The relative and interactive impact of multiple risk factors in schizophrenia spectrum disorders: a combined register-based and clinical twin study

BACKGROUND

Research has yielded evidence for genetic and environmental factors influencing the risk of schizophrenia. Numerous environmental factors have been identified; however, the individual effects are small. The additive and interactive effects of multiple risk factors are not well elucidated. Twin pairs discordant for schizophrenia offer a unique opportunity to identify factors that differ between patients and unaffected co-twins, who are perfectly matched for age, sex and genetic background.

METHODS

Register data were combined with clinical data for 216 twins including monozygotic (MZ) and dizygotic (DZ) proband pairs (one or both twins having a schizophrenia spectrum diagnosis) and MZ/DZ healthy control (HC) pairs. Logistic regression models were applied to predict (1) illness vulnerability (being a proband v. HC pair) and (2) illness status (being the patient v. unaffected co-twin). Risk factors included: A polygenic risk score (PRS) for schizophrenia, birth complications, birth weight, Apgar scores, paternal age, maternal smoking, season of birth, parental socioeconomic status, urbanicity, childhood trauma, estimated premorbid intelligence and cannabis.

RESULTS

The PRS [odds ratio (OR) 1.6 (1.1-2.3)], childhood trauma [OR 4.5 (2.3-8.8)], and regular cannabis use [OR 8.3 (2.1-32.7)] independently predicted illness vulnerability as did an interaction between childhood trauma and cannabis use [OR 0.17 (0.03-0.9)]. Only regular cannabis use predicted having a schizophrenia spectrum diagnosis between patients and unaffected co-twins [OR 3.3 (1.1-10.4)].

CONCLUSION

The findings suggest that several risk factors contribute to increasing schizophrenia spectrum vulnerability. Moreover, cannabis, a potentially completely avoidable environmental risk factor, seems to play a substantial role in schizophrenia pathology.

Differentiation of neurodegenerative parkinsonian syndromes by volumetric magnetic resonance imaging analysis and support vector machine classification

BACKGROUND

Clinical differentiation of parkinsonian syndromes is still challenging.

OBJECTIVES

A fully automated method for quantitative MRI analysis using atlas-based volumetry combined with support vector machine classification was evaluated for differentiation of parkinsonian syndromes in a multicenter study.

METHODS

Atlas-based volumetry was performed on MRI data of healthy controls (n = 73) and patients with PD (204), PSP with Richardson's syndrome phenotype (106), MSA of the cerebellar type (21), and MSA of the Parkinsonian type (60), acquired on different scanners. Volumetric results were used as input for support vector machine classification of single subjects with leave-one-out cross-validation.

RESULTS

The largest atrophy compared to controls was found for PSP with Richardson's syndrome phenotype patients in midbrain (-15%), midsagittal midbrain tegmentum plane (-20%), and superior cerebellar peduncles (-13%), for MSA of the cerebellar type in pons (-33%), cerebellum (-23%), and middle cerebellar peduncles (-36%), and for MSA of the parkinsonian type in the putamen (-23%). The majority of binary support vector machine classifications between the groups resulted in balanced accuracies of >80%. With MSA of the cerebellar and parkinsonian type combined in one group, support vector machine classification of PD, PSP and MSA achieved sensitivities of 79% to 87% and specificities of 87% to 96%. Extraction of weighting factors confirmed that midbrain, basal ganglia, and cerebellar peduncles had the largest relevance for classification.

CONCLUSIONS

Brain volumetry combined with support vector machine classification allowed for reliable automated differentiation of parkinsonian syndromes on single-patient level even for MRI acquired on different scanners. © 2016 International Parkinson and Movement Disorder Society.

Manual MRI morphometry in Parkinsonian syndromes

BACKGROUND

Several morphometric magnetic resonance imaging parameters may serve for differential diagnosis of parkinsonism. The objective of this study was to identify which performs best in clinical routine.

METHODS

We acquired multicentric magnetization-prepared rapid gradient echo sequences in patients with Parkinson's disease (n=204), progressive supranuclear palsy (n=106), multiple system atrophy-cerebellar, (n = 21); multiple system atrophy-parkinsonian (n = 60), and healthy controls (n = 73), performed manual planimetric measurements, and calculated receiver operator characteristics with leave-one-out cross-validation to propose cutoff values.

RESULTS

The midsagittal midbrain area was reduced in PSP versus all other groups (P < 0.001). The midsagittal pons area was reduced in MSA-cerebellar, MSA-parkinsonian, and PSP versus PD patients and healthy controls (P < 0.001). The midbrain/pons area ratio was lower in PSP (P < 0.001) and higher in MSA-cerebellar and MSA-parkinsonian versus PD and PSP (P < 0.001).

