Dynamic markers of altered gait rhythm in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a disorder marked by loss of motoneu rons. We hypothesized that subjects with ALS would have an altered gait rhy thm, with an increase in both the magnitude of the stride-to-stride fluctua tions and perturbations in the fluctuation dynamics. To test for this locom otor instability, we quantitatively compared the gait rhythm of subjects wi th ALS with that of normal controls and with that of subjects with Parkinso n's disease (PD) and Huntington's disease (HD), pathologies of the basal ga nglia. Subjects walked for 5 min at, their usual pace wearing an ankle-worn recorder that enabled determination of the duration of each stride and of stride-to-stride fluctuations. We found that the gait of patients with ALS is less steady and more temporally disorganized compared with that of healt hy controls. In addition, advanced ALS, HD, and PD were associated with cer tain common, as well as apparently distinct, features of altered stride dyn amics. Thus stride-to-stride control of gait rhythm is apparently compromis ed with ALS. Moreover, a matrix of markers based on gait dynamics may be us eful in characterizing certain pathologies of motor control and, possibly, in quantitatively monitoring disease progression and evaluating therapeutic interventions.