Effects of botulinum toxin on pathophysiology in spasmodic dysphonia

Patient-Perceived Vocal Effort Immediately Following Voice Tasks in Adductor Laryngeal Dystonia (ADLD)

PURPOSE

This study examined the relationship between patient-perceived vocal effort (VE) using a 100-mm visual analog scale (VE-VAS) and the OMNI Vocal Effort Scale (OMNI-VES) when measures were obtained after a vocal activity. A second purpose was to evaluate how VE related to other voice assessment measures.

METHOD

Fifty-three speakers with adductor laryngeal dystonia (ADLD) provided speech recordings. Directly after this vocal activity, speakers rated VE using the VE-VAS and the OMNI-VES. Speakers provided ratings of their own voice quality severity using a 100-mm VAS (ADLD-OS) and completed the Voice-Related Quality of Life (V-RQOL) scale. Ten experienced speech-language pathologists rated a subset of available speech samples (n = 39) for overall voice severity using a 100-mm VAS (SLP-OS).

RESULTS

There was a strong, significant correlation (r = 0.78, P < 0.001) between the VE-VAS and the OMNI-VES. Both VE measures were strongly and significantly correlated with speakers' ratings of their voice: VE-VAS vs ADLD-OS, r = 0.75, P < 0.001; OMNI-VES vs ADLD-OS, r = 0.85, P < 0.001. In contrast, mostly weak correlations were found between perceived VE and V-RQOL total and physical domains, respectively (VE-VAS vs V-RQOL: r = -0.21 to -0.19, P > 0.05; OMNI-VES vs V-RQOL: r = -0.37 to -0.44, P < 0.01). Finally, VE measures were moderately and significantly related to SLPs' auditory-perceptual measures of voice severity: VE-VAS vs SLP-OS, r = 0.50, P < 0.001; OMNI-VES vs SLP-OS, r = 0.57, P < 0.001.

CONCLUSIONS

ADLD speakers' perceptions of VE are strongly related when measures are obtained directly after a vocal activity, regardless of the VE scale. VE is strongly related to speaker-rated voice quality severity, but weakly related to V-RQOL. Measures of VE obtained directly after a vocal activity are moderately related to clinicians' perceptions of overall voice quality severity.

Treatment Outcome Measures for Spasmodic Dysphonia: A Systematic Review

PURPOSE

This systematic review aims to identify instruments used to evaluate treatment outcomes for people with spasmodic dysphonia.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Spasmodic dysphonia: introductory phonetic analyses

Adductor spasmodic dysphonia (ADSD) is a neurological dystonia characterised by involuntary adductor spasms of the larynx during speech. Spasm frequency is often reported to increase during syllables that begin with voiced speech sounds, especially glottal stops. Because of its underlying physical and acoustic complexities, the voicing contrast in American English (AE) appears unlikely to interact consistently with a singular physical phenomenon like laryngeal spasm. This retrospective study investigated additional phonetic contrasts and their relationship to spasm frequency. Standardised, 144-word recordings of 36 participants with adductor spasmodic dysphonia were analysed. Productions were coded for rater-perceived syllable stress, voiced/voiceless onset, vowel/consonant onset, and word-onset place and manner of production. Phonetic contexts were compared using independent sample t-tests and Kruskal-Wallis statistics. Contexts in which spasm varied significantly included stressed/unstressed syllables, content/function words, and multisyllabic/monosyllabic words. Study results reaffirm the clinical usefulness of standardised ADSD/ABSD sentences during differential diagnosis but conflict with previous studies that report a connection between ADSD spasm and phoneme voicing.

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.

Spasmodic dysphonia: An overview of clinical features and treatment options

Spasmodic dysphonia (SD) is considered a rare focal laryngeal dystonia characterized by task-specific voice dysfluency resulting from selective intrinsic laryngeal musculature hyperfunction. Symptoms may be attenuated by a sensory trick. Although SD can be seen at times in generalized dystonia syndrome, it is typically a sporadic phenomenon, and the involvement of the laryngeal adductor muscles is more common than that of the abductor muscles. This research reviews the literature for the pathogenesis, clinical characteristics, treatment options, and current management methods of SD. Technological advances have enabled clinicians to better understand the connection between laryngeal function and dysfunction. Refinements in imaging and genetic investigation techniques have helped better understand the underlying mechanisms of this neurolaryngology disorder. Currently, the standard of care for SD is the symptomatic management of botulinum toxin (BT) chemodenervation. This is supported by a large body of literature attesting to its efficacy in many different research studies, particularly in the uncomplicated adductor form of the disorder. Efforts towards surgical treatment predate the development of BT treatment by a decade, but the long-term efficacy has not been proven and, further research is expected. Symptom relief in patients with abductor SD and dystonia with tremors after surgical and BT treatments and those in patients remains suboptimal.

Botulinum Neurotoxin Therapy in the Clinical Management of Laryngeal Dystonia

Laryngeal dystonia (LD), or spasmodic dysphonia (SD), is a chronic, task-specific, focal movement disorder affecting the larynx. It interferes primarily with the essential functions of phonation and speech. LD affects patients' ability to communicate effectively and significantly diminishes their quality of life. Botulinum neurotoxin was first used as a therapeutic agent in the treatment of LD four decades ago and remains the standard of care for the treatment of LD. This article provides an overview of the clinical application of botulinum neurotoxin in the management of LD, focusing on the classification for this disorder, its pathophysiology, clinical assessment and diagnosis, the role of laryngeal electromyography and a summary of therapeutic injection techniques, including a comprehensive description of various procedural approaches, recommendations for injection sites and dosage considerations.

Globus Pallidus Interna and Ventral Intermediate Nucleus of the Thalamus Deep Brain Stimulation for Adductor Laryngeal Dystonia: a Case Report of Blinded Analyses of Objective Voice Outcomes in 2 Patients

BACKGROUND

Adductor laryngeal dystonia (ADLD) is a substantially debilitating focal progressive neurological voice disorder. Current standard of care is symptomatic treatment with repeated injections of botulinum toxin into specific intrinsic laryngeal muscles with extremely variable and temporary benefits. We report the use of bilateral deep brain stimulation (DBS) of globus pallidus (GPi) for long-term improvement of ADLD voice symptoms.

OBJECTIVE

To investigate the effects of bilateral DBS of the GPi and ventral intermediate nucleus (VIM) of the thalamus on vocal function in 2 patients with ADLD associated with voice and hand tremor.

METHODS

Blinded objective and quantitative analyses of voice were conducted before and after treatment in 2 female patients (70 and 69 years). Paired t-tests were conducted to compare voice measurements pre-GPi and post-GPi and VIM-DBS. A 2-way analysis of variance was conducted to determine the interaction between target (GPi/VIM) and time (pre/post) for each voice measure.

RESULTS

Although the follow-up period differed between patients, the GPi-DBS implanted patient had notable improvement in vowel voicing (%), extent of tremor intensity (%), and overall speech intelligibility (%), compared with preoperative status. GPi-DBS also resulted in significant improvement in cepstral peak prominence (dB). VIM-DBS resulted in a significantly greater change in the tremor rate (Hz).

