53. Cryosurgery of brain tumors with ultrasound neuronavigation control

Abstract

Goal of study: To estimate the results of brain tumor surgery with cryodestruction usage. Materials and methods: The cryodestruction of neuroepithelial tumors was performed in 18 patients. We used a new cryosurgical apparatus. This method of working is based on the passive liquid nitrogen supply and the active evacuation of nascent gaseous one. Tumor stereobiopsy was performed before the cryoprobe introduction. Cryosurgery was performed by introducing the cryoprobe into the tumor with ultrasound neuronavigation control. MRI of the brain was performed before the operation and 1, 3 and 7 days after it on all patients. The efficiency of the cryodestruction and the diagnostic value of ultrasound navigation to control ice-ball generation and postoperative changes in cryodestruction and surrounding zones were estimated. Results: The ultrasound neuronavigation enabled clear visualization of the tumor, the immersion of cryoprobe and ice-ball formation. With ultrasonography a cryoprobe looked like a hyperechoic structure with an acoustic shadow as in all cases with metal equipment. An iceball looked like a hypoechoic tissue near the cryoprobe with hyperechoic contour with 2–3 mm thickness. Pre- and postoperative MRI permitted a comparison of the zones of tumor and cryodestruction. The postoperative MRI showed that there was intracerebral cyst formation in the zone of cryodestruction of the tumor. This cyst had plain clear borders. There was no residual tumor tissue. Haemorrhage of cryodestruction and surrounding zones was not detected. According to MRI the clearest visualization of cryodestruction zone was up to 3 days. There was no extension of perifocal edema within first 3 days, however, an insignificant one was found by the 7th postoperative day. The contrast accumulation at the border of destruction zone was marked by the 5th day, it was the effect of delimiting gliosis formation. Conclusion: Cryodestruction enables the destruction of brain tumors efficiently in a given volume. Ultrasound neuronavigation is an effective method of monitoring ice-ball formation in the brain during freezing and thawing in real time. This method allows destruction of the tumors which are located in functionally significant brain areas and attempts at removal is associated with a high risk of disability and death.