The symptoms of ulnar nerve entrapment are manifested in the hand and forearm. The chief complaint of patients are numbness and paresthesia (prickling and tingling sensation) in the ring (fourth) and small (fifth) fingers, ulnar side of the hand (palm), and pain in the elbow. As the disorder advances, the mobility of the hand and affected fingers become impaired due to weakness of the muscles in the area. This results in difficulty with pinching motion between the thumb and index finger (as when picking objects) and grip with the hand. In the chronic stage, patients may present with an ulnar "claw hand" described as curling up of the small and ring fingers (metacarpophalangeal joint in extension and interphalangeal in flexion) secondary to a dysfunction or imbalance between extrinsic and intrinsic muscles of the hand.

Current provocative tests used to diagnose ulnar nerve entrapment include Tinel‘s test, elbow flexion, pressure (compression) per se, elbow flexion combined with pressure, and palpation of affected area for nerve tenderness and thickening. Yet, the specificity and sensitivity of these tests as diagnostic indicator for an entrapped ulnar nerve remains below the standards.

Classification of cubital tunnel syndrome according to severity of symptoms:

Grade I: Mild

• Infrequent paresthesia
• Decreased sensitivity to stimulation of palmar and dorsal surfaces of the small finger, and medial aspect of the ring finger
• Normal motor functions

Grade II: Moderate

• Persistent paresthesia
• Hypoesthesia of the palmar and dorsal surfaces of the small finger and medial aspect of the ring finger
• Mild muscle weakness innervated by the ulnar nerve
• Evidence suggestive of early muscular atrophy

Grade III: Severe symptoms

• Marked paresthesia
• Sensory loss of the palmar and dorsal surfaces of the small finger and medial aspect of the ring finger
• Functional and motor difficulties
• Atrophy of intrinsic muscles of the hand
• Claw hand ("Hand of Benediction")

Symptoms manifestation caused by entrapment and impingement of the ulnar nerve at the Guyon’s canal consist of:

• Atrophy of muscles, mainly the hypothenar and interossei with sparing of the thenar muscles
• Weak finger abduction and adduction movement (interossei)
• Weak thumb adduction movement (adductor pollicis)
• Sensory loss and pain involving the palmar surface of the small finger and medial aspect of the ring finger

Clinical assessments often suffice to establish the diagnosis of ulnar nerve entrapment. However, conduction studies are recommended when clinical findings are unclear and when surgery is being considered as part of the treatment strategy.

Electrodiagnostic studies consisted of nerve conduction study and often times needle electromyography (EMG), are useful in validating the diagnosis of ulnar nerve entrapment and establishing baseline results and in ruling out other possible causes of peripheral nervous system disorder [19].

MRI and ultrasonography are also useful confirmatory tests for ulnar nerve entrapment [20] [21] [22] [23] [24]. For instance, ultrasonography serves to detect altered ultrasound waves and thickened ulnar nerve, a commonly observed presentation of ulnar nerve entrapment. On the other hand, MRI shows enlarged nerve and increased signal intensity on T2-weighted or short T1 inversion recovery (STIR) sequences [21]. The results of MRI may vary with the specific cause.

Treatment of ulnar nerve entrapment involves night splinting, with elbow extended at 45 degrees, and use of elbow pad at daytime. Surgery is recommended if symptoms fail to improve or resolve with conservative treatment.

Indications for surgical decompression of ulnar nerve entrapment:

• Symptoms do not improve after 6-12 weeks.
• Development of palsy or paralysis
• Evidence of persistent lesion such as muscle wasting or curling of ring and small fingers (claw hand)

The method of choice for ulnar nerve entrapment at the elbow is decompression with anterior transposition. The ulnar nerve is transferred to a suitable site away from the original lesion while being stretched a few centimeters to decrease the tension imposed upon it when the elbow is flexed [25]. The primary advantage is that transfers the ulnar nerve from an unsuitable bed to one that is less scarred. However, this method is more technically complicated than simple ulnar compression and with it comes the risk of devascularization of the nerve.

Alternatively, subcutaneous transposition is frequently used in the case of athletes (gymnasts) whose activity involves throwing and who do not present muscular atrophy. The procedure is simple and appropriate for resolving subluxation and traction on the nerve [26]. However, the nerve may be hypersensitive on account of its new superficial location and the blood supply to the nerve may be disrupted with the transposition.

