carpal tunnel syndrome
Median nerve entrapment at the wrist is the most common entrapment neuropathy, with compression typically occurring in the carpal tunnel. This results in carpal tunnel syndrome (CTS), a condition characterized by wrist and arm pain, along with hand paresthesia. While CTS often affects both hands, symptoms are usually more severe in the dominant hand. It is a prevalent condition, impacting approximately 5% of the U.S. population. Caucasians are at the highest risk, and women are affected more frequently than men, with a 3:1 ratio between the ages of 45 and 60.
CTS treatment is primarily a clinical diagnosis. While numerous causes have been reported, most cases are idiopathic. The underlying pathophysiology typically involves demyelination. When evaluating a patient suspected of CTS, electromyography and nerve conduction studies (EMG/NCS) aim to:
(a) identify focal slowing or conduction block of median nerve fibers across the carpal tunnel,
(b) rule out median neuropathy at the elbow,
(c) exclude brachial plexopathy, and
(d) eliminate cervical radiculopathy as a potential cause.
However, in approximately 10%–25% of CTS cases, routine nerve conduction studies may appear normal despite clear clinical symptoms. In such instances, the electrodiagnosis may be missed unless more sensitive nerve conduction techniques are employed. These advanced studies typically compare the median nerve with another nerve in the hand, increasing the diagnostic yield from roughly 75% with standard motor and sensory studies to approximately 95% with more specialized testing.