Neuropsychological correlates of brain atrophy in Parkinson's disease: a CT-scan study

Biomarkers and non-motor symptoms as a function of motor symptom asymmetry in early Parkinson's disease

INTRODUCTION

The longitudinal trajectories of cognitive-neuropsychiatric symptoms from the early stages of Parkinson's disease, as a function of motor symptom asymmetry at the onset of the disease, remain to be fully explored. Moreover, the relationship to biomarkers warrants further investigation.

METHODOLOGY

Non-motor and biospecimen data from 413 patients with Parkinson's disease, dissociating predominantly left-sided motor symptoms patients (n = 179), predominantly right-sided motor symptoms patients (n = 234), and matched healthy controls (n = 196), were extracted from the Parkinson's Progression Marker Initiative database during a 3-Year follow-up. Non-parametric and conservative corrections for multivariate comparisons were carried out on neuropsychiatric and biomarker data.

RESULTS

A decline for global cognitive efficiency scores in predominantly right-sided motor symptoms patients was observed, whereas depressive and anxiety symptoms were greater overtime for predominantly left-sided motor symptoms patients. Biomarker analysis revealed that predominantly right-sided patients expressed decreased levels of total-tau and phospho-tau over time, while left-sided patients didn't differ from healthy controls.

CONCLUSION

From the early course of the disease, the existence of different clinical phenotypes is proposed, associated to emerging evidences of distinct pathological pathways and a left-hemispheric vulnerability for cognitive decline.

Axial Signs and Magnetic Resonance Imaging Correlates in Parkinson's Disease

Background:

Age-related brain changes may contribute to axial features in Parkinson's disease (PD).

Objectives:

To determine if ventricular volume and white matter high signal changes (WMC) are related to motor signs in PD and controls independent of age.

Methods:

Patients were rated with the Unified Parkinson's Disease Rating Scale (subscore A: tremor, rigidity, bradykinesia, and facial expression; subscore B: speech and axial impairment). Steps and time taken to walk 9.144 meters were measured. Total ventricular volume (TVV) and intracranial volume (ICV) were measured on T1-weighted MRI using manual tracing software. WMC were rated on axial T2-weighted, dual-echo or FLAIR MR images using a visual scale.

Results:

TVV (cm3) (PD: 36.48 ± 15.93; controls: 32.16 ± 14.20, p = 0.21) and WMC did not differ between groups (PD: 3.7 ± 4.2; controls: 3.2 ± 3.1, p = 0.55). Age correlated positively with ICV-corrected TVV and WMC in PD (cTVV: r = 0.48, p = 0.003; WMC: r=0.42, p=0.01) and controls (cTVV: r = 0.31, p = 0.04; WMC: r=0.44, p=0.003). Subscore B (r = 0.42, p = 0.01) but not subscore A (r = 0.25, p = 0.14) correlated with cTVV in PD. Steps and walking time correlated with cTVV and WMC in PD; cadence correlated with cTVV and steps with WMC in controls. Age-adjustment eliminated correlations.

Conclusion:

Subscore B, but not subscore A correlated positively with ventricular volume in PD, though this association was accounted for by age. Age-related brain change super-imposed on PD may contribute to axial features.

Anxiety in Parkinson's disease: a critical review of experimental and clinical studies

Parkinson's disease (PD) is the second most common neurodegenerative disorder affecting about 1% of the population older than 60 years. Classically, PD is considered as a movement disorder, and its diagnosis is based on the presence of a set of cardinal motor signs that are the consequence of a pronounced death of dopaminergic neurons in the substantia nigra pars compacta. There is now considerable evidence showing that the neurodegenerative processes leading to sporadic PD begin many years before the appearance of the characteristic motor symptoms, and that additional neuronal fields and neurotransmitter systems are also involved in PD, including olfactory structures, amygdala, caudal raphe nuclei, locus coeruleus, and hippocampus. Accordingly, adrenergic and serotonergic neurons are also lost, which seems to contribute to the anxiety in PD. Non-motor features of PD usually do not respond to dopaminergic medication and probably form the major current challenge in the clinical management of PD. Additionally, most studies performed with animal models of PD have investigated their ability to induce motor alterations associated with advanced phases of PD, and some studies begin to assess non-motor behavioral features of the disease. The present review attempts to examine results obtained from clinical and experimental studies to provide a comprehensive picture of the neurobiology and current and potential treatments for anxiety in PD. The data reviewed here indicate that, despite their high prevalence and impact on the quality of life, anxiety disorders are often under-diagnosed and under-treated in PD patients. Moreover, there are currently few clinical and pre-clinical studies underway to investigate new pharmacological agents for relieving these symptoms, and we hope that this article may inspire clinicians and researchers devote to the studies on anxiety in PD to change this scenario. This article is part of a Special Issue entitled 'Anxiety and Depression'.

