Brain activity related to phonation in young patients with adductor spasmodic dysphonia

Laryngeal Sensory Symptoms in Spasmodic Dysphonia

OBJECTIVE

The purpose of this research was to determine whether an association between laryngeal hypersensitivity (LH) and spasmodic dysphonia (SD) exists using the LH Questionnaire (LHQ). This study also explored the prevalence of self-reported upper respiratory infection (URI) at the time of SD onset across SD phenotypes.

METHODS

Individuals with and without SD were recruited to complete an online survey measure. All respondents provided demographic information and completed the LHQ. Participants with SD were also asked to provide information about their diagnosed SD subtype and pattern of onset, including whether onset was associated with a URI. The percentage of respondents with and without SD who were classified with LH was determined based on the LHQ. Scores on the LHQ were also compared between the non-SD and the SD groups, as well as between SD phenotypes (adductor SD, abductor SD, and mixed)).

RESULTS AND CONCLUSIONS

Significant associations were found between ADSD and LH, mixed SD and LH, and URI at time of SD onset and increased severity of LH symptoms. These findings suggest that laryngeal sensory symptoms may potentially contribute to or result from motor spasms in SD and/or have implications for its pathophysiology.

Hyperactive sensorimotor cortex during voice perception in spasmodic dysphonia

Spasmodic dysphonia (SD) is characterized by an involuntary laryngeal muscle spasm during vocalization. Previous studies measured brain activation during voice production and suggested that SD arises from abnormal sensorimotor integration involving the sensorimotor cortex. However, it remains unclear whether this abnormal sensorimotor activation merely reflects neural activation produced by abnormal vocalization. To identify the specific neural correlates of SD, we used a sound discrimination task without overt vocalization to compare neural activation between 11 patients with SD and healthy participants. Participants underwent functional MRI during a two-alternative judgment task for auditory stimuli, which could be modal or falsetto voice. Since vocalization in falsetto is intact in SD, we predicted that neural activation during speech perception would differ between the two groups only for modal voice and not for falsetto voice. Group-by-stimulus interaction was observed in the left sensorimotor cortex and thalamus, suggesting that voice perception activates different neural systems between the two groups. Moreover, the sensorimotor signals positively correlated with disease severity of SD, and classified the two groups with 73% accuracy in linear discriminant analysis. Thus, the sensorimotor cortex and thalamus play a central role in SD pathophysiology and sensorimotor signals can be a new biomarker for SD diagnosis.

A microstructural neural network biomarker for dystonia diagnosis identified by a DystoniaNet deep learning platform

This research identified a microstructural neural network biomarker for objective and accurate diagnosis of isolated dystonia based on the disorder pathophysiology using an advanced deep learning algorithm, DystoniaNet, and raw structural brain images of large cohorts of patients with isolated focal dystonia and healthy controls. DystoniaNet significantly outperformed shallow machine-learning pipelines and substantially exceeded the current agreement rates between clinicians, reaching an overall accuracy of 98.8% in diagnosing different forms of isolated focal dystonia. These results suggest that DystoniaNet could serve as an objective, robust, and generalizable algorithmic platform of dystonia diagnosis for enhanced clinical decision-making. Implementation of the identified biomarker for objective and accurate diagnosis of dystonia may be transformative for clinical management of this disorder.

Isolated dystonia is a neurological disorder of heterogeneous pathophysiology, which causes involuntary muscle contractions leading to abnormal movements and postures. Its diagnosis is remarkably challenging due to the absence of a biomarker or gold standard diagnostic test. This leads to a low agreement between clinicians, with up to 50% of cases being misdiagnosed and diagnostic delays extending up to 10.1 y. We developed a deep learning algorithmic platform, DystoniaNet, to automatically identify and validate a microstructural neural network biomarker for dystonia diagnosis from raw structural brain MRIs of 612 subjects, including 392 patients with three different forms of isolated focal dystonia and 220 healthy controls. DystoniaNet identified clusters in corpus callosum, anterior and posterior thalamic radiations, inferior fronto-occipital fasciculus, and inferior temporal and superior orbital gyri as the biomarker components. These regions are known to contribute to abnormal interhemispheric information transfer, heteromodal sensorimotor processing, and executive control of motor commands in dystonia pathophysiology. The DystoniaNet-based biomarker showed an overall accuracy of 98.8% in diagnosing dystonia, with a referral of 3.5% of cases due to diagnostic uncertainty. The diagnostic decision by DystoniaNet was computed in 0.36 s per subject. DystoniaNet significantly outperformed shallow machine-learning algorithms in benchmark comparisons, showing nearly a 20% increase in its diagnostic performance. Importantly, the microstructural neural network biomarker and its DystoniaNet platform showed substantial improvement over the current 34% agreement on dystonia diagnosis between clinicians. The translational potential of this biomarker is in its highly accurate, interpretable, and generalizable performance for enhanced clinical decision-making.

