Lookup NU author(s): Dr Supriyo Choudhury,
Dr Mark Baker,
Professor Stuart Baker
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
Background: Writer’s cramp (WC) is a task-specific focal hand dystonia presenting with pain, stiffness and/or tremor while writing. We explored the involvement of cortical and brainstem circuits by measuring intermuscular coherence (IMC) and pre-pulse inhibition of the blink reflex. Methods: IMC was measured in 10 healthy controls, 20 WC patients (10 with associated tremor) while they performed a precision grip task at different force levels. Blink responses were evaluated in 9 healthy controls and 10 WC patients by stimulating the right supraorbital nerve and recording surface EMG from the orbicularis oculi muscles bilaterally. Pre-pulse inhibition involved conditioning this stimulation with a prior shock to the right median nerve (100ms interval), and measuring the reduction in the R2 component of the blink reflex. Results: Significant IMC at 3-7Hz was present in WC patients, but not in healthy controls. Compared to healthy controls, in WC patients the R2 component of the blink reflex showed significantly less pre-pulse inhibition. IMC at 3-7 Hz could reliably discriminate WC patients from healthy controls.Conclusion: Cortical or sub-cortical circuits generating theta (3-7Hz) oscillations might play an important role in the pathogenesis of WC. Moreover, the lack of pre-pulse inhibition implicates abnormalities in brainstem inhibition in the emergence of WC. IMC may merit further development as an electrodiagnostic test for focal dystonia.
Author(s): Choudhury S, Singh R, Chatterjee P, Trivedi S, Shubham S, Baker MR, Kumar H, Baker SN
Publication type: Article
Publication status: Published
Journal: Frontiers in Neurology
Online publication date: 02/07/2018
Acceptance date: 11/06/2018
Date deposited: 19/06/2018
ISSN (electronic): 1664-2295
Publisher: Frontiers Research Foundation
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