Hemocfynamic Aspects. Cerebral Angiomas

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2 Hemocfynamic Aspects of Cerebral Angiomas Werner Hassler Acta Neurochirurgica Supplementum 37 Springer-Verlag Wien New York

3 Werner Hassler, M.D. Department of Neurosurgery, University of Tiibingen, Federal Republic of Germany Translated by Helmuth Steinmetz, Tiibingen, Federal Republic of Germany With 137 Figures Product Liability: The publisher can give no guarantee for information about drug dosage and application thereof contained in this book. In every individual case the respective user must check its accuracy by consulting other pharmaceutical literature. This work is subject to copyright All rights are reserved, whether the whole or part of the material is concerned, specifically those of translation, reprinting, re-use of illustrations, broadcasting, reproduction by photocopying machine or similar means, and storage in data banks by Springer-VerlagfWien Library of Congress Cataloging-in-Publication Data. Hassler, W. (Werner) Hemodynamic aspects of cerebral angiomas. (Acta neurochirurgica. Supplementum; 37) Bibliography: p. I. Brain-Blood-vessels-Surgery. 2. Hemangioma-Surgery. 3. Hemodynamics. 4. Brain-Blood-vessels-Radiography. 5. Ultrasonic encephalography. 6. Surgery, Experimental. I. Title. II. Series. [DNLM: I. Brain Neoplasms-blood supply. 2. Hemangioma-blood supply. WI AC8661 no. 37/ WL358 H355h) RD594.2.H ' ISSN ISBN-13 : e-isbn-13 : DOl: /

4 To M echthild, Sabine and Christine

5 Foreword Up to date, the treatment of arteriovenous racemose angiomas of the brain remains unsatisfactory. Intraoperative hemorrhages, post-embolizational or postoperative deficits depending on the site and size of the A VM as well as inoperability of rare angioma types have promoted the technical improvement of diagnostic and therapeutic approaches. Nevertheless, some pathophysiological problems of A VM hemodynamics have not been solved. Many angiographical studies, observations during embolization and operation, dopplersonographical and other perfusion measurements provided some insight. Sufficient animal models have yet to be developed in order to elucidate the pathophysiological mechanisms. This monograph describes A V fistula models in cats and rats, both conventional and newly developed, which allow a better comparison with human cerebral angiomas than previous ones. The most important result is that the model of the breakthrough of arterial pressure waves into the capillaries following a failure of cerebrovascular regulation cannot be confirmed. Rather, according to the findings in precapillary vessels presented here, the regulation functions normally so that a breakdown of regulation cannot be responsible for global brain edema often seen after removal of angiomas. The regulation was demonstrated using different methods, most important of which being the CO 2 response of brain vessels to varying CO 2 contents of the inhaled air. Angiographical, dopplersonographical and perioperative dopplersonographical as well as intraoperative measurements of flow and pressure have been applied. Angiographic and transcranial Doppler findings concur following removal of angiomas and fistulas in humans and animal models. The conclusion was reached that pressure passive rupture of thin-walled vessels must be seen as the cause for intra- and postoperative bleeding. As it was the case with other authors, no sufficient method was available to detect the pressure drop between arterioles and the venous part of the capillary system. The question remains to what extent minimal increases in this pressure gradient playa role in the development of edema since regulation was proved solely by the CO 2 response, and it is unknown whether minimal restrictions of regulation exist which may nevertheless be hemodynamically relevant. Finally, the characteristics of large angioma feeders are studied. Their calibers initially remain enlarged in spite of preserved regulation. At the same time, brain vessels, especially the larger segments like the carotid, react within a few hours to the exclusion of arteriovenous fistulas showing a sensible constriction of vessel walls in humans and animals as well. The question of arterial or venous thromboses is also discussed. For the clinician, the results mean that he has to focus his operative technique even more than before to the preservation of major inflows and outflows of the angioma until the end of the operation and occlude the many small feeders at a moment when pressure-dependent rupture can be avoided because large shunts are still patent. The main problem with postoperative hemorrhage is not the rupture of larger vessels but that of small ones which should be adequately thrombosed at the end of the operation. Application of this modern technique should reduce risks of postoperative bleeding. The microsurgical experience as accumulated in the past few years by several modern centers strongly suggests this approach. However, some questions remain open such as whether large angiomas should be operated upon in several stages in short intervals as recommended by Spetzler. On the contrary, large malformations can be removed in one session in spite of increased risk of edema. This has been Ya~argil's practice up until now since he quite rightly anticipates the possibility of hemorrhage from residual

