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Wrist News

Squeezing Scissors Enlarges Wrist Nerve

A good workout can cause muscles to bulge. Now there's proof that the median nerve in the wrist bulges when the hand gets a workout. Using a pair of scissors is enough to enlarge this nerve where it passes inside the carpal tunnel of the wrist. Formed by ligaments and bones, the carpal tunnel encloses eight finger tendons, a thumb tendon, and the median nerve.

Investigators think the added nerve size is from fluid that builds up around the nerve and from blood that flows into "reserve" vessels in the nerve. These reserve vessels are believed to stay empty until there's activity or injury in the nerve.

An ultrasound machine was used to see the size of the median nerve in the wrists of 40 people. Comparing 19 men and 21 women, researchers observed that women tended to have smaller nerve canals. And women had larger median nerves on average than men.

Participants used scissors to repeatedly cut small pieces of doweling for five minutes. Ultrasound measurements were taken after each person completed the activity, and again five and ten minutes later.

Ten minutes after cutting, all participants still showed marked enlargement in the median nerve. But women averaged significantly greater increases in nerve size. Women had an increase of 17.6 percent; men showed only a 2.7 percent enlargement. None of the participants complained of pain, numbness, or tingling in the 24-hour period following the cutting activity.

The researchers feel the increased nerve size is normal and begins to go away shortly after the activity. Again, they believe this change is due to extra blood and fluid that fills in and around the nerve during certain hand actions. They suggest that more studies are needed to determine how hand activities affect the median nerve in the wrist.


Nicola Massey-Westropp, B AppScOT, et al. The Effect of a Standard Activity on the Size of the Median Nerve as Determined by Ultrasound Visualization. In The Journal of Hand Surgery. July 2001. Vol. 26A. No. 4. Pp. 649-654.

12/18/2001

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