CORRELATION OF INTRAOPERATIVE ULTRASOUND WITH HISTOPATHOLOGIC FINDINGS AFTER TUMOR RESECTION IN SUPRATENTORIAL GLIOMAS - A METHOD TO IMPROVE GROSS TOTAL TUMOR RESECTION

The aim of this study was to evaluate whether intra-operative ultrasou nd (=IOUS) is a suitable tool to detect residual tumour tissue after g ross total resection in supratentorial gliomas. During a period of 18 months 45 patients with supratentorial gliomas (38 high-grade and 9 lo w-grade, according to the WHO-grading system [42]) were operated on. A series of 78 biopsies was taken from the resection cavity under conti nuous sonographic control at the end of surgery. Gross total tumour re section was intended in 34 patients (=76%). The biopsy specimens were matched with the sonographic features at each biopsy site. The sonogra phic appearance of the resection margins were classified into 2 groups : (1) Irregular hyperechoic areas extending from the cavity into the i so-echogenic brain tissue and (2) a dense small (less than or equal to 3 mm in diameter) rather regular hyperechoic rim surrounding the rese ction cavity. 47 out of 53 biopsies taken from hyperechoic areas (grou p 1) (36 high-grade/11 low-grade) revealed solid tumour tissue (=89%). 34 (=72%) of these 47 areas were microscopically assessed as inconspi cuous by the surgeon. 6 samples (4 high-grade/2 low-grade) contained t umour infiltration zone. 25 biopsies (23 high-grade/2 low-grade) taken from the hyperechoic rim [group 2] were diagnosed as follows: Normal brain tissue in 11, tumour infiltration zone in 8 and solid tumour tis sue in 6 cases. Of 34 cases with ''gross total removal'' according to the surgeon's assessement 25 showed sonographic signs of residual tumo ur tissue, which was confirmed histologically as solid tumour tissue i n 22 of these cases. It is concluded, that IOUS following resection of supratentorial gliomas can detect residual tumour tissue with high sp ecificity and thus improve gross total resection. However, a thin hype rechoic rim surrounding the resection cavity (less than 3 mm in diamet er) is a non-specific finding, which can mask thin residual tumour lay ers and therefore needs further evaluation of its nature.