Is It Really Carpal Tunnel Syndrome?  The Double Crush Hypothesis
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This note is based on a report in CTDNews, Sept 93.  The report "Is
it really carpal tunnel syndrome?" covers some research by Upton and
McComas in 1973 (!) that led to the so called double crush hypothesis,
which says that pain diagnosed as due to CTS may actually be due to
nerve compression and/or irritation, often in the spine or shoulder,
manifesting itself elsewhere, often in the wrist.  The nerve in the
wrist or elbow is susceptible to compression/irritation because it has
already been irritated by compression in the neck.

Upton and McComas conducted an electromyographic study of 115 CTS
patients, finding that 81 of them had neck neural lesions.   Neural
Function Analysis, who sell related neurological tests, did a study of
248 CTS patients, finding that 228 had ONLY neck nerve irritation, while
12 had double crush (neck and wrist) and 7 had shoulder problems (from
the brachial plexus).  Only three patients had median nerve irritation
(the normally accepted cause of CTS, as you may be aware).  The
researchers conclude that it this hypothesis is correct, treatment
should be directed not at a single site but at all vulnerable points
along the course of the nerve - to the neck and the wrist or elbow.

This may explain why CTS patients do not always get good results from
carpal tunnel release surgery, to say the least.

I have no connection with CTDNews, but since I have quoted them so
liberally I should say that their journal is very interesting, including
updates on research, RSI tools, workplace setup, and more.  The CTD in the
title stands for Cumulative Trauma Disorder, an alternative term for RSI
used in the US.

All this stuff fits pretty well with the adverse mechanical tension
(AMT) theory.  Many non-medical therapists who treat RSI are aware of
the role of tight muscles in referred pain like this.

If all this is true, there is more hope for many people than they may
currently believe - AMT and other muscle-release treatments have helped
many people to a considerable degree of recovery, though most still have
to be careful about the amounts and types of hand use that they indulge
in.

Richard Donkin
CIS: 100272,1772