Brain Activity in Patients With Unilateral Vocal Fold Paralysis Detected by Functional Magnetic Resonance Imaging

OBJECTIVES

Understanding brain activity in response to unilateral vocal fold paralysis is essential to determine the neural compensatory mechanism underlying adaptation to voice disorders and to develop novel and improved rehabilitation programs for these disorders. We aimed to clarify brain activity during phonation (prolonged vowel, |i:|) in patients with chronic left vocal fold paralysis (LVFP) and compare with that in normal controls.

STUDY DESIGN

Case-control study.

METHODS

This functional magnetic resonance imaging (fMRI) study of an event-related task comprised 12 individuals with LVFP of more than 6 months duration and 12 healthy controls. The experimental task alternated phonation (prolonged vowel, |i:|) and no phonation (rest) conditions. The functional images obtained were single-shot gradient-echo echo-planar imaging. The volumes were acquired parallel to the anterior-posterior commissure plane and were sensitive to BOLD contrast. Data sets were processed and statistically analyzed using Statistical Parametric Mapping 8 software. Within-group analyses were conducted by applying the one-sample t test (P < 0.001, uncorrected). A random-effects analysis was used for group comparison.

RESULTS

The LVFP group showed significantly higher brain activity in the right premotor areas, left parietal lobule, right primary somatosensory areas, and bilateral supplementary motor area and lower brain activity in the auditory-related areas of the superior temporal gyrus. There were no significant correlations of the percent signal change on fMRI with disease duration, maximum phonation time, or age.

CONCLUSION

Patients with chronic unilateral vocal fold paralysis have stronger activity during voluntary phonation in various central networks. More detailed information on the central nervous system regions related to voluntary phonation from early to chronic phase is needed to understand the compensatory mechanisms in vocal fold paralysis and to establish an effective rehabilitation program. This is the first report to investigate brain activity in chronic unilateral vocal fold paralysis.

Transcranial magnetic stimulation and functional magnet resonance imaging evaluation of adductor spasmodic dysphonia during phonation

BACKGROUND

Reduced intracortical inhibition is a neurophysiologic finding in focal dystonia that suggests a broader problem of impaired cortical excitability within the brain. A robust understanding of the neurophysiology in dystonia is essential to elucidate the pathophysiology of the disorder and develop new treatments. The cortical silent period (cSP) is a reliable, non-invasive method to measure intracortical inhibition in the primary motor cortex associated with a muscle of interest. In adductor spasmodic dysphonia (AdSD), cSP of the laryngeal motor cortex (LMC) which directly corresponds to the affected musculature, the thyroarytenoid (TA), has not been examined.

OBJECTIVE

This work evaluated the cSP of the LMC and the relationship between cSP and functional magnetic resonance imaging (fMRI) blood-oxygen-level dependent (BOLD) activation in people with AdSD (n = 12) compared to healthy controls (CTL, n = 14).

RESULTS

Shortened LMC cSP were observed bilaterally in people with AdSD vs CTL (F(1, 99) = 19.5226, p < 0.0001), with a large effect size (η2 = 0.1834). Between-group fMRI analysis revealed greater activation in bilateral LMC in the AdSD > CTL contrast as compared to CTL > AdSD contrast. Correlation analysis showed that people with AdSD have positive correlation of left LMC BOLD activation and the cSP. Further, the right LMC cSP lacks either positive or negative associations with BOLD activation. CTL individuals displayed both positive and negative correlations between cSP and BOLD activation in the left LMC. In CTL, the LMC cSP and BOLD activation showed exclusively negative correlations in both hemispheres.

CONCLUSION

In AdSD, the cortical activation during phonation may not be efficiently or effectively associated with inhibitory processes, leading to muscular dysfunction. These findings may give insight into the maladaptive cortical control during phonation in people with AdSD.