CONCLUSIONS

The midsagittal midbrain area most reliably identified PSP, the midsagittal pons area MSA-cerebellar. The midbrain/pons area ratio differentiated MSA-cerebellar and PSP better than the magnetic resonance-Parkinson index. © 2017 International Parkinson and Movement Disorder Society.

Longitudinal changes of cortical microstructure in Parkinson's disease assessed with T1 relaxometry

BACKGROUND

Histological evidence suggests that pathology in Parkinson's disease (PD) goes beyond nigrostriatal degeneration and also affects the cerebral cortex. Quantitative MRI (qMRI) techniques allow the assessment of changes in brain tissue composition. However, the development and pattern of disease-related cortical changes have not yet been demonstrated in PD with qMRI methods. The aim of this study was to investigate longitudinal cortical microstructural changes in PD with quantitative T1 relaxometry.

METHODS

13 patients with mild to moderate PD and 20 matched healthy subjects underwent high resolution T1 mapping at two time points with an interval of 6.4 years (healthy subjects: 6.5 years). Data from two healthy subjects had to be excluded due to MRI artifacts. Surface-based analysis of cortical T1 values was performed with the FreeSurfer toolbox.

RESULTS

In PD patients, a widespread decrease of cortical T1 was detected during follow-up which affected large parts of the temporo-parietal and occipital cortices and also frontal areas. In contrast, age-related T1 decrease in the healthy control group was much less pronounced and only found in lateral frontal, parietal and temporal areas. Average cortical T1 values did not differ between the groups at baseline (p = 0.17), but were reduced in patients at follow-up (p = 0.0004). Annualized relative changes of cortical T1 were higher in patients vs. healthy subjects (patients: - 0.72 ± 0.64%/year; healthy subjects: - 0.17 ± 0.41%/year, p = 0.007).

CONCLUSIONS

In patients with PD, the development of widespread changes in cortical microstructure was observed as reflected by a reduction of cortical T1. The pattern of T1 decrease in PD patients exceeded the normal T1 decrease as found in physiological aging and showed considerable overlap with the pattern of cortical thinning demonstrated in previous PD studies. Therefore, cortical T1 might be a promising additional imaging marker for future longitudinal PD studies. The biological mechanisms underlying cortical T1 reductions remain to be further elucidated.

Subtypes of mild cognitive impairment in patients with Parkinson's disease: evidence from the LANDSCAPE study

OBJECTIVE

Inconsistent results exist regarding the cognitive profile in patients with Parkinson's disease with mild cognitive impairment (PD-MCI). We aimed at providing data on this topic from a large cohort of patients with PD-MCI.

METHODS

Sociodemographic, clinical and neuropsychological baseline data from patients with PD-MCI recruited in the multicentre, prospective, observational DEMPARK/LANDSCAPE study were analysed.

RESULTS

269 patients with PD-MCI (age 67.8±7.4, Unified Parkinson's Disease Rating Scale (UPDRS-III) scores 23.2±11.6) were included. PD-MCI subtypes were 39.4% non-amnestic single domain, 30.5% amnestic multiple domain, 23.4% non-amnestic multiple domain and 6.7% amnestic single domain. Executive functions were most frequently impaired. The most sensitive tests to detect cognitive dysfunctions were the Modified Card Sorting Test, digit span backwards and word list learning direct recall. Multiple stepwise regression analyses showed that global cognition, gender and age, but not education or disease-related parameters predicted PD-MCI subtypes.

CONCLUSIONS

This study with the so far largest number of prospectively recruited patients with PD-MCI indicates that non-amnestic PD-MCI is more frequent than amnestic PD-MCI; executive dysfunctions are the most typical cognitive symptom in PD-MCI; and age, gender and global cognition predict the PD-MCI subtype. Longitudinal data are needed to test the hypothesis that patients with PD-MCI with specific cognitive profiles have different risks to develop dementia.

Verbal memory declines more in female patients with Parkinson's disease: the importance of gender-corrected normative data

BACKGROUND

Data on gender-specific profiles of cognitive functions in patients with Parkinson's disease (PD) are rare and inconsistent, and possible disease-confounding factors have been insufficiently considered.

METHOD

The LANDSCAPE study on cognition in PD enrolled 656 PD patients (267 without cognitive impairment, 66% male; 292 with mild cognitive impairment, 69% male; 97 with PD dementia, 69% male). Raw values and age-, education-, and gender-corrected Z scores of a neuropsychological test battery (CERAD-Plus) were compared between genders. Motor symptoms, disease duration, l-dopa equivalent daily dose, depression - and additionally age and education for the raw value analysis - were taken as covariates.

RESULTS

Raw-score analysis replicated results of previous studies in that female PD patients were superior in verbal memory (word list learning, p = 0.02; recall, p = 0.03), while men outperformed women in visuoconstruction (p = 0.002) and figural memory (p = 0.005). In contrast, gender-corrected Z scores showed that men were superior in verbal memory (word list learning, p = 0.02; recall, p = 0.02; recognition, p = 0.04), while no difference was found for visuospatial tests. This picture could be observed both in the overall analysis of PD patients as well as in a differentiated group analysis.

