Altered sensory system activity and connectivity patterns in adductor spasmodic dysphonia

Tobias Mantel,Michael Welte,Bernhard Haslinger,Christian Dresel,Tobias Meindl,Angela Jochim,Claus Zimmer

doi:10.1038/s41598-020-67295-w

Abstract

Adductor-type spasmodic dysphonia (ADSD) manifests in effortful speech temporarily relievable by botulinum neurotoxin type A (BoNT-A). Previously, abnormal structure, phonation-related and resting-state sensorimotor abnormalities as well as peripheral tactile thresholds in ADSD were described. This study aimed at assessing abnormal central tactile processing patterns, their spatial relation with dysfunctional resting-state connectivity, and their BoNT-A responsiveness. Functional MRI in 14/12 ADSD patients before/under BoNT-A effect and 15 controls was performed (i) during automatized tactile stimulus application to face/hand, and (ii) at rest. Between-group differential stimulation-induced activation and resting-state connectivity (regional homogeneity, connectivity strength within selected sensory(motor) networks), as well as within-patient BoNT-A effects on these differences were investigated. Contralateral-to-stimulation overactivity in ADSD before BoNT-A involved primary and secondary somatosensory representations, along with abnormalities in higher-order parietal, insular, temporal or premotor cortices. Dysphonic impairment in ADSD positively associated with left-hemispheric temporal activity. Connectivity was increased within right premotor (sensorimotor network), left primary auditory cortex (auditory network), and regionally reduced at the temporoparietal junction. Activation/connectivity before/after BoNT-A within-patients did not significantly differ. Abnormal ADSD central somatosensory processing supports its significance as common pathophysiologic focal dystonia trait. Abnormal temporal cortex tactile processing and resting-state connectivity might hint at abnormal cross-modal sensory interactions.

Highlights

Adductor-type spasmodic dysphonia (ADSD) manifests in effortful speech temporarily relievable by botulinum neurotoxin type A (BoNT-A)
Focal laryngeal dystonia (FLD) is a debilitating task-specific focal dystonia (TSFD) affecting the laryngeal muscles, resulting in phonation impairment that can be classified into a number of overlapping clinical phenotypes[1]
BoNT-A-associated alterations of cortical activity have been reported in orofacial non-TSFD during both motor task and somatosensory processing[15,16], but conflicting observations have been made during phonation in spasmodic dysphonia[4,5]

Summary

Introduction

Adductor-type spasmodic dysphonia (ADSD) manifests in effortful speech temporarily relievable by botulinum neurotoxin type A (BoNT-A). Previous studies have outlined several functional and structural cortical abnormalities in the disease involving cortices of the phonation network[3], including altered phonation-related activity using functional MRI (fMRI)[4,5,6] or transcranial magnetic stimulation[7], resting-state connectivity[8] and grey matter structure[9] in primary and higher-order (mostly inferior parietal, pre-/ supplementary motor) sensorimotor cortices in ADSD. This work aimed at characterizing (i) patterns of abnormal central tactile stimulus processing in ADSD, (ii) possible spatial relations between areas of altered stimulation-related activity and dysfunctional (long-range and regional) connectivity at rest, and (iii) possible effects of BoNT-A treatment on the above findings, avoiding confounds by motor execution, BoNT-A-modulated muscle function, or acute compensation mechanisms

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