Compression of the ulnar nerve at the elbow, causing numbness and tingling.
The ulnar nerve runs from the neck down the inner arm and passes through a narrow passage behind the bony point on the inside of the elbow, known as the cubital tunnel. This is the same nerve responsible for the sharp tingling felt when you knock your "funny bone." When the nerve is compressed or irritated at this point, the result is ulnar nerve entrapment, also called cubital tunnel syndrome.
It is the second most common nerve compression in the upper limb after carpal tunnel syndrome. Because the ulnar nerve supplies sensation to the ring and little fingers and controls many of the small muscles of the hand, entrapment can affect both feeling and fine hand function, and in longstanding cases can lead to visible weakness and muscle wasting in the hand.
The cubital tunnel narrows whenever the elbow is bent, so prolonged or repeated elbow flexion is the most common contributor to ulnar nerve entrapment. This includes sleeping with the elbow bent, resting on the elbow for long periods, and frequent phone use with the arm flexed.
Other contributors include direct pressure on the nerve from leaning on a hard surface, previous elbow fracture or injury that has altered the shape of the tunnel, bony spurs from arthritis narrowing the space, and, less commonly, a cyst or other mass pressing on the nerve. In many cases no single cause is identified.
Typical symptoms of ulnar nerve entrapment include:
Symptoms that are constant, rather than coming and going with position, or that include visible muscle wasting, generally warrant more prompt assessment.
Assessment includes a history of aggravating positions and activities, examination of hand strength and sensation, and often a nerve conduction study to confirm the diagnosis, localise the compression, and gauge its severity.
Many cases of ulnar nerve entrapment improve with non-surgical treatment: avoiding prolonged elbow flexion and direct pressure on the elbow, wearing a splint at night to keep the elbow straighter during sleep, and activity modification. Physiotherapy and simple pain relief can also help.
Surgery, most commonly ulnar nerve transposition or decompression, is considered when symptoms are persistent despite non-surgical treatment, or when there is significant or progressive weakness or muscle wasting, where earlier surgery tends to give the nerve the best chance of recovery.
The outlook depends largely on how long the nerve has been compressed and how severe the compression is at the time of treatment. Milder, intermittent symptoms often settle well with non-surgical measures.
Where surgery is needed, tingling and pain typically improve first, with strength recovering more gradually over months. In longstanding cases with established muscle wasting, some recovery of strength can still occur, but it may not be complete, which is why earlier assessment tends to give better results.
Ulnar nerve entrapment, or cubital tunnel syndrome, is a common and treatable cause of tingling, pain and weakness affecting the elbow and hand. Many cases respond to activity changes and splinting, and where surgery is needed, outcomes are generally good, particularly when treated before significant weakness develops. Persistent numbness in the ring and little fingers, or hand weakness, is worth having assessed.
For a comparison with a similar nerve condition affecting the wrist, see carpal tunnel vs cubital tunnel syndrome.
