Objective
To determine the reasons for discontinuation of Botulinum Toxin Type A injections for spasmodic dysphonia (SD), at our institution.
Introduction
Spasmodic dysphonia is an uncommon neurological disorder of the larynx and one of the focal dystonias. SD is characterized by involuntary spasms of the laryngeal muscles. These interfere with the stability of phonatory positioning of the vocal folds. The two primary variants of SD are adductor (strain-strangled) and abductor (intermittent whisper), which occur in a 10:1 ratio. Symptoms may improve or disappear when yawning, laughing or singing. State-of-the-art treatment usually includes periodic injections of Botulinum Toxin Type A into the affected muscles 1 though various behavioral and surgical treatments have also been devised. The surgical treatments are typically directed at structural alterations and/or denervation / renervation of some or all of the recurrent laryngeal nerve 2, 3.
Vocal fold injections of Botulinum Toxin Type A injections typically provide dramatic relief of vocal symptoms and limitations experienced by patients with SD, especially those with the adductor variant. However, some patients discontinue treatment without notice. Occasional negative comments of generally satisfied patients were used to generate a questionnaire. The following potential reasons for discontinuation were noted: needle phobia; insufficient improvement; unpleasant initial effects of overly breathy voice and/or dysphagia for liquids; shortness of breath (abductor variant); logistical difficulty due to distance traveled; time waited for requested appointment; incorrect diagnosis; and reduction or remission of symptoms. The main goal of the survey was to improve patient care; however, some of the findings may be of general use.
Some of the following thoughts were considered in developing the survey.
Dosing and initial side effects
The ideal dose of botulinum toxin varies between patients. There is no known dose requirement correlation with patient age, weight or type/severity of dysfunction. Therefore the physician must start each new patient at some dosage and then adjust upwards or downwards based upon patient response. It may take two or more injections to determine the optimum dose. If the initial dose is too high, the patient may experience excessive side effects for from days to weeks before achieving the normalized voice. These may include weakening of voice toward or to a whisper, coughing on liquids, and shortness of breath (abductor injections only). On the other hand, if the dose is too low, the degree and duration of benefit may be disappointingly short.
Procedure/Needle phobia
Although many patients experience some manageable degree of anxiety in facing an injection due to needle phobia, for the rare patient, it is so traumatic (especially in anticipation) that sedation is required. The technique of administration also affects patient comfort, with some patients finding the EMG method 1, 4, 5 less unpleasant than a visually guided method using fiberscope or laryngeal telescope 6, 7, 8, 9 while others find the reverse to be true. The occasional hematoma or bruise may add to patient aversion to the procedure as well.
Result variability
Three-dimensional placement of medication in the laryngeal muscles can vary between injections in the same patient even in the best of hands, regardless of method. Consequently, side effects and benefits may vary, even if only slightly, from injection to injection.
Treatment Cost
Because this is an uncommon disease, the combination of expertise, medication cost, and sophisticated equipment requirements together make the procedure expensive. Especially before Botulinum Toxin Type A became widely known and accepted treatment for this disorder, insurance sometimes refused to cover this treatment; some other patients may not have had insurance.
Wrong diagnosis, remission or diminution of symptoms
It seemed possible that some patients may have been misdiagnosed and might have discovered for themselves that they did not need Botulinum Toxin Type A on an ongoing basis. Alternatively, some with SD might have gone into remission, a phenomenon that has been reported, if rarely. Still others might have experienced lessening of symptoms such that Botulinum Toxin Type A no longer seemed necessary to maintain a functional voice.
It appeared that a mail survey might confirm these postulates or suggest other reasons why some patients chose to discontinue treatment.
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