Spasmodic Dysphonia Research Articles

Efficacy and Safety of Zolpidem for Focal Dystonia After Neurosurgical Treatments: A Retrospective Cohort Study.

Although there are several reports of the significant efficacy of zolpidem for treating dystonia, zolpidem is still considered an anecdotal treatment. Here, we evaluated the efficacy and safety of zolpidem for treating residual dystonia in patients who previously received various neurosurgical treatments majorly including deep brain stimulation and radiofrequency ablation. We retrospectively reviewed medical records from January 2021 to September 2021 to identify patients with dystonia who had been prescribed zolpidem after undergoing neurosurgery. Twenty patients were enrolled in this study, including those with blepharospasm (two), tongue dystonia (four), mouth dystonia (one), spasmodic dysphonia (two), cervical dystonia (six), focal hand dystonia (three), hemidystonia (two), blepharospasm with cervical dystonia (one), and mouth dystonia with cervical dystonia (one). Single doses of zolpidem ranged between 2.5 and 10 mg, while daily dosages ranged from 10 to 30 mg. The zolpidem dose prescribed was 5–10 mg, with single and daily doses of 7 ± 2.9 and 14.5 ± 6.0 mg, respectively. With zolpidem administration, the participants' Burke-Fahn-Marsden Dystonia Rating Scale-Movement Scale score significantly improved from 8.1 ± 6.7 to 3.7 ± 2.5 (50.6% improvement, p < 0.0001). Improvements in arm dystonia, blepharospasm, and spasmodic dysphonia were observed using the Arm Dystonia Disability Scale, Jankovic Rating Scale, and Voice Handicap Index, respectively. No improvements were observed in cervical dystonia on the Toronto Western Spasmodic Torticollis Rating Scale. Drowsiness, including three cases each of mild and moderate drowsiness, was the most frequent adverse effect (30%), which persisted for 2–3 h. Transient amnesia and rapid eye movement sleep behavior disorder occurred in two patients and one patient, respectively. Although our findings suggest that zolpidem can be a valuable treatment option for patients with residual dystonia after neurosurgical treatments, the beneficial effects for cervical dystonia were limited.

Treatment Outcome Measures for Spasmodic Dysphonia: A Systematic Review

This systematic review aims to identify instruments used to evaluate treatment outcomes for people with spasmodic dysphonia. Electronic database (PubMed, Cochrane Library, Embase, and CINAHL) searches and hand-searching identified studies that evaluated treatment approaches for spasmodic dysphonia which included pre and post outcome data. A total of 4714 articles were retrieved from searching databases; 1165 were duplicates. Titles and abstracts of 3549 were screened, with 171 being selected for full-text review. During full-text review, 101 articles were deemed suitable for inclusion. An additional 24 articles were identified as suitable for inclusion through hand-searching of reference lists. Data was extracted from 125 studies, identifying 220 outcome measures. As per the World Health Organization's International Classification of Functioning (ICF), the majority measured body functions (n = 212, 96%). Outcomes that explored communication and participation in everyday life and attitudes towards communication (ie, activity and participation domains) were infrequent (n = 8; 4%). Quality of life, a paradigm outside of the scope of the ICF, was also captured by four outcome measures. No instruments evaluating communication partners' perspectives were identified. Currently there is no unified approach to the measurement of outcomes in SD treatment research. Development and implementation of a core outcome set is recommended to facilitate improved understanding of the efficacy of current and new treatment options.

Characterization of sedation and anesthesia complications in patients with alternating hemiplegia of childhood.

