Brain Activity Associated With Tics in Patients With Tourette Syndrome
Condition: Tourette Syndrome
MeSH terms: Tourette Syndrome; Syndrome
Study type: Observational

Summary: 
      This study will examine brain activity associated with the involuntary urges or uncontrolled
      movements, called "tics," experienced by people who have Tourette syndrome (TS). Before
      people with TS actually develop a tic, whether it is a movement or a vocal tic (like a cough
      or bark), they feel the urge to tic. This study will look at brain activity during the time
      of this urge and how brain activity may differ in people with TS and without TS.

      Healthy normal volunteers and patients with TS between 14 and 65 years of age may be eligible
      for this study. Patients must have sensory tics in the facial region and must experience at
      least a moderate premonitory urge. Candidates are screened with a medical history, brief
      physical examination, and a questionnaire.

      Participants undergo the following procedures:

        -  Magnetoencephalography (MEG): This test records magnetic field changes produced by brain
           activity. During the test, the subjects are seated in the MEG recording room and a cone
           containing magnetic field detectors is lowered onto their head. Electrodes (small metal
           disks) are placed on both sides of the face near the jaw. The recording may be made
           while the subject receives small currents from the electrodes on the jaw. Subjects may
           be asked a few questions about what they felt during the procedure.

        -  Magnetic resonance imaging (MRI): This test uses a strong magnetic field and radio waves
           to obtain images of body organs and tissues. During the procedure, the subject lies on a
           table that can slide in and out of the scanner-a metal cylinder. Subjects may be asked
           to lie still for up to 30 minutes at a time. They can communicate with the staff at any
           time during the scan.

        -  Somatosensory evoked responses: This test examines how sensory information travels form
           the nerves to the spinal cord and brain in the nervous system. An electrode placed on
           the arm, leg, or face delivers a small electrical stimulus that may tingle and cause a
           twitch of a hand, foot, or face muscle. Additional electrodes may sometimes be placed on
           the scalp, neck, and over the collarbone to record how the impulse from the stimulus
           travels over nerve pathways.

      Patients in the study are contacted for follow-up after the study. Follow-up will be
      conducted by phone or email, according to the patients' convenience, and will consist of
      reaffirming that there were no adverse events.
    

Detailed description: 
      OBJECTIVES:

      This study will examine the spatiotemporal dynamics of sensory tics in patients with Tourette
      syndrome (TS). We will also investigate the possible existence of a sensory gating problem.
      By investigating somatosensory evoked responses from stimulation of the trigeminal nerve
      (tSERs) on affected versus unaffected sides of the face, we hope to identify differences in
      the SER waveforms that suggest sensory abnormalities. We will use a series of short trains of
      stimulations on the affected side to examine habituation, subsequently performing a time-

      frequency analysis to seek indicators of decreased sensory gating. This study will examine,
      specifically:

      Whether the cortical neurocircuitry involved in the elicitation of tSERs differs in patients
      with tic disorders from controls.

      If SERs differ in a sensory tic facial region of patients, compared to the same spot on an
      unaffected side of the face.

      Whether in controls and patients with sensory tics on both sides of their body, tSERs on both
      sides of the face are symmetrical.

      If there is a lack of habituation in tic patients to tSERs in a short-train click paradigm,
      compared to controls.

      The location for sources of abnormalities in either paradigm.

      STUDY POPULATION:

      Twenty patients and 10 control subjects will be studied. Subjects can be of any race, gender,
      handedness, or age between 14 and 65 years.

      DESIGN:

      This study will compare tSERs in normal volunteers to those in TS patients. Patients with
      bilateral sensory tics will be contrasted with those who have unilateral sensory tics,
      comparing power of the response at latencies on affected versus unaffected sides. Subjects
      will be seated in the MEG and instructed to "feel the delivered sensation, and try not to tic
      for seventy seconds, without counting". The trigeminal nerve will be electrically stimulated
      at 0.25 Hz for 30 seconds, which will be followed by head localization and subsequent rest
      for tic release. To evaluate sensory gating, the design is similar except the trigeminal
      stimulation will occur in short trains. Patients will be surveyed to determine if the
      instructions intensified sensory tics.

      OUTCOME MEASURES:

      We will compare the power of averaged tSERs at latencies, comparing face sides in patients
      and comparing patients' active face side with controls' dominant face side. The power of
      frequency components at latencies will be considered. We will locate the sources of
      differential tSER activity.
    

Keywords: Sensory Processing; Magnetoencephalogram; Tourete Syndrome; Trigeminal Nerve; Tics; TS; Healthy Volunteer; HV