ABSTRACT
Background: Ethmoid Skull Base (ESB) is anarticulation of ethmoid roof with Lateral Lamella ofCribriform plate (LLCP). An increased LLCP heightwas observed to increase the vulnerability of ESB tosurgical injuries. Aim and Objectives: The present studywas undertaken to analyze the configuration of thelateral lamella of cribriform plate, the ethmoid roof withrespect to Keros type of olfactory fossa. Material andMethods: Aretrospective Computed Tomographic (CT)study was done with 60 Coronal Paranasal Sinuses(PNS) scans and LLCP height was determined bysubtracting Medial Ethmoid Roof Point (MERP) fromCP heights and classified according to Keros. Thedifference between Medial Ethmoid Roof Point(MERP) and Lateral Ethmoid Roof Point (LERP)heights in both anterior and posterior planes indicatesthe direction of ethmoid roof slope. Results: Theaverage height of the LLCP was between 1.53 to 8.55mm with a mean (SD) of 3.77 mm 1.66 and majoritybelonged to Keros type I. Overall mean differencebetween LERP and MERP was 5.43 0.74 mm inanterior and 4.43 0.63 mm in posterior planes. In boththe planes irrespective of the sides the height of theLERPwas higher in relation to medial side. Conclusion:Keros type I was the most common type and the slope ofanterior ethmoid roof is steeper compared to posterior.This preoperative knowledge about the configuration ofLLCPas well as the ethmoid roof contour is vital duringendonasal ethmoidal surgeries.
ABSTRACT
During Endoscopic Sinus Surgeries (ESS), the most important anatomical structures that need preoperative visualisation and evaluation are the lateral lamella and ethmoidal skull base as many reports of complications due to injury of these structures exist. Ethmoidal Skull Base (ESB) extends from the superior attachment of lateral lamella of cribriform plate to the junction of the lamina papyracea. The aim is to study and evaluate ESB using coronal sinus CT images. Methods: Sixty coronal sinus CT scan images at the level of visualization of anterior ethmoidal artery canal were taken for studying the ESB on both sides. A horizontal line bisecting the orbit was taken as the base line reference for inferior extent. The height of the ESB was measured and classified into high, moderate and low ESB by taking 7 mm as upper limit and 4 mm as lower limit. Mean height of ESB in the study group was computed and its difference among gender and sides were noted and statistically analysed. Results: ESB varied between 3.7 mm to 15.4 mm with mean height of 10.05 mm. Low ESB was found only in females and there was no statistically significant side asymmetry of ESB height. Conclusions: Preoperative recognition of low ESB and alerting the surgeon of the potential for iatrogenic injury by measuring the height of ESB needs to become a standard practice in order to minimize the complications during ESS.