A positive correlation between fractional white matter volume and the response of Parkinson disease patients to subthalamic stimulation

BACKGROUND

Since optimal patient selection is essential for the success of subthalamic nucleus (STN) stimulation, the identification of reliable outcome predictors is important. The purpose of this study was to identify new imaging characteristics sufficiently reliable to predict treatment results.

METHOD

Using preoperative magnetic resonance imaging studies of 21 Parkinson disease (PD) patients treated by STN stimulation, we performed whole brain-based analysis of voxel-based morphometry (VBM) data. Intracranial structures segmented into the gray matter fraction (GMF), white matter fraction (WMF), and cerebrospinal fluid fraction (CSFF) were subjected to univariate and multivariate analysis of the correlation between fractional volumes and postoperative improvement rates using the Unified PD Rating Scale (UPDRS).

FINDINGS

At 3 months after surgery, the WMF was significantly correlated with improvement rated on the total UPDRS (p = 0.006), UPDRS part II (activities of daily living; p = 0.008), UPDRS part III (motor; p = 0.005). In contrast, there was no significant correlation between the effect of STN stimulation and GMF or the effect of stimulation and CSFF. The WMF also showed a significant correlation with postoperative scores in the "on" drug and "on" stimulation state (total UPDRS, p = 0.027; UPDRS part II, p = 0.019; UPDRS part III, p = 0.034).

CONCLUSIONS

Our data indicate that patients with a larger white matter volume benefited from STN stimulation whereas the volume of other brain structures was not correlated with its effect. We posit that preserved connectivity between components of the basal ganglia-thalamocortical circuit may be required for the effectiveness of electrical stimulation. VBM may represent a powerful tool to predict the response of patients with advanced PD to STN stimulation.

Linguistic correlates of asymmetric motor symptom severity in Parkinson's Disease

Asymmetric motor severity is common in Parkinson's Disease (PD) and provides a method for examining the neurobiologic mechanisms underlying cognitive and linguistic deficits associated with the disorder. In the present research, PD participants (N=31) were assessed in terms of the asymmetry of their motor symptoms. Interviews with the participants were analyzed with the Linguistic Inquiry and Word Count (LIWC) program. Three measures of linguistic complexity - the proportion of verbs, proportion of function words, and sentence length - were found to be affected by symptom asymmetry. Greater left-side motor severity (and hence greater right-hemisphere dysfunction) was associated with the production of significantly fewer verbs, function words, and shorter sentences. Hence, the production of linguistic complexity in a natural language context was associated with relatively greater right hemisphere involvement. The potential neurobiological mechanisms underlying this effect are discussed.

Side and type of motor symptom influence cognition in Parkinson's disease

It is well known that many patients with Parkinson's disease experience neuropsychological decline. However, the nature and extent of mental status change varies widely, with some patients showing mild or no cognitive impairments and others exhibiting frank dementia. Research has shown that several clinical disease parameters may differentially correlate with patterns of neuropsychological dysfunction. The present study examined side and type of motor symptom at disease onset and their relationship to cognition in idiopathic Parkinson's disease (PD). We identified 58 patients who initially presented with one of the following symptom profiles: right-side tremor onset (RSO-T; n = 15), right-side bradykinesia/rigidity onset (n = 12), left-side tremor onset (n = 19), and left-side bradykinesia/rigidity onset (n = 12). There were no differences between groups in disease duration, overall mental status, education, or depression severity. We administered a battery of neuropsychological measures to the four PD subgroups and a group of matched control subjects (n = 40). MANCOVAs controlling for age revealed patients with RSO-T performed significantly better than the other three PD subgroups across the entire neuropsychological battery. Further, the RSO-T subgroup performed comparably to controls. In contrast, the other three PD subgroups showed widespread cognitive deficits. These findings suggest an intricate relationship between motor symptom and side of disease onset and it is the combination of these factors that may influence the disease course and extent of cognitive deterioration. Furthermore, patients who develop tremor on the right side of their body represent a distinct subgroup of PD patients who exhibit relative sparing of cognitive function.

Cognitive functioning after pallidotomy for refractory Parkinson's disease

BACKGROUND

Earlier approaches to pallidotomy for refractory Parkinson's disease had significant complication rates. More recent approaches show fewer complications, but the effect of pallidotomy on cognition is unclear. The current study was conducted to examine the neuropsychological effects of unilateral pallidotomy.

METHODS

Neuropsychological testing was performed on patients with medically refractory, predominantly unilateral Parkinson's disease at baseline and after unilateral ventral pallidotomy (n=28) or after an equivalent period without surgery in control patients (n=10).

