Carpal tunnel syndrome (CTS) is the most common nerve compression disorder, with a lifetime incidence of 10%. That means 30 million people in the United States will get it. It involves irritation or injury of the median nerve at the wrist, that causes the following symptoms: pain, numbness, tingling and/or weakness. Patients typically feel these symptoms in the palm, thumb and first 2-3 fingers.
The carpal tunnel is a small space, stuffed with 9 tendons and the median nerve. Any process that encroaches upon the tunnel will generate increased pressure. Since the nerve is the softest structure within the tunnel, it usually is the most easily injured. Osteoarthritis can increase pressure from bony overgrowth or spurs. Tendonitis, with accompanying inflammation and swelling, increases the volume of the tunnel contents and leads to elevation of pressure on the nerve. In addition repeated minor insults over years can create scarring or fixation of the nerve to the walls of the tunnel and the tendons, leading to nerve irritation during activity.
Evaluation for CTS involves physical stress testing at the wrist to evoke symptoms, and a detailed assessment of hand muscle strength. The electrodiagnostic exam (EDX), which includes a nerve conduction study (NCS) and needle electromyogram (EMG), is the “gold standard” to confirm a diagnosis of CTS. NCS involves stimulating the nerve and measuring for impulse slowing across the wrist, or loss of response amplitude due to „blocking‟ of the signal. EDX is essential to rule out other sites of nerve injury (such as a herniated disk in the neck) as the cause of symptoms.
Neuromuscular ultrasound (NMUS) has become a vital tool that adds new information about how the median nerve is injured. NMUS can image the nerve and quantify the degree of swelling. NMUS is also a dynamic study that can be performed during hand activity, often revealing hand or forearm muscles that intrude into the tunnel and compress the nerve. Such information is useful to advise of practical methods to avoid further nerve injury.
A diagnosis of CTS often evokes fear because many patients assume it requires surgery for treatment. In fact, there are many non-operative approaches that may be effective. It is essential to avoid stressful postures and activities which challenge the carpal tunnel or median nerve. Simple bracing of the wrist at night minimizes pressure on the nerve that develops when the wrist is bent forward or backward. Custom-molded braces can be fabricated by special therapists for improved fit, tolerance, and effectiveness. Stretching exercises elongate the ligament and other structures which surround the nerve, helping to enlarge the tunnel and decrease pressure on the nerve. Physical therapy may be useful to apply forms of heating (to loosen tight tissues), instruct in stretching methods, and apply manual techniques (mobilization or manipulation). Oral and topical medications decrease inflammation around the nerve and relieve symptoms. Finally, steroid injection directly into the carpal tunnel is a powerful method to decrease nerve swelling and irritation, leading to rapid improvement. More advanced cases and those that do not respond to these conservative measures may require surgery to decompress the nerve.