[Complication after Embolization of an AVM with Onyx]. / Komplikation nach Embolisation einer AVM mit Onyx.

Report on a 34-year-old woman with an arteriovenous malformation (AVM) in the area of the right hippocampus. On the basis of an interdisciplinary indication for step-by-step embolization of the AVM, the first partial embolization with Onyx occurred successfully and without complications. 10 days later, the second partial embolization also turned out well, but during retraction of the microcatheter an exit of Onyx happened into the guiding catheter in spite of continuous aspiration. From there the embolic material was carried off to the carotid T during the control angiography. Despite several efforts of retraction and fragmentation of the dislocated Onyx, finally infarctions with hemiparesis and aphasia resulted in the areas of the terminal branches of the left middle cerebral artery and the left pericallosal artery. However, the expert opinion could not ascertain a malpractice in the treatment of the AVM. Therefore, a suit was not filed against the interventional neuroradiologist.

Internal carotid artery injury during functional endoscopic sinus surgery and its management.

Rupture of the internal carotid artery (ICA) during functional endoscopic sinus surgery (FESS) is a rare complication, which can potentially result in death. Only a few cases have been reported in the literature thus far. We present four cases with an ICA bleeding during sphenoidotomy. The treatment is discussed and an emergency plan to manage the heavy arterial bleeding is presented.

Three-dimensional visualization of neurovascular relationships in the posterior fossa: technique and clinical application.

OBJECT: The goal of this study was to describe the authors' technique for three-dimensional (3D) visualization of neurovascular relationships in the posterior fossa at the surface of the brainstem. This technique is based on the processing of high-resolution magnetic resonance (MR) imaging data. The principles and technical details involved in the accurate simultaneous visualization of vessels and cranial nerves as tiny structures are presented using explicit and implicit segmentation as well as volume rendering. METHODS: In this approach 3D MR constructive interference in steady state imaging data served as the source for image processing, which was performed using the Linux-based software tools SegMed for segmentation and Qvis for volume rendering. A sequence of filtering operations (including noise reduction and closing) and other software tools such as volume growing are used for a semiautomatic coarse segmentation. The subsequent 3D visualization in which implicit segmentation is used for the differentiation of cranial nerves, vessels, and brainstem is achieved by allocating opacity and color values and adjusting the related transfer functions. This method was applied to the presurgical evaluation in a consecutive series of 55 patients with neurovascular compression syndromes and the results were correlated to surgical findings. The potential for its use, further developments, and remaining problems are discussed. CONCLUSIONS: This method provides an excellent intraoperative real-time virtual view of difficult anatomical relationships.

CT angiography of intracranial aneurysms: a focus on postprocessing.

Computed tomographic (CT) angiography is a well-known tool for detection of intracranial aneurysms and the planning of therapeutic intervention. Despite a wealth of existing studies and an increase in image quality due to use of multisection CT and increasingly sophisticated postprocessing tools such as direct volume rendering, CT angiography has still not replaced digital subtraction angiography as the standard of reference for detection of intracranial aneurysms. One reason may be that CT angiography is still not a uniformly standardized method, particularly with regard to image postprocessing. Several methods for two- and three-dimensional visualization can be used: multiplanar reformation, maximum intensity projection, shaded surface display, and direct volume rendering. Pitfalls of CT angiography include lack of visibility of small arteries, difficulty differentiating the infundibular dilatation at the origin of an artery from an aneurysm, the kissing vessel artifact, demonstration of venous structures that can simulate aneurysms, inability to identify thrombosis and calcification on three-dimensional images, and beam hardening artifacts produced by aneurysm clips. Finally, an algorithm for the safe and useful application of CT angiography in patients with subarachnoid hemorrhage has been developed, which takes into account the varying quality of equipment and software at different imaging centers.

Standardized evaluation of CT angiography with remote generation of 3D video sequences for the detection of intracranial aneurysms.

Computed tomography (CT) angiography is a well-known imaging technique commonly applied to both the detection and therapy planning of intracranial aneurysms. For this purpose, current studies predominantly focus on three-dimensional (3D) representations of CT angiographic volumes obtained with varying visualization approaches on different computers. Interactive manipulation performed by users individually is an important prerequisite for data analysis. However, this leads to inconsistent and barely reproducible 3D visualization results. Furthermore, the quality of any 3D representation depends on the applied visualization strategy (eg, maximum-intensity projection, shaded-surface display, direct volume rendering). To overcome these limitations, the authors present a novel method for standardized visualization of CT angiographic volumes, consisting of three steps: (a) transfer of the image data to a remote high-end graphics workstation, (b) automatic 3D visualization with high-resolution direct volume rendering, and (c) consecutive video generation performed according to a standardized protocol. The recorded video sequences are transferred for evaluation to a local desktop computer. In the experimental setup, high-quality videos based on 3D visualizations were produced in less than 60 minutes per patient. Although aneurysms above the skull base are usually visualized with excellent quality, the analysis of aneurysms at the skull base is still difficult.

