Controversies in failed back surgery syndrome.
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Diskectomy↗
Biomedical subjects
B Schaller
Publications and source records attributed to B Schaller.
Subcranial approach in the surgical treatment of anterior skull base trauma.
Fractures of the anterior skull base, because of the region's anatomical relationships, are readily complicated by neurological damage to the brain or cranial nerves. This review highlights the use of a subcranial approach in the operative treatment of injuries of the anterior skull base and compares it to the more traditional neurosurgical transcranial approach. The extended anterior subcranial approach takes advantage of the specific features of injuries in this region and allows direct access to the central anterior cranial base in order to repair fractures, close CSF fistulae and relieve of optic nerve compression. It avoids extensive frontal lobe manipulation. The success of the approach in achieving the aims of surgery with low morbidity is reviewed.
Brain Injuries↗
[Positron emission tomography in neuroscience. An integrative part of clinical diagnostic methods and experimental research].
The role of molecular neuroimaging techniques is increasing in the understanding of pathophysiological mechanism of diseases. To date, positron emission tomography is the most powerful tool for the non-invasive study of biochemical and molecular processes in humans and animals in vivo. With the development in radiochemistry and tracer technology, a variety of endogenously expressed and exogenously introduced genes can be analyzed by PET. This opens up the exciting and rapidly field of molecular imaging, aiming at the non-invasive localisation of a biological process of interest in normal and diseased cells in animal models and humans in vivo. Besides its usefulness for basic research positron emission tomography has been proven to be superior to conventional diagnostic methods in several clinical indications. This is illustrated by detection of biological or anatomic changes that cannot be demonstrated by computed tomography or magnetic resonance imaging, as well as even before symptoms are expressed. The present review summarizes the clinical use of positron emission tomography in neuroscience that has helped elucidate the pathophysiology of a number of diseases and has suggested strategies in the treatment of these patients. Special reference is given to the neurovascular, neurodegenerative and neurooncological disease.
Animals↗
Different compartments of intracranial pressure and its relationship to cerebral blood flow.
BACKGROUND: The classical "Kellie-Monroe" doctrine considering the intracranial volume to be a closed system that is confined within the nearly rigid skull, conserves different mass, and has equal vascular inflow and outflow. Several experimental and clinical studies have given evidence that this is not entirely true from the (patho)physiologic point of view, even so our understanding of this phenomenon is incomplete. METHODS: Review from the literature. RESULTS: The present literature review revokes this classical doctrine and suggests a more differentiated description for the dynamic of intracranial pressure (ICP): instead of the previously suggested lumped-parameter models, the authors describe different intracranial compartments that are related to different brain regions. CONCLUSION: This has the advantage of great practical use on the one hand and allows the demonstration of relevant intercompartimental intracranial pressure differences. In addition, these ICP differences can be revealed to different ICP compartments and to its relationship to CBF. Special reference is given to determine appropriate forms for the nonconstant resistance and compliance parameters.
Brain Diseases↗
Influences of brain tumor-associated pH changes and hypoxia on epileptogenesis.
OBJECTIVE: The pathophysiological changes related to epileptic activity in peri- and intra-tumoral tissue are complex and have been only partly understood until now; possible mechanisms involve different structural, biochemical and histological tumor-related alterations. METHODS: Medical databases were searched for evidence on influence of brain tumor-associated pH changes and hypoxia on epileptogenesis. RESULTS: During the perioperative period, tumor-related hypoxia and acidity related to tumor neovascularization by vascular endothelial growth factor (VEGF) in combination with angiopoietins 1/2 (ang 1/2), may be a major factor contributing to outcomes involving epileptic activity after surgical tumor removal. Because anaerobic fermentation produces far less ATP than oxidative phosphorlyation per molecule of glucose, increased activity of the glycolytic pathway is necessary to maintain free ATP levels in the hypoxic cell. In mammalian cells, this metabolic switch is regulated by the transcription factor hypoxia-inducible factor-1. CONCLUSIONS: From the molecular point of view, therapeutic implications for the perioperative period may have relevance for the future.
Brain Neoplasms↗
Cerebral venous infarction: the pathophysiological concept.
Cerebral venous occlusion represents an often underdiagnosed cause for acute or slowly progressive neurological deterioration. The underlying pathophysiological basis is not well understood, but is different from those of arterial occlusion reflecting therefore different anatomical and physiological features of the cerebral venous system. Extensive collateral circulation within the cerebral venous system allows for a significant degree of compensation in the early stages of venous occlusion. Elevated cerebral venous pressure due to cerebral venous occlusion can result in a spectrum of phenomena including a dilated venous and capillary bed, development of interstitial edema, increased cerebrospinal fluid production, decreased cerebrospinal fluid absorption and rupture of venous structures (hematoma). All of these pathophysiological changes may explain the clinical observation that cerebral venous occlusion, if promptly diagnosed and adequately managed, contains reversible alterations and need not always lead to venous infarction. The present review outlines this different pathophysiological behavior of venous compared to arterial occlusion in the cerebral vasculature; special reference is given to the effect of these changes on the therapeutic impact.
