Interhemispheric difference of pallidal local field potential activity in cervical dystonia

Background Cervical dystonia (CD) produces involuntary neck muscle contractions that result in abnormal and often asymmetrical postures of the head and neck. Basal ganglia oscillatory activity in the 3-12Hz band correlating with involuntary muscle activity suggests a role in the pathophysiology of primary dystonia. Despite the asymmetrical postures seen with CD, no comparison of interhemispheric differences of pallidal local field potential (LFP) activity has been reported. Objective The aim of this study was to examine the interhemispheric differences of LFP power in globus pallidus interna (GPi) in CD patients and compare these with their predominant head excursion identified as torticollis, laterocollis and retrocollis. Methods LFPs were recorded from bilateral GPi in 11 patients with CD using microelectrodes during deep brain stimulation surgery. LFP power was measured in right and left GPi separately. The mean percentage of total GPi LFP power in 4-30Hz frequency band on each brain side was determined and related to their predominant CD symptoms. Results Interhemispheric difference in the mean percentage of LFP power in 4-12Hz and 13-30Hz band frequencies was found in patients with torticollis and laterocollis regardless of excursion direction. However, patients with retrocollis did not show interhemispheric difference in LFP activity in any band frequency. Conclusions Interhemispheric differences in synchronisation of pallidal LFP activity in 4-12Hz and 13-30Hz bands are related to the CD clinical condition, suggesting that these frequencies are important in the pathophysiology of dystonia.