CONCLUSIONS

Normative data corrected for gender and other sociodemographic variables are relevant, since they may elucidate a markedly different cognitive profile compared to raw scores. Our study also suggests that verbal memory decline is stronger in women than in men with PD. Future studies are needed to replicate these findings, examine the progression of gender-specific cognitive decline in PD and define different underlying mechanisms of this dysfunction.

Advanced stages of PD: interventional therapies and related patient-centered care

During the last decades, symptomatic treatment of motor symptoms of Parkinson's disease (PD) improved continuously and is reflected by long-range independency of the patient during the disease course. However, advanced stages of PD still represent an important challenge to patients, caregivers and treating physicians. In patients with advanced PD, interventional therapy strategies are increasingly applied. These device-related treatment strategies using pump-based continuous dopaminergic stimulation (CDS) or deep brain stimulation (DBS) opened new treatment options especially if motor complications predominate. Well-designed clinical studies on these interventional therapeutic approaches provided class 1 evidence for the efficacy of DBS and CDS in advanced PD and opened new perspectives for their use in earlier disease stages also. Therefore, careful selection of patients amenable to the (semi)invasive therapy options becomes more and more important and requires an interdisciplinary setting that accounts for (i) optimal patient information and awareness, (ii) selection of best individual treatment modality, (iii) training of relatives and caregivers, (iv) management of complications, and (v) follow-up care. Here, we address these topics by summarizing current state-of-the-art in patient selection, providing specificities of treatment options and troubleshooting, and defining steps towards an optimized patient-centered care. Interventional therapies pioneer in the area of individualized treatment approaches for PD, and may be complemented in the future by biomarker-based improved stratification and by closed-loop systems for adaptive therapeutic strategies. In the present review, we summarize the proceedings of an Expert Workshop on Parkinson's disease held on November 22, 2014 in Frankfurt, Germany.

Does Navigated Transcranial Stimulation Increase the Accuracy of Tractography? A Prospective Clinical Trial Based on Intraoperative Motor Evoked Potential Monitoring During Deep Brain Stimulation

BACKGROUND:

Tractography based on diffusion tensor imaging has become a popular tool for delineating white matter tracts for neurosurgical procedures.

OBJECTIVE:

To explore whether navigated transcranial magnetic stimulation (nTMS) might increase the accuracy of fiber tracking.

METHODS:

Tractography was performed according to both anatomic delineation of the motor cortex (n = 14) and nTMS results (n = 9). After implantation of the definitive electrode, stimulation via the electrode was performed, defining a stimulation threshold for eliciting motor evoked potentials recorded during deep brain stimulation surgery. Others have shown that of arm and leg muscles. This threshold was correlated with the shortest distance between the active electrode contact and both fiber tracks. Results were evaluated by correlation to motor evoked potential monitoring during deep brain stimulation, a surgical procedure causing hardly any brain shift.

RESULTS:

Distances to fiber tracks clearly correlated with motor evoked potential thresholds. Tracks based on nTMS had a higher predictive value than tracks based on anatomic motor cortex definition (P &lt; .001 and P = .005, respectively). However, target site, hemisphere, and active electrode contact did not influence this correlation.

CONCLUSION:

The implementation of tractography based on nTMS increases the accuracy of fiber tracking. Moreover, this combination of methods has the potential to become a supplemental tool for guiding electrode implantation.

Ultrasound-based motion analysis demonstrates bilateral arm hypokinesia during gait in heterozygous PINK1 mutation carriers

Carriers of a single heterozygous PINK1 (PTEN-induced putative kinase 1) gene mutation provide an ideal opportunity to study the development of parkinsonian motor signs from the very beginning. Measuring tools that reliably represent mild motor symptoms could also facilitate the assessment of future neuroprotective therapies and early diagnosis of Parkinson's disease (PD). We investigated nine family members carrying a heterozygous PINK1 mutation in comparison with 25 age-matched healthy controls. Arm kinematics were quantified during treadmill walking at four different speeds using ultrasound-based motion analysis. Heterozygous PINK1 mutation carriers showed a bilateral reduction of arm swing amplitudes (P = 0.003) and arm anteversion (P = 0.001), which was more pronounced on the predominantly affected body side but also was present, albeit to a lesser degree, contralaterally (amplitude P = 0.01, anteversion P = 0.002, repeated measures analysis of covariance [rmANCOVA]). Single post-hoc comparisons revealed similar results for all speeds on both body sides (P < 0.05) except for 2.0 km/h on the less affected side. A single heterozygous mutation in the PINK1 gene is associated with a bilateral dopaminergic dysfunction in this family. Ultrasound-based three-dimensional motion analysis of arm swing during gait is a suitable tool to quantify even subtle hypokinesia in mildly affected PINK1 mutation carriers, which tends to be easily overlooked on the less affected body side during clinical examination. Therefore, this technique is a promising application in early stage PD and in at-risk populations for the disease.

