Introduction
Spasmodic dysphonia is a dystonia (muscle spasms) involving the muscles of the voicebox resulting in involuntary attacks of a strangled sounding voice. Treatment is botox injection to the involved muscles resulting in a decrease of such spasms thereby resulting in a more smooth-sounding voice.
Unfortunately, there are side effects with botox injections to the voicebox including aspiration, dysphagia, breathy voice, etc for a short period of time prior to the good voice. Typically, one week of side effects results in about 3 months of a good voice.
Research into this area typically has been to try and maximize the duration of a good voice while decreasing the duration of side effects.
A prior paper published by Dr. Chang tried to establish what the correct dose is to maximize a good voice and minimize side effects.
This book chapter tries to determine if age influences botox response.
Age and Botox Responses
What was found is a positive correlation between age and duration of normal voice and duration of side effects after botox injection. Age did not appear to play a role in the severity of side effects experienced by patients. However, the number of BTX-A injections received by a given patient was negatively correlated with duration of normal voice and side effects to a degree greater than age.
What does this mean?
Age must be taken into consideration when deciding on what dose of botox to inject since as a patient becomes older, one may see a slow increase in not only duration of normal voice, but also duration of side effects reported. Stated another way, for a given dose, the duration of side effects is larger for an older patient compared with a younger one. However, as the cumulative number of injections a patient receives increases over time, the duration of normal voice and side effects would be expected to decrease slowly.
Reference:
Age as a Factor in Responses to Botulinum Toxin Injection in Adductor Spasmodic Dysphonia Patients pp. 101-112
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