Alternating hemiplegia of childhood (AHC) pathophysiology suggests predisposition to sedation and anesthesia complications. Hypotheses: 1) AHC patients experience high rates of sedation-anesthesia complications. 2) ATP1A3 mutation genotype positivity, age, and AHC severity correlate with more severe complications. 3) Prior short QTc correlates with cardiac rhythm complications. Analysis of 34 consecutive AHC patients who underwent sedation or anesthesia. Classification of complications: mild (not requiring intervention), moderate (intervention), severe (intervention, risk for permanent injury or potential life-threatening emergency). Fisher Exact test, Spearman correlations. These patients underwent 129 procedures (3.79±2.75 procedures/patient). Twelve (35%) experienced complications during at least one procedure. Fourteen/129 procedures (11%) manifested one or more complications (2.3% mild, 7% moderate, 1.6% severe). Of the total 20 observed complications, six (33.3%) were severe: apneas (2), seizures (2), bradycardia (1), ventricular fibrillation that responded to resuscitation (1). Moderate complications: non-life-threatening bradycardias, apneas, AHC spells or seizures. Complications occurred during sedation or anesthesia and during procedures or recovery periods. Patients with disease-associated ATP1A3 variants were more likely to have moderate or severe complications. There was no correlation between complications and age or AHC severity. Presence of prior short QTc correlated with cardiac rhythm complications. After this series was analyzed, another patient had severe recurrent laryngeal dystonia requiring tracheostomy following anesthesia with intubation. During sedation or anesthesia, AHC patients, particularly those with ATP1A3 variants and prior short QTc, are at risk for complications consistent with AHC pathophysiology. Increased awareness is warranted during planning, performance, and recovery from such procedures.

DYT-TUBB4A (DYT4 Dystonia): Clinical Anthology of 11 Cases and Systematized Review.

ABSTRACTBackgroundDYT‐TUBB4A, formerly known as DYT4, has not been comprehensively described as only one large family and three individual cases have been published. We have recently described an in depth genetic and protein structural analysis of eleven additional cases from four families with four new pathogenic variants. We aim to report on the phenomenology of these cases suffering from DYT‐TUBB4A and to perform a comprehensive review of the clinical presentation and treatment responses of all DYT‐TUBB4A cases reported in the literature.Cases and Literature ReviewThe clinical picture was typically characterized by laryngeal dystonia (more than three quarters of all cases), associated with cervical dystonia, upper limb dystonia and frequent generalization. Extension of the dystonia to the lower limbs, creating the famous “hobby horse” gait, was present in more than 20% of cases (in only one of ours). Globus pallidus pars interna (GPi) deep brain stimulation (DBS), performed in 4 cases, led to a good improvement with greatest benefit in motoric and less benefit in laryngeal symptoms. Medical treatment was generally rather poorly effective, except some benefit from propranolol, tetrabenazine and alcohol intake.ConclusionLaryngeal involvement is a hallmark of DYT‐TUBB4A. Symptomatic treatment with GPi‐DBS led to the greatest benefit in motoric symptoms. Nevertheless, TUBB4A mutations remain an exceedingly rare cause of laryngeal or other isolated dystonia and regular screening of TUBB4A mutations for isolated dystonias has a very low yield.

Development of Medical Device and Surgical Technique for Spasmodic Dysphonia

Development of Medical Device and Surgical Technique for Spasmodic Dysphonia

Acoustic Voice Analysis during Phonation Onset, Measured from High-Speed Videoendoscopy in Connected Speech

Adductor spasmodic dysphonia (AdSD) is a neurological voice disorder, which affects the control of intrinsic muscles of the larynx during speech. Our previous research has shown that high-speed videoendoscopy (HSV) can be used to measure the glottal attack time for patients with AdSD during connected speech. This study builds upon that to analyze the acoustic signal during the phonation onset and prephonatory adjustments. The phonation onset events are quantified using the HSV data that were obtained simultaneously with the acoustic data. We analyze the power and energy waveform of the acoustic signal during vocal folds’ first contact, first oscillation, and transitory behaviors, extracted from high-temporal resolution HSV data. The data were obtained from five patients with AdSD and five vocally normal participants. The data were recorded while the participant produced: 2 productions of vowel /i/ at habitual pitch and loudness, 2 with a soft glottal attack and 2 with a hard glottal attack, six CAPE-V sentences, and the “Rainbow Passage.” The HSV system included a monochrome high-speed camera coupled with a flexible nasolaryngoscope. The results of this study could assist for more accurate clinical management of adductor spasmodic dysphonia.

