Effects of Bilateral Subthalamic Stimulation on Cognitive Function in Parkinson Disease

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Abstract
IN THE 1990s, surgical stimulation techniques were introduced to treat patients with Parkinson disease (PD) in whom pharmacological treatment failed.1 Although there is growing evidence of the beneficial effects of chronic bilateral subthalamic deep brain stimulation (STN-DBS) on PD motor symptoms,2-7 its influence on neuropsychological functions has not yet been investigated thoroughly. Although STN-DBS does not produce a global frontal deterioration,6,8 a negative effect in specific prefrontal functions (eg, phonetic verbal fluency)8,9 and verbal and visuospatial memory9 has been described. However, reports of performance on a prefrontal measure, the Trail-Making B Test, are contradictory. Although Trépanier et al9 found poorer performance, Ardouin et al8 found improvement after STN-DBS, a discrepancy that may be due to methodological differences. For instance, in the study by Trépanier et al,9 the neuropsychological assessment was performed while patients were under the effects of levodopa, whereas in the study by Ardouin et al,8 it was performed while some patients were receiving and others were free of levodopa.