THE CLINICAL SYNDROME

• One of the most common forms of entrapment neuropathies seen in clinical practice is ulnar nerve entrapment at the elbow.

• The ulnar nerve can be compressed at the elbow by an aponeurotic band that extends from the medial epicondyle of the humerus to the medial border of the olecranon.

• Direct trauma to the ulnar nerve at the elbow, as well as repetitive motion of the elbow, can also cause this condition.

• There are a few different names for ulnar nerve entrapment at the elbow, including tardy ulnar palsy, cubital tunnel syndrome, and ulnar nerve neuritis.

• This entrapment neuropathy presents itself as pain in the lateral forearm, along with associated paresthesias that radiate to the wrist and to the ring and little fingers.

• On the affected side, some patients also experience pain in the medial aspect of the scapula, which may be another symptom.

• If left untreated, ulnar nerve entrapment at the elbow can lead to progressive motor deficits and, in the end, flexion contracture of the fingers that are affected.

• The onset of symptoms is typically preceded by a motion or pressure on the elbow that is repeated on a regular basis, such as leaning on the elbow while lying on the floor.

• It's possible that direct trauma to the ulnar nerve as it enters the cubital tunnel could result in a clinical presentation that's very similar to this one.

• Patients who are prone to nerve syndromes, such as diabetics and alcoholics, have an increased likelihood of developing ulnar nerve entrapment at the elbow.

SIGNS AND SYMPTOMS

• Tenderness was located over the ulnar nerve at the elbow in the patient's physical examination findings.

• A positive Tinel sign is typically seen over the ulnar nerve as it travels beneath the aponeurosis in the majority of cases. With careful manual muscle testing, it is possible to identify a weakness in the intrinsic muscles of the forearm and hand that are innervated by the ulnar nerve.

• However, early on in the progression of cubital tunnel syndrome, the only other physical finding besides tenderness over the nerve may be a loss of sensation on the ulnar side of the little finger.

  • This can be the only symptom of cubital tunnel syndrome.

• When viewed from above with the palm facing downward, the best way to diagnose muscle atrophy in the intrinsic hand muscles is to examine the hand from above.

• Patients who are experiencing ulnar nerve entrapment at the elbow frequently display a positive Froment sign.

• This is because the adductor pollicis brevis and flexor pollicis brevis muscles become weak as a result of the condition.

• Patients who suffer from significant muscle weakness as a result of ulnar nerve entrapment at the elbow also exhibit a positive Wartenberg sign.

• These patients frequently complain that their little finger becomes caught outside the pants pocket when they reach for their car keys.

• Patients who are experiencing symptoms of ulnar nerve entrapment at the elbow might also have a positive result on an adduction test for the little finger.

TESTING

• Electromyography and nerve conduction velocity studies are extremely sensitive diagnostic tools.

• A competent electromyographer can diagnose ulnar nerve entrapment at the elbow with a high degree of accuracy, as well as distinguish ulnar nerve entrapment from other neuropathic causes of pain that may mimic it, such as radiculopathy and plexopathy.

• Plain radiographs are recommended for all patients who present with ulnar nerve entrapment at the elbow in order to determine whether or not there are any hidden bony disorders.

• It is also recommended to perform an ultrasound examination in order to identify any other abnormalities that may be to blame for the compression of the ulnar nerve at the elbow.

• In the event that surgical intervention is being considered, magnetic resonance imaging (MRI) of the affected elbow may help to more precisely define the pathologic process that is responsible for the nerve entrapment (for example, a bone spur or a thickening of the aponeurotic band).

• If a tumor of the brachial plexus, such as Pancoast's tumor or another type of brachial plexus tumor, is suspected, chest radiographs with apical lordotic views may be of assistance.

• In the event that the diagnosis is uncertain, screening laboratory tests, which include a complete blood count, erythrocyte sedimentation rate, antinuclear antibody testing, and automated blood chemistry, should be carried out in order to eliminate other potential reasons for the patient's pain.