Usefulness of Water-Resistance Straw Phonation in Discrimination of Adductor-Type Spasmodic Dysphonia and Muscle Tension Dysphonia

Objectives: Although Adductor-type spasmodic dysphonia (AdSD) and Muscle tension dysphonia (MTD) show similar phonetic symptoms, the causes and treatment methods are different. Therefore, discrimination is necessary for the proper treatment of the two diseases. The purpose of this study is to investigate the usefulness of Water-resistance straw phonation (WSP) as a diagnostic therapy for the differentiation of AdSD and MTD. To that end, Both patients with AdSD and MTD performed WSP, and their voices was measured before and after diagnostic therapy.Methods: A total of 27 (18 MTD, 9 AdSD) individuals participated in this study. The MTD group (4 male, 14 female) mean age was 30.01 years and the AdSD (2 male, 7 female) group mean age was 31.03. Both groups were treated with diagnostic therapy using WSP which took approximately 90 seconds. The acoustic analysis and auditory–perceptual assessment were completed after diagnostic therapy.Results: The MTD group was significantly lower in Jitter Percent (Jitter) (p= .003), Pitch Perturbation Quotient (PPQ) (p= .007), Fundamental Frequency Variation (vF0) (p= .004), Shimmer Percent (Shimmer) (p= .010), Amplitude Perturbation Quotient (APQ) (p= .012), Peak to Peak Amplitude Variation (vAm) (p= .005) and auditory–perceptual grade (p= .007). However, the AdSD group was not significantly different for all variables after performing the WSP.Conclusion: WSP is one of the methods that relieve laryngeal hypertension. In this study, the voice improvement of the MTD group after diagnostic therapy using WSP meant that the laryngeal hypertension was relieved. This change indicates a high probability of MTD as opposed to AdSD. Whereas, no improvement or worsening of the voice problem suggests neither the probability of MTD nor no confirmation of AdSD. Therefore, a diagnostic therapy using WSP may be useful as one of the evaluation methods for discrimination between AdSD and MTD.

What Can Altered Auditory Feedback Paradigms Tell Us About Vocal Motor Control in Individuals With Voice Disorders?

The goal of this review article is to provide a summary of the progression of altered auditory feedback (AAF) as a method to understand the pathophysiology of voice disorders. This review article focuses on populations with voice disorders that have thus far been studied using AAF, including individuals with Parkinson's disease, cerebellar degeneration, hyperfunctional voice disorders, vocal fold paralysis, and laryngeal dystonia. Studies using AAF have found that individuals with Parkinson's disease, cerebellar degeneration, and laryngeal dystonia have hyperactive auditory feedback responses due to differing underlying causes. In persons with PD, the hyperactivity may be a compensatory mechanism for atypically weak feedforward motor control. In individuals with cerebellar degeneration and laryngeal dystonia, the reasons for hyperactivity remain unknown. Individuals with hyperfunctional voice disorders may have auditory-motor integration deficits, suggesting atypical updating of feedforward motor control. These findings have the potential to provide critical insights to clinicians in selecting the most effective therapy techniques for individuals with voice disorders. Future collaboration between clinicians and researchers with the shared objective of improving AAF as an ecologically feasible and valid tool for clinical assessment may provide more personalized therapy targets for individuals with voice disorders.

Detection of Vocal Fold Image Obstructions in High-Speed Videoendoscopy During Connected Speech in Adductor Spasmodic Dysphonia: A Convolutional Neural Networks Approach

Adductor spasmodic dysphonia (AdSD) is a neurogenic voice disorder, affecting the intrinsic laryngeal muscle control. AdSD leads to involuntary laryngeal spasms and only reveals during connected speech. Laryngeal high-speed videoendoscopy (HSV) coupled with a flexible fiberoptic endoscope provides a unique opportunity to study voice production and visualize the vocal fold vibrations in AdSD during speech. The goal of this study is to automatically detect instances during which the image of the vocal folds is optically obstructed in HSV recordings obtained during connected speech. HSV data were recorded from vocally normal adults and patients with AdSD during reading of the "Rainbow Passage", six CAPE-V sentences, and production of the vowel /i/. A convolutional neural network was developed and trained as a classifier to detect obstructed/unobstructed vocal folds in HSV frames. Manually labelled data were used for training, validating, and testing of the network. Moreover, a comprehensive robustness evaluation was conducted to compare the performance of the developed classifier and visual analysis of HSV data. The developed convolutional neural network was able to automatically detect the vocal fold obstructions in HSV data in vocally normal participants and AdSD patients. The trained network was tested successfully and showed an overall classification accuracy of 94.18% on the testing dataset. The robustness evaluation showed an average overall accuracy of 94.81% on a massive number of HSV frames demonstrating the high robustness of the introduced technique while keeping a high level of accuracy. The proposed approach can be used for efficient analysis of HSV data to study laryngeal maneuvers in patients with AdSD during connected speech. Additionally, this method will facilitate development of vocal fold vibratory measures for HSV frames with an unobstructed view of the vocal folds. Indicating parts of connected speech that provide an unobstructed view of the vocal folds can be used for developing optimal passages for precise HSV examination during connected speech and subject-specific clinical voice assessment protocols.

