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Changes in recruitment of motor cortex excitation and inhibition in patients with drug-induced tardive syndromes

Khedr, EM; Al Fawal, B; Abdelwarith, AM; Saber, M; Tony, AAH; El-Bassiony, A; Rothwell, JC; (2018) Changes in recruitment of motor cortex excitation and inhibition in patients with drug-induced tardive syndromes. Neurophysiologie Clinique 10.1016/j.neucli.2018.10.001. (In press).

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Abstract

OBJECTIVES: It has recently been suggested that drug-induced tardive syndromes (TS) might be due to maladaptive plasticity, which increases motor excitability in cerebral cortex and basal ganglia. In order to test this hypothesis, we performed the first measurements of cortical excitability in TS. METHODS: Motor cortex excitability was examined using transcranial magnetic stimulation (TMS) in 22 TS patients and compared with that in 20 age and sex-matched healthy individuals. Resting and active motor threshold (RMT, AMT) and input-output curves (I/O curves) assessed corticospinal excitability. The duration of the contralateral silent period (cSP) at a range of stimulation intensities and ipsilateral silent period (iSP) were used as measures of inhibition. RESULTS: There were no significant differences in RMT and AMT between patients and controls, although the input-output curves were significantly steeper in patients. The cSP (at different stimulus intensities) and iSP were both longer in the patients compared to the control group. However, most of this difference could be accounted for by increased recruitment of motor evoked potentials (MEPs) in patients. CONCLUSION: TS is characterized by hyperexcitability of corticospinal output that might contribute to the lack of selectivity in muscle recruitment and contribute to excess involuntary movement. The findings are opposite to those in naturally-occurring hyperkinesia such as Sydenham's and Huntington's chorea, suggesting a fundamental difference in the pathophysiology.

Type: Article
Title: Changes in recruitment of motor cortex excitation and inhibition in patients with drug-induced tardive syndromes
Location: France
DOI: 10.1016/j.neucli.2018.10.001
Publisher version: https://doi.org/10.1016/j.neucli.2018.10.001
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: Contralateral cortical silent period, Cortical excitability, Drug-induced extrapyramidal, Input–output curve, Motor threshold, Tardive dyskinesia, Tardive syndrome, Transcallosal inhibition, Transcranial magnetic stimulation
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > UCL Queen Square Institute of Neurology
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > UCL Queen Square Institute of Neurology > Clinical and Movement Neurosciences
URI: http://discovery.ucl.ac.uk/id/eprint/10062074
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