Lisa M. Bunn

Prospective analysis of falls in dominant ataxias

In a previous retrospective study, we demonstrated that falls are common and often injurious in dominant spinocerebellar ataxias (SCAs) and that nonataxia features play an important role in these falls. Retrospective surveys are plagued by recall bias for the presence and details of prior falls. We therefore sought to corroborate and extend these retrospective findings by means of a prospective extension of this fall study. 113 patients with SCA1, SCA2, SCA3 or SCA6, recruited from the EuroSCA natural history study, were asked to keep a fall diary in between their annual visits to the participating centres. Additionally, patients completed a detailed questionnaire about the first three falls, to identify specific fall circumstances. Relevant disease characteristics were retrieved from the EuroSCA registry. 84.1% of patients reported at least one fall during a time period of 12 months. Fall-related injuries were common and their frequency increased with that of falls. The presence of nonataxia symptoms was associated with a higher fall frequency. This study confirms that falls are a frequent and serious complication of SCA, and that the presence of nonataxia symptoms is an important etiological factor in its occurrence.

Stance instability in spinocerebellar ataxia type 6.

Balance impairment is a principal symptom of cerebellar disease, but is poorly understood partly because subjects with heterogenous cerebellar and extracerebellar lesions have often been studied. Spinocerebellar ataxia type 6 (SCA6) provides an opportunity to understand balance dysfunction associated with a relatively homogenous cerebellar lesion. This study investigated stance instability in SCA6 and how it is affected by varying stance width. Body sway, as well as its directional preponderance and distribution across joints, was measured three‐dimensionally in 17 SCA6 and 17 matched healthy control subjects. Subjects stood for 40 seconds on a stable surface with their eyes open and feet positioned at various stance widths (32, 16, 8, 4, and 0 cm). SCA6 subjects swayed faster than controls at every stance width. Decreasing the stance width produced a disproportionate increase in sway speed in SCA6 subjects, compared to controls. Directional preponderance of sway was dependent on stance width, but did not differ between groups. Joint instability was increased by reducing stance width in both groups, but there was greater instability of the ankle joint in the roll plane in the SCA6 group. Measures of global instability correlated strongly with disease severity measured with the Scale for the Assessment and Rating of Ataxia (r = 0.79). The sway characteristics suggest a disruption of sensorimotor processing for balance control in SCA6. The correlation with disease severity implies that balance impairment is a feature of progression of SCA6 clinical syndrome. With stance width standardized, the instability measures employed could provide sensitive, continuous outcome measures of longitudinal or therapeutic change.

Training balance with opto-kinetic stimuli in the home: a randomized controlled feasibility study in people with pure cerebellar disease:

Objective: To investigate the feasibility of a randomized controlled trial of a home-based balance intervention for people with cerebellar ataxia. Design: A randomized controlled trial design. Setting: Intervention and assessment took place in the home environment. Participants: A total of 12 people with spinocerebellar ataxia type 6 were randomized into a therapy or control group. Both groups received identical assessments at baseline, four and eight weeks. Interventions: Therapy group participants undertook balance exercises in front of optokinetic stimuli during weeks 4–8, while control group participants received no intervention. Main measures: Test–retest reliability was analysed from outcome measures collected twice at baseline and four weeks later. Feasibility issues were evaluated using daily diaries and end trial exit interviews. Results: The home-based training intervention with opto-kinetic stimuli was feasible for people with pure ataxia, with one drop-out. Test–retest reliability is strong (intraclass correlation coefficient >0.7) for selected outcome measures evaluating balance at impairment and activity levels. Some measures reveal trends towards improvement for those in the therapy group. Sample size estimations indicate that Bal-SARA scores could detect a clinically significant change of 0.8 points in this functional balance score if 80 people per group were analysed in future trials. Conclusions: Home-based targeted training of functional balance for people with pure cerebellar ataxia is feasible and the outcome measures employed are reliable.

Sensorimotor processing for balance in spinocerebellar ataxia type 6.

We investigated whether balance impairments caused by cerebellar disease are associated with specific sensorimotor processing deficits that generalize across all sensory modalities. Experiments focused on the putative cerebellar functions of scaling and coordinate transformation of balance responses evoked by stimulation of single sensory channels.

Standardized Assessment of Hereditary Ataxia Patients in Clinical Studies

Hereditary ataxias are a heterogeneous group of degenerative diseases of the cerebellum, brainstem, and spinal cord. They may present with isolated ataxia or with additional symptoms going beyond cerebellar deficits. There are an increasing number of clinical studies with the goal to define the natural history of these disorders, develop biomarkers, and investigate therapeutic interventions. Especially, early and preclinical disease stages are currently of particular interest.