title: Verbal fluency in essential tremor patients: the effects of deep brain stimulation.
abstract: OBJECTIVE
  To assess the effects of different frequencies of thalamic Deep-Brain-Stimulation (DBS) on cognitive performance of patients suffering from Essential Tremor (ET).
  
  
  METHODS
  In 17 ET-patients with thalamic-DBS, Tremor-Rating-Scale (TRS), standardized phonemic and semantic verbal fluency (VF), Stroop-Color-Word-Test and Digit-span-test were investigated in three randomized stimulation-settings: i) high-frequency stimulation (HFS), ii) low-frequency stimulation (LFS) and iii) OFF-stimulation (DBS-OFF). Paired-samples t-test for TRS and one-way repeated measures analysis of variance for cognitive performance were calculated.
  
  
  RESULTS
  Tremor was reduced during HFS (MeanTRS-HFS = 12.9 ± 9.6) compared to DBS-OFF (MeanTRS-OFF = 44.4 ± 19.8, P < .001) and to LFS (MeanTRS-10 Hz = 50.0 ± 24.2; P < .001). While performance of Stroop-task and digit-span remained unaffected by stimulation-settings (P > .05), phonemic and semantic VF differed significantly between the three conditions (FPvf = 5.28, FSvf = 3.41, both P < .05). Post-hoc comparisons revealed significant differences for both phonemic and semantic VF between LFS (MeanPvf-10 Hz = 54.6 ± 9.2, MeanSvf-10 Hz = 56.4 ± 7.9) and HFS (MeanPvf-ON = 48.3 ± 11.4, MeanSvf-ON = 51.1 ± 11.0, both P < .05), while DBS-OFF (MeanPvf-OFF = 51.2 ± 9.3, MeanSvf-OFF = 53.6 ± 12.9) and HFS and DBS-OFF and LFS did not differ significantly (P > .05).
  
  
  CONCLUSIONS
  HFS compared to LFS or DBS-OFF significantly reduced tremor but simultaneously worsened VF while working memory and cognitive inhibition remained unaffected. In contrast, LFS enhanced VF but did not ameliorate tremor. The data emphasize the relevance of thalamocortical loops for verbal fluency but also suggest that more sophisticated DBS-regimes in ET may improve both motor and cognitive performance.
authors.affiliation: Department of Neurology, University Hospital Cologne, Cologne, Germany. Electronic address: david.pedrosa@uk-koeln.de.
authors.forename: David J
authors.initials: DJ
authors.lastname: Pedrosa
authors.affiliation: Department of Neurology, University Hospital Cologne, Cologne, Germany.
authors.forename: Michelle
authors.initials: M
authors.lastname: Auth
authors.affiliation: Department of Neurology, University Hospital Cologne, Cologne, Germany.
authors.forename: K Amande M
authors.initials: KA
authors.lastname: Pauls
authors.affiliation: Department of Stereotaxy and Functional Neurosurgery, University Hospital Cologne, Cologne, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Runge
authors.affiliation: Department of Stereotaxy and Functional Neurosurgery, University Hospital Cologne, Cologne, Germany.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Maarouf
authors.affiliation: Department of Neurology, University Hospital Cologne, Cologne, Germany; Cognitive Neuroscience, Institute of Neuroscience and Medicine (INM-3), Research Center Jülich, Germany.
authors.forename: Gereon R
authors.initials: GR
authors.lastname: Fink
authors.affiliation: Department of Neurology, University Hospital Cologne, Cologne, Germany.
authors.forename: Lars
authors.initials: L
authors.lastname: Timmermann
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D003071:Cognition; D046690:Deep Brain Stimulation / Q000009:adverse effects / Q000523:psychology*; D004567:Electrodes, Implanted; D020329:Essential Tremor / Q000150:complications / Q000628:therapy*; D005260:Female; D006801:Humans; D008297:Male; D008570:Memory, Short-Term; D008875:Middle Aged; D015233:Models, Statistical; D009483:Neuropsychological Tests; D011446:Prospective Studies; D012660:Semantics; D013060:Speech; D057190:Stroop Test; D013788:Thalamus / Q000473:pathology; D055815:Young Adult
keywords: Cognitive impairment; Deep brain stimulation; Thalamus; Verbal fluency