Consistent affection of the central somatosensory system in spinocerebellar ataxia type 2 and type 3 and its significance for clinical symptoms and rehabilitative therapy

The spinocerebellar ataxias type 2 (SCA2) and type 3 (SCA3) are progressive, currently untreatable and ultimately fatal ataxic disorders, which belong to the group of neurological disorders known as CAG-repeat or polyglutamine diseases. Since knowledge regarding the involvement of the central somatosensory system in SCA2 and SCA3 currently is only fragmentary, a variety of somatosensory disease signs remained unexplained or widely misunderstood. The present review (1) draws on the current knowledge in the field of neuroanatomy, (2) describes the anatomy and functional neuroanatomy of the human central somatosensory system, (3) provides an overview of recent findings regarding the affection of the central somatosensory system in SCA2 and SCA3 patients, and (4) points out the underestimated pathogenic role of the central somatosensory system for somatosensory and somatomotor disease symptoms in SCA2 and SCA3. Finally, based on recent findings in the research fields of neuropathology and neural plasticity, this review supports currently applied and recommends further neurorehabilitative approaches aimed at maintaining, improving, and/or recovering adequate somatomotor output by enforcing and changing somatosensory input in the very early clinical stages of SCA2 and SCA3.