Botulinum Toxin Treatment for Uncommon Phenotypes of Laryngeal Adductor Breathing Dystonia

Laryngeal adductor breathing dystonia (LABD) is a rare form of focal, task-specific respiratory dystonia affecting the laryngeal muscles of unknown aetiology. Unlike classical laryngeal dystonia (spasmodic dysphonia), LABD is not primarily characterised by impaired speech, but rather by dysfunction of respiratory laryngeal control. The hallmark pathophysiological alteration consists of involuntary, action-induced adductor spasms of the laryngeal muscles during respiration, particularly during inspiration. LABD must be distinguished from inducible laryngeal obstruction (ILO), a broader, heterogeneous condition encompassing episodic, stimulus-triggered supraglottic or glottic closure, associated with asthma, reflux, or psychological triggers, that is generally not task-specific and lacks the neurological substrate characteristic of dystonia. In contrast, LABD is a persistent, effort-dependent, neurologically driven dystonia, demonstrable by paradoxical adductor spasms on fibreoptic laryngoscopy during normal inspiration and confirmed electromyographically by paradoxical thyroarytenoid muscle activation instead of the expected inspiratory relaxation. Traditional treatments, including respiratory retraining, speech therapy, biofeedback, psychotherapy, benzodiazepines, dopamine-blocking agents, and anticholinergic drugs, have proved largely ineffective. Tracheostomy may be required in cases of severe respiratory compromise. Botulinum toxin type A (BoNT/A) injections have been reported to successfully reduce inspiratory stridor in selected patients. Here, we present three cases of LABD displaying distinct phenotypes, in which typical features were associated with involvement of extra-laryngeal cranial districts, further expanding the known phenotypic spectrum of this condition.