CONCLUSION

Changes in phonatory function provide preliminary support for the use of bilateral GPi-DBS for treatment of ADLD and bilateral VIM-DBS for vocal tremor predominant ADLD. Future studies with larger sample sizes and standardized follow-up periods are needed to better assess the role of DBS for ADLD.

Factors influencing long-term treatment response to botulinum toxin injection for spasmodic dysphonia

OBJECTIVE

The purpose of this study was to evaluate the outcomes of long-term botulinum toxin type A (BoNTA) treatment for adductor spasmodic dysphonia (AdSD) and to determine the factors predictive of treatment response by investigating dose stability and average intervals.

DESIGN

Retrospective cohort study.

SETTING

Academic tertiary medical centre.

EXPOSURES

A total of 470 patients with adductor spasmodic dysphonia, who received electromyography-guided BoNTA injections over 12 years, were retrospectively enrolled in this study.

MAIN OUTCOMES AND MEASURES

The patients' demographic data, baseline voice dynamics and treatment profiles (dose, frequency and intervals) were evaluated. Factors correlating with the dose adjustment ratio (number of increasing dosing/total number of BoNTA toxin injections) and changes in intervals between injections were statistically analysed.

RESULTS

A total of 122 patients, who received ≥ 4 injections and whose average treatment interval was < 240 days, were finally evaluated. Of them, 115 (94.3%) were female and seven (5.7%) were male, and the mean age at initial treatment was 34.89 ± 13.07 and 41.14 ± 12.71 years, respectively. On average, patients received 18.00 ± 13.33 injections (1.67 ± 0.60 U/injection) to alternating unilateral vocal folds. The treatment period was 65.07 ± 43.28 months and the mean interval between injections was 4.16 ± 1.28 months. The mean dose adjustment ratio among patients who received ≥ 4 injections was 0.15 ± 0.13, and dose changes occurred 4.36 times/patient. The patients' age and gender significantly affected the treatment response, where younger or female patients showed greater dosing variability and shorter intervals between injections. However, the baseline voice dynamics (voice handicap index, fundamental frequency, jitter, shimmer, noise-to-harmonic ratio, maximum phonation time and degree of voice breaks) did not predict the dose adjustment ratio or interval changes. In addition, patients with fluctuating doses showed lower age and higher VHI subscale scores, and patients with short-treatment interval (< 100 days) showed higher SDF0.

CONCLUSIONS

Almost all patients received stable low doses of BoNTA over time, irrespective of the baseline results. Patients' age, gender and VHI scores were correlated with poor treatment responses, such as frequent dose changes and shorter intervals between injections.

Alternating Unilateral Versus Bilateral Injections of Botulinum Toxin for the Treatment of Adductor Spasmodic Dysphonia

OBJECTIVE

This study aimed to compare the long-term efficacy, durability, and dose and interval stability between alternating unilateral and bilateral injections of botulinum neurotoxin type A for the treatment of adductor spasmodic dysphonia.

STUDY DESIGN

Retrospective cohort study.

SETTING

Academic tertiary medical center.

METHODS

A total of 137 patients (105 alternating unilateral and 32 bilateral injections) who were administered ≥5 injections of botulinum neurotoxin type A were included in this study. The mean dosage change, dose adjustment ratio (number of dose increases/total number of injections), and stability of treatment responses were compared between the alternating unilateral and bilateral injection groups.

RESULTS

Long-term changes in the mean dosages for alternating unilateral (mean ± SD, -0.010 ± 0.048 IU) and bilateral (-0.042 ± 0.142 IU) injections did not differ between groups (P = .225), suggesting that both methods follow a decreasing dosing trend over time. The dose adjustment ratio also did not differ between groups (P = .077), although a longer average treatment interval (P < .001) and duration of hoarse voice (P = .045) were found in the bilateral injection group. The proportion of stable patients who did not increase injection dose and had regular follow-up did not differ between the groups.

CONCLUSION

Both alternating unilateral and bilateral injection methods showed a long-term decreasing dosing trend, with comparable levels of efficacy, durability, and stability for treating adductor spasmodic dysphonia. Our findings indicate that alternating unilateral injections can be routinely performed with fewer side effects, albeit at shorter treatment intervals, than bilateral injections.

Altered sensory system activity and connectivity patterns in adductor spasmodic dysphonia

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.

Retrospective review of dosing trends in botulinum toxin injections for the treatment of adductor spasmodic dysphonia in a long-term cohort

Background

Botulinum toxin A (BT) is the gold standard treatment for adductor spasmodic dysphonia (AdSD) with established use for greater than thirty years. The spasmodic dysphonia (SD) literature would benefit from additional long-term cohort data, especially in the Canadian population. The goals of this study were to evaluate whether BT dosage required to achieve acceptable voice shifts over time and to elucidate differences in the subgroups of patients receiving unilateral vocal fold (UVF) injections.

Methods

Patient records were retrospectively reviewed at the regional tertiary Voice Clinic for AdSD patients from 1996 to 2017 to identify AdSD patients treated with serial BT injections. Descriptive statistics, paired t-tests for time between treatments and ANOVA tests were used to evaluate trends in subgroup age.

Results

One-hundred and twenty-six patients (61% female, mean age = 53 ± 15.5 years) met inclusion criteria and received laryngeal EMG-guided BT injections for up to twenty-two years and as many as 79 treatments. The mean total BT dosage for our population was 1.54 ± 0.35 Units per side. The majority of subjects had decreasing doses over time with a small subgroup having slowly increasing doses. Comparing treatment dosages between unilateral and bilateral injection groups, injection dosage per vocal fold was 1.65 ± 0.62 with time between injections was significantly shorter for the unilateral injection group (mean = 105 days, SD ± 19.8 days, p = 0.005) compared to the bilateral injection subgroup (137 ± 35.7 days, p < 0.005). The mean age of the unilateral injection population as younger at 42.4 ± 11.8 years (p = 0.004).

Conclusion

The majority of patients in this study had decreasing BT injection dosages over time, with a smaller proportion having slowly increasing doses, thought to be likely relating to disease severity. The unilateral vocal fold injections were well tolerated despite needing more frequent injections, and found to be more prevalent in the younger age group.

Central Effects of Botulinum Neurotoxin-Evidence from Human Studies

For more than three decades, Botulinum neurotoxin (BoNT) has been used to treat a variety of clinical conditions such as spastic or dystonic disorders by inducing a temporary paralysis of the injected muscle as the desired clinical effect. BoNT is known to primarily act at the neuromuscular junction resulting in a biochemical denervation of the treated muscle. However, recent evidence suggests that BoNT’s pharmacological properties may not only be limited to local muscular denervation at the injection site but may also include additional central effects. In this review, we report and discuss the current evidence for BoNT’s central effects based on clinical observations, neurophysiological investigations and neuroimaging studies in humans. Collectively, these data strongly point to indirect mechanisms via changes to sensory afferents that may be primarily responsible for the marked plastic effects of BoNT on the central nervous system. Importantly, BoNT-related central effects and consecutive modulation and/or reorganization of the brain may not solely be considered “side-effects” but rather an additional therapeutic impact responsible for a number of clinical observations that cannot be explained by merely peripheral actions.

