Corticomuscular coherence in asymptomatic first-degree relatives of patients with essential tremor
Funding agencies: Drs. J. Raethjen, M. Muthuraman, H. Hellriegel, and G. Deuschl received support for the research presented in this article from the German Research Council (Deutsche Forschungsgemeinschaft [DFG]; SFB 855) Project D2.
Relevant conflicts of interest/financial disclosures: Nothing to report.
Full financial disclosures and author roles may be found in the online version of this article.
Correspondence to: Dr. M. Muthuraman, Department of Neurology, University Hospital Schleswig Holstein, Campus Kiel, Schittenhelmstraße 10, 24105 Kiel, Germany; firstname.lastname@example.org
Essential tremor (ET) follows an autosomal dominant type of inheritance in the majority of patients, yet its genetic basis has not been identified. Its exact origin is still elusive, but coherence measurements between electromyography tremor bursts and electroencephalography unequivocally demonstrate a correlation.
We tested these measurements in 37 healthy first-degree relatives (children) of patients with essential tremor (ET) and a group of 37 age-matched and sex-matched controls. Pooled coherence spectra of the maximally coherent electroencephalogram electrodes were computed for ET relatives and controls.
The maximal coherence and its frequency were significantly higher in ET relatives than in controls during the pinch grip task and during slow hand movements. Electromyography amplitude (root-mean-square) was slightly but significantly greater in ET relatives, whereas 2-Hz to 40-Hz power and spectral peak frequency were not different.
The presymptomatic alteration in corticomuscular interaction may reflect a role of genetic factors. © 2013 Movement Disorder Society