SURG-36. CLINICO-RADIOLOGICAL PARAMETERS, MOLECULAR AND CHROMOSOMAL ALTERATIONS AFFECTING SURGICAL OUTCOME OF PETROCLIVAL MENINGIOMAS

Abstract

Abstract Petroclival meningiomas were reviewed for correlation of extent of resection with clinico-radiological parameters and molecular/chromosomal alterations. 53 surgical procedures in 50 patients of petroclival meningioma were performed. Cavernous sinus and sellar extension were present in 37(69.8%) and 5(9.4%) respectively; contralateral extension in 10(20%). Modified anterior transpetrous rhomboid-MATRA (44=83.0%) was the most commonly used approach, followed by retrosigmoid (2=3.8%), and combined (7=13.2%) approaches. Hypointense tumors on T2-weighted MRI (OR:5.85;95%CI:1.70-20.41) and presence of brainstem edema (OR:4.53;95%CI:1.36-15.12) were found to be significant factors increasing the likelihood of subtotal resection-STR (p = 0.004 & p = 0.011 respectively). In the presence of both tumor T2-hypointensity and brainstem edema, there was significant increase in the likelihood of STR (p = 0.001;OR:25;95%CI:3.52-177.48). The most common cranial nerve to suffer new-onset deficit postoperatively was found to be VI nerve(19=35.8%) followed by V(9=16.9%) and VII(8=15.8%) nerves. On long-term follow-up, 38 patients had good outcome. Out of the 16 cases for which molecular analysis was performed, no specimen was found to have pTERT-C228T,C250T, AKT-1, E17K and SMO-L412F,W535L mutations. Eight (50.0%) cases showed H3K27me3 loss while 5 (31.25%) had hemizygous CDKN2A deletion. All(100%) patients harboring H3K27me3 loss and/or hemizygous CDKN2A deletion had cavernous sinus extension compared to 62.5% patients without H3K27me3 loss and 72.7% with hemizygous CDKN2A retention. Similarly, hemizygous CDKN2A deletion and H3K27me3 loss are associated with increase in the rate of brainstem edema from 27.3% to 60% and 25% to 50% respectively. Cases (n = 4) with both these alterations have 100% cavernous sinus extension and 75% chances of brainstem edema and lack of arachnoid plane. The MATRA is a versatile approach for petroclival meningiomas with good surgical outcome and acceptable complication rates. T2 hypointense tumor and brainstem edema on pre-operative imaging are significant predictors of STR. H3K27me3 loss and hemizygous CDKN2A deletion may be associated with cavernous sinus extension suggesting their role in tumor spread.