Animals↗
Failed back surgery syndrome: the role of symptomatic segmental single-level instability after lumbar microdiscectomy.
Segmental instability represents one of several different factors that may cause or contribute to the failed back surgery syndrome after lumbar microdiscectomy. As segmental lumbar instability poses diagnostic problems by lack of clear radiological and clinical criteria, only little is known about the occurrence of this phenomenon following primary microdiscectomy. Retrospectively, the records of 2,353 patients were reviewed according to postoperative symptomatic segmental single-level instability after lumbar microdiscectomy between 1989 and 1997. Progressive neurological deficits increased (mean of 24 months; SD: 12, range 1-70) after the initial surgical procedure in 12 patients. The mean age of the four men and eight women was 43 years (SD: 6, range 40-77). The main symptoms and signs of secondary neurological deterioration were radicular pain in 9 of 12 patients, increased motor weakness in 6 of 12 patients and sensory deficits in 4 of 12 patients. All 12 symptomatic patients had radiological evidence of segmental changes correlating with the clinical symptoms and signs. All but one patient showed a decrease in the disc height greater than 30% at the time of posterior spondylodesis compared with the preoperative images before lumbar microdiscectomy. All patients underwent secondary laminectomy and posterior lumbar sponylodesis. Postoperatively, pain improved in 8 of 9 patients, motor weakness in 3 of 6 patients, and sensory deficits in 2 of 4 patients. During the follow-up period of 72+/-7 months, one patient required a third operation to alleviate spinal stenosis at the upper end of the laminectomy. Patients with secondary segmental instability following microdiscectomy were mainly in their 40s. Postoperative narrowing of the intervertebral space following lumbar microdiscectomy is correlated to the degree of intervertebral disc resection. It can therefore be concluded that (1) patients in their 40s are prone to postoperative narrowing of the intervertebral disc space and hence subsequent intervertebral instability and (2) that a small extent of intervertebral disc resection and preservation of the "segmental frame" may be beneficial in those patients. The present study demonstrated for the first time that the degree of extensive operative techniques in microdiscectomy increased the risk of subsequent segmental instability. In addition, narrowing of the intervertebral space of more than 30% represents a clear radiological sign of segmental instability.
Adult↗
[Facial nerve rehabilitation after cerebellopontile angle surgery].
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Anastomosis, Surgical↗
Trigeminocardiac reflex. A clinical phenomenon or a new physiological entity?
The trigemino-cardiac reflex (TCR) is defined as the sudden onset of parasympathetic dysrhythmia, sympathetic hypotension, apnea or gastric hypermotility during stimulation of any of the sensory branches of the trigeminal nerve. The sensory nerve endings of the trigeminal nerve send neuronal signals via the Gasserian ganglion to the sensory nucleus of the trigeminal nerve, forming the afferent pathway of the reflex arc. This afferent pathway continues along the short internuncial nerve fibers in the reticular formatio to connect with the efferent pathway in the motor nucleus of the vagus nerve. Clinically, the trigemino-cardiac reflex has been reported to occur during craniofacial surgery, balloon-compression rhizolysis of the trigeminal ganglion, and tumor resection in the cerebellopontine angle. Apart from the few clinical reports, the physiological function of this brainstem-reflex has not yet been fully explored. From experimental findings, it may be suggested that the trigemino-cardiac reflex represents an expression of a central neurogenic reflex leading to rapid cerebrovascular vasodilatation generated from excitation of oxygen-sensitive neurons in the rostral ventrolateral medulla oblongata. By this physiological response, the adjustments of the systemic and cerebral circulations are initiated to divert blood to the brain or to increase blood flow within it. As it is generally accepted that the diving reflex and ischemic tolerance appear to involve at least partially similar physiological mechanisms, the existence of such endogenous neuroprotective strategies may extend the actually known clinical appearance of the TCR and include the prevention of other potentially brain injury states as well. This may be in line with the suggestion that the TCR is a physiological, but not a pathophysiological entity.
Afferent Pathways↗
Decompressive hemicraniectomy in a new cat model. Methodological description of the PET study protocol.