RESULTS

Pallidotomy patients showed no significant changes from baseline to retesting relative to the control group for any measure. Across all of the tests administered, only five of the surgery patients showed a significant decline, and of these five none declined on more than one test. Depression did not relate to preoperative or postoperative cognition. The pallidotomy group showed a significant improvement in motor functioning and activities of daily living whereas the control group did not. These measures were not associated with the neuropsychological test scores at baseline or retest.

CONCLUSIONS

Stereotactic unilateral ventral pallidotomy does not seem to produce dramatic cognitive declines in most patients.

Movement disorders in adult hydrocephalus

In a prospective series of symptomatic adult hydrocephalus characterized by gait disturbance, cognitive impairment, and/or urinary incontinence, 88 of 118 patients (75%) had additional akinetic, tremulous, hypertonic, or hyperkinetic movement disorders. Their prevalence was highest in patients with idiopathic normal pressure hydrocephalus (NPH) of the elderly (56/65 patients, 86%), and they were less frequent in patients with secondary NPH (10/15, 66%), with nonhydrodynamic atrophic/other hydrocephalus (20/33, 61%), and with obstructive hydrocephalus/aqueductal stenosis (2/5, 40%). Akinetic symptoms were found in 73 of 118 patients (62%), and the most frequent movement disorder was upper extremity bradykinesia (55%). Akinetic, tremulous, hypertonic, and hyperkinetic movement disorders were exclusively secondary to causes not related to hydrocephalus in 24 of 118 patients (20%). The proportion of patients with movement disorders not attributable to only such causes was highest in the idiopathic NPH group (44/65, 68%). Thirteen of 118 patients (11%) presented with a parkinsonian syndrome. There was evidence for coexistent Parkinson's disease in four of these patients. Parkinsonism was found to be secondary to NPH in five patients and was found improved after shunting. Akinetic symptoms in patients with NPH generally responded favorably to CSF diversion, which was evident in 80% of a subset of this group. Various other movement disorders did not show definite improvement. The high prevalence of bradykinesia and other akinetic symptoms in NPH and the beneficial effect of shunting on such symptoms suggest that NPH may cause a more generalized disorder of motor function.

[Dementia in Parkinson's disease. Critical evaluation of the literature]

In the last 30 years, Parkinson's disease has been object of great progress. The majority of patients reaches a longer life with quality because of the modern therapeutic approach. However, dementia that can occur in the evolutive process, has its neuropathology not completely defined until now. There are lesions in the basal ganglia, in the ventral area of the mesencephalic tegmentum in the thalamus, in the substantia nigra and in the frontal cortex. The presence of Lewy bodies in the cortex is associated with dementia, in the same way that the anatomopathological features of Alzheimer's disease, in many cases. Dementia should have a multifactorial basis. Different types of neurotransmitters, like serotonin, acetylcholine and dopamine, or even hormones, like cortisol, may be altered in a great number of demented parkinsonians. Depression, found in up to 40% of patients, have been related as a risk factor for dementia, present approximately in 25% of cases. Studies in this area are still conflicting, with some confirming the relation among depression, cortical atrophy, hypercortisolemia and Parkinson's disease. Neuropsychologic studies show that the dementia in Parkinson's disease is of subcortical type. It is also known that parkinsonians, even those without cognitive deficiencies clinically significant, present deficits if submitted to more detailed neuropsychological tests. It is assumed, so, that cognitive impairments are intrinsic to the disease, varying its expression among patients. Dementia shall be diagnosed based on the criteria established in the diagnostic and statistical manual of mental disorders of the American Psychiatry Association, as well as computed tomography and magnetic resonance. For treatment, parkinsonian dementia does not recognize efficacious agents until now.

A quantitative morphometrical study of neuron degeneration in the substantia nigra in Parkinson's disease

We studied the pigmented neurons of the substantia nigra (SN) from 8 controls and 20 patients with Parkinson's disease (PD) using a computerized morphometric methodology. On the basis of neuronal topography, several anatomic regions were outlined in the SN. In these subregions the area, perimeter, diameter of the cell bodies and cell numbers were measured and were counted in the controls and PD patients. The measurements were made at the level of the exit of the third cranial nerve from the brain stem. In PD patients, when the whole SN was considered, the mean area, mean perimeter and diameter of the pigmented cell bodies were significantly reduced by 35%, 20% and 21% respectively from the control mean values. Regionally, the pigmented neuron area in the medial ventral part (VM), medial dorsal part (DM), lateral ventral part (VL), lateral dorsal part (DL) and pars lateralis part (PL) showed a significant reduction of 33-41% as compared to controls. In these subregions, a significant decrease in PD patients from the control mean values was seen both in the pigmented neuron perimeter, by 19-26%, and the diameter by 19-25%. This decrease in cell size suggests that, in PD patients, the remaining pigmented neurons in the SN are in a process of degeneration and atrophy. In PD patients the number of pigmented neurons in the whole SN decreased about 76% from control values. Evaluation of the influence of cell size on the apparent quantity of cells in sections indicates, however, that in PD patients the impact of true loss of pigmented neurons is far more dramatic than the impact of their decrease in size.

