Bunn, L.M.; (2011) Sensory mechanisms of balance control in cerebellar disease. Doctoral thesis , UCL (University College London).

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Abstract

A wealth of evidence exists to suggest that the cerebellum has an important role in the integration of vestibular, proprioceptive and visual sensory signals. Human bipedal balance depends on sensory integration and balance impairment is a common feature of cerebellar disease. I test the hypothesis that disrupted sensori-motor processing is responsible for balance impairment in cerebellar disease. Balance control in subjects with pure cerebellar disease (SCA6) was compared with matched healthy subjects using a mix of traditional clinical and laboratory-based tests. Sensory processing was explored using a novel combination of tools designed to deliver single-sensory channel balance perturbations. The vestibular, proprioceptive and visual channels were stimulated with galvanic vestibular stimulation, vibration and visual scene motion respectively. Standing balance was explored using 3D whole body motion analysis. Sway speed when standing quietly with eyes open was significantly increased in those with SCA6 and strongly correlated with disease severity scores. Responses to isolated vestibular stimulation suggest largely normal vestibulo-motor processing in SCA6 subjects. Responses had normal latency and magnitude. Response direction followed head position in the normal way suggesting intact vestibulo-proprioceptive integration. Vision had a normal attenuating effect on response magnitude suggesting intact vestibulo-visual integration. Responses to isolated vestibular, proprioceptive and visual stimuli responses were compared to investigate whether there might be a predominant deficit in any one channel. Vestibular and proprioceptive stimuli evoked largely normal responses. In contrast, visual stimuli consistently evoked abnormally large responses with significant timing delays. Increases in SCA6 response magnitudes to moving visual stimuli strongly correlated with disease severity scores. This finding is the first to point to a specific change in sensori-motor processing in cerebellar disease. This finding could contribute to balance impairments but is unlikely to explain balance impairment observed with the eyes closed. Overall sensory processing for balance control in SCA6 is largely intact.

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