Sensorimotor Functions, Visuospatial Perception, and Visuospatial Abilities in Spinocerebellar Ataxias and other Cerebellar Ataxias

Background and Objectives
Spinocerebellar ataxias (SCAs) and other neurodegenerative cerebellar ataxias (N-SCAs) involve alterations in cerebellar structure and function, affecting motor control and sensorimotor integration but also cognitive functions such as visuospatial processing. The cerebellum is essential for sensorimotor functions, and it contributes to cognition. The study aims to assess sensorimotor functions, visuospatial perception, and abilities as well as visuoconstructive functions in ataxic patients.
Methods
This cross-sectional observational study was conducted at the Neurology Units of Helsingborg Hospital and Skåne University Hospital in southern Sweden. We included patients with SCA, patients with N-SCA, and controls. Neurocognitive and motor tests were administrated. Self-report scales were used to measure anxiety, depression, and insomnia symptoms. The Scale for the Assessment and Rating of Ataxia was used to assess ataxia severity. The diagnosis was verified by whole-genome sequencing before the study which was performed on EDTA blood collected from the ataxic patients to verify the SCA diagnosis.
Results
The study included patients with SCA (n = 22, age = 53.5 ± 16.2, education = 14.5 ± 4.4, 63% females), patients with N-SCA (n = 24, age = 48.7 ± 21.7, education = 14.4 ± 3.5, 25% females), and controls (n = 65, age = 46 ± 14.6, education = 15.4 ± 2.5, 57% females). Most patients with SCA (77.2%) and N-SCA (87.6%) exhibited moderate-maximal ataxia severity. Both patient groups showed impairments in sensorimotor functions as well as in visuoconstructive functions, visuospatial perception, and abilities. Sensorimotor performance was significantly associated with all cognitive outcomes, and moderate-strong correlations were found between ataxia severity and cognitive performance. No significant differences were observed between SCA and N-SCA in age at symptom onset, disease duration, progression rate, or ataxia severity. Regression analyses indicated weak effects of age (R2 = 0.04–0.19, 95% CI) and depression (R2 = 0.03–0.11, 95% CI), weak-strong effects of ataxia severity (R2 = 0.19–0.67, 95% CI), and weak-moderate effects of disease duration (R2 = 0.10–0.45, 95% CI) on test performance. Biological sex had no significant effect.
Discussion
Cerebellar ataxia severity is moderately strongly associated with impairments in sensorimotor function, visuoconstructive functions, visuospatial perception, and abilities, indicating that ataxic patients are affected not only in motor function but also in higher cognitive functions. Cerebellar changes are presumed to primarily underlie the functional deficits in these patients, although noncerebellar pathologies may have contributed to the observed impairments.