Neuropsychological and quality of life outcomes 12 months after unilateral thalamic stimulation for essential tremor

Abstract

Objectives: To evaluate the one year cognitive, mood state, and quality of life (QoL) outcomes of unilateral thalamic deep brain stimulation (DBS) for essential tremor (ET). Methods: 40 patients diagnosed with ET completed comprehensive neuropsychological assessments about one month before and three and 12 months after DBS electrode implantation. Data were subjected to multivariate analyses, and significant results were further analysed using univariate techniques. Results: Analyses revealed statistically significant improvements on a cognitive screening measure and in aspects of fine visuomotor and visuoperceptual functions, verbal memory, mood state, and QoL. No group-wise declines in cognition were observed, but more patients showed declines than improvements on language and visual memory tests. Semantic verbal fluency declined significantly in four (10%) of the patients. In these four patients, diminished lexical verbal fluency was present at baseline. Conclusion: Cognitive, mood, and QoL outcomes after one year of DBS for ET are favourable; there were no overall deleterious effects on cognition, and DBS was accompanied by a significant reduction in anxiety and improvements in quality of life. However, preoperative verbal fluency diminution may predispose to further fluency declines after DBS. E ssential tremor (ET), one of the most common movement disorders, renders a disabling, non-uniform, bilateral effect primarily on the upper limbs, although the lower limbs, head, face, voice, and trunk may be affected to a lesser extent.1 Despite the high prevalence of this disorder (estimates range from 1% to 22% of the elderly population 2 ), neither its pathophysiology nor its functional mechanisms are well understood. There is debate about whether the tremors of ET and Parkinson's disease (PD) are associated, 2 and whether PD and ET are different manifestations of the same disorder.3 From a cognitive standpoint, recent studies of ET reveal patterns of cognitive changes that qualitatively overlap those seen in PD, but are more circumscribed and less severe. [4][5][6][7]

Effects on cognition and quality of life with unilateral magnetic resonance–guided focused ultrasound thalamotomy for essential tremor

“…14,18,24,29,38 Huss et al demonstrated no difference in the change in reported QOL between bilateral Vim DBS and unilateral procedures, including DBS and MRgFUS thalamotomy. 22 A randomized controlled study of MRgFUS thalamotomy described significant reductions of 46% in QUEST scores from baseline to 3 months after ablation as compared with a 3% reduction in the sham group.…”

“…14,34,38,40 In patients with ET, it has been suggested that there are complex, widespread alterations of white mater fiber integrity in both motor and nonmotor networks. 25 Thus, theoretically, thalamic procedures can produce disruption in the neuroanatomical pathway connecting the prefrontal cortex and subcortical areas, resulting in frontal lobe dysfunction.…”

“…And certainly, there have been some studies with positive results of DBS in enhancing visuoperceptual or verbal memory function or in causing no significant effects on higher cognitive function even in the long term. 14,19,38 However, DBS has also caused cognitive side effects, such as those related to language, visual memory, and verbal fluency. 7,38 Interestingly, there has been a report of a subtle diminution in verbal memory in the DBS-on state versus the DBS-off state.…”

Effects of Deep Brain Stimulation in the Caudal Zona Incerta on Verbal Fluency

“…Dysphasia has not been reported by other groups performing DBS in the cZi or prelemniscal radiation [10], but it is common after thalamotomy, occurring in up to 42% of the patients operated in the dominant hemisphere [23,24,25,26,27,28,29,30,31]. There are also data indicating that VIM DBS might have negative effects on verbal fluency [6,8]. It might, therefore, be suspected that the dysphasia previously seen after cZi DBS, as well as the reduction of verbal fluency in this material, might be caused by the electrode passage through the ventrolateral thalamus situated closely above the cZi (fig.…”

“…Even though these findings strongly suggest a role for the basal ganglia in verbal fluency, the exact neuroanatomical and functional nature of this role is not fully understood. This, in combination with the more limited knowledge regarding the effects of DBS on verbal fluency in other targets and for other conditions [5,6,7,8], makes it difficult to decide whether reduced verbal fluency might be considered as more or less specific for STN DBS in PD, or as a more or less unavoidable part of any DBS procedure for movement disorders.…”