Objective: To evaluate the evidence regarding (1) deep brain stimulation (DBS) effectiveness in case of postoperative cognitive deterioration, (2) the impact of preoperative cognition on DBS effectiveness, and (3) the impact of DBS on cognition in Parkinson’s disease (PD).

Background: DBS is efficacious for treating motor symptoms in PD. However, the impact of DBS on cognition and the impact of cognition on DBS effectiveness remain unclear.

Method: Literature searches were performed on MEDLINE, EMBASE and CENTRAL (Cochrane library). Primary outcomes were OFF-drug Unified Parkinson Disease Rating Scale (UPDRS) part III score and cognitive test scores. Secondary outcomes included the ON-drug UPDRS part III score, levodopa equivalent daily dose (LEDD), and incidence of dementia.

Results: The improvement in OFF-drug and ON-drug UPDRS part III score and LEDD did not differ between patients with postoperative declining cognition compared to patients with stable cognition during follow-up (5 studies) (Figure 1). The mean difference in the OFF-drug UPDRS III score was not different (1.79 points, 95% CI -5.21 to 8.79) between patients with cognitive impairment versus patients with normal cognition at baseline (1 study). DBS moderately decreased verbal fluency compared to best medical treatment (24 studies) (Figure 2). However, this decline in verbal fluency appeared to be transient, with no statistically significant difference observed between DBS and best medical treatment 12 months after surgery. For all other cognitive domains, the decline after DBS was either small (i.e., attention/concentration and psychomotor speed) or not statistically significant. No statistically significant differences were observed in dementia incidence in the DBS group compared to best medical treatment.

Conclusion: DBS motor effectiveness in PD does not appear to be influenced by cognition. DBS in PD seems cognitively safe, except for a moderate decline in verbal fluency. Further research is warranted.

Figure 1

Figure 2

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MDS Abstracts - https://www.mdsabstracts.org/abstract/bidirectional-interplay-between-dbs-and-cognition-in-parkinsons-disease-a-systematic-review/