Publications by authors named "Benedikt M Frey"

10 Publications

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Safety and efficacy of intravenous thrombolysis in stroke patients on prior antiplatelet therapy in the WAKE-UP trial.

Neurol Res Pract 2020 20;2:40. Epub 2020 Nov 20.

Klinik und Poliklinik für Neurologie, Kopf- und Neurozentrum, University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg, Germany.

Background: One quarter to one third of patients eligible for systemic thrombolysis are on antiplatelet therapy at presentation. In this study, we aimed to assess the safety and efficacy of intravenous thrombolysis in stroke patients on prescribed antiplatelet therapy in the WAKE-UP trial.

Methods: WAKE-UP was a multicenter, randomized, double-blind, placebo-controlled clinical trial to study the efficacy and safety of MRI-guided intravenous thrombolysis with alteplase in patients with an acute stroke of unknown onset time. The medication history of all patients randomized in the WAKE-UP trial was documented. The primary safety outcome was any sign of hemorrhagic transformation on follow-up MRI. The primary efficacy outcome was favorable functional outcome defined by a score of 0-1 on the modified Rankin scale at 90 days after stroke, adjusted for age and baseline stroke severity. Logistic regression models were fitted to study the association of prior antiplatelet treatment with outcome and treatment effect of intravenous alteplase.

Results: Of 503 randomized patients, 164 (32.6%) were on antiplatelet treatment. Patients on antiplatelet treatment were older (70.3 vs. 62.8 years,  <  0.001), and more frequently had a history of hypertension, atrial fibrillation, diabetes, hypercholesterolemia, and previous stroke or transient ischaemic attack. Rates of symptomatic intracranial hemorrhage and hemorrhagic transformation on follow-up imaging did not differ between patients with and without antiplatelet treatment. Patients on prior antiplatelet treatment were less likely to achieve a favorable outcome (37.3% vs. 52.6%,  = 0.014), but there was no interaction of prior antiplatelet treatment with intravenous alteplase concerning favorable outcome ( = 0.355). Intravenous alteplase was associated with higher rates of favorable outcome in patients on prior antiplatelet treatment with an adjusted odds ratio of 2.106 (95% CI 1.047-4.236).

Conclusions: Treatment benefit of intravenous alteplase and rates of post-treatment hemorrhagic transformation were not modified by prior antiplatelet intake among MRI-selected patients with unknown onset stroke. Worse functional outcome in patients on antiplatelets may result from a higher load of cardiovascular co-morbidities in these patients.
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http://dx.doi.org/10.1186/s42466-020-00087-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7678217PMC
November 2020

White matter integrity and structural brain network topology in cerebral small vessel disease: The Hamburg city health study.

Hum Brain Mapp 2021 Apr 8;42(5):1406-1415. Epub 2020 Dec 8.

Department of Neurology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.

Cerebral small vessel disease is a common finding in the elderly and associated with various clinical sequelae. Previous studies suggest disturbances in the integration capabilities of structural brain networks as a mediating link between imaging and clinical presentations. To what extent cerebral small vessel disease might interfere with other measures of global network topology is not well understood. Connectomes were reconstructed via diffusion weighted imaging in a sample of 930 participants from a population based epidemiologic study. Linear models were fitted testing for an association of graph-theoretical measures reflecting integration and segregation with both the Peak width of Skeletonized Mean Diffusivity (PSMD) and the load of white matter hyperintensities of presumed vascular origin (WMH). The latter were subdivided in periventricular and deep for an analysis of localisation-dependent correlations of cerebral small vessel disease. The median WMH volume was 0.6 mL (1.4) and the median PSMD 2.18 mm /s x 10 (0.5). The connectomes showed a median density of 0.880 (0.030), the median values for normalised global efficiency, normalised clustering coefficient, modularity Q and small-world propensity were 0.780 (0.045), 1.182 (0.034), 0.593 (0.026) and 0.876 (0.040) respectively. An increasing burden of cerebral small vessel disease was significantly associated with a decreased integration and increased segregation and thus decreased small-worldness of structural brain networks. Even in rather healthy subjects increased cerebral small vessel disease burden is accompanied by topological brain network disturbances. Segregation parameters and small-worldness might as well contribute to the understanding of the known clinical sequelae of cerebral small vessel disease.
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http://dx.doi.org/10.1002/hbm.25301DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7927298PMC
April 2021

Linking cortical atrophy to white matter hyperintensities of presumed vascular origin.

J Cereb Blood Flow Metab 2020 Dec 1:271678X20974170. Epub 2020 Dec 1.

