Cubital tunnel syndrome is a condition where patients develop compression of the ulnar nerve as it passes around the elbow. The ulnar nerve supplies sensation to the little and ring fingers in the hand and also innervates many of the small muscles within the hand that control finger movement. It also supplies some of the muscles that help flex the wrist and fingers.
The ulnar nerve passes behind the medial epicondyle. This is the bony prominence that can be felt on the inside of the elbow. The ulnar nerve travels through a tight tunnel in this area. On occasions, the nerve can be compressed at this region.
If there is pressure on the nerve, this may result in reduced conduction of electrical activity along the nerve, and this causes intermittent episodes of altered sensation in the little and ring fingers.
As the condition progresses, symptoms may become more frequent. In severe cases, patients may end up with persistent numbness in the ulnar nerve distribution. The muscles supplied by the ulnar nerve may lose their innervation and patients may experience weakness in their hand function. There may be some changes in the shape of the hand due to wasting of the muscles.
Cubital tunnel syndrome sometimes affects both arms.
Causes of cubital tunnel syndrome
Any direct trauma to the elbow region can cause irritation of the ulnar nerve. Repetitive pressure on this region such as leaning on the arm can sometimes cause ulnar nerve symptoms. Keeping the arms in a tightly flexed position for an extended period can also cause some stretching of the ulnar nerve and result in sensory symptoms.
As well as having reduced quality of sensation, patients may also experience an intermittent pins and needles sensation in their little and ring fingers. They may experience difficulty holding their arms in particular postures such as holding a telephone. They may start to develop a feeling of weakness in the hands or a sensation of clumsiness.
The diagnosis is often made on the basis of the history the patient provides. Patients will often give a clear range of symptoms affecting the ulnar nerve distribution.
In most cases, nerve conduction studies are requested to define the extent of the restriction in conduction velocity. The studies also help to confirm the level at which the nerve is being compressed. Some patients may have ulnar nerve symptoms that relate to compression of the nerve elsewhere.
In cases of proven ulnar nerve compression at the cubital tunnel, the nerve can be decompressed through a simple incision on the inside of the elbow. Surgery aims to take the pressure off the nerve and prevent further deterioration in nerve function.
In cases where patients have already suffered wasting of the muscles in the hand, it is difficult to predict how much recovery they will achieve. The aim is to release the nerve before the patient starts to experience muscle wasting and loss of hand function.