Use of ultrasound to guide botulinum toxin injections for voice problems caused by involuntary contractions of the larynx

INTERVENTION: This is a randomized controlled parallel‐group clinical trial with single masking of outcome assessors, including 40 adult participants with adductor laryngeal dystonia and a clinical indication for botulinum toxin type A injection, randomly allocated in a one‐to‐one ratio to two groups of 20 participants. The randomization sequence will be computer‐generated using random blocks of variable sizes and stratified by se Xand presence of vocal tremor, with allocation concealment performed using opaque numbered envelopes prepared by an independent researcher and allocation revealed only after confirmation of eligibility and signing of the informed consent form. Participants and physicians performing the injections will not be masked because of the nature of the procedure, while speech‐language pathologists assessing the outcomes and analysts evaluating the voice recordings will remain masked to group allocation, and voice samples will be coded for blinded analysis. Intervention group: 20 participants will receive a single unilateral percutaneous injection of botulinum toxin type A into the thyroarytenoid and lateral cricoarytenoid muscle comple Xunder real‐time ultrasound guidance, using a linear transducer positioned over the larynx, identification of the glottic plane and target muscle, and in‐plane needle insertion under continuous visualization until the target site is reached. Botulinum toxin type A will be reconstituted as 100 units in 1 milliliter of sterile saline solution and administered at a dose of 1 to 2.5 units per target site according to the institutional therapeutic protocol. Control group: 20 participants will receive a single unilateral percutaneous injection of the same botulinum toxin type A using the same therapeutic regimen but with the conventional technique without ultrasound guidance, using external anatomical landmarks to identify the cricothyroid membrane, local antisepsis, needle insertion approximately 3 millimeters lateral to the midline at an angle of 30 to 45 degrees, and confirmation of positioning through tactile and phonatory landmarks. After injection, participants will remain under observation for approximately 30 minutes. Both groups will be assessed before treatment and again at 14, 42 and 90 days, for a total follow‐up period of 12 weeks, with standardized clinical and voice assessments, voice recordings and systematic recording of therapeutic response and adverse events CONDITION: Dystonic Disorders; Dysphonia ; Nervous System Diseases INCLUSION CRITERIA: Adults aged 18 years or older; confirmed diagnosis of adductor laryngeal dystonia (adductor spasmodic dysphonia), established by an otolaryngologist and a specialized speech‐language pathologist; formal clinical indication for botulinum toxin type A injection according to the institutional protocol of the HC‐UFPR; clinically stable condition and absence of contraindications to botulinum toxin administration; voluntary agreement to participate in the study documented by written informed consent. PRIMARY OUTCOME: A greater reduction in the Voice Handicap Index‐10 score is expected in the group receiving ultrasound‐guided botulinum toxin injection compared with the conventional injection group, assessed as the change from baseline to 90 days after treatment, with the between‐group mean difference as the main effect parameter and a reduction of at least 6 points also considered a clinically relevant response Greater improvement in auditory‐perceptual voice quality is expected in the ultrasound‐guided injection group, assessed by the change in the total Grade, Roughness, Breathiness, Asthenia and Strain scale score from baseline to 90 days after treatment, using standardized voice samples independently rated by two blinded assessors, with a total score ranging from 0 to 12 and a reduction of at least 1 point in overall severity also considered a clinical improvement SECONDARY OUTCOME: A reproducible ultrasonographic protocol for assessment of laryngeal structures is expected, measured by interobserver agreement in the identification of anatomical landmarks and ultrasonographic planes, the proportion of examinations yielding diagnostically valid images and the mean acquisition time in minutes, using the kappa coefficient for categorical variables and the intraclass correlation coefficient for continuous measures Better technical performance of botulinum toxin injection is expected with ultrasound guidance, assessed by a higher proportion of successful target muscle access on the first attempt, fewer needle redirections, shorter total procedure time in minutes and greater positioning accuracy determined by objective ultrasonographic criteria and double observation Earlier and sustained improvement in Voice Handicap Index‐10 scores and Grade, Roughness, Breathiness, Asthenia and Strain scale scores is expected in the ultrasound‐guided injection group, assessed as changes from baseline at 14, 42 and 90 days after treatment and by comparing the longitudinal score trajectories between groups Greater patient‐reported clinical improvement and perceived voice quality are expected in the ultrasound‐guided injection group, assessed using the 7‐point Patient Global Impression of Change scale at 42 and 90 days and a 0‐to‐10 visual analogue scale during follow‐up, with higher scores indicating greater perceived improvement and treatment satisfaction Improvement in objective acoustic voice parameters is expected in the ultrasound‐guided injection group, assessed at baseline and 14, 42 and 90 days after treatment using standardized voice recordings, including reductions in jitter and shimmer, an increase in harmonic‐to‐noise ratio and improvement in spectral centroid and bandwidth parameters Longer duration of vocal benefit is expected in the ultrasound‐guided injection group, measured in days from the peak perceived improvement after treatment until return to the pretreatment voice condition, using information obtained from a structured symptom diary and clinical interview during follow‐up, with time to any subsequent need for botulinum toxin reinjection also recorded Lower incidence and severity of adverse events are expected in the ultrasound‐guided injection group during the 90‐day follow‐up, with breathy voice, dysphagia, cough, aspiration, local pain and hematoma recorded together with their duration and severity, and breathy voice lasting more than 14 days and dysphagia of grade 2 or higher considered adverse events of special interest The artificial intelligence model is expected to demonstrate discriminatory ability to identify laryngeal dystonia and distinguish pretreatment from post‐treatment voice samples, assessed primarily by the area under the receiver operating characteristic curve and additionally by accuracy, sensitivity, specificity, positive predictive value, negative predictive value, F1 score, calibration, Brier score and agreement with expert classification in an independent participant‐level test set