Department of Neurology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.

We examined the relationship between white matter hyperintensities (WMH) and cortical neurodegeneration in cerebral small vessel disease (CSVD) by investigating whether cortical thickness is a remote effect of WMH through structural fiber tract connectivity in a population at increased risk of CSVD. We measured cortical thickness on T1-weighted images and segmented WMH on FLAIR images in 930 participants of a population-based cohort study at baseline. DWI-derived whole-brain probabilistic tractography was used to define WMH connectivity to cortical regions. Linear mixed-effects models were applied to analyze the relationship between cortical thickness and connectivity to WMH. Factors associated with cortical thickness (age, sex, hemisphere, region, individual differences in cortical thickness) were added as covariates. Median age was 64 [IQR 46-76] years. Visual inspection of surface maps revealed distinct connectivity patterns of cortical regions to WMH. WMH connectivity to the cortex was associated with reduced cortical thickness ( = 0.009) after controlling for covariates. This association was found for periventricular WMH ( = 0.001) only. Our results indicate an association between WMH and cortical thickness via connecting fiber tracts. The results imply a mechanism of secondary neurodegeneration in cortical regions distant, yet connected to subcortical vascular lesions, which appears to be driven by periventricular WMH.
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http://dx.doi.org/10.1177/0271678X20974170DOI Listing
December 2020

Higher white matter hyperintensity lesion load is associated with reduced long-range functional connectivity.

Brain Commun 2020 20;2(2):fcaa111. Epub 2020 Jul 20.

Department of Neurology, University Medical Center Hamburg-Eppendorf, Germany.

Cerebral small vessel disease is a common disease in the older population and is recognized as a major risk factor for cognitive decline and stroke. Small vessel disease is considered a global brain disease impacting the integrity of neuronal networks resulting in disturbances of structural and functional connectivity. A core feature of cerebral small vessel disease commonly present on neuroimaging is white matter hyperintensities. We studied high-resolution resting-state EEG, leveraging source reconstruction methods, in 35 participants with varying degree of white matter hyperintensities without clinically evident cognitive impairment in an observational study. In patients with increasing white matter lesion load, global theta power was increased independently of age. Whole-brain functional connectivity revealed a disrupted network confined to the alpha band in participants with higher white matter hyperintensities lesion load. The decrease of functional connectivity was evident in long-range connections, mostly originating or terminating in the frontal lobe. Cognitive testing revealed no global cognitive impairment; however, some participants revealed deficits of executive functions that were related to larger white matter hyperintensities lesion load. In summary, participants without clinical signs of mild cognitive impairment or dementia showed oscillatory changes that were significantly related to white matter lesion load. Hence, oscillatory neuronal network changes due to white matter lesions might act as biomarker prior to clinically relevant behavioural impairment.
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http://dx.doi.org/10.1093/braincomms/fcaa111DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7585696PMC
July 2020

Network Localisation of White Matter Damage in Cerebral Small Vessel Disease.

Sci Rep 2020 06 8;10(1):9210. Epub 2020 Jun 8.

Department of Neurology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.

Cerebral small vessel disease (CSVD) is a widespread condition associated to stroke, dementia and depression. To shed light on its opaque pathophysiology, we conducted a neuroimaging study aiming to assess the location of CSVD-induced damage in the human brain network. Structural connectomes of 930 subjects of the Hamburg City Health Study were reconstructed from diffusion weighted imaging. The connectome edges were partitioned into groups according to specific schemes: (1) connection to grey matter regions, (2) course and length of underlying streamlines. Peak-width of skeletonised mean diffusivity (PSMD) - a surrogate marker for CSVD - was related to each edge group's connectivity in a linear regression analysis allowing localisation of CSVD-induced effects. PSMD was associated with statistically significant decreases in connectivity of most investigated edge groups except those involved in connecting limbic, insular, temporal or cerebellar regions. Connectivity of interhemispheric and long intrahemispheric edges as well as edges connecting subcortical and frontal brain regions decreased most severely with increasing PSMD. In conclusion, MRI findings of CSVD are associated with widespread impairment of structural brain network connectivity, which supports the understanding of CSVD as a global brain disease. The pattern of regional preference might provide a link to clinical phenotypes of CSVD.
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http://dx.doi.org/10.1038/s41598-020-66013-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7280237PMC
June 2020

The Influence of Cortico-Cerebellar Structural Connectivity on Cortical Excitability in Chronic Stroke.

