Manual for clinical language tractography

Wir stellen ein benutzerfreundliches, standardisiertes Protokoll für die Traktografie der wichtigsten Sprachfaserbündel des perisylvischen Sprachnetzwerks vor. Die Traktografie benötigt diffusionsgewichtete Magnetresonanztomografie (dMRT) Bilder, während die region of interest (ROI)-Definition auf strukturellen T1 MPRAGE (magnetization-prepared radio-frequency pulses and rapid gradient-echo) MRT-Vorlagen basiert, ohne eine räumliche Normalisierung in den Montreal Neurological Institute (MNI)-Raum. ROI’s für fünf sprachrelevante Faserbündel wurden in einer axialen, koronalen oder sagittalen Ansicht von T1 MPRAGE Bildern visualisiert. Die ROI’s wurden auf der Grundlage der obligaten Wege der Faserbündel definiert, die sich aus der Literatur und eigenen Erfahrungen in der peritumoralen Traktografie ableiten lassen. Die resultierende Anleitung wurde für jedes Faserbündel bei 10 gesunden Probanden und 10 Patienten von einem Experten und drei Untersuchern bewertet. Insgesamt wurden 300 ROI’s gesetzt und verglichen. Die angestrebten Sprachfaserbündel konnten in 88% der ROI-Paare verfolgt werden, basierend auf dem Ergebnis der Blindstudie. Die Auswertung ergab, dass die Präzision der ROI’s nicht mit der unterschiedlichen Erfahrung der Untersucher zusammenhängt. Unser Leitfaden stellt eine standardisierte Sprach-Traktografie Methode für die routinemäßige, präoperative Aufarbeitung und für Forschungskontexte vor. Die ROI-Platzierungsanleitung, die auf leicht zu identifizierenden anatomischen Landmarken basiert, hat sich auch bei unerfahrenen Untersuchern als benutzerfreundlich und genau erwiesen.We introduce a user-friendly, standardized protocol for tractography of the major language fiber bundles of the perisylvian language network. The introduced method uses dMRI (diffusion magnetic resonance imaging) images whereas the region of interest (ROI)-definition is based on structural T1 magnetization-prepared radio-frequency pulses and rapid gradient-echo (MPRAGE) MRI templates, without a spatial normalization to Montreal Neurological Institute (MNI) space. ROI’s for five language relevant fiber bundles were visualized on an axial, coronal or sagittal view of T1 MPRAGE images. The ROI’s were defined based upon the tracts’ obligatory pathways, derived from literature and own experiences in peritumoral tractography. The resulting guideline was evaluated for each fiber bundle in 10 healthy subjects and 10 patients by one expert and three test persons. Overall 300 ROI’s were evaluated and compared. The targeted language fiber bundles could be tracked in 88% of the ROI pairs, based on the raters’ result blinded ROI placements. The evaluation indicated that the precision of the ROI’s didn’t relate to the varying experience of the raters. Our guideline introduces a standardized language tractography method for routine preoperative work up and for research contexts. The ROI placement guideline based on easy to identify anatomical landmarks proved to be user-friendly and accurate, also in inexperienced test persons

The digital twin in neuroscience: from theory to tailored therapy

Digital twins enable simulation, comprehensive analysis and predictions, as virtual representations of physical systems. They are also finding increasing interest and application in the healthcare sector, with a particular focus on digital twins of the brain. We discuss how digital twins in neuroscience enable the modeling of brain functions and pathology as they offer an in-silico approach to studying the brain and illustrating the complex relationships between brain network dynamics and related functions. To showcase the capabilities of digital twinning in neuroscience we demonstrate how the impact of brain tumors on the brain’s physical structures and functioning can be modeled in relation to the philosophical concept of plasticity. Against this technically derived backdrop, which assumes that the brain’s nonlinear behavior toward improvement and repair can be modeled and predicted based on MRI data, we further explore the philosophical insights of Catherine Malabou. Malabou emphasizes the brain’s dual capacity for adaptive and destructive plasticity. We will discuss in how far Malabou’s ideas provide a more holistic theoretical framework for understanding how digital twins can model the brain’s response to injury and pathology, embracing Malabou’s concept of both adaptive and destructive plasticity which provides a framework to address such yet incomputable aspects of neuroscience and the sometimes seemingly unfavorable dynamics of neuroplasticity helping to bridge the gap between theoretical research and clinical practice

The effect of CSF drain on the optic nerve in idiopathic intracranial hypertension

Background: Elevation of intracranial pressure in idiopathic intracranial hypertension induces an edema of the prelaminar section of the optic nerve (papilledema). Beside the commonly observed optic nerve sheath distention, information on a potential pathology of the retrolaminar section of the optic nerve and the short-term effect of normalization of intracranial pressure on these abnormalities remains scarce. Methods: In this exploratory study 8 patients diagnosed with idiopathic intracranial hypertension underwent a MRI scan (T2 mapping) as well as a diffusion tensor imaging analysis (fractional anisotropy and mean diffusivity). In addition, the clinical presentation of headache and its accompanying symptoms were assessed. Intracranial pressure was then normalized by lumbar puncture and the initial parameters (MRI and clinical features) were re-assessed within 26 h. Results: After normalization of CSF pressure, the morphometric MRI scans of the optic nerve and optic nerve sheath remained unchanged. In the diffusion tensor imaging, the fractional anisotropy value was reduced suggesting a tissue decompression of the optic nerve after lumbar puncture. In line with these finding, headache and most of the accompanying symptoms also improved or remitted within that short time frame. Conclusion: The findings support the hypothesis that the elevation of intracranial pressure induces a microstructural compression of the optic nerve impairing axoplasmic flow and thereby causing the prelaminar papilledema. The microstructural compression of the optic nerve as well as the clinical symptoms improve within hours of normalization of intracranial pressure