Temporal specificity of abnormal neural oscillations during phonatory events in laryngeal dystonia.

Laryngeal dystonia is a debilitating disorder of voicing in which the laryngeal muscles are intermittently in spasm resulting in involuntary interruptions during speech. The central pathophysiology of laryngeal dystonia, underlying computational impairments in vocal motor control, remains poorly understood. Although prior imaging studies have found aberrant activity in the CNS during phonation in patients with laryngeal dystonia, it is not known at what timepoints during phonation these abnormalities emerge and what function may be impaired. To investigate this question, we recruited 22 adductor laryngeal dystonia patients (15 female, age range = 28.83–72.46 years) and 18 controls (eight female, age range = 27.40–71.34 years). We leveraged the fine temporal resolution of magnetoencephalography to monitor neural activity around glottal movement onset, subsequent voice onset and after the onset of pitch feedback perturbations. We examined event-related beta-band (12–30 Hz) and high-gamma-band (65–150 Hz) neural oscillations. Prior to glottal movement onset, we observed abnormal frontoparietal motor preparatory activity. After glottal movement onset, we observed abnormal activity in the somatosensory cortex persisting through voice onset. Prior to voice onset and continuing after, we also observed abnormal activity in the auditory cortex and the cerebellum. After pitch feedback perturbation onset, we observed no differences between controls and patients in their behavioural responses to the perturbation. But in patients, we did find abnormal activity in brain regions thought to be involved in the auditory feedback control of vocal pitch (premotor, motor, somatosensory and auditory cortices). Our study results confirm the abnormal processing of somatosensory feedback that has been seen in other studies. However, there were several remarkable findings in our study. First, patients have impaired vocal motor activity even before glottal movement onset, suggesting abnormal movement preparation. These results are significant because (i) they occur before movement onset, abnormalities in patients cannot be ascribed to deficits in vocal performance and (ii) they show that neural abnormalities in laryngeal dystonia are more than just abnormal responses to sensory feedback during phonation as has been hypothesized in some previous studies. Second, abnormal auditory cortical activity in patients begins even before voice onset, suggesting abnormalities in setting up auditory predictions before the arrival of auditory feedback at voice onset. Generally, activation abnormalities identified in key brain regions within the speech motor network around various phonation events not only provide temporal specificity to neuroimaging phenotypes in laryngeal dystonia but also may serve as potential therapeutic targets for neuromodulation.

Importance of acoustic analysis in the differential diagnosis of adductor spasmodic and muscle tension dysphonia besides fiberoptic video laryngoscopy

Importance of acoustic analysis in the differential diagnosis of adductor spasmodic and muscle tension dysphonia besides fiberoptic video laryngoscopy

