Hemodynamic Aspects of Cerebral Angiomas

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 response of 2 brain vessels to varying CO contents of the inhaled air. Angiographical, dopplersonographical and 2 perioperative dopplersonographical as well as intraoperative measurements of flow and pressure have been applied.

Inhalt

I. Introduction.- 1. History.- 2. Aim of the Study.- 3. Hemodynamic Principles of Cerebral Perfusion.- 3.1. Hemodynamics in Normal Blood Vessels.- 3.2. Cerebral Perfusion and Autoregulation.- 4. Hemodynamics in Cerebral Angiomas.- 4.1. Hemodynamics of Angioma Feeding Arteries.- 4.2. Hemodynamics in the Angioma.- 4.3. Brain Perfusion and Angioma.- 4.4. Hemodynamic Changes After Angioma Exclusion.- II. Animal Experiments.- 1. Experimental Arteriovenous Fistulae.- 1.1. The Fistula Models of Spetzler and of Scott.- 1.2. Own Fistula Models.- 1.3. Topics of Our Experimental Investigations.- 2. Materials and Methods.- 2.1. Anaesthesia.- 2.2. Surgical Procedure.- 2.3. Blood Pressure Measurements.- 2.4. Electromagnetic Measurements of Flow Rate.- 2.5. Dopplersonographic Measurements of Flow Velocity.- 2.6. Measurements of Microcirculation (Laser Doppler).- 2.7. Angiography.- 3. Results of the Fistula Models in Rats.- 3.1. Direct AV Fistula (T-fistula).- 3.1.1. Electromagnetic Flow Measurements.- 3.1.2. Intraoperative Doppler Sonography.- 3.1.3. Blood Pressure.- 3.1.4. Angiography.- 3.2. Indirect AV Fistula (H-fistula).- 3.2.1. Electromagnetic Measurements.- 3.2.2. Doppler Sonography.- 3.2.3. Blood Pressure Measurements.- 3.2.4. Angiography.- 3.2.5. Long-term Experiments.- 3.2.6. Autoregulation Experiments.- 4. Results of Fistula Models in Cats.- 4.1. Flow Rates and Blood Pressure in the H-fistula Model.- 4.2. Dopplersonographic Measurements.- 4.3. Measurements in Varying Fistula Flow.- 4.4. High Flow Velocities and Vessel Wall Vibrations.- 4.5. Autoregulation in Acute and Chronic H-fistulas.- 4.6. 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.- 1. Materials and Methods.- 2. Results.- 3. Discussion.- 4. Summary and Conclusion.- IV. Transcranial Doppler Sonography in Angioma Patients.- 1. Introduction, Methods and Normal Values.- 1.1. Transcutaneous Recording Methods.- 1.2. Transcranial Doppler Sonography.- 1.3. Normal Values.- 1.4. Discussion (Normal Values).- 2. Transcranial Doppler Sonography in Angioma Patients (Normocapnia).- 2.1. Preoperative Recordings.- 2.1.1. Flow Characteristics of Angioma Supplying Arteries.- 2.1.2. Discrimination of Spastic and Angioma Feeding Arteries.- 2.1.3. Transcranial dopplersonographic Recordings and Angiographical Vessel Diameter.- 2.1.4. Altered Blood Distribution and Steal Effects.- 2.1.5. Compression Tests in Angiomas.- 2.1.6. Special Cases.- 2.1.7. Flow Characteristics of Angioma Veins.- 2.1.8. Flow Characteristics of Cerebral Arteries.- 2.2. Postoperative Recordings in Angioma Patients.- 2.2.1. Flow Characteristics in Former Angioma Feeders.- 2.2.2. Flow Characteristics in Neighboring Brain Arteries After AVM Removal.- 2.2.3. Special Case With Early Hemorrhage After Surgery.- 2.3. Discussion.- 2.4. Summary.- 3. CO2 Reactivity, Normal Values and Findings in Angioma Patients.- 3.1. Method.- 3.2. Terminology.- 3.3. Normal Values.- 3.4. CO2 Reactivity in Angioma Patients.- 3.5. CO2 Reactivity of Brain Arteries in the Angiogram.- 3.6. CO2 Reactivity After AVM Removal.- 3.7. CO2 Reactivity Before and After Partial Embolization.- 3.8. Special Cases.- 3.9. Discussion.- V. Intraoperative Studies in Angioma Patients.- 1. Intraoperative Methods (History).- 2. Topics of Our Intraoperative Measurements.- 3. Methods Used in This Study.- 3.1. Microvascular Intraoperative Doppler Sonography.- 3.2. Electromagnetic Measurements of Flow Rate.- 3.3. Intravasal Pressure Measurements.- 4. Operative Strategy and Preparation of Vessels to Be Measured.- 5. Measurements Before AVM Removal.- 5.1. Doppler Sonography Before AVM Removal.- 5.2. Electromagnetic Measurements of Flow Rate.- 5.3. Intravasal Pressure Measurements.- 6. Measurements After AVM Removal.- 6.1. Doppler Sonography After AVM Removal.- 6.2. Intravasal Pressure Measurements After AVM Removal.- 6.3. Electromagnetic Measurements.- 7. CO2 Reactivity of Vessels Supplying Angioma and Brain Before and After AVM Exclusion.- 7.1. CO2 Reactivity Before AVM Removal.- 7.2. CO2 Reactivity After AVM Removal.- 8. Discussion.- 9. Summary of Intraoperative Measurements.- VI. Final Conclusions.- References.