Academic journal article Journal of Singing

Botulinum Toxin Injection for Laryngeal Dystonias in Singers

Academic journal article Journal of Singing

Botulinum Toxin Injection for Laryngeal Dystonias in Singers

Article excerpt

INTRODUCTION

BOTULINUM TOXIN INJECTIONS HAVE BEEN USED since the 1980s to treat a number of medical conditions caused by abnormal or unwanted muscular activity.1 Botulinum toxin is a protein produced by the bacterium, Clostridium botulinum. It binds to nerve endings, thus preventing their normal signaling to muscles and inducing a partial paralysis (paresis). In high doses, this toxin is lethal; however in much smaller, therapeutic doses, botulinum toxin has improved modern medicine, allowing for the relief of symptoms in several medical conditions. Singing teachers should be familiar with this therapeutic modality and its effects on voice.

In the U.S., botulinum toxin is available primarily as Botox, or onobotulinum toxin A (Allergan, Irvine), Dysport, or abobotulinum toxin A (Galderma, Switzerland), Xeomin, or incobotulinum toxin A (Merz, Germany), and Myobloc, or rimabotulinum toxin B (Solstice Neurosciences, San Francisco). Botox, Dysport, and Xeomin must be reconstituted allowing for control over the final concentration while Myobloc comes in concentrations of 500 mouse units/0.1ml. Botox is the most commonly used formulation of botulinum toxin for laryngeal dystonias in the U. S. It is important to appreciate that dosing for each product is not interchangeable. For example, Botox is 2.5-4 times more potent than Dysport; in other words, Dysport doses are often 2.5-4 times those of Botox to achieve a similar clinical effect.2 For the treatment of spasmodic dysphonia, Botox was found to be 52.3 times more potent than Myobloc in a comparison study.3 Compared to Botox, Myobloc has been shown to have a faster onset of action, a shorter duration of effect, and a larger radius of diffusion.4 The dosing described in this article will be based on Botox preparation unless otherwise specified.

Botulinum toxin might be of particular interest to singers because it has been used to treat a number of voice disorders. This article describes the clinical uses of botulinum toxin to manage spasmodic dysphonia, singer's dystonia, essential vocal tremor, unilateral and bilateral laryngeal synkinesis, paradoxical vocal fold motion, and occupational oromandibular dystonia. It should be remembered that a comprehensive neurolaryngologic workup is recommended to evaluate for other possible causes of the patient's presenting signs and symptoms prior to initiating treatment.

Spasmodic Dysphonia

Spasmodic dysphonia (SD) is a laryngeal dystonia that occurs when speaking. A dystonia is a condition characterized by abnormal muscle movement and tone. Spasmodic dysphonia is most common in middle-aged women, and typically symptoms develop gradually.5 Initially, symptoms are not usually observed during singing, laughing, crying, or speaking in an atypical manner, such as high-pitched voice used to talk with children or animals. However, advanced SD affects all forms of phonation. There are two main types of SD. The adductor type (AdSD) pulls the vocal folds together causing voice breaks in words and a strained or strangled voice quality. Patients with AdSD may try to compensate by whispering. The abductor type (AbSD) pulls the vocal folds apart causing breathy breaks in the voice, or a whispered voice quality.6

Adductor spasmodic dysphonia is far more common than the abductor type (10:l);7 but rarely, patients may have both simultaneously (mixed laryngeal dystonia). The disorder must be differentiated from hyperfunctional and psychogenic dysphonias, as well as essential vocal tremor (EVT), or other vocal tremor, which can be present in up to 25% of patients with AdSD.8 In most patients with SD, only the intrinsic muscles of the larynx are affected. However, some patients also have involuntary muscle contractions in other parts of the body, such as the eyelids.9 The cause of SD is unknown, but it may be associated with a number of genetic and environmental factors, including history of intense voice use, tremor, blepharospasm (involuntary contraction of the eyelid), and family history of voice disorders. …

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