Time filter

Source Type

Heeze, Netherlands

Gupta D.,Radboud University Nijmegen | Ossenblok P.,Epilepsy Center Kempenhaeghe | Van Luijtelaar G.,Radboud University Nijmegen
Medical and Biological Engineering and Computing | Year: 2011

To describe the spatial and temporal profiles of connectivity networks and sources preceding generalized spike-and-wave discharges (SWDs) in human absence epilepsy. Nonlinear associations of MEG signals and cluster indices obtained within the framework of graph theory were determined, while source localization in the frequency domain was performed in the low frequency bands with dynamic imaging of coherent sources. The results were projected on a three-dimensional surface rendering of the brain using a semi-realistic head model and MRI images obtained for each of the five patients studied. An increase in clustering and a decrease in path length preceding SWD onset and a rhythmic pattern of increasing and decreasing connectivity were seen during SWDs. Beamforming showed a consistent appearance of a low frequency frontal cortical source prior to the first generalized spikes. This source was preceded by a low frequency occipital source. The changes in the connectivity networks with the onset of SWDs suggest a pathologically predisposed state towards synchronous seizure networks with increasing connectivity from interictal to preictal and ictal state, while the occipital and frontal low frequency early preictal sources demonstrate that SWDs are not suddenly arising but gradually build up in a dynamic network. © 2011 International Federation for Medical and Biological Engineering.

Kleine B.U.,Radboud University Nijmegen | Boekestein W.A.,Spectrum | Arts I.M.P.,Radboud University Nijmegen | Zwarts M.J.,Epilepsy Center Kempenhaeghe | And 3 more authors.
Clinical Neurophysiology | Year: 2012

Objective: To compare the prevalence of fasciculation potentials (FPs) with F-responses between patients with amyotrophic lateral sclerosis (ALS) and patients with benign fasciculations. Methods: In seven patients with ALS and seven patients with benign fasciculations, high-density surface EMG was recorded for 15. min from the gastrocnemius muscle. Template matching was used to search for pairs of FPs with a repetition within 10-110. ms. Results: Interspike interval (ISI) histograms were constructed from 282 pairs of benign fasciculations and from 337 FP pairs in ALS. Peaks attributable to F-waves were found at latencies of 32. ms (benign) and 35. ms (ALS). Five patients with benign fasciculations and four patients with ALS had FPs with F-waves. Conclusions: F-waves of FPs occur in both conditions - therefore they are not diagnostically helpful. Significance: F-waves confirm the distal origin of FPs for an individual axon. The occurrence of these FPs in a benign condition suggests that the generation of ectopic discharges in the distal axons is not specific to progressive neurodegeneration. © 2011 International Federation of Clinical Neurophysiology.

Hurks P.P.M.,Maastricht University | Hendriksen J.G.M.,Academic Hospital Maastricht | Hendriksen J.G.M.,Epilepsy Center Kempenhaeghe
Child Neuropsychology | Year: 2011

Time estimation is believed to be an adaptive function in human life. In the present study, prospective and retrospective time estimation are studied in both clinical-referred school-aged children with ADHD-C and healthy community control children, while examining more specifically the effects of type of time estimation task, length of time intervals (i.e., ranging from 3-90 s), and continuous scaling of the main ADHD symptom clusters (i.e., inattention vs. hyperactivity/impulsiveness). On a prospective verbal time estimation test, children with ADHD-C showed significant more overestimation compared to controls. For the majority of short-to-medium time intervals, this overestimation was predicted only by the continuous levels of impulsiveness or a disturbed self-regulation, indicating a dysregulation of the internal clock in ADHD. The same holds for the retrospective time estimation task. In contrast, an ADHD-related underestimation on the prospective time reproduction task was found for the longer intervals. In contrast to verbal time estimation, levels of inattention, and not the levels of impulsiveness, predicted underestimation on the time reproduction task. Our results point thereby towards parallel networks for regulating attention/working memory versus impulse regulation/inhibition as potential loci for dysfunction. These results are in contrast to the frequently cited global inhibitory executive function deficit hypothesis. © 2010 Psychology Press, an imprint of the Taylor & Francis Group, an Informa business.

