Neuropsychological characteristics of parkinsonian patients with lateralized motor impairment

Does the side of onset influence symptom severity in Parkinson's disease? A systematic review and meta-analysis

Parkinson's disease (PD) is a neurodegenerative movement disorder characterized by motor symptoms that initially manifest unilaterally. Whilst some studies indicate that right-side onset is associated with greater symptom severity, others report no differences between right-side and left-side onset patients. The present meta-analysis was thus designed to reconcile inconsistencies in the literature and determine whether side of onset affects PD symptom severity. Following the PRISMA guidelines 1013 studies were initially identified in database and grey literature searches; following title and abstract, and full text, screening 34 studies met the stringent inclusion criteria (n = 2210). Results of the random-effects meta-analysis indicated no difference in symptom severity between PD patients with left-side (n = 1104) and right-side (n = 1106) onset. As such, the meta-analysis suggests that the side of onset should not be used to predict symptom trajectory or to formulate prognoses for PD patients. The current meta-analysis was the first to focus on the relationship between the side of onset and symptom severity in PD. However, the studies included were limited by the common exclusion of left-handed participants. Future research would benefit from exploring other factors that may influence symptom severity and disease progression in PD, such as asymmetric loss of nigrostriatal dopaminergic neurons.

The effect of Parkinson's disease subgroups on verbal and nonverbal fluency

BACKGROUND

Parkinson's disease (PD) leads to deficits in executive function, including verbal and nonverbal fluency, as a result of compromised frontostriatal circuits. It is unknown whether deficits in verbal and nonverbal fluency in PD are driven by certain subgroups of patients, or how strategy use may facilitate performance.

PARTICIPANTS

Sixty-five nondemented individuals with PD, including 36 with right-body onset (RPD; 20 with tremor as their initial symptom, 16 nontremor) and 29 with left-body onset (LPD; 14 with tremor as their initial symptom, 15 nontremor), and 52 normal control participants (NC) took part in the study.

MEASUREMENTS

Verbal fluency was assessed using the FAS and Animals tests. Nonverbal fluency was assessed using the Ruff Figural Fluency Test.

RESULTS

Both RPD and LPD were impaired in generating words and in using clustering and switching strategies on phonemic verbal fluency, whereas different patterns of impairment were found on nonverbal fluency depending on the interaction of side of onset and initial motor symptom (tremor vs. nontremor). Strategy use correlated with number of correct responses on verbal fluency in LPD, RPD, and NC. By contrast, on nonverbal fluency, strategy use correlated with correct responses for RPD and LPD, but not for NC.

CONCLUSION

Our findings demonstrate the importance of considering subgroups in PD and analyzing subcomponents of verbal and nonverbal fluency (correct responses, errors, and strategies), which may depend differently on the integrity of dorsolateral prefrontal cortex, inferior frontal cortex, and anterior cingulate cortex.

Motor symptoms at onset of Parkinson disease and risk for cognitive impairment and depression

OBJECTIVE

To determine whether side and type of initial motor symptoms in Parkinson disease (PD) predict risk for later development of cognitive impairment or depressive symptoms.

METHODS

We recruited 124 non-demented patients with PD to participate in a cohort study of cognitive function and depressive symptoms that used validated neuropsychological tests and a depressive symptom inventory. We first reviewed the patients' charts to determine their initial motor symptom and side of onset, and then classified the patients into 4 groups: right-sided onset tremor, right-sided onset bradykinesia/rigidity, left-sided onset tremor, and left-sided onset bradykinesia/rigidity. We excluded patients with bilateral symptom onset. We used analysis of variance on neuropsychological test performance and depressive symptoms to determine whether group classification affected risk of cognitive impairment or depressive symptoms. We controlled our analyses for disease duration and motor severity as measured by the Unified Parkinson Disease Rating Scale Part III motor score.

