Objective: This study examined cognitive outcomes after deep brain stimulation (DBS) of ventral intermediate nucleus of the thalamus (VIM). Duration of anesthesia exposure and additional surgical parameters were also explored.

Background: DBS of the VIM is a well-established therapy for refractory essential tremor (ET) [1]. The number of surgeries required for this therapy varies, as DBS lead placement and battery implantation can be performed simultaneously or in staged procedures. Postoperative cognitive decline associated with various types of surgery and anesthesia is well described [2-6]. While there have been many studies of cognitive outcomes after DBS for ET, [7, 8] there are limited studies specifically examining the effect of anesthesia and surgical approach [9]. Therefore, this study aims to evaluate this association within our institution.

Method: We reviewed patients that underwent VIM DBS for ET from 2014-2024, and those with pre- and post-DBS comprehensive cognitive assessments were selected. Anesthetic exposure was evaluated using number of surgeries, duration of surgeries, number and doses of medications used as well as anticholinergic burden (ACB) [10]. Paired sample t-test was performed to measure changes post- intervention (alpha = 0.008 post Bonferroni correction). Multivariate linear regression models and partial correlations (while controlling for years of education) were used to evaluate statistically significant relationships.

Results: 31 patients met inclusion criteria, with an average age of 67.8 ± 7.7 yrs. Demographics and details of the surgical approach are shown in Table 1. Of 24 compared cognitive measures, only semantic verbal fluency showed statistically significant change after DBS (pre-DBS 18.35 ± 5.21 vs. post-DBS 16.26 ± 0.81; p=0.004) [Figure 1]. There was a trend towards declined semantic fluency with bilateral procedures as compared to a unilateral or staged approach, not reaching statistical significance. Number and duration of surgeries, time between cognitive testing, number and doses of anesthetic medications used, and ACB had no significant effect on change in semantic fluency.

Conclusion: There was no significant correlation between exposure to anesthesia and adverse cognitive outcomes in our ET patients treated with DBS. This study highlights the cognitive safety of a variety of surgical and anesthetic approaches.

Figure 1. Decline in semantic verbal fluency score

Table 1. Demographics and surgical approach

References: 1. Vaillancourt, D.E., et al., Deep brain stimulation of the VIM thalamic nucleus modifies several features of essential tremor. Neurology, 2003. 61(7): p. 919-25.
2. Cottrell, J.E. and J. Hartung, Anesthesia and Cognitive Outcome in Elderly Patients: A Narrative Viewpoint. J Neurosurg Anesthesiol, 2020. 32(1): p. 9-17.
3. Ancelin, M.L., et al., Long-term post-operative cognitive decline in the elderly: the effects of anesthesia type, apolipoprotein E genotype, and clinical antecedents. J Alzheimers Dis, 2010. 22 Suppl 3: p. 105-13.
4. Taylor, J., et al., Association between surgical admissions, cognition, and neurodegeneration in older people: a population-based study from the UK Biobank. Lancet Healthy Longev, 2024. 5(9): p. 100623.
5. Vacas, S., D.J. Cole, and M. Cannesson, Cognitive Decline Associated With Anesthesia and Surgery in Older Patients. JAMA, 2021.
6. Monk, T.G. and C.C. Price, Postoperative cognitive disorders. Curr Opin Crit Care, 2011. 17(4): p. 376-81.
7. Cernera, S., M.S. Okun, and A. Gunduz, A Review of Cognitive Outcomes Across Movement Disorder Patients Undergoing Deep Brain Stimulation. Front Neurol, 2019. 10: p. 419.
8. Al Ali, J., et al., Cognitive outcomes in patients with essential tremor treated with deep brain stimulation: a systematic review. Front Hum Neurosci, 2024. 18: p. 1319520.
9. Holewijn, R.A., et al., Cognitive and psychiatric outcomes in the GALAXY trial: effect of anaesthesia in deep brain stimulation. J Neurol Neurosurg Psychiatry, 2024. 95(3): p. 214-221.
10. Boustani, M., Campbell, N., Munger, S., Maidment, I., & Fox, C., Impact of Anticholinergics on the Aging Brain: A Review and Practical Application. Aging Health, 2008. 4(3): p. 311-320.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/cognitive-outcomes-in-thalamic-deep-brain-stimulation-for-essential-tremor-evaluating-effect-of-anesthetic-exposure-and-surgical-approach/