Noncosmetic uses of botulinum toxin in otolaryngology
ABSTRACTBotulinum toxin has several noncosmetic uses in otolaryngology. It is the primary treatment for spasmodic dysphonia and may be effective in select patients who have essential tremor of the voice. It may also be used to treat swallowing difficulties caused by cricopharyngeal dysfunction.
KEY POINTS
- Botulinum toxin can be injected with a variety of approaches directly into the affected muscle exhibiting abnormal contractions.
- Depending on the muscles involved, side effects may include breathiness or difficulty swallowing for a period soon after injection.
- Injections can be repeated as needed as the toxin wears off.
- Some conditions are more amenable to treatment than others. Benefit can be enhanced by altering the dosage or injection site.
ESSENTIAL TREMOR OF THE VOICE
Essential tremor is an action tremor that can occur with voluntary movement. It can occur anywhere in the body, often the head or hand, but the voice can also be affected. About half of cases are hereditary. Essential tremor of the voice causes a rhythmic oscillation of pitch and intensity.
Consultation with a neurologist is recommended to evaluate the cause, although voice tremor is often idiopathic and occurs in about 30% of patients with essential tremor in the arms or legs, as well as in about 30% of patients with spasmodic dysphonia. Extremity tremor can usually be successfully managed medically, but this is not true for voice tremor.
Botulinum toxin injection is the mainstay of treatment for essential tremor of the voice, although its success is marginal. About two-thirds of patients have some degree of improvement from traditional botulinum toxin injections in the true vocal fold.8
The results of treatment are likely to be inconsistent because tremor tends to involve several different muscles used in voice production, commonly in the soft palate, tongue base, pharyngeal walls, strap muscles, false vocal folds, and true vocal folds. A location-oriented tremor scoring system9 can help identify the involved muscles to guide injections. Treatment is less likely to be successful in patients with multiple sites of voice tremor. Injection into the false vocal fold, true vocal fold, and interarytenoid muscle10 can safely be performed; injections into the palate, tongue base, and strap muscles are to be avoided because of the high risk of postinjection aspiration.
Patients who have good results can have repeat treatments as needed. The dosage of botulinum toxin is adjusted according to response, side effects (eg, breathy voice, dysphagia), and patient preference.
CRICOPHARYNGEUS MUSCLE DYSFUNCTION: TROUBLE SWALLOWING
Dysfunction of the cricopharyngeus muscle causes difficulty swallowing, especially swallowing solid foods. It can be attributed to a mechanical stricture or to hyperfunction (spasm).
Mechanical stricture at the esophageal inlet frequently occurs in patients who have had a total laryngectomy for advanced laryngeal cancer. Fibrosis tends to be worse in patients who have also undergone radiation therapy.
Stricture can be treated with botulinum toxin injections and dilation. Conservative treatment is preferred to surgical myotomy for patients with complex postlaryngectomy anatomy and scarring from radiation therapy.
Cricopharyngeus muscle spasm or hyperfunction can be an important cause of dysphagia, especially in the elderly. Patients should be evaluated with barium esophagography or a modified barium swallow. The finding of a cricopharyngeal “bar” provides evidence of contraction of the muscle that impedes the passage of food.
Botulinum toxin injections for cricopharyngeus muscle dysfunction (Figure 2) can be effective in some cases, especially if the toxin is injected bilaterally. However, because the cricopharyngeus muscle plays an important role in preventing esophageal reflux into the laryngopharynx, botulinum toxin injection in patients with substantial hiatal hernia or laryngopharyngeal reflux disease should only be done with caution. In addition, treatment of reflux disease should be considered in any patient undergoing botulinum toxin injection for cricopharyngeus muscle dysfunction.
Most patients require repeat injections when the toxin wears off, although occasionally one or two injections provide long-term or permanent relief. Dosages are adjusted for the patient’s age, the presence of other swallowing problems, and reflux. Patients may experience increased difficulty swallowing for 1 or 2 weeks after the procedure and so should be counseled to eat slowly and carefully.