Comprehensive imaging of ischemic stroke with multisection CT.

Computed tomography (CT) is an established tool for the diagnosis of ischemic or hemorrhagic stroke. Nonenhanced CT can help exclude hemorrhage and detect "early signs" of infarction but cannot reliably demonstrate irreversibly damaged brain tissue in the hyperacute stage of ischemic stroke. Further evaluation of patients with ischemic stroke should include differentiation between reversible and irreversible brain damage, which is essential for choosing an appropriate therapy. Perfusion CT provides information about brain perfusion, which permits differentiation of irreversibly damaged brain tissue from reversibly impaired "tissue at risk." CT angiography can help detect stenosis or occlusion of extra- and intracranial arteries. Multisection CT allows the combined use of all three imaging modalities-nonenhanced CT, perfusion CT, and CT angiography-to rapidly obtain comprehensive information regarding the extent of ischemic damage in acute stroke patients. Specific patterns of findings are typically seen in ischemic stroke and can be analyzed more accurately with the combined use of multisection CT and MR imaging. Nevertheless, prospective studies involving a large number of patients will be needed to ascertain the treatment of choice for patients with each of these patterns of findings.

Post-apoplectic reorganization of cortical areas processing passive movement and tactile stimulation--a neuromagnetic case study.

Magnetoencephalography (MEG) was used in a patient with right centro-parietal stroke to investigate the cortical processing of tactile pneumatic stimulation and passive movement of the impaired left and unaffected right-hand index finger. Source localization of somatosensory evoked magnetic fields (SEF) recorded 2 weeks after infarction demonstrated a spatial displacement of the contralateral SI generators in the affected hemisphere. The distance between SI sources activated by either stimulation technique was noticeably enlarged in comparison to the left hemisphere and to previous data from 12 healthy subjects. Follow-up MEG after 6 months revealed a closer spatial arrangement of the two modality-specific SEF generators and a diminution of the interhemispheric asymmetry of proprioception-related SI sources. The topographical alterations were accompanied by clear clinical improvement of both joint position sense and tactile sensation. The occurrence of ipsilateral SI activity following passive movement of only the impaired index finger might suggest a disinhibition of subthreshold, transcallosal excitatory pathways.

Cyst-like cerebral lesions in tuberous sclerosis.

Known brain manifestations of tuberous sclerosis (TSC) are cortical sclerotic tubera, giant cell astrocytomas, subependymal calcified nodules in the lateral walls of the lateral ventricles, and white matter heterotopias. In addition, small cyst-like lesions in the white matter have been described. We report on three TSC patients with hitherto undescribed large cyst-like cerebral lesions in subcortical and white matter locations. We emphasize that cystoid brain degeneration is a rare but typical cerebral manifestation of TSC and suggest that, in patients with such lesions, TSC should be taken into consideration.

Somatotopic organization of the ventral and dorsal finger surface representations in human primary sensory cortex evaluated by magnetoencephalography.

Cortical reorganization of the subtly differentiated hand map after peripheral nerve injury might be better understood if there was a topographic conception of the homuncular representation of the dorsal finger surfaces in humans, in addition to the well-established sequential rostrocaudal array of the ventral finger aspects in cortical area 3b. In the present magnetoencephalographic study, tactile pneumatic stimulation was delivered to the fingertip and to the ventral and dorsal proximal phalanx of each digit of the dominant hand in 20 right-handed volunteers. Source localization of equivalent current dipoles underlying the recorded somatosensory evoked magnetic field was performed using a Cartesian coordinate system established by the anatomical landmarks nasion and preauricular points. Of the first major peak of each somatosensory evoked field, the region with the maximum field power (root-mean-square across channels) was selected for source reconstruction. Analysis of variance for repeated measures yielded significant results with respect to the arrangement of digits along the vertical coordinate axis, demonstrating a sequential array from the most inferiorly located D1 to the most superiorly located D5 for all different stimulus positions. This is the first study providing evidence for a sequential topographical arrangement of not only the ventral but also the dorsal surface representations of the individual digits in the human somatosensory cortex. The study contributes to a better understanding of the somatosensory hand representation in human primary cortex and provides useful information with regard to cortical plasticity studies in patients with peripheral nerve injuries at the upper extremity.