P18.01.A A MORPHOMETRIC ANALYSIS OF 40 DRY ASIAN SKULLS TO INVESTIGATE ANATOMICAL VARIABILITY IN THE SUPRASELLAR REGION AND ITS IMPLICATIONS IN MENINGIOMA SURGERY

Abstract

Abstract INTRODUCTION Meningiomas are the most common type of primary brain tumour and when symptomatic, are usually treated by surgical resection. Removing skull-base meningiomas is challenging and subtotal resection remains common, despite utilising the latest surgical METHODS . In the suprasellar region, surgery is particularly high risk and carries a 10-20% rate of postoperative visual impairment. This morphometric analysis of 40 dry skulls furthers our understanding of anatomical variability of 3 structures in the suprasellar region: the limbus sphenoidale (LS), prechiasmatic sulcus (PS) and optic strut (OS). Understanding suprasellar anatomical variability is vital for neurosurgeons operating within the region to reduce complication rates and in achieving gross total resection. METHODS Variants of the LS (A, B and C) are defined according to descriptions used from a previous study. Curved and straight lengths of the LS are measured using metal callipers and string. Between the three variants, statistical analysis is used to compare differences in lengths, and the ratio between their curved and straight length. PS angle, length and width are measured according to previous studies’ definitions. OS position is determined by measuring its distance from the LS and a drawn midline. Skulls are grouped using PS variables and OS position according to adapted classification systems used in previous studies. RESULTS Variants A, B and C of the LS exhibited incidences of 33.33%, 52.82% and 15.39%, respectively. Limbus ratio was significantly different (p<0.05) between variants. Average sulcal angle was 32 ± 13.3°, whilst sulcal type ranked in prevalence: narrow flat sulci (34.21%)> very narrow steep (28.95%)> very narrow flat (21.05%) > narrow steep (15.79%). 32.50% and 18.42% of struts exhibited notable differences in their distances from the midline and from the LS, respectively. CONCLUSION The present study improves our understanding of the prevalence of anatomical variants within the suprasellar region and has implications for meningioma surgery. The type C variant is an overhanging ridge, underneath which meningiomas could be hidden from a surgeon’s view during transcranial procedures. Only two studies have previously documented the type C variant, whose incidence in the present study (15.39%) is within the boundaries of previous research; patients with this variant might require removal of the landmark during surgery to achieve gross total resection. The PS displayed varying degrees of steepness, and skulls were on average steeper than previously documented populations. A considerable proportion of skulls exhibited notable differences in left and right OS position. Establishing PS morphology and OS position preoperatively might be helpful in reducing the risk of visual impairment in future operations through better understanding the course of the optic nerve.