The Use of Botulinum Toxin for Treatment of the Dystonias

Dystonias are characterized by involuntary muscle contractions, twisting movements, abnormal postures, and often tremor in various body regions. However, in the last decade several studies have demonstrated that dystonias are also characterized by sensory abnormalities. While botulinum toxin is the gold standard therapy for focal dystonia, exactly how it improves this disorder is not entirely understood. Neurophysiological studies in animals and humans have clearly demonstrated that botulinum toxin improves dystonic motor manifestations by inducing chemodenervation, therefore weakening the injected muscles. In addition, neurophysiological and neuroimaging evidence also suggests that botulinum toxin modulates the activity of various neural structures in the CNS distant from the injected site, particularly cortical motor and sensory areas. Concordantly, recent studies have shown that in patients with focal dystonias botulinum toxin ameliorates sensory disturbances, including reduced spatial discrimination acuity and pain. Overall, these observations suggest that in these patients botulinum toxin-induced effects encompass complex mechanisms beyond chemodenervation of the injected muscles.

The Expanding Therapeutic Utility of Botulinum Neurotoxins

Botulinum neurotoxin (BoNT) is a major therapeutic agent that is licensed in neurological indications, such as dystonia and spasticity. The BoNT family, which is produced in nature by clostridial bacteria, comprises several pharmacologically distinct proteins with distinct properties. In this review, we present an overview of the current therapeutic landscape and explore the diversity of BoNT proteins as future therapeutics. In recent years, novel indications have emerged in the fields of pain, migraine, overactive bladder, osteoarthritis, and wound healing. The study of biological effects distal to the injection site could provide future opportunities for disease-tailored BoNT therapies. However, there are some challenges in the pharmaceutical development of BoNTs, such as liquid and slow-release BoNT formulations; and, transdermal, transurothelial, and transepithelial delivery. Innovative approaches in the areas of formulation and delivery, together with highly sensitive analytical tools, will be key for the success of next generation BoNT clinical products.

Phenomenology, genetics, and CNS network abnormalities in laryngeal dystonia: A 30-year experience

OBJECTIVE

Laryngeal dystonia (LD) is a functionally specific disorder of the afferent-efferent motor coordination system producing action-induced muscle contraction with a varied phenomenology. This report of long-term studies aims to review and better define the phenomenology and central nervous system abnormalities of this disorder and improve diagnosis and treatment.

METHODS

Our studies categorized over 1,400 patients diagnosed with LD over the past 33 years, including demographic and medical history records and their phenomenological presentations. Patients were grouped on clinical phenotype (adductor or abductor) and genotype (sporadic and familial) and with DNA analysis and functional magnetic resonance imaging (fMRI) to investigate brain organization differences and characterize neural markers for genotype/phenotype categorization. A number of patients with alcohol-sensitive dystonia were also studied.

RESULTS

A spectrum of LD phenomena evolved: adductor, abductor, mixed, singer's, dystonic tremor, and adductor respiratory dystonia. Patients were genetically screened for DYT (dystonia) 1, DYT4, DYT6, and DYT25 (GNAL)-and several were positive. The functional MRI studies showed distinct alterations within the sensorimotor network, and the LD patients with a family history had distinct cortical and cerebellar abnormalities. A linear discriminant analysis of fMRI findings showed a 71% accuracy in characterizing LD from normal and in characterizing adductor from abductor forms.

CONCLUSION

Continuous studies of LD patients over 30 years has led to an improved understanding of the phenomenological characteristics of this neurological disorder. Genetic and fMRI studies have better characterized the disorder and raise the possibility of making objective rather than subjective diagnoses, potentially leading to new therapeutic approaches. Laryngoscope, 128:S1-S9, 2018.

Direct central nervous system effects of botulinum neurotoxin

Local intramuscular injections of botulinum neurotoxin type A (BoNT/A) are effective in the treatment of focal dystonias, muscle spasms, and spasticity. However, not all clinical effects of BoNT/A may be explained by its action at peripheral nerve terminals. For example, the therapeutic benefit may exceed the duration of the peripheral neuroparalysis induced by the neurotoxin. In cellular and animal models, evidence demonstrates retrograde transport of catalytically active BoNT/A in projection neurons. This process of long-range trafficking is followed by transcytosis and action at second-order synapses. In humans, several physiological changes have been described following intramuscular delivery of BoNT/A. In particular, clinical studies have documented a decrease in Renshaw cell-mediated inhibition (i.e., recurrent inhibition), which may be important therapeutically for normalizing uncoordinated movements and overflow of muscle activity. In this review, we present data obtained in animal and experimental models that support direct central actions of BoNT/A mediated via retrograde axonal trafficking. We also discuss the reorganization of central circuitry induced by BoNT/A in patients, and the potential contribution of these effects to the therapeutic efficacy of the neurotoxin.

Speech-Language Pathology Evaluation and Management of Hyperkinetic Disorders Affecting Speech and Swallowing Function

Background

Hyperkinetic dysarthria is characterized by abnormal involuntary movements affecting respiratory, phonatory, and articulatory structures impacting speech and deglutition. Speech–language pathologists (SLPs) play an important role in the evaluation and management of dysarthria and dysphagia. This review describes the standard clinical evaluation and treatment approaches by SLPs for addressing impaired speech and deglutition in specific hyperkinetic dysarthria populations.

Methods

A literature review was conducted using the data sources of PubMed, Cochrane Library, and Google Scholar. Search terms included 1) hyperkinetic dysarthria, essential voice tremor, voice tremor, vocal tremor, spasmodic dysphonia, spastic dysphonia, oromandibular dystonia, Meige syndrome, orofacial, cervical dystonia, dystonia, dyskinesia, chorea, Huntington’s Disease, myoclonus; and evaluation/treatment terms: 2) Speech–Language Pathology, Speech Pathology, Evaluation, Assessment, Dysphagia, Swallowing, Treatment, Management, and diagnosis.

Results

The standard SLP clinical speech and swallowing evaluation of chorea/Huntington’s disease, myoclonus, focal and segmental dystonia, and essential vocal tremor typically includes 1) case history; 2) examination of the tone, symmetry, and sensorimotor function of the speech structures during non-speech, speech and swallowing relevant activities (i.e., cranial nerve assessment); 3) evaluation of speech characteristics; and 4) patient self-report of the impact of their disorder on activities of daily living. SLP management of individuals with hyperkinetic dysarthria includes behavioral and compensatory strategies for addressing compromised speech and intelligibility. Swallowing disorders are managed based on individual symptoms and the underlying pathophysiology determined during evaluation.

