Cognitive Effects of Subthalamic Nucleus Stimulation in Parkinson’s Disease: A Controlled Study

Abstract

Background: Subthalamic nucleus deep brain stimulation (STN-DBS) improves motor function in selected patients with Parkinson’s disease (PD) but can be associated with variable changes in cognitive functions. Methods: We studied 21 patients selected for STN-DBS and compared 6-month clinical and neuropsychological outcomes between those who underwent surgery (n = 9) and those who voluntarily refused it (n = 12). Results: Motor and quality of life outcomes were markedly superior in the STN-DBS group versus controls. A wide neuropsychological battery was administered, and the whole sample showed a statistically significant worsening in phonemic verbal fluency, time to perform the Trail Making Test part B, Digit Symbol score of WAIS-III and color-naming score of the Stroop Test. In comparison to controls, a trend to a slightly worse deterioration in phonemic verbal fluency was observed in the STN-DBS patients and was significantly correlated with reductions in the <smlcap>l</smlcap>-dopa-equivalent daily dose (r = 0.850, p = 0.007). Conclusion: Our study confirms the safety of STN-DBS from a cognitive standpoint; a reduction in verbal fluency at 6 months after surgery can also be related to PD progression and medication reduction.

Does early verbal fluency decline after STN implantation predict long-term cognitive outcome after STN-DBS in Parkinson's disease?

“…Even though the procedure is not considered to cause major cognitive side-effects, it is associated with changes in executive function, in particular decreased verbal fluency (VF) [2]. Several factors are thought to predict cognitive decline following STN-DBS, such as advanced age, axial signs, levodopa resistant symptoms, visual hallucinations, vascular lesion load, and poor baseline cognitive performance [3,4].…”

Expectation modulates the effect of deep brain stimulation on motor and cognitive function in tremor-dominant Parkinson's disease

“…Thus, negative expectation regarding the effect of STN-DBS on motor function did not only modulate the magnitude of resting tremor but additionally had an adverse effect on a cognitive function often affected in PD patients treated with STN-DBS [6][7][8][9]. This suggests an expectation-induced generalization of a nocebo response manifesting on motor as well as on cognitive functions.…”

“…Although both treatments generally lead to improvement in motor symptoms, tremor is usually more effectively supressed by STN-DBS as compared to dopamine replacement therapy (for a review see [4]). Moreover, while STN-DBS does not affect overall cognitive function [5,6], adverse effects of therapeutic STN-DBS have been reported for verbal fluency [7][8][9].…”

Different outcomes of phonemic verbal fluency in Parkinson’s disease patients with subthalamic nucleus deep brain stimulation

“…It has been proven that DBS suppresses motor symptoms and reduces the total dose of the antiparkinsonian drugs 2,3 . Among the adverse effects of STN-DBS in patients with PD, the postoperative decline in verbal fluency is well documented 4,5,6,7,8,9,10,11 . However, there are fewer studies about the effect of the stimulation per se, comparing on-and off-stimulation conditions 12,13,14 .…”

“…Also, the majority of previous studies pointed to a negative effect of STN-DBS on verbal fluency when they studied postsurgical patients 22 . Some of the studies on pre-and post-DBS have found a decline in phonemic fluency 5,7,10 , others a decline in semantic fluency 6 and still others in both verbal fluency tasks 4,8,9 .…”