Michael Buchfelder

YNICL Journal 2018 Journal Article

Coregistrating magnetic source and magnetic resonance imaging for epilepsy surgery in focal cortical dysplasia

• Burkhard S. Kasper
• Karl Rössler
• Hajo M. Hamer
• Arnd Dörfler
• Ingmar Blümcke
• Roland Coras
• Julie Roesch
• Angelika Mennecke

Background: Epilepsy surgery for focal cortical dysplasia type II (FCD II) offers good chances for seizure freedom, but remains a challenge with respect to lesion detection, defining the epileptogenic zone and the optimal resection strategy. Integrating results from magnetic source imaging from magnetoencephalography (MEG) with magnetic resonance imaging (MRI) including MRI postprocessing may be useful for optimizing these goals. Methods: We here present data from 21 adult FCD II patients, investigated during a 10 year period and evaluated including magnetic source imaging. 16 patients had epilepsy surgery, i.e. histopathologically verified FCD II, and a long follow up. We present our analysis of epileptogenic zones including MEG in relation to structural data according to MRI data and relate these results to surgical outcomes. Results: FCD II in our cohort was characterized by high MEG yield and localization accuracy and MEG showed impact on surgical success-rates. MEG source localizations were detected in 95.2% of patients and were as close as 12.3 ± 8,1 mm to the MRI-lesion. After a mean follow up of >3 years, we saw >80% Engel I outcomes, with more favourable outcomes when the MEG source was completely resected (Fishers exact test 0,033). Conclusion: We argue for a high value of conducting a combined MEG-MRI approach in the presurgical workup and the resection strategy in patients with FCD II related epilepsy.

YNICL Journal 2017 Journal Article

The delta between postoperative seizure freedom and persistence: Automatically detected focal slow waves after epilepsy surgery

• Margit Schönherr
• Hermann Stefan
• Hajo M. Hamer
• Karl Rössler
• Michael Buchfelder
• Stefan Rampp

OBJECTIVE: In this study, we use a novel automated method for localization and quantitative comparison of magnetoencephalographic (MEG) delta activity in patients with and without recurrent seizures after epilepsy surgery as well as healthy controls. METHODS: We identified the generators of delta activity by source location in frequency domain between 1 and 4 Hz in spontaneous MEG data. Comparison with healthy control subjects by z-transform emphasized relative changes of activation in patients. The individual results were compared to spike localizations and statistical group analysis was performed. Additionally, MEG results were compared to 1-4 Hz activity in invasive EEG (iEEG) in two patients, in whom this data was available. RESULTS: Patients with recurrent seizures exhibited significantly increased focal MEG delta activity both in comparison to healthy controls and seizure free patients. This slow activity showed a correlation to interictal epileptic activity and was not explained by consequences of the resection alone. In two patients with iEEG, iEEG analysis was concordant with the MEG findings. SIGNIFICANCE: The quantity of delta activity could be used as a diagnostic marker for recurrent seizures. The close relation to epileptic spike localizations and the resection volume of patients with successful second surgery imply involvement in seizure recurrence. This initial evidence suggests a potential application in the planning of second epilepsy surgery.

YNIMG Journal 2010 Journal Article

Insight into the patterns of cerebrospinal fluid flow in the human ventricular system using MR velocity mapping

• Andreas Stadlbauer
• Erich Salomonowitz
• Wilma van der Riet
• Michael Buchfelder
• Oliver Ganslandt

The patterns of cerebrospinal fluid (CSF) flow within the human ventricular system are still not fully understood in all their complexity. Knowledge is based on either the interpretation of CSF flow curves or computational simulations. Both approaches only provide an incomplete insight into the spatial and temporal dynamics of CSF flow. Time-resolved three-dimensional magnetic resonance velocity mapping has previously been used to investigate normal and pathologic blood flow patterns in the human vascular system. Here we used this technique to study the spatial and temporal dynamics of CSF flow in the ventricular system of 40 normal volunteers. Classification of the patterns of CSF flow based on calculation of three-dimensional particle path lines over the cardiac cycle revealed one uniform flow pattern for the lateral ventricles, three categories for the third and two categories for the fourth ventricle. We found no significant aging effects on either the presence of a specific CSF flow pattern or on CSF flow velocities. Our results provide the first detailed demonstration of the patterns of CSF flow within the human ventricular system.