CT measurement of suprasellar cistern predicts rate of cognitive decline in Alzheimer's disease

Previous studies reveal significant relationships between some quantitative computed tomography (CT) measures and level of cognitive functioning in patients with Alzheimer's disease (AD). This study was designed to determine whether measurements from CT scans of AD patients could predict future rates of decline in cognitive function. Subjects were 8 men and 19 women diagnosed with probable AD. CT measures included bifrontal ratio, bicaudate ratio, and areas of lateral ventricles, third ventricle, and suprasellar cistern (SSC). Measures of cognitive and adaptive functioning were obtained at the time of the scan and on follow-up. Of the CT measures, the SSCR (SSC corrected for intracranial area) was the most highly correlated with Mini-Mental State Exam (MMSE) score and other cognitive measures at the time of the scan. Follow-up data were obtained for those 20 individuals who were mildly to moderately demented at the time of the scan (MMSE > or = 10). Rate of change was calculated for each neuropsychological measure. The SSCR correlated significantly with rate of change for MMSE and other measures of cognitive and adaptive functioning. This study demonstrates that CT measurement of the SSC can predict the subsequent rate of neurocognitive decline in AD patients.

Abnormal refractoriness in patients with Parkinson's disease after brief withdrawal of levodopa treatment

Two pairwise matched groups of patients with mild to moderate Parkinson's disease and a group of normal age matched controls were used to investigate the effects on simple and choice reaction time (RT) of brief withdrawal of levodopa therapy. Comparisons within and across these groups disclosed a selective effect of levodopa withdrawal. After about 12 hours of levodopa deprivation, patients exhibited an exaggeration of normal refractoriness, the well established tendency for RT to increase progressively as the delay between a response and the next imperative signal is reduced below 0.5 s. Increased refractoriness was at least as great for simple as choice RT. Choice RT on trials involving repetition (as opposed to alternation) of the previous response, however, showed no tendency towards greater impairment by brevity of the recovery period or by withdrawal of medication, eliminating an effector based account. With longer recovery periods, RT was unaffected by medication; indeed, unmedicated patients were as fast as normal subjects under these conditions. Even at the briefest delays, fully medicated patients did not differ from normal controls. The paper concludes with a critical review of chronometric studies of medication effects in Parkinson's disease.

Neuropsychological characteristics of parkinsonian patients with lateralized motor impairment

Parkinsonians with predominantly unilateral signs provide an interesting experimental means to evaluate if asymmetric nigro-striatal degeneration may affect neuropsychological functions. The aim of our study was to establish if the side of onset of idiopathic Parkinson's disease, right (PDR) or left (PDL), determines a selective pattern of cognitive performances. Furthermore, we verified if PDR and PDL groups show a different frequency of dementia. PDR and PDL patients with at least seven years of disease duration, matched for age, schooling, severity of extrapyramidal symptomatology and index of lateralization, were evaluated by using an extensive neuropsychological battery aimed at assessing hemispheric cognitive asymmetries. Current side of greater motor impairment was the same as the one affected at the onset of the disease. Only subtle differences in the profile of neuropsychological dysfunction emerged from the comparison of PDR and PDL subjects. Moreover, the number of parkinsonians showing dementia syndrome was the same in both groups. Our results suggest that the side of onset of motor impairment does not significantly influence the cognitive performances in PD. Subcortical anatomic and/or functional asymmetries seem to play a less important role in the intellectual functions than in motor activities.

Side of onset of motor symptoms influences cognition in Parkinson's disease

Studies attempting to relate cognitive impairment to asymmetry of motor symptoms in Parkinson's disease (PD) have found contradictory results. We examined 88 patients with unilateral onset of idiopathic PD who underwent a comprehensive neuropsychological assessment, including language, visuospatial abilities, abstraction and reasoning, attention and mental tracking, set shifting, and memory. Patients whose motor signs began on the left side of the body consistently performed more poorly on the battery of cognitive measures than did patients with right-side onset. Significant differences were found on immediate and delayed verbal recall, word retrieval, semantic verbal fluency, visuospatial analysis, abstract reasoning, attention span, and mental tracking. These differences could not be attributed to differences in the overall severity of motor symptoms at the time of cognitive assessment, or the current pattern of motor asymmetry. This finding suggests that damage to right-hemisphere dopamine systems plays a disproportionately greater role in PD-related cognitive decline than a presumably comparable left-hemisphere dopamine depletion.