The carpal tunnel is an opening in the wrist formed by the carpal bones and the transverse carpal ligament. Carpal tunnel syndrome is the compression of the median nerve as it passes through this space. The median nerve functions to provide sensation and motor function to the thumb and middle three fingers.
Any condition that exerts pressure on the median nerve at the wrist can cause carpal tunnel syndrome. Common causes include trauma, obesity, pregnancy, osteoarthritis, rheumatoid arthritis, diabetes, hypothyroidism, and repetitive stress injuries related to work. Repetitive movements involving the wrist typically lead to tendon inflammation, which causes pressure on the median nerve. Additional mechanical risk factor include frequently subjecting the hands to cold temperatures. Other causes and risk factors also include having a small carpal tunnel possibly due to heredity, female gender and increasing age. In general women have smaller carpal tunnels. Pregnancy and menopause can lead to hormonal changes that can potentiate carpal tunnel syndrome. Some endocrine abnormalities such as hypothyroidism and an overactive pituitary gland also serve as risk factors. Rare diseases leading to deposition of certain substances in and near the carpal tunnel can cause median nerve irritation. These include amyloidosis, sarcoidosis, multiple myeloma and leukemia.
Carpal tunnel syndrome is associated with pain, numbness and tingling. These symptoms are common at night or on upon waking up in the morning. A common distribution of symptoms includes the thumb, the adjacent two fingers and half of the ring finger. The rest of the hand and the forearm can be affected as well. Symptoms can progress to last the entire day and eventually cause diminished grip strength. Activities such as typing can become difficult. Without the appropriate treatment, muscle wasting can develop and the ability to differentiate hot from cold can be compromised. Symptoms can worsen with use or with prolonged immobility of the affected hand as well.
The diagnosis starts with a history. Your physician will ask you when your symptoms started, what makes them worse and if you have sustained any injuries to the wrist or hand. You will most likely be asked about your family history as well.
The physical exam includes looking for swelling at the wrist, assessing for tenderness and muscle atrophy, and testing sensation in the fingers. Specific physical exam tests that are used to diagnose carpal tunnel syndrome include:
Electrodiagnostic studies such as electromyography and nerve conduction velocity can help establish the diagnosis of carpal tunnel syndrome as can imaging studies. X-rays can help detect arthritis or fractures. An ultrasound can be used to detect irregularities in the median nerve and nearby soft tissues.
Conservative measures to treat carpal tunnel syndrome include workplace maneuvers such as raising or lowering your chair, moving your computer keyboard to a different position or replacing it with a more ergonomic one. A physical therapist can help with therapy sessions, by recommending a suitable splint to wear and teaching hand exercises. Non-steroidal anti-inflammatory medications such as ibuprofen can help improve symptoms as can warm compresses. If symptoms persist, steroid injections performed by an appropriately trained physician are a good option.
If these measures fail to sustainably improve symptoms, surgery can be performed to increase the size of the carpal tunnel. This usually alleviates pressure on the median nerve and helps diminish symptoms. The transverse carpal ligament that covers the carpal tunnel at the base of palm is cut or “released” This procedure is often called a “Carpal Tunnel Release”. Carpal tunnel surgery is usually followed with a course of physical therapy.