Onset of Mild Cognitive Impairment in Parkinson Disease

Abstract

Objective Characterize the onset and timing of cognitive decline in PD from the first recognizable stage of cognitively symptomatic PD - mild cognitive impairment (PD-MCI) - to PD dementia (PDD). Thirty-nine participants progressed from PD to PDD and 25 remained cognitively normal. Method Bayesian estimated disease-state models described the onset of an individual’s cognitive decline across 12 subtests with a changepoint. Results Subtests measuring working memory, visual imagery, and crystalized memory changed significantly 3–5 years before their first non-zero CDR and progressively worsened from PD to PD-MCI to PDD. Crystalized memory deficits were the hallmark feature of imminent conversion of cognitive status. Episodic memory tasks were not sensitive to onset of PD-MCI. For cognitively intact PD, all 12 subtests showed modest linear decline without evidence of a changepoint. Conclusions Longitudinal disease-state models support a prodromal dementia stage (PD-MCI) marked by early declines in working memory and visuospatial processing beginning 5 years prior to clinical diagnosis of PDD. Cognitive declines in PD affect motor ability (bradykinesia), working memory and processing speed (bradyphrenia) resulting in PD-MCI where visuospatial imagery and memory retrieval deficits manifest before eventual development of overt dementia. Tests of episodic memory may not be sufficient to detect and quantify cognitive decline in PD.

Correlation of Visuospatial Ability and EEG Slowing in Patients with Parkinson’s Disease

“…Patients in the Digit Span group A have a shorter disease duration than patients in the Digit Span group B. This result contrasts with some recent findings which have shown a reduction of working memory capacity in PD-patients as the disease progresses [71, 72]. Hence, our result might be caused by the sampling process based on a right-skewed sample..…”

Abnormal resting‐state functional connectivity in posterior cingulate cortex of Parkinson's disease with mild cognitive impairment and dementia

“…Meanwhile, the decreased FC strength between the PCC of the PDD group and regions including the middle frontal gyrus, right thalamus, and angular gyrus is related to impaired episodic memory, which was not observed in the PD‐MCI group, indicating that episodic memory may be retained in PD‐MCI patients and damaged in PDD patients. A recent study has claimed that a decline in episodic memory may not be adequate to assess cognitive decline in PD patients and that PD‐MCI patients may display an early decline in working memory and visuospatial processing before a clinical declaration of PDD . Therefore, functional connectivity between the PCC and other regions such as middle frontal gyrus, right thalamus, and angular gyrus is also involved in the progression of PD‐CI.…”

“…and visuospatial processing before a clinical declaration of PDD. 29 Therefore, functional connectivity between the PCC and other regions such as middle frontal gyrus, right thalamus, and angular gyrus is also involved in the progression of PD-CI.…”

Which figure copy test is more sensitive for cognitive impairment in Parkinson's disease: Wire cube or interlocking pentagons?

“…Visuospatial dysfunction is an early feature of PD-MCI [1], predicts a more aggressive rate of cognitive decline [2,3,19] and is severely affected in PD-D [1,20,21]. Historically, the most frequently used figure-copy test of visuospatial function has been interlocking pentagons incorporated into the MMSE and the ACE.…”