RESULTS

There were no differences in any cognitive measure by side and type of initial motor symptoms. The right-sided onset tremor group had the lowest depressive symptom scores, and no patient in any group reported severe depressive symptoms.

CONCLUSIONS

Our findings suggest that patterns of nigral cell loss correlating to the initial side and type of motor symptoms in PD are not related to the risk of later cognitive impairment. By contrast, patients with right-sided onset of tremor seem to have a lower risk of depressive symptoms than patients with other presentations.

Neuropsychology, neuroimaging or motor phenotype in diagnosis of Parkinson's disease-dementia: which matters most?

Parkinson's disease (PD) is a neurodegenerative disorder affecting not only the motor system but also the cognitive and behavioral domains. Although there are many studies addressing the issue of cognition, a universally recognized method to diagnose patients with dementia is still lacking. The aim of this study was to determine which neuropsychological test is the most reliable in the diagnosis of dementia in PD and to establish if mini mental state examination (MMSE) is enough to detect this condition. We studied 200 consecutive PD patients through an extensive neuropsychological battery, clinical evaluation and brain magnetic resonance imaging over a period of 4 years. A logistic regression model was used to evaluate the interplay between possible risk factors and the accuracy of different neuropsychological tests. PD patients with dementia performed significantly worse in all the tests as compared to patients with PD alone: phonological verbal fluency, attentional matrices, Rey auditory verbal learning test and digit span were the most useful tools. Age and disease duration were correlated with cognitive impairment. No relevant differences were detected in phenotype, affected body side at onset, levodopa equivalent daily dose or neuroimaging findings (except for the occurrence of atrophy). Despite reasonable accuracy of MMSE (90%), its positive predictive value is only 74%. Using at least 3 neuropsychological tests, among those more significant detected with logistic regression analysis, the positive predictive value rises to 91%. In conclusion, the use of an extensive neuropsychological battery is still recommended in the diagnosis of dementia in PD.

Behavioral and personality features in patients with lateralized Parkinson's disease

BACKGROUND

Dopamine neurotransmission plays a key role in several brain activities, including motor, cognitive, and behavioral functions. Parkinson's disease (PD) typically begins with asymmetrical motor features related to asymmetrical dopamine denervation. This study was designed to examine whether distinct cognitive, behavioral, and personality features are related to this asymmetry.

METHODS

Fifty-six patients with mild PD and lateralized motor features were grouped according to dominant side of motor features and evaluated using a neuropsychological assessment focused on attention and executive functions, impulse control disorders, and personality inventory.

RESULTS

There were no differences in neuropsychological functions between patients with right and left lateralized PD, but differences occurred in personality features. Patients with motor impairment predominant on the left-hand side had prevalence of hypomania and conversion profile.

CONCLUSIONS

This study suggests that side dominance of dopaminergic denervation may be related to personality features in patients with PD that could influence behavioral aspects.

Verbal and visuospatial memory in lateral onset Parkinson disease: time is of the essence

OBJECTIVE

This investigation sought to study immediate and delayed verbal and visuospatial recall in Parkinson disease (PD) patients with left hemibody (LHO) and right hemibody (RHO) onset of motor symptoms and to examine the role of mental processing speed in recall of this information.

BACKGROUND

Research is mixed regarding material specific memory impairments in LHO and RHO PD. However, earlier research has not used a factorial approach in investigating material specific memory in LHO and RHO PD. We hypothesized that LHO PD patients would exhibit an increase in performance following the delayed verbal free recall trial and either decline or stability in performance on the delayed visuospatial free recall trial. The opposite pattern was hypothesized for RHO PD patients.

METHOD

The Hopkins Verbal Learning Test-revised (HVLT-R) and the Brief Visuospatial Memory Test-revised (BVMT-R) were administered to a sample of 28 LHO PD patients and 36 RHO PD patients. The Stroop Color-word Test was administered as a measure of mental processing speed.