Positron emission tomography (PET) is increasingly used to quantify regional hemodynamic and metabolic changes in different animal models. Most of these (multitracer) studies provided important early data on already functionally altered brain tissue, indicating selective vulnerability by a large variability in the functional blood flow threshold of individual neurons. To fill the gap between experimental studies at early time points and rather late clinical studies at well-defined but singular time points, we repeatedly measured cerebral blood flow (CBF), cerebral metabolic rate of oxygen (CMRO2), oxygen extraction rate and cerebral metabolic rate of glucose (CMRglc) in three cats before and up to 28 h after decompressive hemicraniectomy on normal brain tissue. Decompressive hemicraniectomy in the cat decreased CBF, and to a lesser extent CMRO2 and CMRglc 2 h after surgical intervention in normal brain tissue that last for at least 1 day. CBF significantly decreased (p < 0.01) and oxygen extraction fraction (OEF) (p < 0.05) significantly increased. CMRO2 and CMRglc decreased only in regions with most severe CBF reduction. These effects remained for at least a day irrespective of corrective sustaining cranioplasty. The method and data analysis is decreased and discussed in detail in the presented protocol. In conclusion, serial positron emission tomography studies are best suited to repeatedly and non-invasively demonstrate circulatory and biochemical changes by surgical interventions in normal brain tissue for at least one day. The transition of normal brain tissue into misery-perfused or non-viable regions can be followed over time. Such state-of-the-art imaging modalities as sequential high-resolution positron emission tomography provide insight into the dynamic of regional pathophysiology and may thus further justify the development of rational therapeutic strategies for decompressive hemicraniectomy, especially for disease with focal disturbances in cerebral blood flow.
Animals↗
Physiology of cerebral venous blood flow: from experimental data in animals to normal function in humans.
In contrast to the cerebroarterial system, the cerebrovenous system is not well examined and only partly understood. The cerebrovenous system represents a complex three-dimensional structure that is often asymmetric and considerably represent more variable pattern than the arterial anatomy. Particular emphasis is devoted to the venous return to extracranial drainage routes. As the state-of-the-art-imaging methods are playing a greater role in visualizing the intracranial venous system at present, its clinically pertinent anatomy and physiology has gain increasing interest, even so only few data are available. For this reason, experimental research on specific biophysical (fluid dynamic, rheologic factors) and hemodynamic (venous pressure, cerebral venous blood flow) parameters of the cerebral venous system is more on the focus; especially as these parameters are different to the cerebral arterial system. Particular emphasis is devoted to the venous return to extracranial drainage routes. From the present point of view, it seems that the cerebrovenous system may be one of the most important factors that guarantee normal brain function. In the light of this increasing interest in the cerebral venous system, the authors have summarized the current knowledge of the physiology of the cerebrovenous system and discuss it is in the light of its clinical relevance.
Animals↗
Hemispheric dominance for the cortical control of swallowing in humans: a contribution to better understand cortical organization?
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Cerebral Cortex↗
Usefulness of positron emission tomography in diagnosis and treatment follow-up of brain tumors.
Clinical and experimental use of positron emission tomography (PET) is expanding and allows quantitative assessment of brain tumor's pathophysiology and biochemistry. PET therefore provides different biochemical and molecular information about primary brain tumors when compared to histological methods or neuroradiological studies. Common clinical indications for PET contain primary brain tumor diagnosis and identification of the metabolically most active brain tumor reactions (differentiation of viable tumor tissue from necrosis), prediction of treatment response by measurement of tumor perfusion, or ischemia. The interesting key question remains not only whether the magnitude of biochemical alterations demonstrated by PET reveals prognostic value with respect to survival, but also whether it identifies early disease and differentiates benign from malignant lesions. Moreover, an early identification of treatment success or failure by PET could significantly influence patient management by providing more objective decision criteria for evaluation of specific therapeutic strategies. Specially, as PET represents a novel technology for molecular imaging assays of metabolism and signal transduction to gene expression, reporter gene assays are used to trace the location and temporal level of expression of therapeutic and endogenous genes. PET probes and drugs are being developed together as molecular probes to image the function of targets without disturbing them and in mass amounts to modify the target's function as a drug. Molecular imaging by PET helps to close the gap between in vitro to in vivo integrative biology of disease.
Animals↗
A new animal model of cerebral venous infarction: ligation of the posterior part of the superior sagittal sinus in the cat.
