Evaluation of a new method of intraoperative oxygen and blood volume measurement in cerebral AVM

Introduction: Progressive neurological manifestations occur in arteriovenous malformation disease and have, not uniformly, been attributed to an arterial steal phenomenon, determined by the sumping effect the AVM exerts on the intracranial circulation. Spatially discriminating measurements of local tissue oxygenation were not feasible. A new near infrared reflexion spectroscopy based technology (MULTISCAN OS 10) allows non-invasive intraoperative measurements of tissue oxygenation with absolute values. Methods: MULTISCAN OS 10 scans a tissue sector of defined geometry with 0.3 nm intervals at a scan rate of up to 400 HZ in reflection mode. The newly developed algorithms allow the detection of absolute values of total hemoglobin and oxy-hemoglobin in mg/ml tissue was well as oxygen saturation in the range of 0 to 100% in real time. This study deals with 8 patients, which have been operated for moderate or large sized cerebral arteriovenous malformation. The mean age was 41 years. Intraoperatively the AVM surrounding cortical tissue distant to the AVM nidus was measured by MULTISCAN OS 10 before and immediately after resection. Results: Postoperative angiography demonstrated in all cases total removement of the AVM. In 7 patients the intra- and postoperative course was uneventful. Immediately after resection blood volume as well as tissue oxygen saturation increased nearly two fold after. The relative extent of improvement of tissue oxygenation and blood volume was not related to the diameter of AVM nidus. On the contrary absolute cortical blood volume after resection of the AVM was related to nidus size. Conclusion: Blood is shunted directly through the AVM at a cost to vascular territories circumjacent and distant to the AVM nidus. Below a certain oxygenation threshold, symptoms occur as a manifestation of insufficient irrigation to the affected brain areas. In this study we have found more evidence for both steal phenomenon and cortical hyperemic status after AVM resection. MULTISCAN OS 10 is a new and useful tool for in vivo characterization of oxygen in brain tissue. Moreover, therapy and functional monitoring of the cortex is feasible.