Objective: To evaluate if corticospinal tract (CST) dysfunction appears before the cerebellar syndrome in SCA2

Background: Studies of corticospinal tract (CST) function in prodromal spinocerebellar ataxia type 2  are scarce.

Methods: Thirty-seven non-ataxic SCA2 mutation carriers and their age- and sex-matched healthy controls underwent clinical assessment and transcranial magnetic stimulation to determine CST integrity to the right abductor pollicis brevis (APB) and tibialis anterior (TA) muscles.

Results: Non-ataxic SCA2 mutation carriers showed significantly higher resting and active motor thresholds for APB and TA [figure1], and a prolongation of the cortical silent period (CSP) and the central motor conduction times (CMCT), compared to controls. CMCT to TA correlated inversely with predicted time to ataxia onset and correlated directly with CAG repeat size.

Conclusions: Findings provide novel electrophysiological evidence for affection of the CST in prodromal SCA2. Slowed conduction in the CST to the lower limbs predicts time to ataxia onset, and reflects polyglutamine neurotoxicity.                   

References:

1. Velázquez-Pérez L, Rodríguez-Labrada R, Canales-Ochoa N, et al. Progression of early features of spinocerebellar ataxia type 2 in individuals at risk: a longitudinal study. Lancet Neurol 2014a;13(5):482-489.
2. Velázquez-Pérez L, Rodríguez-Labrada R, Cruz-Rivas EM, et al. Comprehensive study of early features in spinocerebellar ataxia 2: delineating the prodromal stage of the disease. Cerebellum 2014b;13(5):568-579

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MDS Abstracts - https://www.mdsabstracts.org/abstract/corticospinal-tract-dysfunction-precede-the-cerebellar-syndrome-in-spinocerebellar-ataxia-2/