Cereb Cortex 2020 03;30(3):1330-1344

Department of Neurology, University Medical Centre Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg, Germany.

Brain imaging has recently evidenced that the structural state of distinct reciprocal cortico-cerebellar fiber tracts, the dentato-thalamo-cortical tract (DTCT), and the cortico-ponto-cerebellar tract (CPCeT), significantly influences residual motor output in chronic stroke patients, independent from the level of damage to the corticospinal tract (CST). Whether such structural information might also directly relate to measures of cortical excitability is an open question. Eighteen chronic stroke patients with supratentorial ischemic lesions and 17 healthy controls underwent transcranial magnetic stimulation to assess recruitment curves of motor evoked potentials of both hemispheres. Diffusion-weighted imaging and probabilistic tractography were applied to reconstruct reciprocal cortico-cerebellar motor tracts between the primary motor cortex and the cerebellum. Tract-related microstructure was estimated by means of fractional anisotropy, and linear regression modeling was used to relate it to cortical excitability. The main finding was a significant association between cortical excitability and the structural integrity of the DTCT, the main cerebellar outflow tract, independent from the level of damage to the CST. A comparable relationship was neither detectable for the CPCeT nor for the healthy controls. This finding contributes to a mechanistic understanding of the putative supportive role of the cerebellum for residual motor output by facilitating cortical excitability after stroke.
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http://dx.doi.org/10.1093/cercor/bhz169DOI Listing
March 2020

Characterization of White Matter Hyperintensities in Large-Scale MRI-Studies.

Front Neurol 2019 26;10:238. Epub 2019 Mar 26.

Department of Neurology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.

White matter hyperintensities of presumed vascular origin (WMH) are a common finding in elderly people and a growing social malady in the aging western societies. As a manifestation of cerebral small vessel disease, WMH are considered to be a vascular contributor to various sequelae such as cognitive decline, dementia, depression, stroke as well as gait and balance problems. While pathophysiology and therapeutical options remain unclear, large-scale studies have improved the understanding of WMH, particularly by quantitative assessment of WMH. In this review, we aimed to provide an overview of the characteristics, research subjects and segmentation techniques of these studies. We performed a systematic review according to the PRISMA statement. One thousand one hundred and ninety-six potentially relevant articles were identified via PubMed search. Six further articles classified as relevant were added manually. After applying a catalog of exclusion criteria, remaining articles were read full-text and the following information was extracted into a standardized form: year of publication, sample size, mean age of subjects in the study, the cohort included, and segmentation details like the definition of WMH, the segmentation method, reference to methods papers as well as validation measurements. Our search resulted in the inclusion and full-text review of 137 articles. One hundred and thirty-four of them belonged to 37 prospective cohort studies. Median sample size was 1,030 with no increase over the covered years. Eighty studies investigated in the association of WMH and risk factors. Most of them focussed on arterial hypertension, diabetes mellitus type II and Apo E genotype and inflammatory markers. Sixty-three studies analyzed the association of WMH and secondary conditions like cognitive decline, mood disorder and brain atrophy. Studies applied various methods based on manual (3), semi-automated (57), and automated segmentation techniques (75). Only 18% of the articles referred to an explicit definition of WMH. The review yielded a large number of studies engaged in WMH research. A remarkable variety of segmentation techniques was applied, and only a minority referred to a clear definition of WMH. Most addressed topics were risk factors and secondary clinical conditions. In conclusion, WMH research is a vivid field with a need for further standardization regarding definitions and used methods.
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http://dx.doi.org/10.3389/fneur.2019.00238DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6443932PMC
March 2019

Association of Extrapyramidal Tracts' Integrity With Performance in Fine Motor Skills After Stroke.

Stroke 2018 12;49(12):2928-2932

From the Department of Neurology, University Medical Center Hamburg-Eppendorf, Germany (L.R., B.M.F., B.C., R.S., L.A.K., M.B., H.B., C.G., G.T.).

