Abstract
Objective: Deep brain stimulation (DBS) targeted to the ventral intermediate (VIM) nucleus of the thalamus is effective for motor symptoms in essential tremor (ET), but there is limited data on cognitive outcomes. We examined cognitive outcomes in a large cohort of ET DBS patients (pre-DBS and 1+ year after DBS).Methods: In a retrospective analysis, we used repeated-measures ANOVA testing to examine whether the age of tremor onset, age at DBS surgery, hemisphere side implanted with lead, unilateral vs. bilateral implantations, and presence of surgical complications influenced the cognitive outcomes. Neuropsychological outcomes of interest were verbal memory, executive functioning, working memory, language functioning, visuospatial functioning, and general cognitive function.Results: We identified 50 ET DBS patients; 29 (58%) males; the mean age of tremor onset was 35.84 (±21.50) years with a median age of 38 years. The mean age at DBS was 68.18 (±10.07) years. There were 37 unilateral 30 left, seven right, and 13 bilateral brain implantations. In the subgroup analysis, there was a significant interaction between assessment (pre vs. post) and age of tremor onset (<38 vs. >38 years); F(1,30) = 4.47; p = 0.043 for working memory. The post hoc testing found improvements for younger onset ET. Similarly, there was a significant interaction between assessment (pre vs. post) and complications vs. no complications subgroups; F(1,45) = 4.34; p = 0.043 for verbal memory with worsening scores seen for ET patients with complications. The remaining tests were not significant.Conclusion: In this large cohort of ET patients with (>30% improvements), DBS was not accompanied by a significant decline in many cognitive domains. These outcomes were possibly related to the selection of patients with normal cognitive functioning before surgery, unilateral DBS implantations for the majority, and selection of patients with optimal response to DBS.
Highlights
Deep brain stimulation (DBS) directed to the ventral intermediate (VIM) nucleus region of the thalamus is an efficacious intervention for the motor symptoms in essential tremor (ET; Wilkes et al, 2020)
We examined whether cognitive outcomes after surgery in each domain of assessment differed according to the baseline characteristics including the age of tremor onset, age at DBS surgery, disease duration, baseline Tremor Rating Scales (TRS) score, unilateral vs. bilateral DBS, right DBS vs. left DBS; the amount of total electrical energy delivered (TEED) and complications during and immediately after surgery
There were no significant effects of age at surgery, duration of ET, baseline tremor severity, and TEED value calculations seen across all domains of cognitive outcomes
Summary
Deep brain stimulation (DBS) directed to the ventral intermediate (VIM) nucleus region of the thalamus is an efficacious intervention for the motor symptoms in essential tremor (ET; Wilkes et al, 2020). VIM DBS impaired the word output dynamics during verbal fluency tasks (Ehlen et al, 2017), whereas Fields et al (2003) observed that there was a significant improvement in general cognitive assessment, verbal memory and visuoperceptual functions following DBS. These studies did not evaluate the baseline factors that influenced cognitive performance following surgery. We sought to examine whether factors including the age of onset for ET, the hemisphere side implanted with the DBS lead, unilateral vs bilateral implantation procedures, and the presence of surgical complications influenced cognitive performance following DBS surgery. We further examined whether disease duration, age at DBS surgery, tremor severity, and the electrical energy used for DBS programming predicted cognitive outcomes
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