White matter damage is related to ataxia severity in SCA3

Spinocerebellar ataxia type 3 (SCA3) is the most frequent inherited cerebellar ataxia in Europe, the US and Japan, leading to disability and death through motor complications. Although the affected protein ataxin-3 is found ubiquitously in the brain, grey matter atrophy is predominant in the cerebellum and the brainstem. White matter pathology is generally less severe and thought to occur in the brainstem, spinal cord, and cerebellar white matter. Here, we investigated both grey and white matter pathology in a group of 12 SCA3 patients and matched controls. We used voxel-based morphometry for analysis of tissue loss, and tract-based spatial statistics (TBSS) on diffusion magnetic resonance imaging to investigate microstructural pathology. We analysed correlations between microstructural properties of the brain and ataxia severity, as measured by the Scale for the Assessment and Rating of Ataxia (SARA) score. SCA3 patients exhibited significant loss of both grey and white matter in the cerebellar hemispheres, brainstem including pons and in lateral thalamus. On between-group analysis, TBSS detected widespread microstructural white matter pathology in the cerebellum, brainstem, and bilaterally in thalamus and the cerebral hemispheres. Furthermore, fractional anisotropy in a white matter network comprising frontal, thalamic, brainstem and left cerebellar white matter strongly and negatively correlated with SARA ataxia scores. Tractography identified the thalamic white matter thus implicated as belonging to ventrolateral thalamus. Disruption of white matter integrity in patients suffering from SCA3 is more widespread than previously thought. Moreover, our data provide evidence that microstructural white matter changes in SCA3 are strongly related to the clinical severity of ataxia symptoms.

The value of putaminal diffusion imaging versus 18-fluorodeoxyglucose positron emission tomography for the differential diagnosis of the Parkinson variant of multiple system atrophy

Differentiating the Parkinson variant of multiple system atrophy (MSA-P) from idiopathic Parkinson's disease (PD) and other forms of atypical parkinsonism can be difficult because symptoms overlap considerably. 18-Fluorodeoxyglucose positron emission tomography (FDG-PET) is a powerful imaging technique that can assist in the diagnosis of MSA-P via detection of putaminal and cerebellar hypometabolism. Recent studies suggest that diffusion-weighted imaging (DWI) might be of similar diagnostic value, as it can detect microstructural damage in the putamen by means of an increased mean diffusivity (MD). The aim of this study was a direct comparison of DWI and FDG-PET by using both methods on the same subject cohort. To this end, combined DWI and FDG-PET were employed in patients with MSA-P (n = 11), PD (n = 13), progressive supranuclear palsy (n = 8), and in 6 control subjects. MD values and FDG uptake ratios were derived from volumetric parcellations of the putamen and subjected to further analysis of covariance (ANCOVA) and receiver operating characteristics analyses. MSA-P was found to be associated with an increased posterior putaminal MD (P < 0.001 in all subgroup comparisons) that correlated strongly with local reductions in FDG uptake (r = -0.85, P = 0.002). DWI discriminated patients with MSA-P from other subgroups nearly as accurately as FDG-PET (area under the curve = 0.89 vs 0.95, P = 0.27 [pooled data]). Our data suggest a close association between the amount of putaminal microstructural damage and a reduced energy metabolism in patients with MSA-P. The clinical use of DWI for the differential diagnosis of MSA-P is encouraged.

Correlation of active contact positions with the electrophysiological and anatomical subdivisions of the subthalamic nucleus in deep brain stimulation

BACKGROUND

The most effective contacts in subthalamic nucleus (STN) deep brain stimulation are reported to be dorsolateral, and suppression of synchronized oscillatory activity might be a mechanism of action.

OBJECTIVES

To analyze the optimal contact position in regard to the anatomical and electrophysiological position and to determine whether oscillatory and bursty activity is more frequent around the active contact.

METHODS

In 21 patients, the clinically most effective contacts were analyzed according to their relative position to the anatomical and electrophysiological STN center, which was assessed by T2-weighted MRI and microrecording. In 12 out of 21 consecutive patients, autocorrelograms of the action potentials within the vicinity of the active contact were compared to the most ventromedial reference contact.

RESULTS

The isocenter of the anatomical and electrophysiological STN had a mean deviation of 0.8 mm (SD 1.45). Thirty-two out of 42 active contacts were found dorsal to the anatomical isocenter of the STN. None of the active contacts were ventral to the STN. Synchronized oscillatory or bursty activity was found in 67% of the patients within the vicinity of the active contact. In 64% of the patients, the ventromedial reference contact showed irregular activity.