6 VIII Foreword angioma parts as well as the rapid enlargement of shunts that have been left in place and that may reach considerable size within a few weeks. Further problems persist which cannot be solved in this context. The main value of this study is the fact that it has thrown light on the pathophysiology of the condition and thereby facilitates further therapeutic progress. Freiburg i. Br., December 1986 Wolfgang Seeger

7 Foreword Repeated transcranial Doppler sonography of intracranial vessels has been proven reliable and useful in investigating pathophysiology after subarachnoid bleeding and trauma. Both in research and in clinical work our basic understanding of the reactions of the cerebral vessels has been increased and has eased clinical decision making. W. Hassler has introduced this method for studying blood-flow phenomena in cerebral and spinal angiomas and fistulas. Animal experiments have shown the method applicable in investigating shunts of the central nervous system. The findings in man demonstrate with great reliability and specificity typical rheological situations of the angiomas, differentiating between those feeders only supplying the brain, those supplying exclusively the angioma and those with mixed function. Doppler sonography may work as a safe, unrisky pre-, intra- and postoperative monitoring system in angioma-surgery, whereas repeated angiography would add a big load to the patient's situation. After introducing Hassler's findings and experience into clinical work we learned that cerebral vasculature is reacting within minutes to different conditions, e.g. CO 2 level, blood pressure, intracranial pressure, and that angiographic findings are reflecting only a moment's situation. The necessity of frequent investigation in critical cerebral vascular situations is very obvious and now possible without any harm to the patient. Most important in the intra- and postoperative course after resection of a cerebral A V -angioma are the facts that CO 2 reactivity of the feeding vessels is preserved and that perfusion of the affected hemisphere drops dramatically, much below normal circulation and that of the contralateral hemisphere. We now know that hypervolemia does not exist in the postoperative phase and that complications in form of hematomas are not due to breakthrough but to incomplete resection or rupture of small feeders. Tiibingen, December 1986 Ernst H. Grote Acknowledgements I would like to take this opportunity to express my gratitude to my teacher Prof. Dr. Wolfgang Seeger who fostered my interest in the hemodynamics of cerebral angiomas and generously afforded me time for the studies. Special thanks also to my present chief, Prof. Dr. Ernst H. Grote who made possible the continuation of my scientific work, to my collaborator Dr. Helmuth Steinmetz and to Dr. Alec Eden for finishing touches as well as to Virginia Miiller for typing the manuscripts. Furthermore, I would like to thank the following: my doctoral candidates Mr. Eble and Mr. Koppermann for their contributions to the experimental part, Prof. Meureth (Anaesthesiology) for entrusting me with the electromagnetical flowmeters, Dr. Blumberg (Neurophysiology) for providing the laser Doppler, Prof. Spatz (Brain Research) and Dr. Zollner (ENT) for making the operating room available. Professor Volk (Neuropathology) and Prof. Staubesand (Anatomy) are thanked for the electrone microscopic evaluations, Dr. Birg for his mathematical assistance, Mr. Ebner for the construction of special instruments, Dr. Roth and Mr. Schuler for taking care of the animals as well as Mr. Pfister, Mrs. Huber and Mr. Eiben for their wonderful photographic work. Tiibingen, December 1986 Werner Hassler