YNIMG Journal 2009 Journal Article

Prediction of visual field deficits by diffusion tensor imaging in temporal lobe epilepsy surgery

• Xiaolei Chen
• Daniel Weigel
• Oliver Ganslandt
• Michael Buchfelder
• Christopher Nimsky

Visual field deficits due to optic radiation injury are a common complication of temporal lobectomy in epilepsy surgery. In this prospective study, diffusion tensor imaging (DTI) based fiber tracking was performed on 48 patients who had temporal lobectomy for pharmaco-resistant epilepsy. Pre- and intra-operative DTI based fiber tracking was used to visualize the optic radiation and to predict the post-operative visual field defects. The course of the optic radiation could be successfully reconstructed by DTI based fiber tracking. There was a significant correlation between the fiber tracking estimation and the outcome of visual field deficits after surgery. The Receiver Operating Characteristic (ROC) curve analysis confirmed the accuracy and validity of prediction of the post-operative visual field deficits comparing pre- and intra-operative fiber tracking results. Intra-operative visualization of the optic radiation may help in avoiding post-operative visual field deficits.

YNIMG Journal 2007 Journal Article

Diffusion tensor imaging and optimized fiber tracking in glioma patients: Histopathologic evaluation of tumor-invaded white matter structures

• Andreas Stadlbauer
• Christopher Nimsky
• Rolf Buslei
• Erich Salomonowitz
• Thilo Hammen
• Michael Buchfelder
• Ewald Moser
• Antje Ernst-Stecken

Fiber tracking is increasingly used to plan and guide neurosurgical procedures of intracranial tumors in the vicinity of functionally important areas of the brain. However, valid data concerning the reliability of tracking with respect to the actual pathoanatomical situation are lacking. We retrospectively correlated fiber tracking based on magnetic resonance (MR) DT imaging with the histopathological data of 25 patients with WHO grade II and III gliomas. Fiber tracking using the Fiber Assignment by Continuous Tracking (FACT) method was performed to investigate the integrity of white matter tracts in the surrounding border zone of the lesions. The tracking procedure was stopped when fractional anisotropy (FA) thresholds=0. 1, 0. 15, 0. 2, 0. 25, and 0. 3, or a tract turning angle >60° were encountered. In 9 patients we were able to reconstruct brain fiber tracts at biopsy loci (2–32% tumor infiltration) using an FA threshold of 0. 15 and 0. 2, but not for a threshold of 0. 25 or 0. 3. The neurological outcome demonstrated potential tumor cell infiltration of functionally intact brain fiber tracts in the range of 2–8%. These findings may be useful in planning therapeutic approaches to gliomas in the vicinity of eloquent brain regions.

YNIMG Journal 2006 Journal Article

Combining fMRI and MEG increases the reliability of presurgical language localization: A clinical study on the difference between and congruence of both modalities

• Peter Grummich
• Christopher Nimsky
• Elisabeth Pauli
• Michael Buchfelder
• Oliver Ganslandt

To avoid neurological impairment during surgery near language-related eloquent brain areas, we performed presurgical functional brain mapping with functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG) in 172 patients using language tasks. For MEG localizations, we used either a moving equivalent-current dipole fit or a current–density reconstruction using a minimum variance beamformer with a spatial filter algorithm. We localized the Wernicke and Broca language areas for every patient. We integrated the results into a frameless stereotaxy system. To visualize the results in the navigation microscope during surgery, we superimposed the fMRI and MEG findings on the brain surface. MEG and fMRI results differed in 4% of cases, and in 19%, one modality showed activation but not the other. In the vicinity of large gliomas, the BOLD (blood oxygenation level-dependent) effect was suppressed in 53% of our patients. Of the 124 patients who had surgery, only 7 patients (5. 6%) experienced a transient language deterioration, which resolved in all cases. We used MEG and fMRI to show different aspects of brain activity and to establish validation between MEG and fMRI. We conclude that measurement by both MEG and fMRI increases the degree of reliability of language area localization and that the combination of fMRI and MEG is useful for presurgical localization of language-related eloquent cortex.

YNIMG Journal 2000 Journal Article

Presurgical noninvasive localization of speech related brain areas by magnetoencephalography confirmed by direct electrocorticography

• Martin Moeller
• Oliver Ganslandt
• Helmut Kober
• Christopher Nimsky
• Michael Buchfelder
• Elisabeth Pauli
• Herman Stefan
• Rudolf Fahlbusch