Klaver-Krol E.G.,Hospital Group Twente ZGT | Zwarts M.J.,Epilepsy Center Kempenhaeghe | ten Klooster P.M.,Radboud University Nijmegen | Rasker J.J.,University of Twente
Clinical and Experimental Rheumatology | Year: 2012

Objective: Fibromyalgia (FM) is a disorder characterised by chronic widespread pain in soft tissues, especially in muscles. Previous research has demonstrated a higher muscle fibre conduction velocity (CV) in painful muscles of FM patients. The primary goal of this study was to investigate whether there is also a difference in CV in non-painful, non-tender point (TP) related muscles between FM patients and controls. The secondary goal was to explore associations between the CV, the number of TPs and the complaints in FM. Methods: Surface electromyography (sEMG) was performed on the biceps brachii muscle of female FM patients (13) and matched healthy controls (13). Short static contractions were applied with the arm unloaded and loaded at 5% and 10% of maximum voluntary force. The CV was derived by cross-correlation method (CV-cc) and inter-peak latency method (CV-ipl). TP score and Fibromyalgia Impact Questionnaire (FIQ) were performed in all participants. Correlations were calculated between the CVs, TP score and items of the FIQ. Results: In FM patients, the CV was higher than in the controls (CV-cc p=0.005; CV-ipl p=0.022). The CV was correlated with the number of TPs in FM patients (r=0.642 and 0.672 for CVcc and CV-ipl, respectively). No correlations were found between the CV and any aspect of health status on the FIQ. Conclusion: The results demonstrate abnormally high muscle membrane conduction velocity in FM, even in non-TP muscles. In addition, a relationship has been found between the high membrane velocity and the number of TPs. © Clinical and experimental rheumatology 2012.

Helmstaedter C.,University of Bonn | Aldenkamp A.P.,Epilepsy Center Kempenhaeghe | Aldenkamp A.P.,Maastricht University | Baker G.A.,University of Liverpool | And 3 more authors.
Epilepsy and Behavior | Year: 2014

It has been long recognized that there is more to epilepsy than seizures. The prevalence of such neurobehavioral abnormalities as cognitive and mood disorders, autism spectrum disorder, and attention deficit and hyperactivity disorder (ADHD) is significantly higher among patients with epilepsy than in the general population. A long-held view that comorbidities of epilepsy represent mere epiphenomena of seizures has undergone substantial transformation during the past decade, as emerging clinical evidence and experimental evidence suggest the involvement of specific neurobiological mechanisms in the evolution of neurobehavioral deficits in patients with epilepsy. Developmental aspects of both epilepsy and its comorbidities, as well as the frequently reported reciprocal connection between these disorders, both add other dimensions to the already complex problem.In light of progress in effective seizure management in many patients with epilepsy, the importance of neurobehavioral comorbidities has become acute, as the latter are frequently more detrimental to patients' quality of life compared with seizures. This calls for a serious increase in efforts to effectively predict, manage, and ideally cure these comorbidities. Coordinated multicenter clinical, translational, and basic research studies focusing on epidemiology, neuropsychology, neurophysiology, imaging, genetics, epigenetics, and pharmacology of neurobehavioral comorbidities of epilepsy are absolutely instrumental for ensuring tangible progress in the field. Clinical research should focus more on new-onset epilepsy and put particular emphasis on longitudinal studies in large cohorts of patients and groups at risk, while translational research should primarily focus on the development of valid preclinical systems which would allow investigating the fundamental mechanism of epilepsy comorbidities.The final goal of the described research efforts would lie in producing an armamentarium of evidence-based diagnostic tools and therapeutic interventions which would at minimum mitigate and at maximum prevent or abolish neurobehavioral comorbidities of epilepsy and, thus, improve the quality of life of those patients with epilepsy who suffer from the said comorbidities. © 2013 Elsevier Inc.

Discover hidden collaborations