Background and Purpose- Tractography by diffusion tensor imaging has extended our knowledge on the contribution of damage to different pathways to residual motor function after stroke. Integrity of the corticospinal tract (CST), for example, has been identified to characterize and predict its course. Yet there is only scarce data that allow a judgment on the impact of extrapyramidal pathways between the basal ganglia on motor function poststroke. We aimed at studying their association with performance in fine motor skills after stroke. Methods- We performed probabilistic tractography and reconstructed nigro-pallidal tracts connecting substantia nigra and globus pallidus, as well as the CST in 26 healthy subjects. Resulting tracts were registered to the individual images of 20 patients 3 months after stroke, and their microstructural integrity was measured by fractional anisotropy. Clinical examination of the patients' gross (grip force) and fine (nine-hole peg test) motor skills was performed 1 year after stroke. For assessment of factors influencing nine-hole peg test, we used a multivariate model. Results- Nigro-pallidal tracts were traceable in all participants, had no overlap to the CST and passed the nucleus subthalamicus. In stroke patients, nigro-pallidal tracts ipsilateral to the stroke lesion showed a significantly reduced fractional anisotropy (ratio, 0.96±0.02; P=0.021). One year after stroke, nine-hole peg test values were significantly slower for the affected hand, while grip force was comparable between both hands. Reduced integrity of the nigro-pallidal tracts was associated with worse performance in the nine-hole peg test ( P=0.040), as was reduced integrity of the CST ( P<0.001) and younger age ( P<0.001). Conclusions- Nigro-pallidal tracts with containing connections of the nucleus subthalamicus represent a relevant part of the extrapyramidal system and specifically contribute to residual fine motor skills after stroke beyond the well-known contribution of the CST. They may deliver supportive information for prediction of motor recovery after stroke.
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http://dx.doi.org/10.1161/STROKEAHA.118.022706DOI Listing
December 2018

Enhanced Effective Connectivity Between Primary Motor Cortex and Intraparietal Sulcus in Well-Recovered Stroke Patients.

Stroke 2016 Feb 7;47(2):482-9. Epub 2016 Jan 7.

From the Department of Neurology (R.S., B.M.F., M.B., B.C., G.T., F.C.H., C.G.) and Department of Medical Biometry and Epidemiology (A.B.), University Medical Center Hamburg-Eppendorf, Hamburg, Germany.

Background And Purpose: Ischemic strokes with motor deficits lead to widespread changes in neural activity and interregional coupling between primary and secondary motor areas. Compared with frontal circuits, the knowledge is still limited to what extent parietal cortices and their interactions with frontal motor areas undergo plastic changes and might contribute to residual motor functioning after stroke.

Methods: Fifteen well-recovered patients were evaluated 3 months after stroke by means of functional magnetic resonance imaging while performing visually guided hand grips with their paretic hand. Dynamic causal modeling was used to investigate task-related effective connectivity between ipsilesional posterior parietal regions along the intraparietal sulcus and frontal key motor areas, such as the primary motor cortex, the ventral premotor cortex, and the supplementary motor area.

Results: Compared with healthy controls of similar age and sex, we observed significantly enhanced reciprocal facilitatory connectivity between the primary motor cortex and the anterior intraparietal sulcus of the ipsilesional hemisphere. Beyond that and as a fingerprint of excellent recovery, the coupling pattern of the parietofrontal network was near-normal. An association between coupling parameters and clinical scores was not detected.

Conclusions: The present analysis further adds to the understanding of the parietofrontal network of the ipsilesional hemisphere as a prominent circuit involved in plastic changes after stroke.
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http://dx.doi.org/10.1161/STROKEAHA.115.011641DOI Listing
February 2016

Cortico-Cerebellar Structural Connectivity Is Related to Residual Motor Output in Chronic Stroke.

Cereb Cortex 2017 01;27(1):635-645

BrainImaging and NeuroStimulation (BINS) Laboratory, Department of Neurology.

Functional imaging studies have argued that interactions between cortical motor areas and the cerebellum are relevant for motor output and recovery processes after stroke. However, the impact of the underlying structural connections is poorly understood. To investigate this, diffusion-weighted brain imaging was conducted in 26 well-characterized chronic stroke patients (aged 63 ± 1.9 years, 18 males) with supratentorial ischemic lesions and 26 healthy participants. Probabilistic tractography was used to reconstruct reciprocal cortico-cerebellar tracts and to relate their microstructural integrity to residual motor functioning applying linear regression modeling. The main finding was a significant association between cortico-cerebellar structural connectivity and residual motor function, independent from the level of damage to the cortico-spinal tract. Specifically, white matter integrity of the cerebellar outflow tract, the dentato-thalamo-cortical tract, was positively related to both general motor output and fine motor skills. Additionally, the integrity of the descending cortico-ponto-cerebellar tract contributed to rather fine motor skills. A comparable structure-function relationship was not evident in the controls. The present study provides first tract-related structural data demonstrating a critical importance of distinct cortico-cerebellar connections for motor output after stroke.
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http://dx.doi.org/10.1093/cercor/bhv251DOI Listing
January 2017