Altered sensory system activity and connectivity patterns in adductor spasmodic dysphonia

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 higherorder 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.

The Central Effects of Botulinum Toxin in Dystonia and Spasticity

“…The functional neuroimaging studies assessing the central effects of BoNT-A in focal dystonias are also summarised in Table 2. increased FC between S1 and S2, decreased FC within the basal ganglia and between the basal ganglia and thalamus or cortex, i.e., partial normalisation of FC; reduced information flow from the putamen and thalamus into the S2, increased influence of the M1 in the caudate nucleus; decreased ReHo in the putamen and S1; no correlation with TWSTRS Mantel et al [76] adductor…”

“…As discussed in previous sections and demonstrated in multiple electrophysiological [ 37 , 38 , 39 , 41 , 90 ] and imaging studies [ 72 , 91 , 92 ] involving peripheral stimulation, dystonia is characterised by abnormal somatosensory processing and considered to be a disorder of sensorimotor integration [ 8 ]. Three studies have therefore evaluated the central effects of BoNT-A by comparing pre-treatment and post-treatment brain responses to external stimulation [ 74 , 75 , 76 ].…”

“…A recent study by Mantel et al [ 76 ] evaluated the effect of BoNT-A in 12 pre-treated patients with adductor-type spasmodic dysphonia using the tactile stimulation paradigm of Dresel et al [ 74 ]. In contrast to the results of Dresel et al [ 74 ], patients hyperactivated a number of cortical areas at baseline (pre-BoNT-A) [ 76 ].…”

“…A recent study by Mantel et al [ 76 ] evaluated the effect of BoNT-A in 12 pre-treated patients with adductor-type spasmodic dysphonia using the tactile stimulation paradigm of Dresel et al [ 74 ]. In contrast to the results of Dresel et al [ 74 ], patients hyperactivated a number of cortical areas at baseline (pre-BoNT-A) [ 76 ]. The contralateral S1 and S2 were overactivated during the stimulation of the right forehead and lip, while the contralateral S1 was also overactivated during the stimulation of the left hand and upper lip.…”

“…A comparison before and after BoNT-A, however, did not reveal any significant changes. The authors of the study suggested that the differences between their results and the results of Dresel et al [ 74 ] are inherent to the differences between the task-specific and non-task-specific forms of dystonia [ 76 ].…”