RESULTS

The results indicated that the RHO group experienced a significant decline in performance on verbal free recall from the immediate to the delayed trials and a significant improvement in performance from the immediate to the delayed visuospatial free recall trials. Additionally, a significant negative correlation was found between mental processing speed and changes in recall from the immediate to the delayed conditions for the RHO group.

CONCLUSIONS

These results indicate that the RHO PD group experienced a significant decline in verbal free recall and a significant improvement in visuospatial free recall from the immediate to the delayed trials and that the LHO PD patients experienced no significant changes. Further, mental processing speed appears to influence the recall of information from the immediate to the delayed conditions.

Does laterality of motor impairment tell us something about cognition in Parkinson disease?

This cross-sectional study investigates the relationship between severity of right- and left-sided motor symptoms and deficits in global cognitive function as well as individual cognitive domains in 117 Parkinson disease patients. Items of the Unified Parkinson Disease Rating Scale Part III were divided into right- and left-sided total scores. Composite scores in verbal fluency, verbal memory, executive function, and visuoperceptual skills were obtained from a full neuropsychological battery. We observed a significant association between right-sided motor impairment and verbal memory, visuoperceptual skills, and verbal fluency, but not executive function. The relationship between right symptoms and verbal fluency was fully mediated by cognitive status, while the relationship between right symptoms and verbal memory as well as visuoperceptual skills was not. Left-sided motor symptoms were not significantly related to any composite cognitive domain. When patients were divided into groups based on the side of predominant symptoms, no group differences were found in performance on the specific cognitive domains. This suggests that the degree of right-sided symptoms is more correlated to specific cognitive domains than is group classification of laterality.

Laterality, region, and type of motor dysfunction correlate with cognitive impairment in Parkinson's disease

We studied the relationship between two screening cognitive measures and off motor Unified Parkinson's Disease Rating Scale (UPDRS) scores in 108 Parkinson's disease patients. Multiple regressions were conducted to examine the UPDRS subscores' unique contributions to cognitive function. When including bradykinesia, rigidity, and postural/gait instability subscores, only bradykinesia predicted Mini Mental Status Examination (MMSE), normalized beta = -0.57, t(104) = -3.31, P < 0.01, and Dementia Rating Scale-2 (DRS-2), normalized beta = -0.45, t(104) = -2.55, P < 0.05. Tremor was not included in the regression analyses because it did not correlate with cognitive function. When including axial and appendicular subscores, only the axial subscore predicted MMSE, normalized beta = -0.39, t(105) = -3.19, P < 0.01, and DRS-2 scores, normalized beta = -0.40, t(106) = -3.28, P < 0.01. When including left-sided and right-sided subscores, only the right-sided symptoms predicted DRS-2 scores, normalized beta = -0.28, t(105) = -2.45, P < 0.05, and showed a trend toward predicting MMSE scores, normalized beta = -0.22, t(105) = -1.95, P = 0.054. We therefore found that right-sided symptoms (for laterality), axial symptoms (for region), and bradykinesia (for type of symptoms) were the best predictors of cognitive function.

Memory for time intervals is impaired in left hemi-Parkinson patients

The basal ganglia have been proposed as one of the neural correlates of timekeeping functions. Both encoding and memory retrieval components for time perception are impaired in Parkinson's disease (PD). The aim of our study was to investigate in hemi-Parkinsonian patients the existence of a specific alteration in memory for time depending on the affected side, to better understand the contribution of the left or right basal ganglia circuits in different components of time perception. Right and left hemi-PD patients performed a time reproduction task in which they were required to reproduce in the same session short (5 s) and long (15 s) time intervals, in off- and on-therapy condition. While the right hemi-PD patients overestimated the shorter interval, only the left hemi-PD group showed the memory migration effect, overestimating the shorter and underestimating the longer time intervals. These results argue for a critical involvement of the right basal ganglia in memory retrieval for time intervals, in the range of seconds.