Sensorimotor Mapping in Patients With Writer's Cramp (IWCToxin)

Grenoble Alpes University Hospital Center (CHU)

Status

Unknown

Conditions

Writer's Cramp

Treatments

Other: Transcranial Magnetic Stimulation (TMS)

Study type

Interventional

Funder types

Other

Identifiers

NCT03085745

IWCToxin

Details and patient eligibility

About

Writer's cramp (WC) is a form of focal dystonia, a movement disorder characterized by sustained or intermittent muscle contractions causing abnormal, often repetitive movements, postures, or both. It typically manifests while writing, making handwriting impossible in the most severe cases. Treatment can be difficult, but one effective and well-tolerated treatment consists in local muscle injections with botulinum toxin. Although clinical improvement seems to be related to focal muscle chemodenervation, central plasticity changes may occur. The main aim of the study is to characterize and quantify the changes in intrinsic hand muscle cortical representations at rest and during isometric contractions of the finger muscles before and after treatment with botulinum toxin and the changes in sensorimotor integration in patients with writer's cramp.

Full description

Fifteen WC patients will be enrolled in the study. A newly developed neuronavigated and robotized Transcranial Magnetic Stimulation (TMS) mapping approach will be used. It will generate a linear mediolateral excitability profile for two intrinsic hand muscle based on the mean Motor Evoked Potentials (MEPs) amplitude at each stimulation site. Changes in excitability profiles will reflect spatial reorganization of cortical motor output maps of the hand muscles. To measure afferent inhibition, the same mapping procedure will be repeated with a brief peripheral electrical stimulation prior the TMS pulse. These Short Afferent Inhibition (SAI) profiles will reflect the influence of the primary sensory cortex over the motor cortex. Finally, the stimulation grid will be translated to the primary somatosensory cortex and a paired pulse TMS paradigm will be applied just after a digital nerve stimulation. It will generate afferent signal processing profiles based on subjective perception for the index finger and the little finger. Participants will be tested before the botulinum toxin injections and at three different time points after the injections (7 days, 1 month and 3 months after). Botulinum toxin injections will be performed using ultrasound guide together with electromyography/nerve stimulation into the clinical affected hand muscles. Muscle selection for injections will be based on clinical criteria of postural deviation of the hand and fingers and responsible muscle forces. The dose will be chosen according to published clinical recommendation concerning starting dose for WC after the clinical examination, usually between 5 and 10 units of Xeomin® both for flexor and extensor hand/forearm muscles.

To precisely assess treatment efficacy, the Writer's Cramp Rating Scale (WCRS) as well as computer-based hand writing analyses and standard sensorimotor tests of hand functions (the Nine Holes Peg Test, a tapping test and a tactile spatial acuity task) will be performed before the injections and at each follow up session.

Enrollment

15 estimated patients

Sex

All

Ages

30 to 80 years old

Volunteers

No Healthy Volunteers

Inclusion criteria

Suffering from a writer's cramp
aged 30-80 years old
Botulinum toxin injection performed in clinical routine for their disease
Affiliated to a social security system
Sufficient intellectual capacities to understand the tasks to perform
Written consent obtained

Exclusion criteria

Impossibility to remain sitting down without pain or discomfort for at least 3 consecutive hours
History or psychiatric or neurological disease, different from dystonia.
Subject under judicial oversight
Subject being within exclusion period
Subject not reachable in case of emergency,
Presence of one or several contraindications to TMS
Subject covered by the following articles from the french Code de la Santé Publique: L1121-5, L1121-6, L1121-7 et L1121-8.