8 Contents I. Introduction. I. History 2. Aim of the Study Hemodynamic Principles of Cerebral Perfusion Hemodynamics in Normal Blood Vessels Cerebral Perfusion and Autoregulation Hemodynamics in Cerebral Angiomas Hemodynamics of Angioma Feeding Arteries Hemodynamics in the Angioma Brain Perfusion and Angioma Hemodynamic Changes After Angioma Exclusion 6 II. Animal Experiments. 7 I. Experimental Arteriovenous Fistulae The Fistula Models of Spetzler and of Scott Own Fistula Models Topics of Our Experimental Investigations 8 2. Materials and Methods Anaesthesia Surgical Procedure Blood Pressure Measurements Electromagnetic Measurements of Flow Rate Dopplersonographic Measurements of Flow Velocity Measurements of Microcirculation (Laser Doppler) Angiography. 10 ). 3. Results of the Fistula Models in Rats Direct AV Fistula (T-fistula) Electromagnetic Flow Measurements Intraoperative Doppler Sonography Blood Pressure Angiography Indirect A V Fistula (H-fistula) Electromagnetic Measurements Doppler Sonography Blood Pressure Measurements Angiography Long-term Experiments Autoregulation Experiments Results of Fistula Models in Cats Flow Rates and Blood Pressure in the H-fistula Model Dopplersonographic Measurements Measurements in Varying Fistula Flow. 20

9 XII Contents 4.4. High Flow Velocities and Vessel Wall Vibrations 4.5. Autoregulation in Acute and Chronic H-fistulas Measurements of Cortical Perfusion and Flow Rates 4.7. Blood-brain Barrier. 5. Discussion and Summary of Animal Experiments III. Angiography in Angioma Patients Before and After Surgery. 33 I. Materials and Methods. 2. Results. 3. Discussion. 4. Summary and Conclusion IV. Transcranial Doppler Sonography in Angioma Patients l. Introduction, Methods and Normal Values 1.1. Transcutaneous Recording Methods Transcranial Doppler Sonography 1.3. Normal Values Discussion (Normal Values) Transcranial Doppler Sonography in Angioma Patients (Normocapnia) Preoperative Recordings Flow Characteristics of Angioma Supplying Arteries Discrimination of Spastic and Angioma Feeding Arteries Transcranial dopplersonographic Recordings and Angiographical Vessel Diameter Altered Blood Distribution and Steal Effects Compression Tests in Angiomas Special Cases Flow Characteristics of Angioma Veins Flow Characteristics of Cerebral Arteries Postoperative Recordings in Angioma Patients Flow Characteristics in Former Angioma Feeders Flow Characteristics in Neighboring Brain Arteries After A VM Removal Special Case With Early Hemorrhage After Surgery 2.3. Discussion 2.4. Summary. 3. CO 2 Reactivity, Normal Values and Findings in Angioma Patients 3.1. Method 3.2. Terminology Normal Values CO 2 Reactivity in Angioma Patients CO 2 Reactivity of Brain Arteries in the Angiogram CO 2 Reactivity After A VM Removal 3.7. CO 2 Reactivity Before and After Partial Embolization Special Cases 3.9. Discussion V. Intraoperative Studies in Angioma Patients I. Intraoperative Methods (History). 2. Topics of Our Intraoperative Measurements. 3. Methods Used in This Study Microvascular Intraoperative Doppler Sonography Electromagnetic Measurements of Flow Rate Intravasal Pressure Measurements

10 Contents XIII 4. Operative Strategy and Preparation of Vessels to Be Measured III 5. Measurements Before A VM Removal. III 5.1. Doppler Sonography Before A VM Removal Electromagnetic Measurements of Flow Rate Intravasal Pressure Measurements Measurements After AVM Removal Doppler Sonography After AVM Removal Intravasal Pressure Measurements After A VM Removal Electromagnetic Measurements CO 2 Reactivity of Vessels Supplying Angioma and Brain Before and After A VM Exclusion CO 2 Reactivity Before AVM Removal CO 2 Reactivity After AVM Removal Discussion Summary of Intraoperative Measurements 125 VI. Final Conclusions. References. Subject Index

11 List of Abbreviations Al horizontal part (A I segment) of ACA P2 P 2 segment of PCA ACA anterior cerebral artery pc0 2 partial pressure of CO 2 AVM arteriovenous malformation PCA posterior cerebral artery BP blood pressure PICA posterior inferior cerebellar artery CBF cerebral blood flow RI resistance index CCA common carotid artery SABP systemic arterial blood pressure ICA internal carotid artery VJC common jugular vein MCA middle cerebral artery VJE external jugular vein PI P I segment of PCA VJI internal jugular vein All transcranial dopplersonographical measurements were done with a 2 MHz pulsed Doppler divice, so that I khz of Doppler shift corresponds to 39 cm/sec of flow velocity.