This study will examine the action of sensory tricks on an occurrence known as surround
inhibition when there is a disorder of muscle tone affecting a single body part in
isolation. Surround inhibition refers to a situation that suppresses unwanted movements,
known as dystonia, in surrounding muscles during voluntary actions. There are
tricks-various actions-that people use to temporarily stop those unwanted movements. Such
tricks can include touching the affected body part, placing an object in the mouth, pulling
the hair, and others. Often these tricks are beneficial early in the illness but become
less effective as it progresses. This study is guided by a hypothesis that sensory tricks
will restore surround inhibition and by another hypothesis that it is the application of the
tricks, not simply sensory input, that is effective in doing that restoring. Emphasis is on
cervical dystonia, involuntary actions affecting the neck, in which the tricks commonly
involve the cheeks and chin. The technique used in the study is transcranial magnetic
Patients ages 18 and older who have cervical dystonia with at least one effective trick and
patients with no effective trick may be eligible for this study. There will also be a
control group of healthy participants.
Participants will be asked to show the sensory trick and may be asked to be videotaped.
During the TMS procedure, they will be seated in a comfortable chair, with hands placed on a
pillow on the lap. Small electrodes-soft strips that stick to the skin-will be placed on the
skin to record the electrical activity of some muscles in the neck that are activated by the
stimulation from TMS. In TMS, there will be a wire coil held over the scalp. A brief
electrical current will be passed through the coil, creating a magnetic pulse that
stimulates the brain. Patients will hear a click and may feel a pulling sensation on the
skin under the coil. There may be muscle twitches of the face, arm, or leg. In addition,
patients may be asked to tense certain muscles slightly or perform other simple actions so
that the coil can be positioned appropriately. Patients will sometimes be asked to bite
down and tap their teeth slightly for about 1-1/2 minutes at a time. They will be asked to
show the sensory trick. The stimulation is usually not painful, although sometimes strong
contractions of the scalp muscles can cause discomfort or a headache. Patients can ask to
have the procedure discontinued at any time. The testing session takes about 2 hours, done
on an outpatient basis.
The purpose of this study is to investigate the mechanism of sensory tricks on surround
inhibition in the motor cortex in focal dystonia. Sensory tricks or Geste antagoniste, are
various manoeuvres used by dystonic patients to transiently diminish their spasms. Many of
these manoeuvres involve motor as well as sensory input and here we use the term 'tricks' to
refer to both phenomena. Little is known of this unique feature that is an evidence for the
abnormality of sensorimotor integration in focal dystonia. The relief of dystonic symptoms
by the application of tricks suggests its potential as a clue to the understanding of the
yet unclear mechanism of dystonia. There is evidence that surround inhibition, a cortical
phenomenon that functions to suppress unwanted movements in surrounding muscles during
voluntary actions, is impaired in dystonia. Since tricks transiently relieve the dystonic
symptoms, we hypothesize that the mechanism of tricks is the normalization of surround
inhibition which is defective in dystonia.
Nineteen patients age 18 or over with cervical dystonia with a minimal of one effective
trick, 15 patients age 18 and over with cervical dystonia with no effective trick will be
recruited for the study.
For patients, the selection criteria are the presence of cervical dystonia and the minimal
of one sensory trick in the patient with trick group, and no trick in the patient without
The interview of dystonic patients will be focused on medical history, neurologic
examination and effectiveness of the patient's tricks which will be accessed by measuring
the degree of head rotation before and during trick application.
The diagnosis of dystonia will rely on review of medical record, history, and clinical
For the patients that are receiving botulinum toxin injections, the evaluation will be
done 3 months after their last injection.
Their gender, age, or ethnic origin will not provide bias for inclusion to the study.
There is no evidence of higher prevalence of dystonia in any particular race, thus the
races and ethnicity of the subjects recruited for this study will approximate that of the
Fifteen normal subjects age 18 and over will be recruited for the control group.
The controls will not have dystonia or any other neurological condition.
All subjects will sign an informed consent prior to participation in the trial, and the
trial will be approved by the NINDS IRB committee.
Exclusion criteria for the trial covering both the normal control and dystonia group will
1. Any concurrent medical or surgical condition as well as neurological or psychiatric
2. Any individual who is on medications with potential influence of the nervous system
function (antidepressants, antianxiolytics, anticonvulsants, antipsychotic,
antiparkinsonian, hypnotics, and stimulants).
3. Patients who have received Botulinum toxin injections within 3 months of starting the
4. Individual who has a pacemaker, an implanted medical pump, a metal plate or medical
object in the skull or eye (for example, after brain surgery)
5. Individual with a history of seizures.