Neuropsychological Profile of Parkin Mutation Carriers with and without Parkinson Disease: The CORE-PD Study

Emerging perspectives on precision therapy for Parkinson's disease: multidimensional evidence leading to a new breakthrough in personalized medicine

PD is a prevalent and progressive neurodegenerative disorder characterized by both motor and non-motor symptoms. Genes play a significant role in the onset and progression of the disease. While the complexity and pleiotropy of gene expression networks have posed challenges for gene-targeted therapies, numerous pathways of gene variant expression show promise as therapeutic targets in preclinical studies, with some already in clinical trials. With the recognition of the numerous genes and complex pathways that can influence PD, it may be possible to take a novel approach to choose a treatment for the condition. This approach would be based on the symptoms, genomics, and underlying mechanisms of the disease. We discuss the utilization of emerging genetic and pathological knowledge of PD patients to categorize the disease into subgroups. Our long-term objective is to generate new insights for the therapeutic approach to the disease, aiming to delay and treat it more effectively, and ultimately reduce the burden on individuals and society.

Cognition in prodromal Parkinson's disease

One characteristic of Parkinson's disease (PD) is a prodromal phase, lasting many years during which both pre-clinical motor and non-motor symptoms occur. Around one-fifth of patients with PD manifest mild cognitive impairment at time of clinical diagnosis. Thus, important challenges are to define the time of onset of cognitive dysfunction in the prodromal phase of PD, and to define its co-occurrence with other specific characteristics. Evidence for cognitive change in prodromal PD comes from various study designs, including both longitudinal and cross-sectional approaches with different target groups. These studies support the concept that changes in global cognitive function and alterations in executive functions occur, and that these changes may be present up to 6 years before clinical PD diagnosis. Notably, this evidence led to including global cognitive impairment as an independent prodromal marker in the recently updated research criteria of the Movement Disorder Society for prodromal PD. Knowledge in this field, however, is still at its beginning, and evidence is sparse about many aspects of this topic. Further longitudinal studies including standardized assessments of global and domain-specific cognitive functions are needed to gain further knowledge about the first appearance, the course, and the interaction of cognitive deficits with other non-motor symptoms in prodromal stage PD. Treatment approaches, including non-pharmacological interventions, in individuals with prodromal PD might help to prevent or delay cognitive dysfunction in early PD.

Cognitive Impairment in Genetic Parkinson's Disease

Cognitive impairment is common in idiopathic Parkinson's disease (PD). Knowledge of the contribution of genetics to cognition in PD is increasing in the last decades. Monogenic forms of genetic PD show distinct cognitive profiles and rate of cognitive decline progression. Cognitive impairment is higher in GBA- and SNCA-associated PD, lower in Parkin- and PINK1-PD, and possibly milder in LRRK2-PD. In this review, we summarize data regarding cognitive function on clinical studies, neuroimaging, and biological markers of cognitive decline in autosomal dominant PD linked to mutations in LRRK2 and SNCA, autosomal recessive PD linked to Parkin and PINK1, and also PD linked to GBA mutations.

Event-related potential changes due to early-onset Parkinson's disease in parkin (PARK2) gene mutation carriers and non-carriers

OBJECTIVE

To investigate cognitive functions in non-demented patients with early-onset Parkinson's disease (PD), and to compare PARK2 gene mutation carriers and non-carriers by means of event-related brain potentials (ERPs).

METHODS

The participants comprised patients with early-onset PD (EOPD) and healthy controls (HC). Patients with EOPD were divided into two groups as carriers of known pathogenic variants of PARK2 gene (EOPD-PC) and non-carriers of genes involved in familial PD (EOPD-NC). ERP data were collected during auditory oddball and visual continuous performance test (CPT).

RESULTS

Both EOPD groups (EOPD-PC and EOPD-NC) displayed reduced and delayed P3 in response to oddball target and CPT NoGo. CPT Go P3 was reduced in EOPD-NC but not in EOPD-PC. Oddball target N1 was reduced and P2 was enhanced in both EOPD-PC and EOPD-NC. In both cognitive tasks, RTs were prolonged and accuracy was lower in EOPD-PC and EOPD-NC.

CONCLUSIONS

We found several EOPD-related neurophysiologic changes, implying impairments in cognitive functions. Pairwise comparisons between EOPD-PC and EOPD-NC revealed no significant ERP marker.

