Repetitive Transcranial Magnetic Stimulation for the Treatment of Focal Hand Dystonia

Multiple Sessions of Low-frequency Repetitive Transcranial Magnetic Stimulation in Focal Hand Dystonia: Clinical and Physiological Effects

Dystonia Medical Research Foundation, National Institutes of Health (NIH), National Center for Research Resources (NCRR)

This study investigated the short term effects of repeated administrations of repetitive-transcranial magnetic stimulation (rTMS) on clinical changes and investigate neurophysiologic responses to rTMS of the activated motor system in patients with FHD.

Purpose: The ability of low-frequency repetitive transcranial magnetic stimulation (rTMS) to enhance intracortical inhibition has motivated its use as a potential therapeutic intervention in focal hand dystonia (FHD). In this preliminary investigation, we assessed the physiologic and behavioral effects of multiple sessions of rTMS in FHD. Methods: 12 patients with FHD underwent five daily-sessions of 1 Hz rTMS to contralateral dorsal premotor cortex (dPMC). Patients held a pencil and made movements that did not elicit dystonic symptoms during rTMS. We hypothesized that an active but non-dystonic motor state would increase beneficial effects of rTMS. Five additional patients received sham-rTMS protocol. The area under curve (AUC) of the motor evoked potentials and the cortical silent period (CSP) were measured to assess changes in corticospinal excitability and intracortical inhibition, respectively. Behavioral measures included pen force and velocity during handwriting and subjective report.

Repetitive Transcranial Magnetic stimulation: 1 Hz rTMS, 1800 pulses, delivered to premotor cortex. Patients held a pencil and made movements that did not elicit dystonic symptoms during rTMS. Intervention was delivered every day for 5 days.

Sham Repetitive Transcranial Magnetic stimulation: 1 Hz rTMS, 1800 pulses, delivered to premotor cortex. Patients held a pencil and made movements that did not elicit dystonic symptoms during rTMS. Intervention was delivered every day for 5 days.

Subjects performed an isometric abduction contraction of the index finger against a strain gauge coupled to a load cell. A single TMS pulse was applied 2-3 s after contraction initiation and subjects were instructed to relax 2-3 s after stimulation. The duration of the CSP was measured on a trial-by-trial basis and was delineated by the first superimposed TMS-evoked EMG spike (onset) and the return of activity to 50% of prestimulus EMG signal (offset). The mean CSP duration was calculated for each block of measurements. The duration of CSP is thought to be related to intracortical GABAergic synapse-mediated inhibition in the stimulated cortical region. Measures of CSP have been shown to be reliable in repeated measures studies to determine an effect of intervention within a group of subjects (Orth and Rothwell 2004; Borich et al., 2009). Values are calculated as the value recorded at the latest time minus the earliest time point.

Inclusion Criteria: Task specific Focal Hand Dystonia Exclusion Criteria: any neurologic condition other than FHD medication for dystonia botulinum toxin within the past three months seizure history pregnancy implanted medical devices

Kimberley TJ, Borich MR, Arora S, Siebner HR. Multiple sessions of low-frequency repetitive transcranial magnetic stimulation in focal hand dystonia: clinical and physiological effects. Restor Neurol Neurosci. 2013;31(5):533-42. doi: 10.3233/RNN-120259.