Objective: Estimate the Reticulospinal tract (RST) activity using StartReact paradigm in patients of SCA12 with clinical and electrophysiological evidence of compromised corticospinal tract (CST) integrity.

Background: Spinocerebellar Ataxia Type 12 (SCA12) is an autosomal-dominant heredodegenerative polyglutamate disorder presenting with adult-onset kinetic tremor of the upper limb and gait ataxia. Clinically, some of these patients demonstrate hyperreflexia in limbs and other signs suggestive of CST involvement. Until now, there has been limited objective evidence of spinal cord involvement in Spinocerebellar Ataxia, including SCA12.

Method: We included six SCA12 patients with hyperreflexia of all four limbs. The test battery included Transcranial Magnetic Stimulation Motor Evoked Potentials (MEPs) and the StartReact paradigm which measures the shortening of reaction time in response to a high intensity sound. StartReact is an indirect measure of RST strength. The mean difference of simple auditory reaction time to startle auditory reaction time was considered the index for RST connectivity.

Results: MEPs could not be elicited at maximum stimulator output in five patients; one had prolonged latency MEPs (36.5 ms). The StartReact index was not significantly different (41 ms vs 45 ms, p >0.5) in the patients compared to 19 control subjects.

Conclusion: In SCA12 patients with evidence of significantly compromised cortical excitability and damage to CST, the functional integrity of RST is relatively preserved. This is not only interesting from a pathophysiological perspective but could be a useful lead for developing rehabilitation strategies in these patients.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/reticulospinal-tract-integrity-in-patients-with-sca12-having-impairment-of-corticospinal-tract-a-clinical-and-electrophysiological-study/