CONCLUSIONS

Synchronized activity in the autocorrelogram correlates with the most effective contact. The optimal localization of the finally stimulated contact is dorsal to the STN isocenter.

Diurnal variation of hypothalamic function and chronic subthalamic nucleus stimulation in Parkinson's disease

BACKGROUND

Deep brain stimulation of the subthalamic nucleus (STN-DBS) improves quality of life in patients with advanced Parkinson's disease (PD), but is associated with neuropsychiatric side effects and weight gain in some individuals. The pathomechanisms of these phenomena are still unknown. Considering anatomical and functional connections of the STN with the hypothalamic-pituitary (HP) system, we prospectively investigated whether chronic STN-DBS alters HP functioning in 11 PD patients.

METHODS

Basal hormone levels of the HP-adrenal (HPA), HP-gonadal and HP-somatotropic axis were determined before surgery as well as 3 and 6 months after electrode implantation. In addition, 24-hour cortisol profiles and dexamethasone suppression tests were obtained. Postoperative hormone changes were correlated with individual neuropsychological test performance, psychiatric status and anthropometric measures.

RESULTS

While PD patients experienced weight gain (p = 0.025) at follow-up, most neuropsychological data and basal HP hormone levels did not change over time. HPA regulation and diurnal rhythmicity of cortisol remained intact in all patients. The 24-hour mean cortisol levels decreased 6 months after surgery (p = 0.002) correlating with improved postoperative depression (p = 0.02).

CONCLUSIONS

Chronic application of high-frequency electrical stimuli in the STN was not associated with HP dysfunction in patients with advanced PD. The diurnal variability of peripheral cortisol secretion as one important element of the endogenous biological clock remained intact. Evening cortisol levels decreased after surgery reflecting a favorable regulation of the cortisol setpoint. STN-DBS can be considered safe from a neuroendocrine perspective, but the origin of unwanted side effects warrants further elucidation.

Glucose metabolism in small subcortical structures in Parkinson's disease

OBJECTIVES

Evidence from experimental animal models of Parkinson's disease (PD) suggests a characteristic pattern of metabolic perturbation in discrete, very small basal ganglia structures. These structures are generally too small to allow valid investigation by conventional positron emission tomography (PET) cameras. However, the high-resolution research tomograph (HRRT) PET system has a resolution of 2 mm, sufficient for the investigation of important structures such as the pallidum and thalamic subnuclei.

MATERIALS AND METHODS

Using the HRRT, we performed [(18)F]-fluorodeoxyglucose (FDG) scans on 21 patients with PD and 11 age-matched controls. We employed three types of normalization: white matter, global mean, and data-driven normalization. We performed volume-of-interest analyses of small subcortical gray matter structures. Voxel-based comparisons were performed to investigate the extent of cortical hypometabolism.

RESULTS

The most significant level of relative subcortical hypermetabolism was detected in the external pallidum (GPe), irrespective of normalization strategy. Hypermetabolism was suggested also in the internal pallidum, thalamic subnuclei, and the putamen. Widespread cortical hypometabolism was seen in a pattern very similar to previously reported patterns in patients with PD.

CONCLUSION

The presence and extent of subcortical hypermetabolism in PD is dependent on type of normalization. However, the present findings suggest that PD, in addition to widespread cortical hypometabolism, is probably characterized by true hypermetabolism in the GPe. This finding was predicted by the animal 2-deoxyglucose autoradiography literature, in which high-magnitude hypermetabolism was also most robustly detected in the GPe.

The tremor network targeted by successful VIM deep brain stimulation in humans

OBJECTIVE

Deep brain stimulation (DBS) of the ventral intermediate nucleus of thalamus (VIM) is a treatment option in medically intractable tremor, such as essential tremor or tremor-dominant Parkinson disease (PD). Although functional studies demonstrated modulation of remote regions, the structural network supporting this is as yet unknown. In this observational study, we analyzed the network mediating clinical tremor modulation.

METHODS

We studied 12 patients undergoing VIM stimulation for debilitating tremor. We initiated noninvasive diffusion tractography from tremor-suppressive VIM electrode contacts. Moreover, we tested for the contribution of primary motor projections in this structural correlate of a functional tremor network, comparing the connectivity of effective DBS contacts with those of adjacent, but clinically ineffective, stimulation sites.

RESULTS

VIM stimulation resulted in decrease of tremor and improvement in quality of life. Tractography initiated from the effective stimulation site reconstructed a highly reproducible network of structural connectivity comprising motor cortical, subcortical, and cerebellar sites and the brainstem, forming the anatomic basis for remote effects of VIM stimulation. This network is congruent with functional imaging studies in humans and with thalamic projections found in the animal literature. Connectivity to the primary motor cortex seemed to play a key role in successful stimulation.

