Effect of hand warming on electrodiagnostic testing results and diagnosis in patients with suspected carpal tunnel syndrome.
Burnham RS, Burnham TR. Effect of hand warming on electrodiagnostic testing results and diagnosis in patients with suspected carpal tunnel syndrome.


OBJECTIVE
To evaluate the effects of hand warming on electrodiagnostic (EDX) parameters of carpal tunnel syndrome (CTS). Specifically, to evaluate the type and magnitude of change in EDX values; to determine whether warming can change the EDX diagnosis of CTS and, if so, to determine whether specific EDX tests are more vulnerable to the effects of warming.


METHODS
Interventional before-after trial.


METHODS
Community EDX laboratory.


METHODS
Consecutive patients (N=33) referred for EDX evaluation of suspected CTS.


METHODS
Each upper limb was tested at room temperature (average hand temperature, 31.9 degrees C) and retested after 20 minutes of heating pad warming (average hand temperature, 33.5 degrees C).


METHODS
Median and ulnar nerve motor and sensory latency, conduction velocity, and amplitude.


RESULTS
Warming resulted in significantly faster transcarpal tunnel sensory and motor conduction (6%-10%), reduced median: ulnar sensory latency to digit 4 difference (23%), and reduced sensory nerve and compound motor action potential amplitude (10% and 13%, respectively). The changes resulted in 15% fewer limbs meeting the EDX conduction velocity criteria of CTS and 9% fewer by median: ulnar sensory latency to digit 4 difference. Waveform amplitudes became abnormally low after warming in 12% of limbs.


CONCLUSIONS
Hand warming using a heating pad for 20 minutes increases median nerve transcarpal tunnel conduction velocity and reduces amplitude. These phenomena introduce potential sources of diagnostic error, particularly in borderline cases. Generally, within hand, between nerve, and within nerve comparison techniques are less susceptible to the conduction velocity effects of warming.
Burnham
Robert S
RS
Division of Physical Medicine and Rehabilitation, Faculty of Medicine, University of Alberta, Alberta, Canada. rburnham@telusplanet.net
Burnham
Taylor R
TR
D000200:Action Potentials; D002349:Carpal Tunnel Syndrome / Q000175:diagnosis*; D004568:Electrodiagnosis / Q000379:methods*; D005260:Female; D006358:Hot Temperature; D006801:Humans; D008297:Male; D008475:Median Nerve; D008875:Middle Aged; D009431:Neural Conduction; D009460:Neurologic Examination / Q000379:methods; D012881:Skin Temperature; D014459:Ulnar Nerve