Reduction of knee torques and leg-related functional abilities in hereditary motor and sensory neuropathy

Our purpose was to evaluate a test battery for measuring progress and the effect of interventions in patients with hereditary motor and sensory neuropathy (HMSN types I and II). For this purpose differences in upper leg strength and functional abilities between patients and healthy persons were quantified. Twenty patients participated in the study. They were matched with healthy control subjects with respect to gender, age, body weight, and height. Because of the high reproducibility and sensitivity of the method, muscle strength was quantified as isokinetic and isometric knee torques on an isokinetic dynamometer. Isokinetic knee extension and flexion torques were recorded for three movement velocities (120, 60, and 30 degrees/sec). An extension endurance test was performed at 80% of maximum voluntary contraction. Time scored activities (for instance, stair climbing) that are mainly related to leg function were measured to determine functional abilities. The torques were lower (p < 0.009) and endurance was less (p = 0.03) for patients than for controls. Time scores were higher (p < 0.013) in patients. A strength reduction in the knee extensors and flexors and a decrease in functional abilities was found even in mildly affected patients. Torques and time scores were correlated, although correlation coefficients were rather low. Our results indicate that both types of test are useful for monitoring lower limb function in HMSN patients.