rTMS in Spasmodic Dysphonia

Focal dystonia is a neurological movement disorder characterized by excessive involuntary muscle contractions of any body part. Spasmodic dysphonia (SD) is a type of focal dystonia characterized by excessive contraction of intrinsic muscles in the larynx, leading to difficulty in speaking and affecting effective communication. The cause of SD is unknown and there are no treatments that produce long-term benefits. Previous studies have suggested that SD and other focal dystonias are associated with decreased inhibition in sensorimotor areas in the brain. However, no studies have investigated the effects of modulating excitability of the laryngeal motor cortex in healthy individuals or SD. The goal of this pilot project is to determine if brain excitability of the laryngeal motor cortex can be changed with low-frequency inhibitory repetitive transcranial magnetic stimulation (rTMS) in individuals with SD and healthy controls. Considering that rTMS at low frequencies (≤1 Hz) produces lasting inhibition in the brain, and that SD is associated with decreased cortical inhibition, the purpose of this pilot study is to determine safety, feasibility and response to 1Hz rTMS to the laryngeal motor cortex in individuals with SD and healthy people. The results will help understand changes associated with the disorder, as well as contribute to the development of future clinical interventions for SD.


Eligibility Criteria:
Inclusion Criteria:

* Primary inclusion for spasmodic dysphonia:

  1. Diagnosis of adductor spasmodic dysphonia
  2. Symptoms at worst severity if receiving regular botulinum injections
* Primary inclusion for healthy participants (controls):

  1. Absence of vocal fold pathology

Exclusion Criteria:

* Primary exclusion for participants with spasmodic dysphonia:

  1. Other forms of dystonia
  2. Vocal fold pathology or paralysis
  3. Diagnosis of voice tremor
  4. Laryngeal surgery
  5. Laryngeal cancer or neurological condition other than dystonia
  6. Contraindication to TMS
  7. Medications with effect on central nervous system
  8. Inability to complete tasks associated with study
  9. Adult lacking ability to consent
* Primary exclusion for healthy participants (controls):

  1. Any health condition or disability that would interfere with participation
  2. Contraindications to TMS
  3. Medications with effect on central nervous system
  4. Adult lacking ability to consent

TMS contraindications:

* The only absolute contraindication to TMS/rTMS is the presence of metallic hardware in close contact to the discharging coil (such as cochlear implants, deep brain stimulator, or medication pumps). In such instances there is a risk of inducing malfunctioning of the implanted devices.
* Conditions classified as of increased or uncertain risk are listed below (Rossi et al., 2009; Rossini et al., 2015). Persons under those circumstances will be excluded from the study.

  1. Pregnancy
  2. Bipolar disorder
  3. Epilepsy or history of seizure episodes in the past two years
  4. Vascular, traumatic, tumoral, infectious, or metabolic lesion of the brain, even without history of seizure, and without anticonvulsant medication
  5. Use of medications that potentially lower seizure threshold
  6. Severe or recent heart disease