Rabbit model with vocal fold hyperadduction

ObjectiveAdductor spasmodic dysphonia (AdSD) is caused by hyperadduction of the vocal folds during phonation, resulting in a strained voice. Animal models are not yet used to elucidate this intractable disease because AdSD has a difficult pathology without a definitive origin. For the first step, we established an animal model with vocal fold hyperadduction and evaluated its validity by assessing laryngeal function. MethodsIn this experimental animal study, three adult Japanese 20-week-old rabbits were used. The models were created using a combination of cricothyroid approximation, forced airflow, and electrical stimulation of the recurrent laryngeal nerves (RLNs). Cricothyroid approximation was added to produce a glottal slit. Thereafter, both RLNs were electrically stimulated to induce vocal fold hyperadduction. Finally, the left RLN was transected to relieve hyperadduction. The sound, endoscopic images, and subglottal pressure were recorded, and acoustic analysis was performed. ResultsSubglottal pressure increased significantly, and the strained sound was produced after the electrical stimulation of the RLNs. After transecting the left RLN, the subglottal pressure decreased significantly, and the strained sound decreased. Acoustic analysis revealed an elevation of the standard deviation of F0 (SDF0) and degree of voice breaks (DVB) through stimulation of the RLNs, and degradation of SDF0 and DVB through RLN transection. Formant bands in the sound spectrogram were interrupted by the stimulation and appeared again after the RLN section. ConclusionThis study developed a rabbit model with vocal fold hyperadduction . The subglottal pressure and acoustic analysis of this model resembled the characteristics of patients with AdSD. This model could be helpful to elucidate the pathology of the larynx caused by hyperadduction, and evaluate and compare the treatments for strained phonation.

Changes in pallidal neural activity following long-term symptom improvement from botulinum toxin treatment in DYT6 dystonia: a case report

BackgroundThe globus pallidus internus is the main target for the treatment of dystonia by deep brain stimulation. Unfortunately, for some genetic etiologies, the therapeutic outcome of dystonia is less predictable. In particular, therapeutic outcomes for deep brain stimulation in craniocervical and orolaryngeal dystonia in DYT6-positive patients are poor. Little is known about the neurophysiology of the globus pallidus internus in DYT6-positive dystonia, and how symptomatic treatment affects the neural activity of this region.Case presentationWe present here the case of a 55-year-old Caucasian female DYT6-dystonic patient with blepharospasm, spasmodic dysphonia, and oromandibular dystonia where single-unit and local field potential activity was recorded from the globus pallidus internus during two deep brain stimulation revision surgeries 4 years apart with no symptomatic improvement. Botulinum toxin injections consistently improved dysphonia, while some of the other symptoms were only inconsistently or marginally improved. Neural activity in the globus pallidus internus during both revision surgeries were compared with previously published results from an idiopathic dystonic cohort. Single-cell firing characteristics and local field potential from the first revision surgery showed no differences with our control group. However, during the second revision surgery, the mean firing rate of single units and local field potential power in the gamma range were lower than those present during the first revision surgery or the control group.ConclusionsSymptoms related to facial movements were greatly improved by botulinum toxin treatment between revision surgeries, which coincided with lower discharge rate and changes in gamma local field oscillations.

Effects of low-frequency repetitive transcranial magnetic stimulation in adductor laryngeal dystonia: a safety, feasibility, and pilot study

PurposeThe effects of neuromodulation are virtually unexplored in adductor laryngeal dystonia (AdLD), a disorder characterized by involuntary contraction of intrinsic laryngeal muscles. Recent findings indicated that intracortical inhibition is reduced in people with AdLD. Low-frequency repetitive transcranial magnetic stimulation (rTMS) induces prolonged intracortical inhibition, but the effects in AdLD are unexplored. This pilot and feasibility study aimed to examine the safety, feasibility, and effects of a single session 1 Hz rTMS over the laryngeal motor cortex (LMC) in people with AdLD and healthy individuals.MethodsThe stimulation location was individualized and determined through TMS-evoked responses in the thyroarytenoid muscles using fine-wire electrodes. 1200 pulses of 1 Hz rTMS were delivered to the left LMC in two groups: Control (n = 6) and AdLD (n = 7). Tolerance, adverse effects, intracortical inhibition, and voice recordings were collected immediately before and after rTMS. Voice quality was assessed with acoustic-based and auditory-perceptual measures.ResultsAll participants tolerated the procedures, with no unexpected adverse events or worsening of symptoms. No significant effects on intracortical inhibition were observed. In the AdLD group, there was a large-effect size after rTMS in vocal perturbation measures and a small-effect size in decreased phonatory breaks.ConclusionsOne rTMS session over the LMC is safe and feasible, and demonstrated trends of beneficial effects on voice quality and phonatory function in AdLD. These preliminary findings support further investigation to assess clinical benefits in a future randomized sham-controlled trial.ClinicalTrials.govNCT02957942, registered on November 8, 2016.