CONCLUSIONS

Patients undergoing DBS provide a unique opportunity to assess an electrophysiologically defined seed region in human thalamus, a technique that is usually restricted to animal research. In the future, preoperative tractography could aid with stereotactic planning of individual subcortical target points for stimulation in tremor and in other disease entities.

Arm swing asymmetry in Parkinson's disease measured with ultrasound based motion analysis during treadmill gait

The reduction of arm swing during gait is a frequent phenomenon in patients with early Parkinson's disease (PD). However, the objective quantification of this clinical sign using treadmill-based gait analysis has not been systematically evaluated so far. We simultaneously measured ultrasound based limb kinematics and spatiotemporal gait parameters during treadmill walking at different speeds in 21 early PD patients in Hoehn and Yahr (HY) stage I, 19 patients with bilateral PD in HY stage II and 25 age-matched controls. Both PD groups showed a highly significant reduction of the arm swing amplitude on the more affected body side (MAS). Decomposing total arm swing resulted in a bilateral decrease of arm retroversion in both PD groups, whereas anteversion was normal on the less affected side of the HY I cohort. Early stage patients exhibited a highly significant, almost threefold increase of the arm swing asymmetry index (I(A)) compared with controls. Reduced retroversion on the MAS and increased arm swing I(A) were the independent variables with the closest association to disease status in a multivariate logistic regression analysis. We conclude that ultrasound based motion analysis during treadmill walking allows reliable investigation of asymmetric arm movements in early PD patients which attenuate with ongoing disease. Impaired active arm retroversion seems to be the earliest sign of upper extremity dysfunction in parkinsonian gait. The measurement of limb kinematics during treadmill gait can broaden our methodological line-up for the analysis of complex motor programs in movement disorders.

Resting state fMRI reveals increased subthalamic nucleus-motor cortex connectivity in Parkinson's disease

Parkinson's disease (PD) is associated with abnormal hypersynchronicity in basal ganglia-thalamo-cortical loops. The clinical effectiveness of subthalamic nucleus (STN) high frequency stimulation indicates a crucial role of this nucleus within the affected motor networks in PD. Here we investigate alterations in the functional connectivity (FC) profile of the STN using resting state BOLD correlations on a voxel-by-voxel basis in functional magnetic resonance imaging (fMRI). We compared early stage PD patients (n=31) during the medication-off state with healthy controls (n=44). The analysis revealed increased FC between the STN and cortical motor areas (BA 4 and 6) in PD patients in accordance with electrophysiological studies. Moreover, FC analysis of the primary motor cortex (M1) hand area revealed that the FC increase was primarily found in the STN area within the basal ganglia. These findings are in good agreement with recent experimental data, suggesting that an increased STN-motor cortex synchronicity mediated via the so called hyperdirect motor cortex-subthalamic pathway might play a fundamental role in the pathophysiology of PD. An additional subgroup analysis was performed according to the presence (n=16) or absence (n=15) of tremor in patients. Compared to healthy controls tremor patients showed increased STN FC specifically in the hand area of M1 and the primary sensory cortex. In non-tremor patients, increased FC values were also found between the STN and midline cortical motor areas including the SMA. Taken together our results underline the importance of the STN as a key node for the modulation of BG-cortical motor network activity in PD patients.

Risk factors for executive dysfunction after subthalamic nucleus stimulation in Parkinson's disease

A slight decline in cognitive functions and especially in executive functioning after deep brain stimulation (DBS) of the nucleus subthalamicus (STN) in patients with Parkinson's disease (PD) has been described. This study evaluated baseline parameters that contribute to a deterioration of cognitive functioning after DBS. We analyzed data from the neuropsychological protocol in a randomized controlled study comparing DBS with best medical treatment (BMT). Change scores were calculated for the cognitive domains "global cognitive functioning," "memory," "working memory," "attention," and "executive function." These domain-specific change scores were correlated with previously defined preoperative parameters. Compared with the BMT group (63 patients), the STN-DBS group (60 patients) showed a significant decline only in the domain executive function 6 months after DBS, which was significantly correlated with age, levodopa-equivalence dosage (LED) and axial subscore of the UPDRS in the off-medication state at baseline. Multiple regression analysis showed that these three factors explained, however, only about 23% of the variance. Patients with higher age, higher baseline LED, and/or higher axial subscore of the UPDRS at baseline have an increased risk for worsening of executive function after STN-DBS. High scores of these factors might reflect an advanced stage of disease progression. As these baseline factors explained the variance of the change score executive function only to a minor proportion, other factors including the surgical procedure, the exact placement of the electrode or postsurgical management might be more relevant for a decline in executive functioning after STN-DBS.

