Gait impairment precedes clinical symptoms in spinocerebellar ataxia type 6

Abstract

Spinocerebellar ataxia type 6 (SCA6) is an inherited ataxia with no established treatment. Gait ataxia is a prominent feature causing substantial disability. Understanding the evolution of the gait disturbance is a key step in developing treatment strategies. We studied 9 gait variables in 24 SCA6 (6 presymptomatic; 18 symptomatic) and 24 controls and correlated gait with clinical severity (presymptomatic and symptomatic). Discrete gait characteristics precede symptoms in SCA6 with significantly increased variability of step width and step time, whereas a more global gait deficit was evident in symptomatic individuals. Gait characteristics discriminated between presymptomatic and symptomatic individuals and were selectively associated with disease severity. This is the largest study to include a detailed characterization of gait in SCA6, including presymptomatic subjects, allowing changes across the disease spectrum to be compared. Selective gait disturbance is already present in SCA6 before clinical symptoms appear and gait characteristics are also sensitive to disease progression. Early gait disturbance likely reflects primary pathology distinct from secondary changes. These findings open the opportunity for early evaluation and sensitive measures of therapeutic efficacy using instrumented gait analysis which may have broader relevance for all degenerative ataxias.