Imaging Studies

Wrist radiographs should not be routinely performed in patients with carpal tunnel syndrome (CTS), because too little useful information is obtained from these images.^[27]Only 0.4% of routine wrist radiographs for CTS have been demonstrated to provide therapeutically significant findings.^[27]

Patients with a history of systemic disorders, wrist trauma, arthritis, or abnormal findings (eg, limited motion) on physical examination for CTS are much more likely to have radiographic findings; Accordingly, use of wrist radiographs in these patients may be indicated.

The American Academy of Orthopaedic Surgeons (AAOS) has recommended against routine use of magnetic resonance imaging (MRI) to diagnose CTS.^[28]

Other Tests

Electrophysiologic diagnostic studies that may be considered include nerve conduction studies^[29]and electromyography (EMG).

In the former, median motor and sensory latencies, as well as conduction velocities, are measured across the wrist. A sensory latency exceeding 3.5 ms or a motor latency exceeding 4.5 ms is considered an abnormal finding. Comparison with the contralateral hand, as well as with ulnar motor and sensory latencies and conduction velocities, can provide additional evidence supporting the diagnosis of CTS.

Distal compound muscle action potential (CMAP) and sensory nerve action potential (SNAP) amplitudes may be decreased in persons with CTS. Minimum F-wave latencies of the median nerve can be prolonged in individuals with CTS.

EMG must be performed with a clinical differential diagnosis in mind; the abductor pollicis brevis is the key muscle to evaluate. Positive findings in persons with CTS include sharp waves, fibrillation potentials, and increased insertional activity.

In the interpretation of electrophysiologic studies, it is important to remember that CTS is a clinical diagnosis. CTS is a constellation of signs and symptoms caused by the compression and slowing of the median nerve at the wrist. Electrophysiologic studies should not be used independently in making a diagnosis.^[30]

Procedures

A catheter may be inserted directly into the carpal canal to measure pressure within the canal. This test is typically used to evaluate acute CTS and can help distinguish between median nerve contusion and compression. The figure of 30 mm Hg is a guide used to determine if the pressure is critically elevated, but physical examination and patient-specific factors can modify the critical pressure.

Treatment & Management

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Media Gallery

Cross sections of carpal canal at levels of proximal and distal carpal rows. Transverse carpal ligament bridges carpal tunnel and is under tension.
Surgical incision for open carpal tunnel release. Incision can be extended proximally across wrist flexion crease for more extended exposure.
Surgical incisions for endoscopic carpal tunnel release (one- and two-incision techniques). Precise location of incisions is critical and depends on individual anatomy.