Discussion

SLPs play an important role in contributing to the differential diagnosis and management of impaired speech and deglutition associated with hyperkinetic disorders.

Spasmodic Dysphonia: A Review. Part 1: Pathogenic Factors

Objective The purpose of this review is to describe the recent advances in identifying possible factors involved in the pathogenesis of spasmodic dysphonia. Spasmodic dysphonia is a task-specific focal laryngeal dystonia characterized by irregular and uncontrolled voice breaks. Pathogenesis of the disorder is poorly understood. Data Sources PubMed, Google Scholar, and Cochrane Library. Review Methods The data sources were searched using the following search terms: ( spasmodic dysphonia or laryngeal dystonia) and ( etiology, aetiology, diagnosis, pathogenesis, or pathophysiology). Conclusions Several potential etiological factors have been proposed by epidemiological, genetic, and neuropathological studies. Spasmodic dysphonia is a rare disorder primarily affecting females beginning in their 40s. Vocal tremor co-occurs in 30% to 60%. Large cohort studies identified risk factors such as a family history of neurological disorders including dystonia and tremor, recent viral illness, and heavy voice use. As none are rare events, a complex interactive process may contribute to pathogenesis in a small proportion of those at risk. Consequences to pathogenesis are neurological processes found in spasmodic dysphonia: loss of cortical inhibition, sensory processing disturbances, and neuroanatomical and physiological differences in the laryngeal motor control system. Implications for Practice Diagnosis of spasmodic dysphonia usually includes speech and laryngoscopic assessment. However, as diagnosis is sometimes problematic, measurement of neurophysiological abnormalities may contribute useful adjuncts for the diagnosis of spasmodic dysphonia in the future.

Central voice production and pathophysiology of spasmodic dysphonia

OBJECTIVE

Our ability to speak is complex, and the role of the central nervous system in controlling speech production is often overlooked in the field of otolaryngology. In this brief review, we present an integrated overview of speech production with a focus on the role of central nervous system. The role of central control of voice production is then further discussed in relation to the potential pathophysiology of spasmodic dysphonia (SD).

DATA SOURCES

Peer-review articles on central laryngeal control and SD were identified from PUBMED search. Selected articles were augmented with designated relevant publications.

REVIEW METHODS

Publications that discussed central and peripheral nervous system control of voice production and the central pathophysiology of laryngeal dystonia were chosen.

RESULTS

Our ability to speak is regulated by specialized complex mechanisms coordinated by high-level cortical signaling, brainstem reflexes, peripheral nerves, muscles, and mucosal actions. Recent studies suggest that SD results from a primary central disturbance associated with dysfunction at our highest levels of central voice control. The efficacy of botulinum toxin in treating SD may not be limited solely to its local effect on laryngeal muscles and also may modulate the disorder at the level of the central nervous system.

CONCLUSION

Future therapeutic options that target the central nervous system may help modulate the underlying disorder in SD and allow clinicians to better understand the principal pathophysiology.

LEVEL OF EVIDENCE

NA.Laryngoscope, 128:177-183, 2018.

Cortical sensorimotor alterations classify clinical phenotype and putative genotype of spasmodic dysphonia

BACKGROUND AND PURPOSE

Spasmodic dysphonia (SD), or laryngeal dystonia, is a task-specific isolated focal dystonia of unknown causes and pathophysiology. Although functional and structural abnormalities have been described in this disorder, the influence of its different clinical phenotypes and genotypes remains scant, making it difficult to explain SD pathophysiology and to identify potential biomarkers.

METHODS

We used a combination of independent component analysis and linear discriminant analysis of resting-state functional magnetic resonance imaging data to investigate brain organization in different SD phenotypes (abductor versus adductor type) and putative genotypes (familial versus sporadic cases) and to characterize neural markers for genotype/phenotype categorization.

RESULTS

We found abnormal functional connectivity within sensorimotor and frontoparietal networks in patients with SD compared with healthy individuals as well as phenotype- and genotype-distinct alterations of these networks, involving primary somatosensory, premotor and parietal cortices. The linear discriminant analysis achieved 71% accuracy classifying SD and healthy individuals using connectivity measures in the left inferior parietal and sensorimotor cortices. When categorizing between different forms of SD, the combination of measures from the left inferior parietal, premotor and right sensorimotor cortices achieved 81% discriminatory power between familial and sporadic SD cases, whereas the combination of measures from the right superior parietal, primary somatosensory and premotor cortices led to 71% accuracy in the classification of adductor and abductor SD forms.

CONCLUSIONS

Our findings present the first effort to identify and categorize isolated focal dystonia based on its brain functional connectivity profile, which may have a potential impact on the future development of biomarkers for this rare disorder.

Evaluation of type II thyroplasty on phonatory physiology in an excised canine larynx model

OBJECTIVES/HYPOTHESIS

Type II thyroplasty is an alternative treatment for spasmodic dysphonia, addressing hyperadduction by incising and lateralizing the thyroid cartilage. We quantified the effect of lateralization width on phonatory physiology using excised canine larynges.

METHODS

Normal closure, hyperadduction, and type II thyroplasty (lateralized up to 5 mm at 1-mm increments with hyperadducted arytenoids) were simulated in excised larynges (N = 7). Aerodynamic, acoustic, and videokymographic data were recorded at three subglottal pressures relative to phonation threshold pressure (PTP). One-way repeated measures analysis of variance assessed effect of condition on aerodynamic parameters. Random intercepts linear mixed effects models assessed effects of condition and subglottal pressure on acoustic and videokymographic parameters.

RESULTS

PTP differed across conditions (P < .001). Condition affected percent shimmer (P < .005) but not percent jitter. Both pressure (P < .03) and condition (P < .001) affected fundamental frequency. Pressure affected vibratory amplitude (P < .05) and intrafold phase difference (P < .05). Condition affected phase difference between the vocal folds (P < .001).

CONCLUSIONS

Hyperadduction increased PTP and worsened perturbation compared to normal, with near normal physiology restored with 1-mm lateralization. Further lateralization deteriorated voice quality and increased PTP. Acoustic and videokymographic results indicate that normal physiologic relationships between subglottal pressure and vibration are preserved at optimal lateralization width, but then degrade with further lateralization. The 1-mm optimal width observed here is due to the small canine larynx size. Future human trials would likely demonstrate a greater optimal width, with patient-specific value potentially determined based on larynx size and symptom severity.

LEVEL OF EVIDENCE

NA Laryngoscope, 2016 127:396-404, 2017.