SIGNIFICANCE

In this study, the confounding effect of normative aging was somewhat excluded compared with many previous studies. In contrast with the many oddball studies in non-demented PD, we clearly observed reduced and prolonged P3 in early-onset PD. Our NoGo P3 findings also contribute to the limited ERP research concerning response inhibition.

Non-motor Symptoms in Parkinson's Disease Patients with Parkin Mutations: More Depression and Less Executive Dysfunction

The purpose of this study was to identify differences between genetically undefined (GU) early-onset Parkinson's disease (EOPD) patients and carriers of Parkin mutations on non-motor symptoms (NMSs). EOPD patients (N = 261) underwent targeted sequencing of Parkinson's disease (PD) related genes. Among them, 53 cases carried homozygous or compound heterozygous Parkin mutations (Parkin group) while 208 did not carry known causative PD mutations or risk factors of GBA or Parkin heterozygous mutations (GU group). NMSs were evaluated by face-to-face interviews, self-completed questionnaires and results on a neuropsychological battery. Linear regression and logistic regression models were applied to assess the predictors of NMSs. Parkin patients had younger ages of onset (AOO) (p < 0.001), longer disease durations (p < 0.001) and lower grades of Hoehn and Yarh (H&Y) (p = 0.007). Results on the neuropsychological battery showed a shorter time in Trail Making Test (TMT) (part B) in Parkin patients (p = 0.034) compared to GU patients. After adjusting for AOO, disease duration, H&Y, and levodopa equivalent daily dose (LEDD), there was a higher depression index on the Beck Depression Inventory (BDI) (p = 0.013) and better performance (p = 0.038) on executive function in the Parkin group compared to the GU group. No significant differences were found for autonomic functions, sleep-wake problems or other domains of cognitive function. Our study showed that the Parkin mutation status might be a good predictor of symptoms of depression without an impact on executive function. While these findings need to be confirmed in larger cohorts, they identify a need to screen for depression. Graphical Abstract Flow chart of genetic tests.

Mild Cognitive Impairment in Patients with Early-Onset Parkinson's Disease

BACKGROUND/AIMS

Few studies have described mild cognitive impairment (MCI) and cognitive characteristics in early-onset Parkinson's disease (EOPD). This study describes attention/working memory, language, memory, visuospatial abilities, executive function, and frequency of MCI and dementia in EOPD.

METHODS

Eighty-one EOPD patients were administered neuropsychological tests and the Beck Depression Inventory. Scores were compared with age/education-appropriate norms and were correlated to years of disease progression and severity of motor symptoms. The frequency of MCI and dementia was determined by the Movement Disorder Society criteria.

RESULTS

Thirty-one percent of patients met the MCI criteria, but none had dementia. Commonly affected domains were memory, visuospatial, and executive function. Cognitive dysfunction was not explained by depression or severity of motor symptoms.

CONCLUSION

One third of EOPD patients presented with MCI, which was not associated with the same risk factors as reported in late-onset Parkinson's disease. MCI could have a different prognostic value in EOPD.

Cognitive changes in prodromal Parkinson's disease: A review

Although other nonmotor phenomena representing possible prodromal symptoms of Parkinson's disease have been described in some detail, the occurrence and characteristics of cognitive decline in this early phase of the disease are less well understood. The aim of this review is to summarize the current state of research on cognitive changes in prodromal PD. Only a small number of longitudinal studies have been conducted that examined cognitive function in individuals with a subsequent PD diagnosis. However, when we consider data from at-risk groups, the evidence suggests that cognitive decline may occur in a substantial number of individuals who have the potential for developing PD. In terms of specific cognitive domains, executive function in particular and, less frequently, memory scores are reduced. Prospective longitudinal studies are thus needed to clarify whether cognitive, and specifically executive, decline might be added to the prodromal nonmotor symptom complex that may precede motor manifestations of PD by years and may help to update the risk scores used for early identification of PD. © 2017 International Parkinson and Movement Disorder Society.

