Focal Hand Dystonia: Individualized Intervention With Repeated Application of Repetitive Transcranial Magnetic Stimulation

Abstract

Objective Examine for individual factors that may predict response to inhibitory repetitive transcranial magnetic stimulation (rTMS) in focal hand dystonia (FHD); present method for determining the optimal stimulation to increase inhibition in a given patient; and examine individual responses to prolonged intervention. Design A single-subject design to determine optimal parameters to increase inhibition for a given subject and to employ the selected parameters 1/wk for 6 weeks, with 1 wk follow up, to determine response. Setting Clinical research laboratory Participants A volunteer sample of 2 subjects with FHD. One participant had TMS responses indicating impaired inhibition, the other had responses within normal limits. Interventions 1200 pulses of 1 Hz rTMS delivered using 4 different stimulation site/intensity combinations: primary motor cortex (M1) at 90% or 110% resting motor threshold (RMT); dorsal premotor cortex (PMd) at 90% or 110% of RMT. The parameters producing the greatest within-session increase in cortical silent period (CSP) duration were then used as intervention. Main outcome measures Response variables included handwriting pressure and velocity, subjective symptom rating, CSP, and short-latency intracortical inhibition and facilitation. Results The individual with baseline TMS responses indicating impaired inhibition responded favorably to the repeated intervention, with reduced handwriting force, increase in CSP and subjective report of “moderate” symptom improvement at 1-wk follow-up. The individual with normal baseline responses failed to respond to the intervention. In both subjects, 90% RMT to PMd produced greatest lengthening of CSP and was used as intervention. Conclusions An individualized understanding of neurophysiologic measures may be indicators of responsiveness to inhibitory rTMS in focal dystonia, with further work needed to determine 3 likely responders vs. non-responders.

Contribution of TMS and rTMS in the Understanding of the Pathophysiology and in the Treatment of Dystonia

“…Indeed, in a pilot study of a 6 week session of inhibitory low frequency rTMS administered over the contralateral dorsal PMC of two focal hand dystonia patients, only the patient with reduced CSP and SICI, which reflects a loss of cortical inhibition, had clinical benefit from rTMS while the other patient without CSP and SICI reduction did not improve (Kimberley et al, 2015a). …”

Therapeutic Use of Non-invasive Brain Stimulation in Dystonia

“…For instance, it has been reported that only patients with a modulation of cortical inhibition do respond to rTMS treatment (Kimberley et al, 2015). …”

Stepping Up to Rethink the Future of Rehabilitation: IV STEP Considerations and Inspirations

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