A new radiological classification for the risk assessment of anterior skull base injury in endoscopic sinus surgery

Abstract

Keros and Gera classifications are widely used to assess the risk of skull base injury during endoscopic sinus surgery. Although, both classifications are useful preoperatively to stratify risk of patients going for surgery, it is not practical to measure the respective lengths during surgery. In this study, we aimed to propose a new radiological classification (Thailand-Malaysia-Singapore (TMS)) to assess the anatomical risk of anterior skull base injury using the orbital floor (OF) as a reference. A total of 150 computed tomography images of paranasal sinuses (300 sides) were reviewed. The TMS classification was categorized into 3 types by measuring OF to cribriform plate and OF to ethmoid roof. Most patients were classified as TMS type 1, Keros type 2 and Gera class II, followed by patients classified as TMS type 3, Keros type 1 and Gera class 1. TMS has significant correlation with Keros classification (p < 0.05). There was no significant correlation between Keros and Gera classifications (p = 0.33) and between TMS and Gera classifications (p = 0.80). The TMS classification has potential to be used for risk assessment of skull base injury among patients undergoing ESS. It serves as an additional assessment besides the Keros and Gera classifications.

Radiological Evaluation of Olfactory Fossa with Cone-Beam Computed Tomography

“…In our study, the most common were Keros type II (71.9%), followed by Keros type I (17.8%), Keros type III (10.3%). While a few studies reported the most common Keros type I [1,2,7,20,21], most studies were the most common type II [3][4][5]8,[13][14][15][17][18][19][22][23][24][25][26][27][28], consistent with our study. The distributions according to the Keros classification in the studies conducted in the Turkish population are presented in Table 6.…”

“…Gera et al [11] reported that the mean LLCPA was 71.7° and they detected the most common type II (62.7%). Abdullah et al [7] reported that detected the mean LLCPA of 70.1° and the most common type II (72.3%). In our study, the mean LLCPA was found to be 74.1°, which is a higher value than in previous studies.…”

“…Gera et al [11] reported a positive correlation between CP depth and LLCPA. Abdullah et al [7] reported a positive correlation between CP depth and LLCPA, MERP and CP heights. In our study, while there was a significant positive correlation between CP depth and NF, MERP and CP heights and LLCPA, there was a significant negative correlation between CP depth and OF width.…”

“…The distributions according to the Keros classification in the studies conducted in the Turkish population are presented in Table 6. Skorek et al [19], Abdullah et al [7] reported the rate of asymmetry according to the Keros classification as 20% and 26%, respectively. We determined the rate of OF showing asymmetry according to the Keros classification as 29.7% (Figure 5).…”

“…It is recommended to evaluate the Gera classification as well as the Keros classification. In the Gera classification; the angle between the horizontal plane continuing from the CP and lateral lamella (LL) and is evaluated and divided into three types: type I (> 80°, low risk), type II (45° to 80°, moderate risk), and type III (< 45°, high risk) [7]. In patients undergoing surgery, evaluation of both classifications with appropriate imaging methods of the region is beneficial to reduce the risk.…”