A review of psychiatric co-morbidity described in genetic and immune mediated movement disorders

Psychiatric symptoms are an increasingly recognised feature of movement disorders. Recent identification of causative genes and autoantibodies has allowed detailed analysis of aetiologically homogenous subgroups, thereby enabling determination of the spectrum of psychiatric symptoms in these disorders. This review evaluates the incidence and type of psychiatric symptoms encountered in patients with movement disorders. A broad spectrum of psychiatric symptoms was identified across all subtypes of movement disorder, with depression, generalised anxiety disorder and obsessive-compulsive disorder being most common. Psychosis, schizophrenia and attention deficit hyperactivity disorder were also identified, with the psychiatric symptoms often predating onset of the motor disorder. The high incidence of psychiatric symptoms across such a wide range of movement disorders suggests a degree of common or overlapping pathogenic mechanisms. Our review demonstrates the need for increased clinical awareness of such co-morbidities, which should facilitate early neuropsychiatric intervention and allied specialist treatment for patients.

Associations among Cognitive Functions, Plasma DNA, and White Matter Integrity in Patients with Early-Onset Parkinson's Disease

Early-onset Parkinson's disease (EOPD) patients are symptomatic at a relatively young age, and the impacts of the disease on both the patients and their caregivers are dramatic. Few studies have reported on the cognitive impairments seen in EOPD, and the results of these studies have been diverse. Furthermore, it is still unclear what microstructural white matter (WM) changes are present in EOPD patients. As such, we conducted this study to investigate the microstructural WM changes experienced by EOPD patients and their association with cognitive function and plasma DNA levels. We enrolled 24 EOPD patients and 33 sex- and age-matched healthy volunteers who underwent complete neuro-psychological testing (NPT) to evaluate their cognitive function and diffusion tensor imaging (DTI) scanning to determine their fiber integrity. The plasma DNA measurements included measurements of nuclear and mitochondrial DNA levels. Fractional anisotropy (FA) maps were compared using voxel-based statistics to determine differences between the two groups. The differences in DTI indices and NPT scores were correlated after adjusting for age, sex, and education. Our results demonstrate that patients with EOPD have elevated nuclear DNA levels and wide spectrums of impairments in NPT, especially in the executive function and visuospatial function domains. Exploratory group-wise comparisons of the DTI indices revealed that the patients with EOPD exhibited lower DTI parameters in several brain locations. These poorer DTI parameters were associated with worse cognitive performances and elevated plasma nuclear DNA levels, especially in the anterior thalamic radiation region. Our findings suggest that the thalamus and its adjacent anterior thalamic radiation may be important in the pathogenesis of EOPD, as they appear to become involved in the disease process at an early stage.

Brain Connectivity Changes in Autosomal Recessive Parkinson Disease: A Model for the Sporadic Form

Biallelic genetic mutations in the Park2 and PINK1 genes are frequent causes of autosomal recessive PD. Carriers of single heterozygous mutations may manifest subtle signs of disease, thus providing a unique model of preclinical PD. One emerging hypothesis suggests that non-motor symptom of PD, such as cognitive impairment may be due to a distributed functional disruption of various neuronal circuits. Using resting-state functional MRI (RS-fMRI), we tested the hypothesis that abnormal connectivity within and between brain networks may account for the patients' cognitive status. Eight homozygous and 12 heterozygous carriers of either PINK1 or Park2 mutation and 22 healthy controls underwent RS-fMRI and cognitive assessment. RS-fMRI data underwent independent component analysis to identify five networks of interest: default-mode network, salience network, executive network, right and left fronto-parietal networks. Functional connectivity within and between each network was assessed and compared between groups. All mutation carriers were cognitively impaired, with the homozygous group reporting a more prominent impairment in visuo-spatial working memory. Changes in functional connectivity were evident within all networks between homozygous carriers and controls. Also heterozygotes reported areas of reduced connectivity when compared to controls within two networks. Additionally, increased inter-network connectivity was observed in both groups of mutation carriers, which correlated with their spatial working memory performance, and could thus be interpreted as compensatory. We conclude that both homozygous and heterozygous carriers exhibit pathophysiological changes unveiled by RS-fMRI, which can account for the presence/severity of cognitive symptoms.

Genetic and Clinical Predictors of Deep Brain Stimulation in Young-Onset Parkinson's Disease

OBJECTIVE

In a cohort of patients with young-onset Parkinson's disease (PD), the authors assessed (1) the prevalence of genetic mutations in those who enrolled in deep brain stimulation (DBS) programs compared with those who did not enroll DBS programs and (2) specific genetic and clinical predictors of DBS enrollment.

