The Effects of Repetitive Paired Associative Stimulation in Dystonia
Condition: Dystonia
MeSH terms: Dystonia; Dystonic Disorders
Study type: Observational

Summary: 
      Background:

      - People with dystonia have serious muscle contractions that cause abnormal movements or
      postures. This significantly affects their daily lives. The common type is called organic.
      The other type is psychogenic. People with this type have typical symptoms plus some
      psychological effects. Researchers will look at how rapid transcranial magnetic stimulation
      (rTMS) of the brain combined with stimulation of a nerve affects the ability to detect
      sensations. They will compare the responses of people with different types of dystonia. They
      will also compare the responses of people with dystonia to responses of people without it.
      This study may help us learn more about the nature of different types of dystonia.

      Objectives:

      - To see whether TMS combined with nerve stimulation affects the brain differently in people
      with different types of dystonia and those without dystonia.

      Eligibility:

        -  Individuals at least 18 years old, who are right-handed and have dystonia.

        -  Healthy volunteers at least 18 years old.

      Design:

        -  Participants will have two clinical visits. Each visit will be a few hours long. They
           can be done on the same day.

        -  Participants will be screened with a medical history and physical exam.

        -  Participants will take several sensory tests. For these tests, electrodes will be placed
           on their skin. The participants will feel small electric shocks during some of the
           tests.

        -  Participants will undergo TMS. For 2 minutes, quick electrical currents will pass
           through a wire coil placed on their head. As this happens, researchers will ask the
           participants to move certain muscles.
    

Detailed description: 
      Objective:

      To investigate the effects of pairing brain and peripheral nerve stimulation in organic and
      psychogenic dystonia to see if this technique can differentiate them.

      Study Population:

      We intend to do an internal pilot study of 6 patients with organic dystonia, 6 patients with
      clinically definite psychogenic dystonia and 6 age-matched healthy volunteers. We will then
      perform an analysis to see how many subjects we need to prove or disprove a difference
      between groups.

      Design:

      Subjects will have a baseline screening visit, electromyography (EMG) and nerve stimulation,
      sensory threshold testing, and measurements of brain excitability using motor evoked
      potentials (MEPs) from transcranial magnetic stimulation (TMS). They will then undergo rapid
      TMS repetitively paired with stimulation of a nerve in the arm. Outcome variables will again
      be measured immediately after (T0), 30 minutes (T30) after, and 60 minutes (T60) after the
      end of brain stimulation.

      Outcome Measures

      Primary outcome variable: Change in MEP amplitudes at T30 from baseline

      Secondary outcome variables:

        -  Input-output curve parameters (measured at baseline, T0, T30, and T60)

        -  Temporal discrimination threshold (TDT)

      Exploratory Measures

        -  Short interval intracortical inhibition (SICI), a measure of inhibition in the motor
           cortex

        -  Influence of Val66Met BDNF polymorphism on the output variables

      Repeated measures analyses of variance (ANOVA) will be used to investigate the following
      three factors on the outcome variables: time (four levels: baseline, T0, T30 and T60) and
      muscle (two levels: APB and FDI) as within-subject factor and group (three levels: organic
      dystonia, psychogenic dystonia, and healthy controls) as between-subjects factor. The model
      of repeated measures ANOVA will include the interactions between the three factors. If the
      interaction between muscle and group is significant, the interaction between time and group
      will be evaluated for each muscle separately. If significance is found for time and/or group,
      then the evaluation will be followed by Tukey Kramer multiple pair-wise comparisons.
    

Time perspective: Prospective
Keywords: rPAS; Dystonia