Abnormalities of sensation

Carpal Tunnel Master And Beyond

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A. Carpal tunnel syndrome is produced by compression of the median nerve at the wrist. As the nerve passes through the unyielding carpal tunnel, it is at risk for compression by the transverse carpal ligament. In most patients, no specific etiology can be determined, but thickening and proliferation of the peritendinous synovium is seen. This condition is very common in RA, in diabetes, during or after pregnancy, and after wrist fracture. It is also seen in postmenopausal women and in patients with the myxedema of thyroid disease.

1. A history of wrist pain and paresthesias in the thumb, index finger, and long finger (the median nerve distribution), frequently occurring at night, is fairly typical. The patient may report being awakened by the pain and paresthesias and needing to shake the hand for relief. The lack of muscle activity at night allows fluid accumulation, and wrist flexion during sleep is thought to account for this exacerbation of symptoms. Patients may also report daytime paresthesias, clumsiness or dropping of objects, and weakness of pinch or grasp.

2. Physical examination may demonstrate a mild flattening of the thenar eminence. Light touch with a cotton applicator along the radial border of the ring finger and both sides of the index finger and thumb will demonstrate a decrease in sensation. Care must be taken to apply the applicator along the palmar surface of the digit, as the dorsum of the fingers is supplied by the radial and ulnar nerves. A decrease in two-point discrimination occurs late in the neuropathy. Thumb opposition, the ability to draw the thumb away from the palm and oppose the thumb pulp to the pulp of the little finger, may be diminished. Tapping the volar surface of the wrist over the median nerve may produce Tinel's sign, which appears as shooting pain in the long or index finger and indicates median nerve compression. Phalen's sign, also helpful, is performed by flexing both wrists for 30 to 60 seconds to elicit median nerve numbness in the affected hand.

3. Electromyography and nerve conduction studies may confirm a delay in nerve conduction across the carpal canal and denervation of thenar musculature.

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