Carpal tunnel syndrome (CTS)

Carpal tunnel syndrome is easily the most common entrapment neuropathy, with a prevalence of 0.2% to 1%.

Nine flexor tendons and the median nerve pass through the carpal tunnel, which is narrowest at its mid-portion.

Carpal tunnel syndrome is the most common of the peripheral nerve entrapment syndromes and is caused by increased pressure on the median nerve within the carpal tunnel. The clinical presentation is generally pain and paresthesias in the distribution of the median nerve.

Carpal tunnel syndrome occurs when the median nerve is compressed by the flexor retinaculum/transverse carpal ligament at the wrist, producing characteristic nocturnal dysesthesias (70%), but occasionally progressing to sensory loss and weakness of thumb abduction.

Pain can radiate into the proximal arm (40%). This condition is bilateral in half of patients and occurs with increased frequency in occupations associated with high levels of repetition and force (meatpackers, shellfish packing, and musicians).

Additionally, patients with more metabolically compromised nerves (diabetics, alcoholics) or those experiencing more swelling (pregnancy) or synovitis (RA) are at increased risk.

How is Carpal tunnel syndrome diagnosed?

What is the MRI appearance of Carpal tunnel syndrome?

MRI findings include enlargement and increased T2-weighted signal intensity of the median nerve proximal to the carpal tunnel, flattening of the nerve within the carpal tunnel, and volar bowing of the flexor retinaculum.

In some cases, MRI may indicate a specific cause of CTS such as fractures and/or dislocations of the distal radius or carpal bones, increased fluid or thickening of the tendon sheath of the flexor tendons, soft tissue masses such as neurogenic tumors or cysts, or an anomalous muscle.

In general, CTS is diagnosed by clinical examination and confirmed by electromyographic and nerve conduction studies. The accuracy and role of MRI for the diagnosis of CTS are controversial, and MRI is probably best reserved for those cases in which the clinical diagnosis is somewhat obscure.

In cases of recurrent CTS following surgical division of the flexor retinaculum, MRI may demonstrate either incomplete division of the flexor retinaculum or postoperative fibrosis as low signal intensity fibrous bands on the superficial margin of the carpal tunnel.


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