Excerpt from Median Neuropathy

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Background

Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy in the upper extremity. The condition is usually bilateral, although the dominant hand tends to be more severely affected.

Pathophysiology

The median nerve crosses from the distal forearm to the hand through the carpal tunnel. The floor of the carpal tunnel is formed by the carpal bones and the roof by the transverse carpal ligament. Compression of the median nerve by the transverse carpal ligament (flexor retinaculum) can occur.

The palmar cutaneous branch of the median nerve leaves the main trunk 5-8 cm proximal to the wrist crease. It provides sensation to the thenar eminence and does not traverse the carpal tunnel. Loss of sensation over the thenar eminence is not part of CTS but suggests a lesion proximal to the wrist.

Frequency

United States

In Rochester, Minnesota, prevalence was estimated to be 125 per 100,000 during the period from 1976-1980. Most cases are idiopathic.

Other studies estimated the prevalence rates for CTS to be 1-5% in the general population and 5-15% in the industrial setting, but the rate is dependent on how CTS is defined.

Epidemiologic studies have demonstrated that the highest incidence of CTS tends to be in poultry processors and meat packing workers, followed by garment workers and automobile assembly workers.

Race

Findings of the 1988 National Health Interview survey indicate that CTS is 1.8 times more prevalent in whites than nonwhites.

Sex

Women are affected more than men. Phalen's series (1970) included 280 women and 96 men (female-to-male ratio 3:1).

Age

Of the patients in Phalen's series (1970), 58% were adults aged 40-60 years.

Please click here to view the full topic text: Median Neuropathy