Dual task effect on postural control in patients with degenerative cerebellar disorders

Background: The cerebellum plays an important role for balance control and the coordination of voluntary movements. Beyond that there is growing evidence that the cerebellum is also involved in cognitive functions. How ataxic motor symptoms are influenced by simultaneous performance of a cognitive task, however, has rarely been assessed and some of the findings are contradictory. We assessed stance in 20 patients with adult onset degenerative almost purely cerebellar disorders and 20 healthy controls during single and dual task conditions (verbal working memory task). To objectively measure postural sway and the impact of somatosensory, visual and vestibular inputs we used static and dynamic posturography with the Sensory Organization Test (SOT). Results: In both groups, cerebellar patients and controls, dual tasking reduced all sway parameters. Reduction of sway path was higher in cerebellar patients and increased with the difficulty of the postural task. The frequency of falls was higher in the patients group especially during the more challenging conditions and dual task performance in particular increased the risk of falls in cerebellar patients. Conclusion: Dual task conditions had a larger impact on sway parameters in patients with chronic cerebellar disorders than in healthy controls and lead to an increased risk of falls. As performing two tasks simultaneously is common and therefore important in daily life dual task exercises should be part of physical therapy programs for cerebellar patients.