The Importance of Cribriform-Lamella Angle in Endoscopic Sinus Surgery
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ORIGINAL ARTICLE
The Importance of Cribriform-Lamella Angle in Endoscopic Sinus Surgery Satish Nair1
•
Ameena Ibrahim1
Received: 18 August 2020 / Accepted: 21 September 2020 Association of Otolaryngologists of India 2020
Abstract The aim of this study is to evaluate cribriformlamella (CL) angle and length of lateral lamella (LL) on CT scan and to correlate CL angle with LL length and Keros classification. Retrospective study analyzing 500 CT scans of PNS was performed at a tertiary care hospital. The CT scan anatomy of anterior cranial base was evaluated for Keros, CL angle and LL length. The relationship between these measurements was studied. Keros type I (75.2%) was the commonest finding in our study. Males have increased depth of olfactory fossa but there were no differences between the sides. Type A angle of CL (66.1%) was the commonest with females having an increased CL angle as compared to males. The LL length was 3.6 mm (± 0.8). There were no significant difference between sex/side of LL. Keros was found to be strongly correlated with the LL length whereas it has mild negative correlation with CL angle. There was no correlation between CL angle and LL length. Keros classification is the commonest criteria used to assess the risk of injury to anterior cranial base. However, we have found that the CL angle has an important role to play in the angulation/slope/level of anterior cranial base during endoscopic sinus surgery. CL angle needs to be considered as an important factor during endoscopic sinus surgery. Keywords Keros Cribriform-lamella angle Lateral lamella length Anterior skull base Endoscopic sinus surgery
& Satish Nair [email protected] 1
Department of ENT-HNS, Apollo Hospitals, Opp. IIM, Bannerghatta Road, Bangalore, Karnataka 560076, India
Introduction Keros in the year 1962, in a landmark publication, described the depth of anterior cranial fossa with a 3 category classification. Since then, it is one of the commonest criteria used by radiologists and endoscopic surgeons to assess the risk of injury to anterior cranial base. In the past few years, there has been further interest in the anterior cranial base anatomy due to the advancement in endoscopic sinus and cranial base surgeries. Keros classified olfactory fossa depth into 1–3 mm, 4–7 mm, 8–16 mm, labeled them as I, II and III categories respectively. Type III is the most dangerous one [1] and was called as ‘dangerous ethmoid’ by Kainz and Stammberger [2]. In addition to Keros, other measurements like the cribriform-lamella angle (CL), lateral lamella length (LL) and height of fovea have been evaluated by various authors. The role of olfactory fossa depth has been already stressed, but limited data regarding the slope of the anterior skull base or angulation of the cribriform-lamella (CL) in the coronal plane is available. This angle might affect the level of the ethmoidal roof relative to the cribriform plate, and consequently could play an important role in endoscopic sinus surgery. We have studied CT PNS images in rega
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