Letter: A Note on Neurosurgical Resection and Why We Need to Rethink Cutting

Peer Reviewe

Diagnostic reliability of the Berlin classification for complex MCA aneurysms—usability in a series of only giant aneurysms

Background and objective The main challenge of bypass surgery of complex MCA aneurysms is not the selection of the bypass type but the initial decision-making of how to exclude the affected vessel segment from circulation. To this end, we have previously proposed a classification for complex MCA aneurysms based on the preoperative angiography. The current study aimed to validate this new classification and assess its diagnostic reliability using the giant aneurysm registry as an independent data set. Methods We reviewed the pretreatment neuroimaging of 51 patients with giant (> 2.5 cm) MCA aneurysms from 18 centers, prospectively entered into the international giant aneurysm registry. We classified the aneurysms according to our previously proposed Berlin classification for complex MCA aneurysms. To test for interrater diagnostic reliability, the data set was reviewed by four independent observers. Results We were able to classify all 51 aneurysms according to the Berlin classification for complex MCA aneurysms. Eight percent of the aneurysm were classified as type 1a, 14% as type 1b, 14% as type 2a, 24% as type 2b, 33% as type 2c, and 8% as type 3. The interrater reliability was moderate with Fleiss's Kappa of 0.419. Conclusion The recently published Berlin classification for complex MCA aneurysms showed diagnostic reliability, independent of the observer when applied to the MCA aneurysms of the international giant aneurysm registry.Peer reviewe

Diagnostic reliability of the Berlin classification for complex MCA aneurysms-usability in a series of only giant aneurysms

BACKGROUND AND OBJECTIVE The main challenge of bypass surgery of complex MCA aneurysms is not the selection of the bypass type but the initial decision-making of how to exclude the affected vessel segment from circulation. To this end, we have previously proposed a classification for complex MCA aneurysms based on the preoperative angiography. The current study aimed to validate this new classification and assess its diagnostic reliability using the giant aneurysm registry as an independent data set. METHODS We reviewed the pretreatment neuroimaging of 51 patients with giant (> 2.5 cm) MCA aneurysms from 18 centers, prospectively entered into the international giant aneurysm registry. We classified the aneurysms according to our previously proposed Berlin classification for complex MCA aneurysms. To test for interrater diagnostic reliability, the data set was reviewed by four independent observers. RESULTS We were able to classify all 51 aneurysms according to the Berlin classification for complex MCA aneurysms. Eight percent of the aneurysm were classified as type 1a, 14% as type 1b, 14% as type 2a, 24% as type 2b, 33% as type 2c, and 8% as type 3. The interrater reliability was moderate with Fleiss's Kappa of 0.419. CONCLUSION The recently published Berlin classification for complex MCA aneurysms showed diagnostic reliability, independent of the observer when applied to the MCA aneurysms of the international giant aneurysm registry

Detecting Corticospinal Tract Impairment in Tumor Patients With Fiber Density and Tensor-Based Metrics

Tumors infiltrating the motor system lead to significant disability, often caused by corticospinal tract injury. The delineation of the healthy-pathological white matter (WM) interface area, for which diffusion magnetic resonance imaging (dMRI) has shown promising potential, may improve treatment outcome. However, up to 90% of white matter (WM) voxels include multiple fiber populations, which cannot be correctly described with traditional metrics such as fractional anisotropy (FA) or apparent diffusion coefficient (ADC). Here, we used a novel fixel-based along-tract analysis consisting of constrained spherical deconvolution (CSD)-based probabilistic tractography and fixel-based apparent fiber density (FD), capable of identifying fiber orientation specific microstructural metrics. We addressed this novel methodology’s capability to detect corticospinal tract impairment. We measured and compared tractogram-related FD and traditional microstructural metrics bihemispherically in 65 patients with WHO grade III and IV gliomas infiltrating the motor system. The cortical tractogram seeds were based on motor maps derived by transcranial magnetic stimulation. We extracted 100 equally distributed cross-sections along each streamline of corticospinal tract (CST) for along-tract statistical analysis. Cross-sections were then analyzed to detect differences between healthy and pathological hemispheres. All metrics showed significant differences between healthy and pathologic hemispheres over the entire tract and between peritumoral segments. Peritumoral values were lower for FA and FD, but higher for ADC within the entire cohort. FD was more specific to tumor-induced changes in CST than ADC or FA, whereas ADC and FA showed higher sensitivity. The bihemispheric along-tract analysis provides an approach to detect subject-specific structural changes in healthy and pathological WM. In the current clinical dataset, the more complex FD metrics did not outperform FA and ADC in terms of describing corticospinal tract impairment.Peer Reviewe