Botulinum Toxin for Laryngeal Dystonia Technique

Updated: Nov 02, 2021
  • Author: Jayita Poduval, MS, MBBS, DNB(ENT), DORL; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Approach Considerations

Keep in mind that the lethal dose of botulinum toxin is 2800-3000 U in a 70-kg male. [5]


Percutaneous Electromyography-Guided Botulinum Toxin Treatment of Laryngeal Dystonia

The EMG-guided method is quicker and more accurate than the method using percutaneous indirect laryngoscopy but is technically more difficult, apart from the necessity of having an EMG apparatus and skill in interpreting the readings and results. [4]

The EMG electrodes are attached to the patient’s skin so as not to obstruct the access area for injection and connected to the EMG machine.

Adductor dysphonia

In adductor dysphonia, the TA-LCA muscle complex is identified with EMG-guided localization. The TA-LCA muscle complex on either side is injected with equivalent amounts of the toxin.

The patient is asked to breathe quietly and to try not to swallow during the procedure. The injection needle may be bent up by 30° to 45° to facilitate access to the injection site, especially in females. [4] The EMG needle is inserted through the cricothyroid membrane approximately 2-3 mm off of the midline toward the side to be injected and advanced superiorly and laterally (see image below).

Needle inserted into the cricoarytenoid muscle for Needle inserted into the cricoarytenoid muscle for botulinum toxin injection.

Entry into the airway produces a characteristic “buzz” in the EMG signal that should alert the surgeon to redirect the needle more laterally or even to restart. The needle is maneuvered within the tissue until the tip lies in an area of crisp motor unit potentials found with EMG. This indicates the position of the muscle complex.

The patient is asked to phonate, and, when a brisk recruitment and a full interference pattern confirm placement, the botulinum toxin is injected (see image below). For optimal localization of the injection, a prephonatory burst of EMG activity must be obtained. [4] In the treatment of adductor laryngeal dystonia with botulinum toxin, unilateral injection into the thyroarytenoid muscle is preferable to bilateral injection in order to avoid complete loss of voice in the immediate post-treatment period. [6]

Laryngeal electromyography recording during inject Laryngeal electromyography recording during injection of botulinum toxin.

Abductor dysphonia

In abductor laryngeal dystonia, the PCA muscle is localized and injected. The PCA muscle on only one side is injected at a time to minimize the risk of airway obstruction and stridor.

The patient is seated upright, and the surgeon palpates the posterior border of the thyroid cartilage on the side to be injected. Using counterpressure from the other 4 fingers on the opposite side of the thyroid cartilage, the larynx is gently rotated to expose its posterior aspect. The needle pierces the skin along the lower half of the posterior border of the thyroid cartilage and is advanced until it stops against the posterior surface of the cricoid. The needle is then pulled back slightly, and the patient is asked to sniff to confirm placement. [4] When this produces brisk recruitment, the toxin is injected.


Percutaneous Indirect Laryngoscopy-Guided Botulinum Toxin Treatment of Laryngeal Dystonia

The cricothyroid membrane is punctured for administration of local anesthesia, instilling approximately 3 mL of 4% lidocaine into the airway. The nasal cavity is anesthetized, and a flexible laryngoscope, attached to a video monitor, is inserted through the nasal cavity and advanced to a level slightly above the vocal folds. An assistant keeps the scope in position to provide exposure and visual feedback during the procedure.

A 1-mL syringe filled with botulinum toxin is attached to a 27-gauge needle, and the needle is placed through the cricothyroid membrane near the midline under video monitoring to confirm the location of the needle tip in the subglottic airway. The needle is angled posterolaterally, and the posterior one third of the membranous vocal fold is injected. The opposite vocal fold is then injected using the same approach.