Abstract
ObjectiveThe decrease in verbal fluency in patients with Parkinson’s disease (PD) undergoing subthalamic nucleus deep brain stimulation (STN-DBS) is usually assumed to reflect a frontal lobe-related cognitive dysfunction, although evidence for this is lacking.MethodsTo explore its underlying mechanisms, we combined neuropsychological, psychiatric and motor assessments with an examination of brain metabolism using F-18 fluorodeoxyglucose positron emission tomography, in 26 patients with PD, 3 months before and after surgery. We divided these patients into two groups, depending on whether or not they exhibited a postoperative deterioration in either phonemic (10 patients) or semantic (8 patients) fluency. We then compared the STN-DBS groups with and without verbal deterioration on changes in clinical measures and brain metabolism.ResultsWe did not find any neuropsychological change supporting the presence of an executive dysfunction in patients with a deficit in either phonemic or semantic fluency. Similarly, a comparison of patients with or without impaired fluency on brain metabolism failed to highlight any frontal areas involved in cognitive functions. However, greater changes in cognitive slowdown and apathy were observed in patients with a postoperative decrease in verbal fluency.ConclusionsThese results suggest that frontal lobe-related cognitive dysfunction could play only a minor role in the postoperative impairment of phonemic or semantic fluency, and that cognitive slowdown and apathy could have a more decisive influence. Furthermore, the phonemic and semantic impairments appeared to result from the disturbance of distinct mechanisms.
Highlights
A moderate decline in verbal fluency is the most frequent neuropsychological side effect of deep brain stimulation of the subthalamic nucleus (STN-DBS) in Parkinson’s disease (PD) [1,2], and seems to concern 30-40% of patients [3]
A comparison of patients with or without impaired fluency on brain metabolism failed to highlight any frontal areas involved in cognitive functions
We investigated the neural substrates of verbal fluency deficits following subthalamic nucleus deep brain stimulation (STN-DBS) in a large cohort of 26 patients with PD using 2-deoxy-2[18F]fluoro-D-glucose (18F-FDG) positron emission tomography (PET), performed 3 months before and after STN-DBS surgery
Summary
A moderate decline in verbal fluency is the most frequent neuropsychological side effect of deep brain stimulation of the subthalamic nucleus (STN-DBS) in Parkinson’s disease (PD) [1,2], and seems to concern 30-40% of patients [3]. As verbal fluency is regarded as an executive function that draws on many other executive processes, including word retrieval, verbal working memory, inhibition and flexibility, its postoperative decline is usually assumed to reflect dysfunction in frontal lobe-related cognitive functions [4,5,6,7] This hypothesis is, in part, supported by three studies that have investigated the relationship between phonemic [8,9] or semantic [10] fluency and brain activity following STN-DBS surgery in patients with PD. It has been suggested that other behavioural changes following surgery, such as increased apathy, play a role [14,19]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