Botulinum neurotoxins for the treatment of focal dystonias: Review of rating tools used in clinical trials

Botulinum neurotoxins (BoNTs) are used to achieve therapeutic benefit in focal dystonia. An expert panel recently reviewed published evidence on the efficacy of BoNTs for the treatment of focal dystonias and produced recommendations for clinical practice. Another panel reviewed the clinimetric properties of rating scales for dystonia and produced recommendations for current usage and future directions. Considering that the strength of evidence derives not only from the quality of the study design, but also from usage of validated outcome measures, we combined the information provided by these two recent reviews and assessed the appropriateness of the rating instruments used in clinical trials on BoNT treatment in focal dystonia. Data sources included all the publications on BoNT treatment for focal dystonias reviewed by the recent evidence-based analysis. We reviewed all rating instruments used to assess primary and secondary outcome following BoNT treatment. The publications were allocated into five topics according to the focal dystonia type reviewed in the meta-analysis: blepharospasm, oromandibular dystonia, cervical dystonia, upper limb dystonia, and laryngeal dystonia. For each topic, papers were divided, according to the terminology used in the meta-analysis, into placebo-controlled, active comparator and methodological or uncontrolled. For each topic we identified the rating tools used in each study class and annotated which were the mostly used in each focal dystonia type. Outcome measures included tools related to motor and non-motor features, such as pain and depression, and functional as well as health-related quality of life features. Patient- and investigator-reported outcomes were also included. Rating instruments were classified as recommended, suggested, listed or not included, based on recommendations produced by the rating scale task force. Both primary and secondary outcome measures were assessed. As a final step we compared current practice, as summarized by the meta-analysis, with the recommendations of the rating scales panel. For blepharospasm, three placebo-controlled trials used suggested scales, one active-comparator study used a recommended scale and three active-comparator studies used suggested scales. For oromandibular dystonia, one placebo-controlled study used a suggested scale. For cervical dystonia, six placebo-controlled trials used a recommended scale, four active-comparator trials used a recommended scale and one active-comparator study used a suggested scale. For upper limb and laryngeal dystonia, no trial used validated instruments. Appropriately designed studies should be based on recommended rating instruments. Therapeutic trials not using clinimetrically tested rating measures do not provide sufficient information on efficacy of BoNT treatment, even if the study design is robust. Further research is needed to develop and validate new tools to assess all types of focal dystonia and to apply them in prospective placebo-controlled clinical trials.

Office-based laryngeal injection of botulinum toxin for paradoxical vocal fold motion in a child

We describe the case of a 13-year-old girl with paradoxical vocal fold motion (PVFM) who failed to improve with repeated medical treatment, speech therapy and psychotherapy, but was successfully treated with botulinum toxin A (BTX-A) injection to the vocal folds. For delivering the BTX-A we used a channeled fiber-optic laryngoscope under local anesthesia, in an office setting. The patient remained asymptomatic of PVFM for 5 months, was successfully treated again with the same method, and had no important side effects.

Treatment of spasmodic dysphonia with a neuromodulating electrical implant

OBJECTIVES/HYPOTHESIS

To investigate the feasibility of an implantable electrical stimulation device to treat spasmodic dysphonia (SD) by neuromodulation of the muscle spindle gamma loop.

STUDY DESIGN

Prospective case series.

METHOD

Five subjects underwent daily stimulation of the left thyroarytenoid muscle (TA) below the level of α-motor neuron activation (AMNA) for 5 consecutive days. Professional and patient voice evaluations were performed. Transcartilagenous placement of an implantable stimulation device lead was investigated in anesthetized porcine and cadaveric human models.

RESULTS

Three of 5 subjects improved in all categories of evaluation. One subject improved in three of four categories. These four subjects described significant carryover of effect after treatment. The fifth subject evidenced improvement until contracting an upper respiratory infection on day 3. Transcartilagenous electrode placement into the porcine TA with muscle stimulation was successful. The electrode lead was passed from the cadaveric larynx to the mastoid tip in the subplatysma layer with an absence of tension.

CONCLUSION

The symptoms of SD improve after electrical stimulation of the TA at levels below AMNA. This is likely through neuromodulation of the muscle spindle gamma loop. Implantation of an electrode into the TA with a postauricular implanted stimulator is feasible with modifications of an already existing device. With further investigation, such a device has the potential to deliver an alternative treatment for SD.

LEVEL OF EVIDENCE

4.

Abnormal striatal dopaminergic neurotransmission during rest and task production in spasmodic dysphonia

Spasmodic dysphonia is a primary focal dystonia characterized by involuntary spasms in the laryngeal muscles during speech production. The pathophysiology of spasmodic dysphonia is thought to involve structural and functional abnormalities in the basal ganglia-thalamo-cortical circuitry; however, neurochemical correlates underpinning these abnormalities as well as their relations to spasmodic dysphonia symptoms remain unknown. We used positron emission tomography with the radioligand [(11)C]raclopride (RAC) to study striatal dopaminergic neurotransmission at the resting state and during production of symptomatic sentences and asymptomatic finger tapping in spasmodic dysphonia patients. We found that patients, compared to healthy controls, had bilaterally decreased RAC binding potential (BP) to striatal dopamine D2/D3 receptors on average by 29.2%, which was associated with decreased RAC displacement (RAC ΔBP) in the left striatum during symptomatic speaking (group average difference 10.2%), but increased RAC ΔBP in the bilateral striatum during asymptomatic tapping (group average difference 10.1%). Patients with more severe voice symptoms and subclinically longer reaction time to initiate the tapping sequence had greater RAC ΔBP measures, while longer duration of spasmodic dysphonia was associated with a decrease in task-induced RAC ΔBP. Decreased dopaminergic transmission during symptomatic speech production may represent a disorder-specific pathophysiological trait involved in symptom generation, whereas increased dopaminergic function during unaffected task performance may be explained by a compensatory adaptation of the nigrostriatal dopaminergic system possibly due to decreased striatal D2/D3 receptor availability. These changes can be linked to the clinical and subclinical features of spasmodic dysphonia and may represent the neurochemical basis of basal ganglia alterations in this disorder.

Evidence-based review and assessment of botulinum neurotoxin for the treatment of movement disorders

Botulinum neurotoxin (BoNT) can be injected to achieve therapeutic benefit across a large range of clinical conditions. To assess the efficacy and safety of BoNT injections for the treatment of certain movement disorders, including blepharospasm, hemifacial spasm, oromandibular dystonia, cervical dystonia, focal limb dystonias, laryngeal dystonia, tics, and essential tremor, an expert panel reviewed evidence from the published literature. Data sources included English-language studies identified via MEDLINE, EMBASE, CINAHL, Current Contents, and the Cochrane Central Register of Controlled Trials. Evidence tables generated in the 2008 Report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology (AAN) review of the use of BoNT for movement disorders were also reviewed and updated. The panel evaluated evidence at several levels, supporting BoNT as a class, the serotypes BoNT-A and BoNT-B, as well as the four individual commercially available formulations: abobotulinumtoxinA (A/Abo), onabotulinumtoxinA (A/Ona), incobotulinumtoxinA (A/Inco), and rimabotulinumtoxinB (B/Rima). The panel ultimately made recommendations for each therapeutic indication, based upon the strength of clinical evidence and following the AAN classification scale. For the treatment of blepharospasm, the evidence supported a Level A recommendation for BoNT-A, A/Inco, and A/Ona; a Level B recommendation for A/Abo; and a Level U recommendation for B/Rima. For hemifacial spasm, the evidence supported a Level B recommendation for BoNT-A and A/Ona, a Level C recommendation for A/Abo, and a Level U recommendation for A/Inco and B/Rima. For the treatment of oromandibular dystonia, the evidence supported a Level C recommendation for BoNT-A, A/Abo, and A/Ona, and a Level U recommendation for A/Inco and B/Rima. For the treatment of cervical dystonia, the published evidence supported a Level A recommendation for all four BoNT formulations. For limb dystonia, the available evidence supported a Level B recommendation for both A/Abo and A/Ona, but no published studies were identified for A/Inco or B/Rima, resulting in a Level U recommendation for these two formulations. For adductor laryngeal dystonia, evidence supported a Level C recommendation for the use of A/Ona, but a Level U recommendation was warranted for B/Rima, A/Abo, and A/Inco. For the treatment of focal tics, a Level U recommendation was warranted at this time for all four formulations. For the treatment of tremor, the published evidence supported a level B recommendation for A/Ona, but no published studies were identified for A/Abo, A/Inco, or B/Rima, warranting a Level U recommendation for these three formulations. Further research is needed to address evidence gaps and to evaluate BoNT formulations where currently there is insufficient or conflicting clinical data.

