Non-amnestic mild cognitive impairment is a prominent aspect in Parkinson’s disease patients being considered for deep brain stimulation

Abstract

Cognitive deficits increase with disease duration in Parkinson’s disease (PD). Patients referred for deep brain stimulation (DBS) usually have advanced disease, and some cognitive deficits are expected pre-operatively. Improved prediction of cognitive risk is one goal for DBS services. As a first step, the detailed cognitive profiles of patients referred for consideration of DBS should be described. This is the aim of this manuscript. We document comprehensively the pre-operative types and prevalence of neuropsychological deficits in advanced PD patients being considered for DBS. Routinely, pre-operatively, we performed neuropsychometric testing in 46 consecutive PD patients attending a DBS clinic to assess suitability for DBS. Five domains were assessed: intellectual, memory, language, perception and executive functions. Patient performance was compared with standard published normative data of the neuropsychological tests. Patients had mild intellectual decline relative to their premorbid IQ. The main impairment of verbal recall memory was on list-learning. Selective impairments on executive tests were found, most commonly (54%) being on the Brixton test, a test of inductive reasoning rarely reported in the PD literature. By contrast, verbal-fluency tasks were unimpaired in a small subgroup. Mild pre-operative neuropsychological impairments of executive and memory cognitive domains are common in a DBS clinic. The natural history of these deficits remains to be determined. The potential relevance to a DBS service is discussed.