Parkinson’s disease (PD) is a pervasive neurodegenerative disorder with a prevalence rate of approximately 150 out of 100,000 individuals in the United States and Western Europe (Checkoway & Nelson, 1999). The most widely recognized motor symptoms associated with PD include a resting tremor, rigidity, slowness of movement (i.e., bradykinesia), freezing, and gait abnormalities. Non-motor symptoms typically consist of depression, hallucinations, sleep disturbances, fatigue, autonomic nervous system impairment, and cognitive deficits (see e.g., Stacy, 2011). The frequency and severity of these nonmotor impairments typically increase with disease duration, and they are not exclusively linked to the motor symptoms (see e.g., Yu et al., 2012).
Although previous research clearly demonstrates that mild-cognitive impairment (MCI) in PD patients does in fact exist (Williams-Gray et al, 2007, 2009), it remains unclear how best to characterize it. Specifically, should MCI be defined based on performance that falls 1 SD below the normative mean, 1.5 SDs, or 2 SDs? Should data be compared to published normative data or to an age- and education matched control group wherein assessments are administered in the same environment by the same researcher? If anterior- and posterior-based tests are good predictors of MCI, does an individual have to perform poorly on all tests given within a specific domain (e.g., four out of four anterior tests), or should some other type of criterion be established?
The present project aims to further examine these questions by administering a series of anterior- and posterior-based tests to a group of non-demented PD patients and their age and education matched controls. Previous research has primarily compared PD and HC participants’ performance against published normative data, with no direct comparisons made with an age and education matched control group. It was hypothesized that PD would perform significantly more poorly across all anterior and posterior tests than age and education matched HC participants. A second goal was to examine cognitive performance variation within individuals with PD in an effort to develop subtypes based on patterns of anterior and posterior deficits. Based on previous literature, it was hypothesized that PD participants would fall into one of four cognitive groups (anterior deficit only, posterior deficit only, both deficit, and neither deficit) and that more patients would exhibit anteriortype compared to posterior-type deficits. Further, to determine MCI in PD, various criteria were used such as two deficits in a single domain with cut offs of 1.5 SD, and 2 SD below control participants. Based on previous research (Dalrymple-Alford et al., 2011), it was hypothesized that two deficits of 1.5 SD below the mean in a single domain would provide categorization that is sensitive enough to detect cognitive impairment, yet conservative enough to avoid false positives. The purpose of this research is to further our understanding of the criteria involved in diagnosing MCI in PD.
Anterior and Posterior Types of Neuropsychological Deficits in Parkinson’s Disease: A Subgroup Classification of CognitiveOutcome.
Undergraduate Review, 10, 126-133.
Available at: http://vc.bridgew.edu/undergrad_rev/vol10/iss1/26
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