Objective: To determine the incidence of overwork weakness in Charcot-Marie-Tooth disease (CMT).
Design: Prospective survey.
Setting: Rehabilitation department for CMT in an Italian tertiary care hospital.
Participants: A total of 106 outpatients with CMT, selected for absence of other causes of weakness (age range, 11-69y), and 48 healthy volunteers (controls).
Interventions: The strength of 2 intrinsic hand muscles (abductor pollicis brevis [APB], first dorsal interosseous) in the dominant and nondominant hands was graded by using manual muscle testing and a modified Medical Research Council (MRC) Scale.
Main outcome measures: The side of the stronger muscle and the difference in strength between the nondominant and dominant muscles.
Results: Muscles were stronger on the nondominant side in 65.57% of patients versus 1.04% of controls, and on the dominant side in .94% of patients versus 84.38% controls. The difference in strength for first dorsal interosseous was .51 in patients and -.32 in controls (P>.01). The difference in strength for APB was .65 in patients and -.35 in controls (P>.01).
Conclusions: CMT muscles in the dominant hand are weaker than in the nondominant hand. This may be the result of overwork weakness.