In nerve compression/entrapment syndromes, a nerve is compressed along its course. This compression leads to irritation of the nerve with pain, numbness, and tingling. As the compression worsens, the nerve fibers begin to die and weakness develops. Over time, the muscles supplied by the nerve atrophy or become smaller. Treatment involves surgical release of the area of compression.
The most common example of nerve entrapment is carpal tunnel syndrome, a disorder that involves median nerve compression at the wrist. The median nerve normally supplies sensation to the thumb, index, and middle fingers, and supplies the muscles to the thumb. Symptoms of median nerve compression include numbness and tingling in the fingers and aching pain in the wrist that may radiate up the forearm. The symptoms are often worse at night. Over time, the hand becomes clumsy and if left untreated, the muscles in the hand that move the thumb may become smaller. Diagnosis is based on the history of symptoms, examination, and electrodiagnostic studies that determine how well the nerve gets its impulse across the wrist.
The compression occurs in the carpal tunnel formed by the wrist bones and a ligament that crosses over the nerve. The size of the tunnel is dependent on the position of the wrist. Flexion and extension both narrow the tunnel and cause increased symptoms. Treatment includes splinting the wrist, taking anti-inflammatory medications, and if these fail, surgical release of the ligament. In most cases, the pain (pins and needles sensations) improve immediately after surgery and all symptoms eventually resolve. In a small number of patients with significant numbness and weakness, symptoms may take many months to recover and in severe cases, no improvement is seen.