Botulinum toxin treatment for adductor spasmodic dysphonia with EMG and endoscopic guidance

Background &amp; Objective: Spasmodic dysphonia is idiopathic focal dystonia characterized by irregular contractions or postural disorders of the laryngeal muscles, resulting in abnormal speech. Progress in laryngoscopy has resulted in development of a precise technique of botulinum toxin (BTX) injection into the thyroarytenoid muscle under visual control. Methods: We used EMG and endoscopic guidance for BTX injection in adductor spasmodic dysphonia (AdSD). Results: Thirty eight patients with AdSD were injected with BTX in 84 treatment sessions. The voice handicap index (VHI) level of the patients were: severe (73.8%), moderate (26.2%) and mild (none). The average VHI score was 74.6 points. After 8 weeks of BTX treatment, the VHI level was: Severe (3.6%), moderate (10.8%), and mild (85.7%). The average VHI score was 27.7 points. The average values of jitter, shimmer and harmonic to noice ratio (HNR) improved statistically (p &lt; 0.05). The incidence of side effects were: breathiness (17.9%), choking (15.5%); hoarseness (8.5%), and dysphagia (4.7%). Conclusions: Injection of BTX under both EMG and laryngoscopy guidance for treatment of adductor spasmodic dysphonia is an effective and safe treatment.

Influence of Phonatory Break Duration and Pause Time on Auditory-Perceptual Ratings of Speech Acceptability and Listener Comfort in Adductor-Type Laryngeal Dystonia

IntroductionThis study empirically evaluated the influence of phonatory break duration and pause time on auditory-perceptual measures of speech produced by 26 adult speakers diagnosed with adductor-type laryngeal dystonia (AdLD). Type of StudyExperimental. MethodsFifteen inexperienced, young adult normal-hearing listeners provided ratings of speech acceptability and listener comfort for samples of running speech. Four phonatory break and pause time conditions were assessed using visual analog scaling methods. All stimuli were randomized for presentation and listeners were presented with experimental stimuli in a counterbalanced manner. ResultsResults indicate that the duration of phonatory breaks directly influenced listener ratings of speech acceptability (P < 0.001) and listener comfort (P < 0.001), with significant differences between original and modified recordings for both. Speech acceptability and listener comfort ratings were strongly correlated across all timing conditions (r = 0.85–0.97). ConclusionsThe duration of phonatory breaks and pauses have significantly influence judgments of speech acceptability and listener comfort for AdLD. This suggests that temporal factors such as phonatory break duration and pause time in AdLD may carry substantial negative impact on listeners’ perception relative to other auditory-perceptual features that co-exist in the signal.

Voice Pathologies Classification Using GMM And SVM Classifiers

In this paper we investigate the proprieties of automatic speaker recognition (ASR) to develop a system for voice pathologies detection, where the model does not correspond to a speaker but it corresponds to group of patients who shares the same diagnostic. One of essential part in this topic is the database (described later), the samples voices (healthy and pathological) are chosen from a German database which contains many diseases, spasmodic dysphonia is proposed for this study. This problematic can be solved by statistical pattern recognition techniques where we have proposed the mel frequency cepstral coefficients (MFCC) to be modeled first, with gaussian mixture model (GMM) massively used in ASR then, they are modeled with support vector machine (SVM). The obtained results are compared in order to evaluate the more preferment classifier. The performance of each method is evaluated in a term of the accuracy, sensitivity, specificity. The best performance is obtained with 12 coefficientsMFCC, energy and second derivate along SVM with a polynomial kernel function, the classification rate is 90% for normal class and 93% for pathological class.This work is developed under MATLAB

Botulinum Toxin Therapy: A Series of Clinical Studies on Patients with Spasmodic Dysphonia in Japan.