• The injection technique that will be described later can be utilized both as a diagnostic tool and a treatment strategy.

DIFFERENTIAL DIAGNOSIS

• The condition known as golfer's elbow is frequently misdiagnosed as ulnar nerve entrapment at the elbow, which explains why many patients who are thought to have golfer's elbow do not respond to conservative treatment methods.

• In patients who have cubital tunnel syndrome, the area of the elbow that is the most tender to palpation is directly over the medial epicondyle, while in patients who have golfer's elbow, the area of the elbow that is the most tender to palpation is directly over the ulnar nerve, which is one inch below the medial epicondyle.

• The condition known as cubital tunnel syndrome needs to be distinguished from cervical radiculopathy, which can affect either the C7 or C8 roots. In addition, the double-crush syndrome can occur when cervical radiculopathy and ulnar nerve entrapment occur at the same time.

• The double-crush syndrome is most frequently observed in patients who also have carpal tunnel syndrome or median nerve entrapment at the wrist.

TREATMENT

• Patients who present with ulnar nerve entrapment at the elbow are candidates for a condensed course of conservative therapy consisting of simple analgesics, nonsteroidal antiinflammatory drugs, or cyclooxygenase-2 inhibitors, in addition to splinting to avoid elbow flexion.

• This is the recommended course of treatment for patients.

• In the event that the patient does not experience a discernible improvement in their symptoms within one week, the following method of administering a careful injection into the ulnar nerve at the elbow is an acceptable next step.

• In order to administer an injection into the ulnar nerve at the elbow, the patient must be positioned in the supine position with the affected arm fully adducted at the patient's side, the elbow slightly flexed, and the dorsum of the hand supported by a towel that has been folded in half.

• A total volume of 5 to 7 milliliters of local anesthetic is drawn up in a sterile syringe that has a capacity of 12 milliliters.

• To the local anesthetic, 80 mg of methylprednisolone is added for the first block, and 40 mg of depot steroid is added for each subsequent block.

• The ulnar nerve sulcus can be found between the olecranon process and the medial epicondyle of the humerus, which are both bony landmarks that are identified by the clinician.

• After cleaning the skin with an antiseptic solution, a needle with a gauge of 25 and a length of 58 millimeters is inserted just proximal to the sulcus.

• The needle is then slowly advanced in a direction that is slightly cephalad.

• When the needle has advanced approximately one centimeter, a powerful paresthesia will be elicited along the course of the ulnar nerve.

• The patient needs to be informed to anticipate this and instructed to exclaim "There!" as soon as they feel the paresthesia taking effect.

• After the paresthesia has been elicited and its distribution has been determined, a gentle aspiration is carried out in order to locate any blood that may be present.

• If the aspiration test result is negative and there is no persistent paresthesia in the distribution of the ulnar nerve, then 5 to 7 mL of local anesthetic solution is slowly injected into the patient while they are closely monitored for signs of local anesthetic toxicity.

• If the aspiration test result is positive, then the procedure continues as normal.

• If it is not possible to induce paresthesia, a similar volume of solution is slowly injected in a fanlike manner just proximal to the notch.

• However, extreme caution must be taken to avoid injecting the solution into the blood vessel.

COMPLICATIONS AND PITFALLS

• There is a risk of developing a permanent neurologic deficit if an ulnar nerve entrapment at the elbow is not diagnosed and treated as soon as it occurs.

• To ensure that the patient is not harmed in any way, the clinician needs to ensure that other potential causes of pain and numbness, such as Pancoast's tumor, have been ruled out as potential contributors to the patient's condition.

• The ulnar nerve block at the elbow is performed with a reasonable amount of risk.

• Inadvertent intravascular injection into the ulnar artery and persistent paresthesia as a result of needle-induced trauma to the nerve are the two major complications that can arise from this procedure.

• Because the nerve travels through the ulnar nerve sulcus and is surrounded by a dense fibrous band, it is important to inject the medication very slowly and stop just proximal to the ulnar nerve sulcus in order to prevent further damage to the nerve.