Abnormal structure-function relationship in spasmodic dysphonia

Spasmodic dysphonia (SD) is a primary focal dystonia characterized by involuntary spasms in the laryngeal muscles during speech production. Although recent studies have found abnormal brain function and white matter organization in SD, the extent of gray matter alterations, their structure-function relationships, and correlations with symptoms remain unknown. We compared gray matter volume (GMV) and cortical thickness (CT) in 40 SD patients and 40 controls using voxel-based morphometry and cortical distance estimates. These measures were examined for relationships with blood oxygen level-dependent signal change during symptomatic syllable production in 15 of the same patients. SD patients had increased GMV, CT, and brain activation in key structures of the speech control system, including the laryngeal sensorimotor cortex, inferior frontal gyrus (IFG), superior/middle temporal and supramarginal gyri, and in a structure commonly abnormal in other primary dystonias, the cerebellum. Among these regions, GMV, CT and activation of the IFG and cerebellum showed positive relationships with SD severity, while CT of the IFG correlated with SD duration. The left anterior insula was the only region with decreased CT, which also correlated with SD symptom severity. These findings provide evidence for coupling between structural and functional abnormalities at different levels within the speech production system in SD.

Spasmodic dysphonia: a laryngeal control disorder specific to speech

Spasmodic dysphonia (SD) is a rare neurological disorder that emerges in middle age, is usually sporadic, and affects intrinsic laryngeal muscle control only during speech. Spasmodic bursts in particular laryngeal muscles disrupt voluntary control during vowel sounds in adductor SD and interfere with voice onset after voiceless consonants in abductor SD. Little is known about its origins; it is classified as a focal dystonia secondary to an unknown neurobiological mechanism that produces a chronic abnormality of laryngeal motor neuron regulation during speech. It develops primarily in females and does not interfere with breathing, crying, laughter, and shouting. Recent postmortem studies have implicated the accumulation of clusters in the parenchyma and perivascular regions with inflammatory changes in the brainstem in one to two cases. A few cases with single mutations in THAP1, a gene involved in transcription regulation, suggest that a weak genetic predisposition may contribute to mechanisms causing a nonprogressive abnormality in laryngeal motor neuron control for speech but not for vocal emotional expression. Research is needed to address the basic cellular and proteomic mechanisms that produce this disorder to provide intervention that could target the pathogenesis of the disorder rather than only providing temporary symptom relief.

A single-centre retrospective review of unilateral and bilateral Dysport injections in adductor spasmodic dysphonia

We reviewed the results and side-effect profile of the Dysport preparation of botulinum toxin A (BTA) in the management of the adductor spasmodic dysphonia. We performed 272 injection episodes in 68 patients, 42 (62%) female, 26 (38%) male. A total of 116 of these injections were unilateral, and 156 were bilateral; 94% of the injections were considered to have been successful with a voice score of 2 or higher. The mean duration of effect (injection intervals) was 128.8 days in the unilateral cohort and 118.7 days in the bilateral (P > 0.05). We injected a relatively lower dose of BTA for unilateral injection episodes in our institution compared to those reported by others to produce comparable results and side-effect profiles.

Hemifacial spasm non-motor and motor-related symptoms and their response to botulinum toxin therapy

Hemifacial spasm (HFS) is a chronic movement disorder which presents as clonic and/or tonic facial muscle contractions frequently accompanied by many other sensory (visual or auditory disturbances, pain), motor (facial weakness, trismus, bruxism, dysarthria) and/or autonomic (lacrimation, salivation) symptoms. The aim of the study was to assess the occurrence of HFS non-motor and motor-related symptoms and their responsiveness to botulinum toxin type A (BTX-A) therapy. 56 HFS patients were included in the open-label design study. Patients were examined three times: before BTX-A injection, and 2 and 12 weeks later. The occurrence of non-motor and motor-related symptoms was assessed by a special questionnaire, and the severity of HFS was rated by the Clinical Global Impression-Severity scale (CGI-S) and depression symptoms by the Beck Depression Inventory (BDI). Over 81% of the patients before BTX-A therapy reported HFS non-motor and motor-related symptoms. Almost 50% of the patients reported more than three symptoms. The most frequent symptoms were: tearing (44.5%), eye irritation (39.3%), facial paraesthesia (26.8%) and hearing of a "clicking" sound (25.0%). 2 weeks after BTX-A injection 75% of the patients did not report any symptoms and 20% reported only one or two. 3 months later the number of symptoms had increased again, with 57% of patients reporting at least one. The number of HFS non-motor and other symptoms did not correlate with the patients' age, disease duration and the presence of neuro-vascular conflict, but were positively correlated with the CGI-S and BDI scores. This study showed that muscle contractions in HFS patients are commonly accompanied by non-motor and other motor-related symptoms and most of them are reduced following BTX-A treatment.

Unilateral versus bilateral thyroarytenoid Botulinum toxin injections in adductor spasmodic dysphonia: a prospective study

Objectives

In this preliminary prospective study, we compared unilateral and bilateral thyroarytenoid muscle injections of Botulinum toxin (Dysport) in 31 patients with adductor spasmodic dysphonia, who had undergone more than 5 consecutive Dysport injections (either unilateral or bilateral) and had completed 5 concomitant self-rated efficacy and complication scores questionnaires related to the previous injections. We also developed a Neurophysiological Scoring (NPS) system which has utility in the treatment administration.

Method and materials

Data were gathered prospectively on voice improvement (self-rated 6 point scale), length of response and duration of complications (breathiness, cough, dysphagia and total voice loss). Injections were performed under electromyography (EMG) guidance. NPS scale was used to describe the EMG response. Dose and unilateral/bilateral injections were determined by clinical judgment based on previous response. Time intervals between injections were patient driven.