Auditory Feedback Control Mechanisms Do Not Contribute to Cortical Hyperactivity Within the Voice Production Network in Adductor Spasmodic Dysphonia

Purpose Adductor spasmodic dysphonia (ADSD), the most common form of spasmodic dysphonia, is a debilitating voice disorder characterized by hyperactivity and muscle spasms in the vocal folds during speech. Prior neuroimaging studies have noted excessive brain activity during speech in participants with ADSD compared to controls. Speech involves an auditory feedback control mechanism that generates motor commands aimed at eliminating disparities between desired and actual auditory signals. Thus, excessive neural activity in ADSD during speech may reflect, at least in part, increased engagement of the auditory feedback control mechanism as it attempts to correct vocal production errors detected through audition. Method To test this possibility, functional magnetic resonance imaging was used to identify differences between participants with ADSD (n = 12) and age-matched controls (n = 12) in (a) brain activity when producing speech under different auditory feedback conditions and (b) resting-state functional connectivity within the cortical network responsible for vocalization. Results As seen in prior studies, the ADSD group had significantly higher activity than the control group during speech with normal auditory feedback (compared to a silent baseline task) in three left-hemisphere cortical regions: ventral Rolandic (sensorimotor) cortex, anterior planum temporale, and posterior superior temporal gyrus/planum temporale. Importantly, this same pattern of hyperactivity was also found when auditory feedback control of speech was eliminated through masking noise. Furthermore, the ADSD group had significantly higher resting-state functional connectivity between sensorimotor and auditory cortical regions within the left hemisphere as well as between the left and right hemispheres. Conclusions Together, our results indicate that hyperactivation in the cortical speech network of individuals with ADSD does not result from hyperactive auditory feedback control mechanisms and rather is likely related to impairments in somatosensory feedback control and/or feedforward control mechanisms.

Quality of Life After Botulinum Toxin Injection in Patients With Adductor Spasmodic Dysphonia; a Systematic Review and Meta-analysis

INTRODUCTION

Adductor spasmodic dysphonia is an extremely disabling voice disorder that negatively impacts a patient's quality of life (QOL). We performed a systematic review to determine if Botulinum Toxin (BT) injections improved voice related QOL in patients with this disorder.

METHODS

PubMed, EMBASE, Web of Science, Cochrane Library, ProQuest, and Scopus from 2000, to and including November 1st, 2018, were searched. We identified randomized controlled trials, controlled trials, and observational studies of the effects of BT injections on the QOL in patients with adductor spasmodic dysphonia. The two authors, separately and individually chose the studies based on inclusion criteria, assessed study quality, and relevant extracted data.

RESULTS

Nine studies used the Voice Handicap Index (VHI). The results showed significant changes pre- to post-BT injection (SMD = -0.357; 95% CI: -0.579, -0.136; z = 3.16; P = 0.002; I-squared = 0.000%). Five studies used the Voice-Related QOL; their results also showed a significant improvement pre- to postinjection (SMD = -2.99; 95% CI: -3.27, -1.32; z = 4.61; P < 0.001; I-squared = 87%). Three other studies used other, shortened versions of the VHI, VHI-10. They also showed significant results (SMD = -0.145; 95% CI: -0.349, 0.06; z = 1.38; P = 0.17; I-squared = 0.000).

CONCLUSION

BT injections positively affect patients' QOL. However, patients' QOL scores may never be normalized, in line with perceptual voice quality and acoustic parameters.

Brain Activity in Patients With Adductor Spasmodic Dysphonia Detected by Functional Magnetic Resonance Imaging

OBJECTIVES

Spasmodic dysphonia (SD) is considered a focal dystonia. However, the detailed pathophysiology of SD remains unclear, despite the detection of abnormal activity in several brain regions. The aim of this study was to clarify the pathophysiological background of SD.

STUDY DESIGN

This is a case-control study.

METHODS

Both task-related brain activity measured by functional magnetic resonance imaging by reading the five-digit numbers and resting-state functional connectivity (FC) measured by 150 T2-weighted echo planar images acquired without any task were investigated in 12 patients with adductor SD and in 16 healthy controls.

RESULTS

The patients with SD showed significantly higher task-related brain activation in the left middle temporal gyrus, left thalamus, bilateral primary motor area, bilateral premotor area, bilateral cerebellum, bilateral somatosensory area, right insula, and right putamen compared with the controls. Region of interest voxel FC analysis revealed many FC changes within the cerebellum-basal ganglia-thalamus-cortex loop in the patients with SD. Of the significant connectivity changes between the patients with SD and the controls, the FC between the left thalamus and the left caudate nucleus was significantly correlated with clinical parameters in SD.

CONCLUSION

The higher task-related brain activity in the insula and cerebellum was consistent with previous neuroimaging studies, suggesting that these areas are one of the unique characteristics of phonation-induced brain activity in SD. Based on FC analysis and their significant correlations with clinical parameters, the basal ganglia network plays an important role in the pathogenesis of SD.