The area of the wrist includes a site of passage (carpal tunnel) for the flexor tendons of the fingers and the median nerve (N. medianus). The median nerve provides sensory innervation for the thumb, index and middle finger, as well as half of the ring finger, and operates a portion of the muscles of the thumb.
The dorsal border of the carpal tunnel consists of the carpal bones and on the anterior aspect a fibrous band. If pressure within the carpal tunnel increases, it results in compression of the nerve.
This can cause inadequate perfusion in the nerve and thereby lead to a functional deficit. The latter manifests itself by numbness or tingling sensations in the above-mentioned fingers. If the nerve is subjected to increased pressure for a longer period of time, this results in a permanent deficit with pronounced sensory disturbances and muscle atrophy of the thenar eminence.
Potential causes are:
- Increased tissue fluids (pregnancy, hormonal disorder)
- Inflammation and swelling of the flexor tendons
- Prolonged operation of vibrating instruments
- Repetitive flexion and extension of the wrist
- Degenerative changes of the wrist
- Wrist fractures
- Tumors or tumorous alterations (e.g. ganglion) within the carpal tunnel
Paresthesia ("falling asleep", tingling) of the above mentioned fingers is typical, at first only during physical exertion and/or at night. Later these symptoms often persist and are accompanied by numbness and hand pain with possible radiation into the forearm as well as arm weakness. The discomfort can often be diminished through shaking of the hands or massage.
The suspected diagnosis is based on patient history and clinical examination. To confirm the diagnosis, the neurologist will perform electrophysiologic testing, which measures the capacity of the nerve to conduct electrical impulses. If we suspect that compression is caused by degenerative changes of the joint or perhaps a ganglion in the carpal tunnel, an x-ray or ultrasound can be performed.
If discomfort and electrophysiologic findings are not very pronounced, conservative therapy without surgery is appropriate. This includes immobilizing the wrist with a brace and administering anti-inflammatory medication. Especially pregnancy-induced symptoms can be relieved effectively by a cortisone infiltration.
If conservative treatment is ineffective or if there exists already relevant sensory dysfunction, muscle atrophy, and/or clearly worsened nerve conductivity, surgery is necessary. In this procedure, the ligament that limits the carpal tunnel on the anterior side of the wrist is cut through. This creates more space for the tendons and the nerve.
The operation can be carried out through a small cutaneous incision in the area of the palm (mini-open) or under camera visualization (endoscopic) through a small incision of the skin in the wrist fold. Both methods have comparable surgical outcomes. The advantage of the endoscopic method is that there is no cut in the strained palm. Both interventions can be performed on an ambulatory basis under local anesthesia.
Follow up care
Right after the operation a bandage is applied and kept in place until the first wound check two or three days later. Thereafter, a protective dressing is worn until removal of the sutures. The hand must be protected during the first two weeks. No heavy objects such as pans, shopping bags, etc. must be carried. After two weeks, effort can be gradually increased up to the pain threshold. Full use is typically possible within four to six weeks. If needed we can arrange for supportive hand therapy to help improve mobility, strength and wound care.
The prognosis depends on the extent of nerve damage at the time of the operation. As long as there is no irreversible injury, sensory function and strength can be fully recovered. However, this may take several weeks or even months, especially with regard to sensation.
After longstanding compression with irreversible damage to the nerve, full recovery is not expected.
Sometimes, even after an initially successful operation, narrowing of the carpal tunnel and nerve compression can redevelop. Reoperation usually requires a larger skin incision, that extends over the wrist, allowing for thorough removal of scar tissue and adhesions. Due to this fact postoperative recovery period is longer than with the primary procedure.