophy. Several surgical methods have been described, for example, decompression, anterior transposition techniques, and medial epicondylectomy. A systematic review showed that simple decompression and decompression with transposition are equally effective in idiopathic UNE. However, the decompression surgery with transposition is associated with more wound infections than simple decompression.

Differential Diagnosis

• Alcohol-related neuropathy

• Amyotrophic lateral sclerosis

• Brachial plexus abnormalities

• Cervical disc disease

• Epicondylitis

• Pancoast tumour

• Thoracic outlet syndrome
• Traumatic peripheral nerve lesions

Enhancing Healthcare Team Outcomes

The ulnar nerve has several potential compression sites along its course. Although the elbow is the most common site of compression, the ulnar nerve is also susceptible to injury at the wrist, forearm, and upper arm. When the primary care provider and nurse practitioner come across patients with ulnar nerve dysfunction, it is important to refer these patients to the neurologist and hand surgeon to first confirm the diagnosis and treatment. Prevention of compression and early diagnosis/treatment is important for its prognosis because the treatment outcome is usually disappointing once the nerve has axonal damage. There are 2 main conservative treatments: reducing the frequency of external compression on the nerve and flexion of the elbow joint. This is expected to decrease the stress placed on the ulnar nerve. The use of elbow splints, elbow pads or sleeves, and physical therapy have been suggested. For patients with mild to moderate symptoms, conservative treatment can be administered. It was shown that in patients with mild symptoms, conservative treatments are proven to be beneficial in about 90% of the patients; however, only 38% of the patients with moderate symptoms respond well to a non-operative method.