METHODS

Subjects were participants from 3 sites (Columbia University, Rush University, and the University of Pennsylvania) in the Consortium on Risk for Early Onset Parkinson's Disease (CORE-PD) who had an age at onset < 51 years. The analyses presented here focus on glucocerebrosidase (GBA), leucine-rich repeat kinase 2 (LRRK2), and parkin (PRKN) mutation carriers. Mutation carrier status, demographic data, and disease characteristics in individuals who did and did not enroll in DBS were analyzed. The association between mutation status and DBS placement was assessed in logistic regression models.

RESULTS

Patients who had PD with either GBA, LRRK2, or PRKN mutations were more common in the DBS group (n = 99) compared with the non-DBS group (n = 684; 26.5% vs. 16.8%, respectively; P = 0.02). In a multivariate logistic regression model, GBA mutation status (odds ratio, 2.1; 95% confidence interval, 1.0-4.3; P = 0.05) was associated with DBS surgery enrollment. However, when dyskinesia was included in the multivariate logistic regression model, dyskinesia had a strong association with DBS placement (odds ratio, 3.8; 95% confidence interval, 1.9-7.3; P < 0.0001), whereas the association between GBA mutation status and DBS placement did not persist (P = 0.25).

CONCLUSIONS

DBS populations are enriched with genetic mutation carriers. The effect of genetic mutation carriers on DBS outcomes warrants further exploration.

Understanding the susceptibility of dopamine neurons to mitochondrial stressors in Parkinson's disease

Mitochondria are undoubtedly changed in Parkinson's disease (PD), and mitochondrial functions are disrupted in genetic and pharmacologic models of PD. However, many of these changes might not truly drive neurodegeneration. PD is defined by the particular susceptibility of nigrostriatal dopamine (DA) neurons, but little is understood about the mitochondria in these cells. Here, we critically review the evidence that mitochondrial stressors cause PD. We then consider how changes in the intrinsic function of mitochondria and in their mass, distribution, and dynamics might synergize with an increased need for mitochondria and produce PD, and the importance of understanding how mitochondria contribute to its pathogenesis.

The neurobiological basis of cognitive impairment in Parkinson's disease

The recent formalization of clinical criteria for Parkinson's disease with dementia (PDD) codifies many studies on this topic, including those assessing biological correlates. These studies show that the emergence of PDD occurs on the background of severe dopamine deficits with, the main pathological drivers of cognitive decline being a synergistic effect between alpha-synuclein and Alzheimer's disease pathology. The presence of these pathologies correlates with a marked loss of limbic and cortically projecting dopamine, noradrenaline, serotonin, and acetylcholine neurons, although the exact timing of these relationships remains to be determined. Genetic factors, such as triplications in the α-synuclein gene, lead to a clear increased risk of PDD, whereas others, such as parkin mutations, are associated with a reduced risk of PDD. The very recent formalization of clinical criteria for PD with mild cognitive impairment (PD-MCI) allows only speculation on its biological and genetic bases. Critical assessment of animal models shows that chronic low-dose MPTP treatment in primates recapitulates PD-MCI over time, enhancing the current biological concept of PD-MCI as having enhanced dopamine deficiency in frontostriatal pathways as well as involvement of other neurotransmitter systems. Data from other animal models support multiple transmitter involvement in cognitive impairment in PD. Whereas dopamine dysfunction has been highlighted because of its obvious role in PD, the role of the other neurotransmitter systems, neurodegenerative pathologies, and genetic factors in PD-MCI remains to be fully elucidated.

Neuropsychological performance in LRRK2 G2019S carriers with Parkinson's disease

BACKGROUND

Ashkenazi Jewish (AJ) LRRK2 carriers are more likely to manifest the postural instability gait difficulty (PIGD) motor phenotype than non-carriers but perform similarly to non-carriers on cognitive screening tests.

OBJECTIVE

To compare the cognitive profiles of AJ with Parkinson's disease (PD) with and without LRRK2 G2019S mutations using a comprehensive neuropsychological battery.

METHODS

We administered a neuropsychological battery to PD participants in the Michael J. Fox Foundation AJ consortium. Participants (n = 236) from Beth Israel Medical Center, NY, Columbia University Medical Center, NY and Tel Aviv Medical Center, Israel included 116 LRRK2 G2019S carriers and 120 non-carriers. Glucocerbrosidase mutation carriers were excluded. We compared performance on each neuropsychological test between carriers and non-carriers. Participants in New York (n = 112) were evaluated with the entire battery. Tel Aviv participants (n = 124) were evaluated on attention, executive function and psychomotor speed tasks. The association between G2019S mutation status (predictor) and each neuropsychological test (outcome) was assessed using linear regression models adjusted for PIGD motor phenotype, site, sex, age, disease duration, education, Unified Parkinson's Disease Rating Scale (UPDRS) Part III, levodopa equivalent dose, and Geriatric Depression Score (GDS).

