engleski

Evaluation of corticobulbar and corticospinal excitability in developmental stuttering: the navigated transcranial magnetic stimulation study

Introduction: Here we present the first assessment of the excitability of corticobulbar and corticospinal projections in adults with developmental stuttering. Methods: Navigated transcranial magnetic stimulation (nTMS) was applied to the primary motor representation (M1) for hand and laryngeal muscle representations over the left and right hemispheres, while recording motor evoked potentials (MEP) from contralateral abductor pollicis brevis and corticobulbar motor evoked potentials (CoMEP) from right cricothyroid muscle in a group of 16 adults with developmental stuttering and 11 control subjects. The following indices of measurement of corticospinal excitability were obtained: resting motor threshold, motor evoked potential (MEP) stimulus- response curve, corticospinal silent period threshold, corticospinal silent period stimulus- response curve. The latency and amplitude of CoMEP recorded from cricothyroid muscle was analysed. Results: 1) nTMS mapping of M1 for hand muscle in both hemispheres revealed significant differences in the duration of silent period at 150 % vs. 160 % and vs. 175 % of silent period motor threshold between the stuttering and the control group in the left and right hemispheres. 2) nTMS mapping of M1 for cricothyroid muscle in both hemispheres revealed: a) significant differences in the amplitude of CoMEPs between the stuttering and the control group in the left and right hemispheres, indicating higher CoMEP amplitudes in the stuttering than in the control group, b) no significant differences between contralateral and ipsilateral CoMEPs in the stuttering compared to the control group, c) significantly more CoMEP responses induced in the control compared to the stuttering group during stimulation of the M1 for laryngeal muscles in the right hemisphere. Discussions: This study provides an evidence of altered projections of corticobulbar and corticospinal pathways in stuttering speakers. The data and nTMS protocol may be useful in future studies investigating pathomechanisms of stuttering in different subtypes of stuttering in adults and children.

stuttering ; cortical excitability ; TMS

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