Results

Low dose unilateral Dysport injection was associated with no significant difference in the patient's outcome in terms of duration of action, voice score (VS) and complication rate when compared to bilateral injections. Unilateral injections were not associated with any post treatment total voice loss unlike the bilateral injections.

Conclusion

Unilateral low dose Dysport injections are recommended in the treatment of adductor spasmodic dysphonia.

Treatment for spasmodic dysphonia: limitations of current approaches

PURPOSE OF REVIEW

Although botulinum toxin injection is the gold standard for treatment of spasmodic dysphonia, surgical approaches aimed at providing long-term symptom control have been advancing over recent years.

RECENT FINDINGS

When surgical approaches provide greater long-term benefits to symptom control, they also increase the initial period of side effects of breathiness and swallowing difficulties. Recent analyses of quality-of-life questionnaires in patients undergoing regular injections of botulinum toxin demonstrate that a large proportion of patients have limited relief for relatively short periods due to early breathiness and loss-of-benefit before reinjection.

SUMMARY

Most medical and surgical approaches to the treatment of spasmodic dysphonia have been aimed at denervation of the laryngeal muscles to block symptom expression in the voice, and have both adverse effects as well as treatment benefits. Research is needed to identify the central neuropathophysiology responsible for the laryngeal muscle spasms in order target treatment towards the central neurological abnormality responsible for producing symptoms.

Recommendations of the Neurolaryngology Study Group on laryngeal electromyography

The Neurolaryngology Study Group convened a multidisciplinary panel of experts in neuromuscular physiology, electromyography, physical medicine and rehabilitation, neurology, and laryngology to meet with interested members from the American Academy of Otolaryngology Head and Neck Surgery, the Neurolaryngology Subcommittee and the Neurolaryngology Study Group to address the use of laryngeal electromyography (LEMG) for electrodiagnosis of laryngeal disorders. The panel addressed the use of LEMG for: 1) diagnosis of vocal fold paresis, 2) best practice application of equipment and techniques for LEMG, 3) estimation of time of injury and prediction of recovery of neural injuries, 4) diagnosis of neuromuscular diseases of the laryngeal muscles, and, 5) differentiation between central nervous system and behaviorally based laryngeal disorders. The panel also addressed establishing standardized techniques and methods for future assessment of LEMG sensitivity, specificity and reliability for identification, assessment and prognosis of neurolaryngeal disorders. Previously an evidence-based review of the clinical utility of LEMG published in 2004 only found evidence supported that LEMG was possibly useful for guiding injections of botulinum toxin into the laryngeal muscles. An updated traditional/narrative literature review and expert opinions were used to direct discussion and format conclusions. In current clinical practice, LEMG is a qualitative and not a quantitative examination. Specific recommendations were made to standardize electrode types, muscles to be sampled, sampling techniques, and reporting requirements. Prospective studies are needed to determine the clinical utility of LEMG. Use of the standardized methods and reporting will support future studies correlating electro-diagnostic findings with voice and upper airway function.

Trans-nasal injection of botulinum toxin

INTRODUCTION

Office-based laryngeal injection for the treatment of a variety of voice disorders is an established practice. Various methods of delivery to the vocal folds are in practice.

AIM

We present a simple and repeatable method of injecting botulinum toxin into the larynx.

METHOD

Botulinum toxin A (Botox) was delivered into the larynx using a channelled fibre-optic laryngoscope under local anaesthetic, in an office setting.

RESULTS

Seven patients received regular botulinum toxin injections, via our preferred method. The treatment intervals and dosage regime varied depending on patient requirements. The procedure was carried out in an office setting, with minimal discomfort and inconvenience to the patient.

CONCLUSION

We present a method of botulinum toxin delivery to the larynx which is simple, easily repeatable and simply learnt by the otolaryngologist familiar with fibre-optic laryngoscope usage. This method is also comfortable and convenient for the patient.

Neurophysiological effects of botulinum toxin type a

Botulinum toxin type A (BoNT-A) acts peripherally by inhibiting acetylcholine release from the presynaptic neuromuscular terminals, thus weakening muscle contraction, and its clinical benefit depends primarily on the toxin's peripheral action. In addition to acting directly at the neuromuscular junction, the toxin alters sensory inputs to the central nervous system, thus indirectly inducing secondary central changes. Some of the long-term clinical benefits of BoNT-A treatment may also reflect plastic changes in motor output after the reorganization of synaptic density.

A reappraisal of the central effects of botulinum neurotoxin type A: by what mechanism?

Botulinum neurotoxin A (BoNT/A) is a metalloprotease that enters peripheral motor nerve terminals and blocks the release of acetylcholine via the specific cleavage of the synaptosomal-associated protein of 25-kDa. Localized injections of BoNT/A are widely employed in clinical neurology to treat several human diseases characterized by muscle hyperactivity. It is generally assumed that the effects of BoNT/A remain localized to the injection site. However, several neurophysiological studies have provided evidence for central effects of BoNT/A, raising the issue of how these actions arise. Here we review these data and discuss the possibility that retrograde axonal transport of catalytically active BoNT/A may explain at least some of its effects at the level of central circuits.

Dosage changes in patients with long-term botulinum toxin use for laryngeal dystonia

OBJECTIVE: To investigate the dosage consistency of botulinum toxin injections in patients with long-term treatment for laryngeal dystonia.

STUDY DESIGN: Chart review.

SUBJECTS AND METHODS: Patients with laryngeal dystonia who had received at least 20 injections to the thyroarytenoid muscle were selected. Change of botulinum toxin dose, patient-reported effective weeks, and intervals between injections were investigated; data from the first five injections were excluded to eliminate initial dose titration.

RESULTS: Fifty-five patients with an average follow-up of 12.5 years were identified. Mean dose of botulinum toxin was 2.37 ± 1.6 U at the sixth injection; there was a decrease in mean dose over time, which became statistically significant at the 13th injection with a mean dose of 2.02 ± 1.16 U. Mean duration of good effect and treatment intervals showed no significant change over time.

CONCLUSION: Botulinum toxin dose needed for a constant response in treatment of laryngeal dystonia decreases over time, without any accompanying change in effective weeks and intervals.

Injection of Botulinum Toxin into External Laryngeal Muscles in Pediatric Laryngeal Paralysis

Objectives:

I undertook to demonstrate the effect of injecting botulinum toxin type A (BTA) into cricothyroid, sternothyroid, and sternohyoid muscles in cases of bilateral laryngeal paralysis (BLP). Tracheostomy remains the consistently reproducible and accepted method to salvage the airway obstruction in BLP. The bypass, however, acknowledges the current lack of knowledge and consensus on the pathogenesis.

Methods:

I performed a retrospective chart review of BLP cases treated with BTA in a tertiary care pediatric center. The injections were performed under direct vision through an open transcervical approach. The main outcome measures used were improvement of airway symptoms and endoscopic findings, tracheostomy requirement, and incidence of recovery of function.

