Cortico-bulbar excitability in abductor laryngeal dystonia disease: the diagnostic role of transcranial magnetic stimulation

Laryngeal Dystonia (LD) is a rare, idiopathic disease affecting the intrinsic muscles of the larynx with a prevalence of 14 per 100, 000 presenting with two phenotypes, the more common adductor LD and the relatively rare abductor LD. Recent works using TMS have indicated reduced inhibition by investigating cortical silent period (cSP) measure, to be characteristic of adductor LD, as well as hand and cervical dystonia. It is agreed that the cSP reflects an intracortical inhibitory process mediated by GABAA and GABAB receptors. However, cSP from the vocal muscle has not been previously reported for the abductor LD. Therefore in our study, we have applied e-field navigated transcranial TMS and provided the first evidence of altered cSP as a measure of corticobulbar excitability in abductor LD. Further studies are needed on a larger number of patients with abductor LD and a comparison of cSP with adductor LD findings. Ultimately, the potential benefit in terms of cSP as a potential marker in terms of rehabilitation should be examined.