QUESTIONS UNDER STUDY: Dural sinus occlusion is an infrequent but potentially devastating cause of stroke. The pathophysiological course of events underlying it is, as yet incompletely understood. METHODS: In a cat model, regional cerebral blood flow (CBF) was measured during control and 2, and 24 hours after superior sagittal sinus occlusion. Around 48 hours after superior sagittal sinus occlusion, experimental settings were terminated by perfusion fixation with 4% paraformaldehyde solution, and haematoxylin and eosin histology. RESULTS: CBF was significantly reduced over the time-period of measurement (p < 0.05) covering about 45% of the brain in planes that were affected by occlusion. Histologically, in all cases signs of subacute venous infarction could be demonstrated. CONCLUSIONS: Based on the newly-developed model of microsurgical ligation of the superior sagittal sinus in cats, we present for the first time an animal model for cerebral venous infarction that leads to a histologically proven subacute venous infarction with a good reproducibility. The further advantage of this model is the fact that it mimics the clinical situation as far as possible by its inter- and intra-individual variance of extension of the venous infarction and by the slow reduction of CBF over 24 hours. Sequential PET imaging is a favourable, non-invasive method to gain further insight into the pathophysiological characteristics of experimental cerebral venous infarction. Therefore, the new-developed cat-model as demonstrated in this study will be of great value for further and more detailed investigations of cerebral-venous infarctions, and for the experimental evaluation of therapeutic strategies.
Animals↗
PET-based molecular imaging in neuroscience.
Positron emission tomography (PET) allows non-invasive assessment of physiological, metabolic and molecular processes in humans and animals in vivo. Advances in detector technology have led to a considerable improvement in the spatial resolution of PET (1-2 mm), enabling for the first time investigations in small experimental animals such as mice. With the developments in radiochemistry and tracer technology, a variety of endogenously expressed and exogenously introduced genes can be analysed by PET. This opens up the exciting and rapidly evolving field of molecular imaging, aiming at the non-invasive localisation of a biological process of interest in normal and diseased cells in animal models and humans in vivo. The main and most intriguing advantage of molecular imaging is the kinetic analysis of a given molecular event in the same experimental subject over time. This will allow non-invasive characterisation and "phenotyping" of animal models of human disease at various disease stages, under certain pathophysiological stimuli and after therapeutic intervention. The potential broad applications of imaging molecular events in vivo lie in the study of cell biology, biochemistry, gene/protein function and regulation, signal transduction, transcriptional regulation and characterisation of transgenic animals. Most importantly, molecular imaging will have great implications for the identification of potential molecular therapeutic targets, in the development of new treatment strategies, and in their successful implementation into clinical application. Here, the potential impact of molecular imaging by PET in applications in neuroscience research with a special focus on neurodegeneration and neuro-oncology is reviewed.
Alzheimer Disease↗
[Cerebellopontine angle surgery. Part 2: Specific remarks].
OBJECTIVES: Cerebellopontine angle tumors are uncommon lesions that can potentially be cured by microsurgical removal. The primary objective of the surgical treatment differs between vestibular schwannoma and meningioma. This feature may be influenced by the site of tumor origin and displacement of neurovascular structures as well as by their different tumor biology. METHODS: A review of the current literature was conducted. RESULTS AND CONCLUSIONS: Relevant cranial nerves and vascular involvement as well as anatomical location with respect to the cerebellopontine angle are discussed for vestibular schwannoma and meningioma. The main factors influencing the surgical outcome are outlined with special reference to facial and cochlear nerve function and cerebrospinal fluid leakage. The retrosigmoid approach offers a comparable success rate for hearing conservation and probably a superior outcome in terms of facial nerve function when compared with the middle fossa approach. The intrameatal limitations of the retrosigmoid approach can be excluded by the intraoperative assistance of an endoscope. The advantages of endoscope-assisted surgery may include improved visualization of relevant structures, more complete tumor removal, and a lowered risk of cerebrospinal fluid leakage.
Cerebellar Neoplasms↗
Zopiclone: some remarks on pharmacokinetics and pharmacodynamics.
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Azabicyclo Compounds↗
[Cerebellopontine angle surgery. Part 1: General remarks].
OBJECTIVES: Cerebellopontine angle tumors, although uniform in location, are diverse with regard to the site of tumor origin and displacement of the neurovascular structures. With the increasing use of magnetic resonance imaging in the diagnosis of brain lesions, the treatment of tumors of the cerebellopontine angle has changed extraordinarily. An appreciation of the vascular and cranial nerve microanatomy and the intimate relationship between neurovascular structures and the tumor is essential for achieving optimal surgical results METHODS: A review was made of the current literature. RESULTS AND CONCLUSIONS: The different treatment options are compared with microsurgical tumor resection with respect to neurological outcome and long-term follow-up. As microsurgical removal is still the treatment of choice for such tumors, the indication for surgical treatment is analyzed and the different surgical approaches to the cerebellopontine angle are described in terms of their frequency of involvement in the surrounding neural and vascular structures with varying tumor size. The etiology of facial and cochlear nerve injury, as well as complications involving other cranial nerves, are discussed with emphasis on pathophysiological and anatomical considerations. In conclusion, the great variation in the anatomical location and the involvement of neurovascular structures in the cerebellopontine angle is demonstrated.
Cerebellopontine Angle↗