Submuscular transposition has been shown to have the least recurrences with severe ulnar nerve compression [27]. It allows transferring of the nerve to an unscarred bed. The procedure is appropriate for patients who are emaciated, preventing hypersensitivity of the nerve in case of subcutaneous transposition. Anterior submuscular transposition is considered the method of choice for athletes who throw. It is, however, technically demanding where extensive dissection is involved and postoperative outcome is poor, with 5-10 percent risk of elbow flexion contracture. Surgical dissection may result in extensive scarring which will make revision difficult in case of recurrence.

Successful surgical intervention has been achieved in 85 to 95 percent of cases, although the benefit is more for sensory rather than for motor functions. Prognosis is influenced by the following observations:

• Motor amplitude of 10 percent of normal indicates low probability of full recovery.
• Nerve regeneration with pain and paresthesia may occur, which are believed due to random generation of impulses of diseased nerves.
• An enlarged ulnar nerve (diameter more than 3.5 mm) at the elbow observed on the initial sonogram is linked to persistent symptoms or signs, with or without treatment [14].
• The result of treatment does not correlate with the baseline clinical features or duration of symptoms prior to treatment.
• Motor conduction velocity diminished or blocked across the elbow signifies good prognosis [15].

Poor surgical prognosis is associated with: age (if more than 50 years); coexisting diabetes or other peripheral polyneuropathy; muscle wasting and denervated ulnar nerve supplied muscles; unresponsive sensory function of the ulnar nerve; and postoperative positioning of the ulnar nerve in connection to the medial epicondyle [16] [17] [18].

The ulnar nerve is vulnerable at the elbow and, rarely, the wrist. A major cause of cubital tunnel syndrome is the habit of leaning on the elbow. Another cause is repeated, excessive flexion of the elbow as seen in baseball pitchers (particularly sliders), which is detrimental to the medial elbow ligaments. Cubital tunnel syndrome is less prevalent than carpal tunnel syndrome.

Conditions that may contribute to ulnar nerve entrapment at or near the elbow are as follows:

• Metabolic dysfunctions as in diabetes
• Temporary surgical closure of the brachial artery [7]
• Subdermal insertion of contraceptive implant [8]
• Transient immobilization under anesthesia
• Venipuncture [9]
• Hemophilia [10] 
• Blunt trauma
• Deformities of limbs and joints as in rheumatoid arthritis
• Nutritional deficiency resulting in muscle atrophy and loss of adipose tissue
• Cigarette smoking [11]

Conditions that may contribute to ulnar nerve entrapment at in the wrist area or Guyon's canal are as follows:

• Blunt injuries
• Fractures
• Presence of ganglionic cysts or tumors
• Aberrant artery
• Idiopathic (hitherto unknown causes)

Cubital tunnel syndrome is primarily seen in individuals who tend to lean on their elbows habitually or who are subjected to repeated flexion of the elbows in the performance of their tasks. The repetitive stress can lead to entrapment and/or compression of the ulnar nerve in the cubital tunnel, the passage formed by the convergence of the medial epicondyle with the flexor carpi ulnaris and ligaments of the olecranon process of the ulna.

Guyon’s canal syndrome is caused by excessive pressure on the wrist and hand such as in weight lifting, holding on to a handlebar in cycling or construction equipment, hence the term, "handle bar palsy". The ulnar nerve becomes sequestered in the canal of Guyon situated between the hook of the hamate and the transverse carpal ligament. Activities that predispose to this syndrome are frequent or too much gripping, twisting, repetitive wrist and hand motions, keeping the hand flexed and the ulna deviated for long periods of time as in gymnastics or manual labor.

Ulnar nerve entrapment at the elbow is alternatively referred to as UNE. UNE is considered the second most common among the various types of focal neuropathy. The most common focal neuropathy is found at the carpal tunnel, also known as the median neuropathy at the wrist.

A study in Italy estimated the annual overall incidence of UNE was 24.7 cases per 100,000 person years, nearly twice as much in men, 32.7 per 100,000 compared to 17.2 per 100,000 in women [12]. From an extensive database obtained from general practice in the United Kingdom, the annual incidence of ulnar neuropathy involving all anatomic locations was 25.2 per 100,000 for men and 18.9 per 100,000 in women [13].