Spasmodic dysphonia (SD) is a rare voice disorder caused by involuntary and intermittent spasms of the laryngeal muscles. Both diagnosis and treatment have been controversial. Therefore, a series of clinical studies has recently been conducted in Japan. A nationwide epidemiological survey revealed that adductor SD predominated (90–95% of all cases; 3.5–7.0/100,000), principally among young women in their 20s and 30s. To facilitate early diagnosis, we created diagnostic criteria for SD and a severity grading system. The diagnostic criteria include the principal and accompanying symptoms, clinical findings during phonation, the treatment response, and the differential diagnoses. The severity grade is determined using a combination of subjective and objective assessments. Botulinum toxin (BT) injection is the treatment of choice; however, there have been few high-quality clinical studies and BT has been used off-label. We conducted a placebo-controlled, randomized, double-blinded clinical trial of BT therapy; this was effective and safe. BT treatment is now funded by the Japanese medical insurance scheme. Studies thus far have facilitated early diagnosis and appropriate therapy; they have fostered patient awareness of SD.

Titanium bridge modification for type 2 thyroplasty to improve device mechanical & safety performance

ObjectiveTitanium bridges are used to separate the thyroid ala during type 2 thyroplasty for adductor spasmodic dysphonia. Revision surgeries have adventitiously indicated that bridge wing failure occurs in the area of the medial hole in some cases. This study investigated the rate and cause of device malfunctions and developed an improved device. MethodsWe conducted a questionnaire survey to determine the number of surgeries performed in Japan up to the end of 2014, and to obtain information about revision cases. In addition, damage analyses were performed on the fracture surfaces of recovered titanium bridges through use of scanning electron microscopy (SEM). ResultsBetween 2002 and 2014, titanium bridges were used in 385 patients. Revision surgery was performed in 19 cases. Revision surgeries revealed that in 11 cases breakage occurred in the wings of the device in the region of the medial hole. However, such fractures were not associated with any signs of recurrence or any adverse events. SEM analyses of fracture surfaces confirmed that fatigue fractures were caused by repeated bending stress in the area of the medial hole. Based on these results, the shape of the hole was changed from round to oval and the wing thickness was increased to prevent breakage. ConclusionsThe wings of titanium bridges may break without any associated signs, symptoms or tissue damage. Based on the malfunctions detected and analyses of the devices recovered following malfunction, changes to the specification were made for commercial development of the titanium bridge.

Vibro-Tactile Stimulation as a Non-Invasive Neuromodulation Therapy for Cervical Dystonia: A Case Study.

Cervical dystonia (CD) is a type of focal dystonia that is characterized by involuntary neck postures. The underlying neurophysiology mechanism of CD is unknown, but there is increasing empirical evidence that motor deficits of CD are associated with somatosensory and proprioceptive deficits in the upper limb area. Vibro-tactile stimulation (VTS) is a non-invasive somatosensory stimulation approach where afferent signals from the vibrated muscle and tactile mechanoreceptors modulate cortical activity. Previous studies have shown that VTS could be an effective neuromodulation therapy for treating laryngeal dystonia. This proof-of-concept study examined the effect of VTS on alleviating the involuntary cervical muscle contractions in a female participant with intermittent torticollis. VTS was applied sequentially on four neck positions: bilateral trapezius (TRP) and bilateral sternocleidomastoid (SCM). Each VTS site was vibrated continuously for six minutes. The kinematics and underlying neck muscle activities during dystonic neck movements were examined with acceleration and surface electromyography (sEMG). To quantify the efficacy of VTS, two acceleration features and one sEMG feature were derived: (1) number of acceleration peaks per minute; (2) peak amplitude of acceleration (PAA); (3) change in power of sEMG after VTS. The frequency of intermittent dystonic neck movements decreased by 60% after VTS. In addition, PAA during dystonic episodes was drastically reduced after VTS when compared to baseline. Third, the effectiveness of VTS in alleviating dystonic muscle spasms depended on the site of vibration. For this participant, the left trapezius muscle was shown as the optimal vibration site reducing sEMG signal power by 15% across all recorded muscles. This case study offered preliminary insight into the assumed effectiveness of neck muscle VTS as a treatment for CD. Our participant experienced pain relief after VTS with measured improvements reflected by electrophysiological and kinematic data. A systematic study with a larger sample size is required in the future to validate the effectiveness of VTS for treating symptoms in CD.