O-06 Motor cortex excitability and conduction time of pyramidal tracts in preclinical SCA1 gene carriers

Abstract

Background Spinocerebellar ataxia type 1 (SCA1) is a neurodegenerative, dominantly inherited disease caused by CAG repeat expansion. It manifests mainly as trunk and limbs ataxia, dysarthria, gaze palsy and peripheral neuropathy. We aimed to assess the functional alterations of corticospinal tracts in preclinical SCA1 gene carriers performed during 4-years follow-up. Methods Transcranial magnetic stimulation (TMS) was carried out in 26 SCA1 gene carries with age at study entry 25.6\u202f±\u202f4.7, CAG repeat number 49.5\u202f±\u202f4.8 and 30 age- and gender-matched healthy controls (HC). Presence of ataxia was assessed by the Scale for Assessment and Rating of Ataxia (SARA). TMS was performed every ± 12\u202fmonths to evaluate motor threshold (MT), silent period (SP) from hypothenar and extensor digitorum brevis muscles, central motor conduction time (CMCT) and motor evoked potentials amplitude (MEPs). Results Baseline SARA score increased from 0.6\u202f±\u202f0.7 to 4.9\u202f±\u202f5.2 points across follow-up. In 43% SCA1 cases MT of lower limbs was elevated and MEPs were in 35% decreased. SP was longer (p\u202f Conclusions In the preclinical SCA1 gene carriers before the onset of overt clinical signs TMS revealed functional alterations of corticospinal pathways. TMS could serve as an objective measure of disease progression in SCA1 patients.