RESULTS

Carriers had longer disease duration (p < 0.001) and were more likely to manifest the PIGD phenotype (p = 0.024). In adjusted regression models, carriers performed better than non-carriers in Stroop Word Reading (p < 0.001), Stroop Interference (p = 0.011) and Category Fluency (p = 0.026).

CONCLUSION

In AJ-PD, G2019S mutation status is associated with better attention (Stroop Word Reading), executive function (Stroop Interference) and language (Category Fluency) after adjustment for PIGD motor phenotype.

Genetic impact on cognition and brain function in newly diagnosed Parkinson's disease: ICICLE-PD study

Parkinson's disease is associated with multiple cognitive impairments and increased risk of dementia, but the extent of these deficits varies widely among patients. The ICICLE-PD study was established to define the characteristics and prevalence of cognitive change soon after diagnosis, in a representative cohort of patients, using a multimodal approach. Specifically, we tested the 'Dual Syndrome' hypothesis for cognitive impairment in Parkinson's disease, which distinguishes an executive syndrome (affecting the frontostriatal regions due to dopaminergic deficits) from a posterior cortical syndrome (affecting visuospatial, mnemonic and semantic functions related to Lewy body pathology and secondary cholinergic loss). An incident Parkinson's disease cohort (n = 168, median 8 months from diagnosis to participation) and matched control group (n = 85) were recruited to a neuroimaging study at two sites in the UK. All participants underwent clinical, neuropsychological and functional magnetic resonance imaging assessments. The three neuroimaging tasks (Tower of London, Spatial Rotations and Memory Encoding Tasks) were designed to probe executive, visuospatial and memory encoding domains, respectively. Patients were also genotyped for three polymorphisms associated with cognitive change in Parkinson's disease and related disorders: (i) rs4680 for COMT Val158Met polymorphism; (ii) rs9468 for MAPT H1 versus H2 haplotype; and (iii) rs429358 for APOE-ε2, 3, 4. We identified performance deficits in all three cognitive domains, which were associated with regionally specific changes in cortical activation. Task-specific regional activations in Parkinson's disease were linked with genetic variation: the rs4680 polymorphism modulated the effect of levodopa therapy on planning-related activations in the frontoparietal network; the MAPT haplotype modulated parietal activations associated with spatial rotations; and APOE allelic variation influenced the magnitude of activation associated with memory encoding. This study demonstrates that neurocognitive deficits are common even in recently diagnosed patients with Parkinson's disease, and that the associated regional brain activations are influenced by genotype. These data further support the dual syndrome hypothesis of cognitive change in Parkinson's disease. Longitudinal data will confirm the extent to which these early neurocognitive changes, and their genetic factors, influence the long-term risk of dementia in Parkinson's disease. The combination of genetics and functional neuroimaging provides a potentially useful method for stratification and identification of candidate markers, in future clinical trials against cognitive decline in Parkinson's disease.

Parkinson's disease with Lewy bodies associated with a heterozygous PARKIN dosage mutation

BACKGROUND

PARKIN-related disease remains incompletely understood. First, the pathogenicity of heterozygous PARKIN mutations is unclear, although some evidence supports causality. Second, unlike sporadic Parkinson's disease (PD), Lewy bodies are present only in a minority of cases. Only one other heterozygote PARKIN carrier with autopsy findings has been described. Our case adds to the broadening pathological and clinical phenotype of PARKIN-related disease.

METHODS

Clinical chart, genetic analysis, and pathological findings of a patient with familial PD are reviewed.

RESULTS

A 44-year-old man developed slowly progressive tremor-predominant PD with excellent response to levodopa. Genetic analysis revealed a heterozygous PARKIN exon 3-4 deletion, also present in 2 family members with early-onset PD. Postmortem examination showed severe neuronal loss in the substantia nigra and nucleus coeruleus with the presence of diffuse Lewy bodies.

CONCLUSIONS

The deletion is unlikely an incidental finding considering family history, age at onset, and the presence of clinical and pathological features not typical of sporadic PD.