Reproducibility and diagnostic accuracy of substantia nigra sonography for the diagnosis of Parkinson's disease

OBJECTIVE

Transcranial sonography (TCS) shows characteristic hyperechogenicity of the substantia nigra (SN) in patients with Parkinson's disease (PD). Although this feature is well established, sufficient observer reliability and diagnostic accuracy are prerequisites for advancements of this method.

METHODS

The authors investigated both aspects in a cross-sectional study with four blinded TCS raters in 22 PD patients and 10 healthy controls.

RESULTS

As expected, the authors found significant bilateral SN hyperechogenicity in PD patients. Quantitative computerised SN planimetry had a substantial intra- (intraclass correlation coefficient (ICC) 0.97 and 0.93 respectively for both hemispheres) and inter-rater reliability (ICC 0.84 and 0.89), while visual semiquantitative echogenicity grading of the SN revealed a moderate intrarater (weighted kappa 0.80 ipsilateral and 0.74 contralateral) and slight (0.33) to fair (0.51) inter-rater reliability only. Diagnostic accuracy measured as the area under the curve of receiver-operating characteristics plots was highest in TCS of the SN opposite the clinically most affected body side (planimetry 0.821, echogenicity grading 0.792) with a hyperechogenic area of 0.24 cm(2) as the optimum cut-off value for the differentiation between PD and controls (sensitivity 79%, specificity 81%).

CONCLUSIONS

The data demonstrate that the observer variability of SN planimetry is low in the hands of experienced investigators. This approach also offers adequate diagnostic accuracy. The authors conclude that reliable SN TCS data on PD can be achieved in clinical routine and multicentre trials when standardised analysis protocols and certain quality criteria of brain parenchyma sonography are met.

Diffusion tensor imaging of white matter involvement in essential tremor

This study set out to determine whether there is white matter involvement in essential tremor (ET), the most common movement disorder. We collected diffusion MRI and analysed differences in fractional anisotropy (FA) and mean diffusivity (MD) between ET patients and control subjects as markers of white matter integrity. We used both classical ROI-based statistics and whole-brain analysis techniques, including voxel-wise analysis with SPM5 and tract-based spatial statistics (TBSS). Using region of interest (ROI) analysis, we found increased MD bilaterally in the inferior cerebellar peduncles (ICP) and reduced FA in the right-sided ICP of ET patients. Whole-brain analyses with TBSS detected increased MD distributed in both motor and nonmotor white matter fibers of ET patients predominantly in the left parietal white matter, while there were no significant FA differences in these areas between ET patients and controls. Voxel-wise analysis with SPM detected significant increase of MD congruent with the highest probability of difference as detected by TBSS. VBM analysis of T1 images did not detect significant differences in either gray or white matter density between our study groups. In summary, we found evidence for changes in white matter MRI properties in ET. The circumscript pathology of the ICP corroborates the pathogenetic concept of the cerebellum and its projections as key structures for tremor generation in ET. Moreover, increased diffusivity in white matter structures of both hemispheres suggests widespread alterations of fiber integrity in motor and nonmotor networks in ET patients. The underlying cause of the DTI changes observed remains to be elucidated.

Progression of subtle motor signs in PINK1 mutation carriers with mild dopaminergic deficit

BACKGROUND

While homozygous mutations in the PINK1 gene cause recessively inherited early-onset Parkinson disease (PD), heterozygous mutations have been suggested as a susceptibility factor.

METHODS

To evaluate this hypothesis, 4 homozygous PINK1 patients with PD and 10 asymptomatic carriers of a single heterozygous mutation from a large German family (family W) were included in this study. Clinical follow-up of the heterozygous mutation carriers 3 years after the initial visit included a detailed videotaped neurologic examination using the Unified Parkinson's Disease Rating Scale III protocol and smell and color discrimination testing. At follow-up, PET with 18-fluorodopa (FDOPA) of 13 family members was obtained in order to evaluate the clinical phenotype in light of nigostriatal dopaminergic functioning. The clinical and PET data were compared to those of healthy controls.

RESULTS

While there was mild worsening of clinical signs in previously affected heterozygous mutation carriers upon follow-up, 3 additional individuals had newly developed signs of possible PD. Hyposmia was found in 7 of the heterozygous mutation carriers, diminished color discrimination in 4. The homozygous mutation carriers who were all definitely affected with PD showed a severe, 60% decrease of caudate and putaminal FDOPA uptake; heterozygous offspring also had a significant 20% putaminal FDOPA uptake reduction compared to controls.

CONCLUSIONS

Our findings strengthen the hypothesis that heterozygous PINK1 mutations act as a susceptibility factor to develop at least subtle Parkinson disease motor and nonmotor signs, as supported by the finding of a reduced striatal dopaminergic FDOPA uptake not only in homozygous but also, albeit to a lesser extent, in heterozygous mutation carriers.

