Cubital tunnel syndrome is the most common type of ulnar nerve entrapment. The ulnar nerve runs along the medial (inside) of the arm and, when entrapped, can become irritated and cause pain or neuropathy. These symptoms can be present on the medial (inside) of the elbow and sometimes radiate down the forearm to the wrist and ring/pinky fingers.
The ulnar nerve is one of three major nerves in the upper extremity. It controls sensation to certain parts of the forearm and hand, including the ring/pinky fingers, as well as motor function to certain muscles in the forearm and hand.
The ulnar nerve takes a circuitous course around the medial aspect (inside) of the elbow. The nerve passes between the ulna and humerus bones beneath a ligament and then courses into the forearm musculature. This unusual course makes the ulnar nerve vulnerable to increased tension at the cubital tunnel when the elbow is bent. At the elbow, the nerve is also prone to irritation from direct pressure or impact since the nerve lies just beneath the skin. The superficial location of the nerve here, sometimes called the “funny bone,” is the reason why you may experience acute pain and an uncomfortable “funny” sensation when you bang your elbow in this location.
While cubital tunnel syndrome is the second most common nerve compression syndrome in the upper extremity, carpal tunnel syndrome is the most common. Carpal tunnel syndrome involves a different nerve (median nerve) compressed in a different location (wrist) than cubital tunnel syndrome. As a result, the presenting symptoms and physical exam findings are different.
Cubital tunnel syndrome symptoms include pain over the ulnar nerve on the inside of the elbow, pain that radiates into forearm, hand and ring/pinky fingers, numbness/tingling in the same distribution, weakness or atrophy of certain small muscles in the hand causing difficulty with fine motor activities.
Cubital tunnel syndrome symptoms may be more pronounced when elbow is flexed (bent) and/or when direct pressure is placed on the cubital tunnel through which the nerve runs (for example leaning the elbow on hard surface).
The type of pain sensation can range from feeling sharp or stabbing at the elbow, to a dull ache in the forearm/wrist/fingers, to a burning or electrical shock sensation.
Cubital tunnel syndrome can be idiopathic (meaning no known cause), caused by anatomic variation of certain muscles or ligaments, resulting in ulnar nerve compression, or as a result of a previous trauma to the arm or elbow that resulted in direct nerve contusion, elbow swelling or bony malalignment putting increased tension on ulnar nerve.
Cubital tunnel syndrome is diagnosed by a physical examination, sometimes in combination with diagnostic studies such as ultrasound, electrodiagnostic studies (such as EMG testing) or a special type of MRI known as magnetic resonance neurography. Diagnostic studies may be needed to either assess the severity of cubital tunnel syndrome and/or to rule out other conditions that can present similarly (for example, nerve compression at the cervical spine or other locations in the upper extremity).
Mild cubital tunnel syndrome with a known cause or provoking factor will sometimes resolve on its own. Other patients have mild symptoms which are not bothersome enough to justify further intervention and can simply be observed.
Persistent pain, worsening numbness/tingling, or worsening hand weakness are concerning symptoms that require evaluation.
Nonsurgical treatment is tried first, and may include observation, an elbow splint or sleeve to keep the elbow extended (especially while sleeping), and/or physical therapy with an occupational or hand therapist. If conservative treatments fail, there are several surgical options for patients with cubital tunnel syndrome.
Surgeries for cubital tunnel syndrome include in situ decompression (also known as cubital tunnel release surgery), subcutaneous ulnar nerve transposition and submuscular ulnar nerve transposition. There are different risks and benefits of each option. You and your surgeon will decide which procedure is best for you based on the severity of your condition, potential previous elbow injury/surgery, and your elbow anatomy.
If you have cubital tunnel syndrome, avoidance of provoking factors is frequently advised. For example, avoiding direct pressure on the cubital tunnel and/or prolonged elbow flexion can be helpful. In some patients, the triceps muscle can contribute to symptoms and, in those patients, isolated triceps strengthening exercises would be discouraged.
Common provoking factors of cubital tunnel syndrome are direct pressure on the cubital tunnel (the “funny bone” region) and prolonged elbow flexion. Avoidance of these two activities can be helpful. Office workers, for example, may need to take breaks away from typing with the elbows bent and avoid resting the elbows on chair arms, which may put pressure on the ulnar nerve.