Cognitive and motor function in long-duration PARKIN-associated Parkinson disease

IMPORTANCE

Data on the long-term cognitive outcomes of patients with PARKIN-associated Parkinson disease (PD) are unknown but may be useful when counseling these patients.

OBJECTIVE

Among patients with early-onset PD of long duration, we assessed cognitive and motor performances, comparing homozygotes and compound heterozygotes who carry 2 PARKIN mutations with noncarriers.

DESIGN, SETTING, AND PARTICIPANTS

Cross-sectional study of 44 participants at 17 different movement disorder centers who were in the Consortium on Risk for Early-Onset PD study with a duration of PD greater than the median duration (>14 years): 4 homozygotes and 17 compound heterozygotes (hereafter referred to as carriers) and 23 noncarriers.

MAIN OUTCOMES AND MEASURES

Unified Parkinson Disease Rating Scale Part III (UPDRS-III) and Clinical Dementia Rating scores and neuropsychological performance. Linear regression models were applied to assess the association between PARKIN mutation status and cognitive domain scores and UPDRS-III scores. Models were adjusted for age, education, disease duration, language, and levodopa equivalent daily dose.

RESULTS

Carriers had an earlier age at onset of PD (P < .001) and were younger (P = .004) at time of examination than noncarriers. They performed better than noncarriers on the Mini-Mental State Examination (P = .010) and were more likely to receive lower scores on the Clinical Dementia Rating (P = .003). In multivariate analyses, carriers performed better than noncarriers on the UPDRS-III (P = .02) and on tests of attention (P = .03), memory (P = .03), and visuospatial (P = .02) cognitive domains.

CONCLUSIONS AND RELEVANCE

In cross-sectional analyses, carriers demonstrated better cognitive and motor performance than did noncarriers with long disease duration, suggesting slower disease progression. A longitudinal follow-up study is required to confirm these findings.

Lower cognitive performance in healthy G2019S LRRK2 mutation carriers

OBJECTIVE

To assess cognitive abilities of healthy first-degree relatives of Ashkenazi patients with Parkinson disease (PD), carriers of the G2019S mutation in the LRRK2 gene.

METHODS

In this observational study, 60 consecutive healthy first-degree relatives (aged 50.9 ± 6.2 years; 48% male; 30 G2019S carriers) were assessed using a computerized cognitive program, the Montreal Cognitive Assessment questionnaire, the Unified Parkinson's Disease Rating Scale Part III, and the Geriatric Depression Scale.

RESULTS

G2019S carriers scored significantly lower on the computerized executive function index (p = 0.04) and on specific executive function tasks (Stroop test, p = 0.007).

CONCLUSION

Carrying the LRRK2 G2019S mutation was associated with lower executive performance in a population at risk for PD.

Cognitive performance of GBA mutation carriers with early-onset PD: the CORE-PD study

OBJECTIVE

To assess the cognitive phenotype of glucocerebrosidase (GBA) mutation carriers with early-onset Parkinson disease (PD).

METHODS

We administered a neuropsychological battery and the University of Pennsylvania Smell Identification Test (UPSIT) to participants in the CORE-PD study who were tested for mutations in PARKIN, LRRK2, and GBA. Participants included 33 GBA mutation carriers and 60 noncarriers of any genetic mutation. Primary analyses were performed on 26 GBA heterozygous mutation carriers without additional mutations and 39 age- and PD duration-matched noncarriers. Five cognitive domains, psychomotor speed, attention, memory, visuospatial function, and executive function, were created from transformed z scores of individual neuropsychological tests. Clinical diagnoses (normal, mild cognitive impairment [MCI], dementia) were assigned blind to genotype based on neuropsychological performance and functional impairment as assessed by the Clinical Dementia Rating (CDR) score. The association between GBA mutation status and neuropsychological performance, CDR, and clinical diagnoses was assessed.

RESULTS

Demographics, UPSIT, and Unified Parkinson's Disease Rating Scale-III performance did not differ between GBA carriers and noncarriers. GBA mutation carriers performed more poorly than noncarriers on the Mini-Mental State Examination (p = 0.035), and on the memory (p = 0.017) and visuospatial (p = 0.028) domains. The most prominent differences were observed in nonverbal memory performance (p < 0.001). Carriers were more likely to receive scores of 0.5 or higher on the CDR (p < 0.001), and a clinical diagnosis of either MCI or dementia (p = 0.004).

CONCLUSION

GBA mutation status may be an independent risk factor for cognitive impairment in patients with PD.