Mild cognitive impairment in Parkinson’s disease: a critical update

Cognitive impairment in Parkinson disease: impact on quality of life, disability, and caregiver burden

AIM

To compare quality of life, level of disability, and caregiver burden in 3 groups of people with Parkinson disease (PD): those with mild cognitive impairment (PD-MCI), those with dementia (PDD), and those with no cognitive impairment (PD-NC).

BACKGROUND

Although the cognitive profile of those with PD-MCI and PDD has been well described, little is known about the personal and clinical impact of cognitive impairment and its impact on caregivers.

METHOD

Quality of life and disability were measured in 3 groups of participants with PD (PD-NC, n=54; PD-MCI, n=48; and PDD, n=25). The PD-MCI group was classified using Movement Disorder Society Task Force consensus criteria. Caregivers (n=102) in the 3 groups were assessed using the Zarit Burden Inventory.

RESULTS

Both quality of life and caregiver burden were similar in the 2 groups without dementia but were significantly different in those with PDD. In contrast, global disability was progressively greater as cognition declined across the 3 PD groups: PD-NC<PD-MCI<PDD and on the Activities of Daily Living scale a step up in impairment was seen with the presence of any cognitive impairment.

CONCLUSIONS

The presence of dementia significantly increases caregiver burden and decreases quality of life. However, even mild levels of cognitive impairment increase disability and overall functional impairment progresses in tandem with cognitive decline.

Neuropsychiatric symptoms in Parkinson's disease with mild cognitive impairment and dementia

Neuropsychiatric symptoms commonly complicate Parkinson's disease (PD), however the presence of such symptoms in mild cognitive impairment (PD-MCI) specifically has not yet been well described. The objective of this study was to examine and compare the prevalence and profile of neuropsychiatric symptoms in patients with PD-MCI (n = 48) to those with PD and no cognitive impairment (PD-NC, n = 54) and to those with dementia in PD (PDD, n = 25). PD-MCI and PDD were defined using specific consensus criteria, and neuropsychiatric symptoms were assessed with the 12-item Neuropsychiatric Inventory (NPI). Self-rated apathy, depression, and anxiety rating scales were also administered. Over 79% of all participants reported at least one neuropsychiatric symptom in the past month. The proportion in each group who had total NPI scores of ≥4 ("clinically significant") was as follows: PD-NC, 64.8%; PD-MCI, 62%; PDD 76%. Apathy was reported in almost 50% of those with PD-MCI and PDD, and it was an important neuropsychiatric symptom differentiating PD-MCI from PD-NC. Psychosis (hallucinations and delusions) increased from 12.9% in PD-NC group; 16.7% in PD-MCI group; and 48% in PDD group. Identifying neuropsychiatric symptoms in PD-MCI may have implications for ascertaining conversion to dementia in PD.

Neuropathology of sporadic Parkinson's disease: evaluation and changes of concepts

Parkinson's disease (PD), one of the most frequent neurodegenerative disorders, is no longer considered a complex motor disorder characterized by extrapyramidal symptoms, but a progressive multisystem or-more correctly-multiorgan disease with variegated neurological and nonmotor deficiencies. It is morphologically featured not only by the degeneration of the dopaminergic nigrostriatal system, responsible for the core motor deficits, but by multifocal involvement of the central, peripheral and autonomic nervous system and other organs associated with widespread occurrence of Lewy bodies and dystrophic Lewy neurites. This results from deposition of abnormal α-synuclein (αSyn), the major protein marker of PD, and other synucleinopathies. Recent research has improved both the clinical and neuropathological diagnostic criteria of PD; it has further provided insights into the development and staging of αSyn and Lewy pathologies and has been useful in understanding the pathogenesis of PD. However, many challenges remain, for example, the role of Lewy bodies and the neurobiology of axons in the course of neurodegeneration, the relation between αSyn, Lewy pathology, and clinical deficits, as well as the interaction between αSyn and other pathologic proteins. Although genetic and experimental models have contributed to exploring the causes, pathomechanisms, and treatment options of PD, there is still a lack of an optimal animal model, and the etiology of this devastating disease is far from being elucidated.