The cubital tunnel syndrome and Guyon's canal syndrome or ulnar tunnel syndrome affect the elbow and the wrist, respectively. Of these two sites, the elbow is more prone to the disorder than the latter. The ulnar nerve may be sequestered when the large bones of the upper extremity (radius, ulna, or humerus) sustain a fracture. Pathology of blood vessels, though rarely, can also cause compression of the ulnar nerve.

Factors responsible for ulnar nerve neuropathy include:

• Excessive and prolonged use of the wrist and elbow
• Dislocation/subluxation of the ulnar nerve from inborn defect in fibrous tissue
• Callus formation from fracture of the humerus
• Osseous outgrowth from the epicondyle or olecranon
• Impingement from an accessory muscle (anconeus epitrochlearis), soft tissue (tumor), ganglionic cyst, hematoma or osteochondroma
• Inflammation of synovial membrane (as in rheumatoid arthritis)
• Infection (e.g. tuberculosis)
• Thickened cubital tunnel ligament

In summary, cubital tunnel syndrome is impingement of the ulnar nerve, caused by prolonged compression of the elbow against a hard surface, fracture of the bones of the forearm and upper arm, excessive flexion of the elbow, bone, and vascular pathologies at the elbow area. Guyon’s canal syndrome is impingement of the ulnar nerve, caused by excessive pressure on the wrist as when holding on to the handle bar in cycling or weight-lifting, or the jackhammer by the construction worker, fracture of the forearm and upper arm bones, and vascular and bone pathologies. Trauma, abnormalities, or pathological conditions in other sites may also contribute to ulnar nerve neuropathy.

The best way to prevent ulnar nerve entrapment from becoming a serious health problem is to seek medical attention as soon as any symptom of pain, tingling, numbness, or difficulty of movement referable to the elbow and wrist, the ring (fourth) and small (fifth) fingers in particular, are suspected. These may be experienced by athletes or gymnasts, construction workers, or any person habitually and excessively using the hand or forearm in performing certain tasks. Consultation with an occupational therapist can help identify the cause of ulnar nerve entrapment.

Ulnar nerve entrapment is the second most frequent abnormality of the peripheral nervous system in the upper limb, after that of the median nerve [1] [2].

Entrapment of the ulnar nerve most likely occurs at the site of elbow region, specifically the cubital tunnel [3], or in the epicondylar (ulnar) groove. The second most probable site of entrapment is at or adjacent to the wrist, particularly at the Guyon's canal [1] [4] [5] [6]. Nerve entrapment is also likely to occur in the forearm, either below the wrist and within the hand, or just above the below.

Ulnar nerve entrapment is caused by habitual or occupational activities that impose excessive stress on the upper extremities such as in sports or manual labor. Predisposing factors are multifarious - traumatic, metabolic, nutritional, idiopathic, deformities, tumors, or iatrogenic. Diagnosis is based on clinical assessment, MRI, ultrasonography and some new techniques such as electromyography. Treatment is conservative or surgical. Prevention is through avoidance of overuse or inappropriate use of the upper extremities.

Ulnar nerve entrapment is a functional disorder whereby the nerve is pinched or compressed by adjoining tissues as it passes through the wrist or elbow, causing pain, and later, more pronounced symptoms. It is the second most common cause of ulnar neuropathy (after the median nerve entrapment).

Two main sites involved are the cubital tunnel or the epicondylar groove at the elbow and Guyon's canal at the wrist. However, impingement may also occur in the forearm between the wrist and the elbow, in the hand, or proximal part of the upper arm.

Impingement or injury of the ulnar nerve may manifest as loss of sensory function and paralysis of the muscles supplied by the nerve. Patients may complain of paresthesia along the ring (fourth) and small (fifth) fingers, with difficulty of hand grip. In advanced stages, there is loss of intrinsic motor function and wasting in the hand, or claw hand (curling of the ring and small fingers). As the ulnar nerve bifurcates at the wrist, only the opponens pollicis, superficial head of the flexor pollicis brevis, and lateral 2 lumbricals are functioning.

Initially, conservative (nonsurgical) treatment is prescribed. Otherwise, if symptoms persist and in the event of continuing weakness or loss of motor function, surgical intervention should be considered. Several surgical strategies are available, with proven satisfactory outcomes.

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