Results:

In total, 24 patients with BLP were identified. Over a 2-year period, 7 patients were treated with BTA. Six patients had congenital idiopathic BLP. One of these had trisomy 7. One patient acquired the paralysis after cardiac surgery. No patients required a tracheostomy, except for the infant with trisomy 7. Six patients recovered function completely, and the seventh recovered it partially (range, 4 weeks to 12 months).

Conclusions:

Injection of BTA into external laryngeal muscles may be an alternative to tracheostomy in BLP. It is proposed that the toxin relaxes the glottic aperture by paralyzing the cricothyroid and strap muscles and that it may aid in appropriate reinnervation of the larynx via mechanisms beyond the neuromuscular junction.

Focal white matter changes in spasmodic dysphonia: a combined diffusion tensor imaging and neuropathological study

Spasmodic dysphonia is a neurological disorder characterized by involuntary spasms in the laryngeal muscles during speech production. Although the clinical symptoms are well characterized, the pathophysiology of this voice disorder is unknown. We describe here, for the first time to our knowledge, disorder-specific brain abnormalities in these patients as determined by a combined approach of diffusion tensor imaging (DTI) and postmortem histopathology. We used DTI to identify brain changes and to target those brain regions for neuropathological examination. DTI showed right-sided decrease of fractional anisotropy in the genu of the internal capsule and bilateral increase of overall water diffusivity in the white matter along the corticobulbar/corticospinal tract in 20 spasmodic dysphonia patients compared to 20 healthy subjects. In addition, water diffusivity was bilaterally increased in the lentiform nucleus, ventral thalamus and cerebellar white and grey matter in the patients. These brain changes were substantiated with focal histopathological abnormalities presented as a loss of axonal density and myelin content in the right genu of the internal capsule and clusters of mineral depositions, containing calcium, phosphorus and iron, in the parenchyma and vessel walls of the posterior limb of the internal capsule, putamen, globus pallidus and cerebellum in the postmortem brain tissue from one patient compared to three controls. The specificity of these brain abnormalities is confirmed by their localization, limited only to the corticobulbar/corticospinal tract and its main input/output structures. We also found positive correlation between the diffusivity changes and clinical symptoms of spasmodic dysphonia (r = 0.509, P = 0.037). These brain abnormalities may alter the central control of voluntary voice production and, therefore, may underlie the pathophysiology of this disorder.

Evidence for the effectiveness of botulinum toxin for spasmodic dysphonia from high-quality research designs

The practice of evidence-based medicine promotes use of the knowledge ascertained from high quality research designs. The objective of this review was to determine what evidence has been provided from high quality research designs (e.g., randomized control trials or high quality prospective, matched group cohort studies), through December of 2006, relative to the effectiveness of botulinum toxin for treating spasmodic dysphonia. Results of the review indicated that no new high quality (Class I or Class II) studies have been published since 2001. One Class I study has been published since 1973, which found significant treatment effects for acoustic and perceptual variables of vocal function. Four Class II studies have been published during this same time frame, all finding significant treatment effects, though the nature of studied factors was variable between investigations. Based on the quality of evidence scale used, botulinum toxin can be considered an effective treatment for adductor spasmodic dysphonia.

Alterations in CNS activity induced by botulinum toxin treatment in spasmodic dysphonia: an H215O PET study

Speech-related changes in regional cerebral blood flow (rCBF) were measured using H(2)(15)O positron-emission tomography in 9 adults with adductor spasmodic dysphonia (ADSD) before and after botulinum toxin (BTX) injection and 10 age- and gender-matched volunteers without neurological disorders. Scans were acquired at rest and during production of continuous narrative speech and whispered speech. Speech was recorded during scan acquisition for offline quantification of voice breaks, pitch breaks, and percentage aperiodicity to assess correlations between treatment-related changes in rCBF and clinical improvement. Results demonstrated that speech-related responses in heteromodal sensory areas were significantly reduced in persons with ADSD, compared with volunteers, before the administration of BTX. Three to 4 weeks after BTX injection, speech-related responses were significantly augmented in these regions and in left hemisphere motor areas commonly associated with oral-laryngeal motor control. This pattern of responses was most strongly correlated with the objective measures of clinical improvement (decreases in the frequency of voice breaks, pitch breaks, and percentage aperiodicity). These data suggest a pathophysiological model for ADSD in which BTX treatment results in more efficient cortical processing of sensory information, making this information available to motor areas that use it to more effectively regulate laryngeal movements.

Botulinum toxin for treating spasmodic dysphonia (laryngeal dystonia): a systematic Cochrane review

BACKGROUND

Spasmodic dysphonia is a neurological voice disorder characterized by involuntary adductor (towards midline) or abductor (away from midline) vocal fold spasms during phonation which result in phonatory breaks. Botulinum toxin is currently the gold standard of treatment.

OBJECTIVE

To determine the efficacy of botulinum toxin therapy for the treatment of spasmodic dysphonia.

DESIGN

Systematic Cochrane review.

SEARCH STRATEGY

The search strategy for this review complied with Cochrane standards. We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (1966 to February 2005), EMBASE (1974 to February 2005), CINAHL (through February 2005), Dissertation Abstracts International (1975 to February 2005) and PsycINFO (1975 to February 2005). The search engine FirstSearch was also used (February 2005). Reference lists for all the obtained studies and other review articles were examined for additional studies.

SELECTION CRITERIA

All randomized control trials where the participants were randomly allocated prior to intervention and in which botulinum toxin was compared to an alternative treatment, placebo or non-treated control group were included.

DATA COLLECTION AND ANALYSIS

Two reviewers independently evaluated all potential studies meeting the selection criteria noted above for inclusion.

MAIN RESULTS

Only one study in the literature met the inclusion criteria. This was the only study identified which reported a treatment/no treatment comparison. It reported significant beneficial effects for fundamental frequency (Fo), Fo range, spectrographic analysis, independent ratings of voice severity and patient ratings of voice improvement.

REVIEWER'S CONCLUSIONS

The evidence from randomized controlled trials supporting the effectiveness of botulinum toxin for management of spasmodic dysphonia is deficient. The lack of supporting evidence from randomized controlled trials results in an inability to draw unbiased generalized conclusions regarding the effectiveness of botulinum toxin for all types of spasmodic dysphonia.

Common movement disorders affecting the larynx: a report from the neurolaryngology committee of the AAO-HNS

Laryngeal physiology depends on dynamic neuromuscular forces acting on a basic framework of cartilage and specialized soft tissues, that is, the vocal folds. A working understanding of this organ in health and disease requires knowledge of specific neurological processes that may affect voice, swallowing, and airway regulation. Neuromuscular impairment continues to be a dominant topic in the study of laryngeal disorders. This subcommittee presentation reviews important aspects of the neurolaryngeal history and physical examination. After this foundation, 4 common movement disorders affecting the larynx are covered in separate subsections. These are stroke, Parkinson's disease, laryngeal tremor, and spasmodic dysphonia. State-of-the-art reviews reflecting our understanding of these clinical issues are presented in this summary.