Klinische Neurophysiologie 2011; 42 - P273
DOI: 10.1055/s-0031-1272720

Impaired isometric force coordination in Huntington's disease

S. Horst 1, S. Bohlen 1, H.W. Lange 1, R. Reilmann 1
  • 1Münster

Background: Assessment of motor phenotype and diagnosis of Huntington's Disease (HD) are based on the Unified HD Rating Scale-Total Motor Score (UHDRS-TMS), a categorical scale. Therefore, results of clinical trials are limited by (1) subjective error, (2) low sensitivity of the categorical scale, and (3) insensitivity in pre-manifest stage. Hence, more objective and quantitative measures of motor phenotype are needed. We have previously shown that impairments in isometric force coordination can be seen in premanifest and manifest HD in a tongue protrusion and lifting task (Reilmann et al. 2010 a,b); impairments correlated with clinical severity as assessed by the UHDRS-TMS and the disease burden score (based on CAG-repeat length and age). In addition, impairments in tongue protrusion and tapping correlated to changes in striatal brain atrophy as assessed by VBM in a multi-center study (Bechtel et al. 2010, Tabrizi et al. 2009, Reilmann pers. comm.). In this study we aimed to investigate whether similar impairments of force coordination can be found in the lower extremity.

Objective: To assess whether impairments in isometric force coordination can be detected in the feet and hands of symptomatic HD subjects compared to controls.

Methods: So far 15 controls and 22 symptomatic HD subjects were assessed. Subjects were instructed to match target forces of 1.5 N and 5 N with the thumb or 1 N, 5 N and 10 N with the big toe (all tasks right and left side, 3 trials each). The target forces were displayed on a monitor and had to be matched for 20s.

Results: All paradigms distinguish controls from symptomatic subjects at p<0.0001. The static coefficient of variability (%), assessing the degree of deviation from the target force normalized to the mean force, was the most robust measure in all matching trials. Comparisons between tasks will be presented.

Conclusions: Assessment of force matching tasks by hand and feet provide quantitative objective measures for severity of motor phenotype in symptomatic HD. Lower extremitiy motor dysfunction can be assessed objectively in HD.