[Early deep brain stimulation for Parkinson's disease]

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is a powerful treatment for advanced Parkinson's disease with levodopa-induced motor complications. Randomized controlled studies have shown that motor fluctuations and quality of life are significantly more improved by STN-DBS than by best medical treatment. The main delay before neurosurgery is currently 14 years after diagnosis. Clinical pilot data suggest that neurosurgery performed already with beginning motor fluctuations and an average disease duration of 7 years may lead to earlier improvement of motor deficits and quality of life, thus preventing disease-related psycho-social decline, and extending the period of beneficial effects of STN-DBS. Results of an ongoing multicenter trial (EARLYSTIM) comparing the effects of STN-DBS and best medical treatment on motor symptoms, quality of life, and psycho-social adaptation will be available in 2 years time and will clarify whether or not early STN-DBS is superior to best medical treatment.

Neurotransmitter changes in dementia with Lewy bodies and Parkinson disease dementia in vivo

OBJECTIVE

Although Parkinson disease with dementia (PDD) and dementia with Lewy bodies (DLB) show a wide clinical and neuropathologic overlap, they are differentiated according to the order and latency of cognitive and motor symptom appearance. Whether both are distinct disease entities is an ongoing controversy. Therefore, we directly compared patients with DLB and PDD with multitracer PET.

METHODS

PET with (18)fluorodopa (FDOPA), N-(11)C-methyl-4-piperidyl acetate (MP4A), and (18)fluorodeoxyglucose (FDG) was performed in 8 patients with PDD, 6 patients with DLB, and 9 patients with PD without dementia vs age-matched controls. Data were analyzed with voxel-based statistical parametric mapping and region of interest-based statistics.

RESULTS

We found a reduced FDOPA uptake in the striatum and in limbic and associative prefrontal areas in all patient groups. Patients with PDD and patients with DLB showed a severe MP4A and FDG binding reduction in the neocortex with increasing signal diminution from frontal to occipital regions. Significant differences between PDD and DLB were not found in any of the radioligands used. Patients with PD without dementia had a mild cholinergic deficit and no FDG reductions vs controls.

CONCLUSIONS

Patients with dementia with Lewy bodies and Parkinson disease dementia share the same dopaminergic and cholinergic deficit profile in the brain and seem to represent 2 sides of the same coin in a continuum of Lewy body diseases. Cholinergic deficits seem to be crucial for the development of dementia in addition to motor symptoms. The spatial congruence of cholinergic deficits and energy hypometabolism argues for cortical deafferentation due to the degeneration of projection fibers from the basal forebrain.

Phosphorus and proton magnetic resonance spectroscopy demonstrates mitochondrial dysfunction in early and advanced Parkinson's disease

Mitochondrial dysfunction hypothetically contributes to neuronal degeneration in patients with Parkinson's disease. While several in vitro data exist, the measurement of cerebral mitochondrial dysfunction in living patients with Parkinson's disease is challenging. Anatomical magnetic resonance imaging combined with phosphorus and proton magnetic resonance spectroscopic imaging provides information about the functional integrity of mitochondria in specific brain areas. We measured partial volume corrected concentrations of low-energy metabolites and high-energy phosphates with sufficient resolution to focus on pathology related target areas in Parkinson's disease. Combined phosphorus and proton magnetic resonance spectroscopic imaging in the mesostriatal region was performed in 16 early and 13 advanced patients with Parkinson's disease and compared to 19 age-matched controls at 3 Tesla. In the putamen and midbrain of both Parkinson's disease groups, we found a bilateral reduction of high-energy phosphates such as adenosine triphophosphate and phosphocreatine as final acceptors of energy from mitochondrial oxidative phosphorylation. In contrast, low-energy metabolites such as adenosine diphophosphate and inorganic phosphate were within normal ranges. These results provide strong in vivo evidence that mitochondrial dysfunction of mesostriatal neurons is a central and persistent phenomenon in the pathogenesis cascade of Parkinson's disease which occurs early in the course of the disease.

Rapid single-scan T2*-mapping using exponential excitation pulses and image-based correction for linear background gradients

A method for fast quantitative T(2)* mapping based on multiple gradient-echo (multi-GE) imaging with correction for static magnetic field inhomogeneities is described, using an exponential excitation pulse. Field gradient maps are obtained from the phase information and modulus data are subsequently corrected, allowing for simple monoexponential T(2)* fitting. Echoes with long echo times suffering from major signal losses due to field inhomogeneities are excluded from the analysis. The acquisition time for a matrix size of 256 x 256, 1 mm in-plane resolution, and 2 mm slice thickness amounts to 15 s per slice. An additional correction for in-plane field gradients further improves accuracy. Phantom experiments show that the method provides accurate T(2)* values for field gradients up to 200 microT/m; for gradients up to 300 microT/m errors do not exceed 15%. In vivo T(2)* values acquired on healthy volunteers at 3T are in excellent agreement with results from the literature.