title: Changes in blink reflex excitability after globus pallidus internus stimulation for dystonia.
abstract: A pathophysiological feature of dystonia is reduced inhibition at various levels of the nervous system, which may be detected in clinically unaffected body parts. Chronic deep brain stimulation (DBS) of the globus pallidus internus (GPi) has emerged as an effective treatment for primary torsion dystonia (PTD), although its mechanism of action and impact on inhibitory abnormalities in dystonia are unknown. We sought to understand the effect of GPi DBS on brainstem excitability in patients with PTD. We measured the blink reflex from orbicularis oculi in response to paired electrical stimulation of the supraorbital nerve at interstimulus intervals of 500 and 1,000 milliseconds in 10 patients with PTD before and at intervals of 1, 3, and 6 months after bilateral GPi DBS and in 10 healthy subjects. Patients were clinically evaluated using the Burke-Fahn-Marsden dystonia rating scale. We found R2 inhibition was significantly decreased in PTD patients compared with control subjects and progressively increased after GPi DBS, which correlated with clinical improvement in dystonia. We conclude that GPi DBS for PTD results in functional reorganization of the nervous system, which includes a long-term increase in brainstem inhibition.
authors.affiliation: Unit of Functional Neurosurgery, Sobell Department Motor Neuroscience and Movement Disorders, Institute of Neurology, London, United Kingdom.
authors.forename: Stephen
authors.initials: S
authors.lastname: Tisch
authors.forename: Patricia
authors.initials: P
authors.lastname: Limousin
authors.forename: John C
authors.initials: JC
authors.lastname: Rothwell
authors.forename: Peter
authors.initials: P
authors.lastname: Asselman
authors.forename: Niall
authors.initials: N
authors.lastname: Quinn
authors.forename: Marjan
authors.initials: M
authors.lastname: Jahanshahi
authors.forename: Kailash P
authors.initials: KP
authors.lastname: Bhatia
authors.forename: Marwan
authors.initials: M
authors.lastname: Hariz
mesh_terms: D000328:Adult; D001767:Blinking / Q000502:physiology*; D046690:Deep Brain Stimulation; D004292:Dominance, Cerebral / Q000502:physiology; D004422:Dystonia Musculorum Deformans / Q000503:physiopathology* / Q000628:therapy; D004576:Electromyography; D005260:Female; D005917:Globus Pallidus / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009433:Neural Inhibition / Q000502:physiology; D012016:Reference Values; D016896:Treatment Outcome