Proposed Radiographic Parameters to Guide Selection of Surgical Approach for Olfactory Groove Meningioma

Objective: Olfactory groove (OG) meningiomas have traditionally been treated with transcranial approaches. With improvement in instrumentation, endoscopic endonasal approaches (EEA) have gained popularity for the resection of these tumors. Although skull base surgeons have become more facile with EEAs, there do not exist clear guidelines to favor EEA versus open resection. We propose considerations based on preoperative radiographic tumor characteristics and its relation to surrounding bony and neurovascular structures to guide surgical approach decision-making.

Methods: A retrospective review of patients who underwent transcranial or EEA resection of OG meningioma between 2003 and 2020 was conducted. Preoperative imaging parameters including maximum anteroposterior (AP) and craniocaudal dimensions, distance from posterior table of frontal sinus, lateral dural tail with respect to midline of orbit, and vascular relationships were collected and used to perform K-means clustering ([Fig. 1]). Postoperative extent of resection, FLAIR volume, and porencephalic volume were measured.

Results: Ninety-four patients underwent resection of OG meningiomas. Seventy-three patients had EEA while 21 patients had a transcranial approach. Unsupervised clustering demonstrated clustering of the tumors based on distance from posterior table, maximum craniocaudal dimension, and maximum AP dimension ([Fig. 2]). Tumors with longer distance from the posterior table and larger craniocaudal dimension or larger AP dimension were more likely to have undergone EEA for resection ([Fig. 3A, C]). As such, patients who underwent EEA demonstrated a higher value of the product of any two of these parameters ([Fig. 3B, D]). The majority of the transcranial tumors had a distance from the posterior table of less than the median suggesting that there is a preference for open approach for tumors with less brain tissue between the exposure and tumor. There was a wide range of maximal AP or craniocaudal dimensions among transcranially approached tumors abutting the posterior table. To determine whether some of these patients would have benefited from EEA, the correlation between posterior table distance, maximal AP dimension, and maximal craniocaudal dimension and postoperative edema (FLAIR volume) and encephalomalacia (porencephalic volume) were measured. While there was no correlation between the distance from the posterior table and postoperative edema and encephalomalacia, tumors with larger AP or craniocaudal dimension had higher volumes of postoperative edema and encephalomalacia ([Fig. 4]).

Conclusion: As the utility of EEA for OG meningioma increases, there is a need to identify parameters to select the appropriate approach to optimize outcomes. Our results suggest that tumors with longer distance from the posterior table with associated large maximal craniocaudal or AP dimensions are most favorably approached through EEA. These tumors likely represent the group of tumors that are at the highest risk of significant brain retraction through transcranial approaches. Tumors with shorter distance from the frontal sinus and smaller AP or craniocaudal dimensions are well suited for both transcranial and EEA approaches. Tumors with shorter distance from the frontal sinus but larger AP or craniocaudal dimensions should be considered for EEA to minimize brain manipulation, postoperative edema, and encephalomalacia. A larger cohort comparison is needed to further establish an endoscopic classification scheme.

Fig. 1 Radiographic parameters collected.

Fig. 2 K-means clustering of olfactory groove meningiomas based on radiographic parameters.

Fig. 3 Tumor with longer distance from posterior table of frontal sinus and larger maximal AP or craniocaudal dimension are more likely to undergo EEA.

Fig. 4 Maximal craniocaudal and AP dimension are positively correlated with post-operative FLAIR and porencephalic volume.

Publication History

Article published online:
15 February 2022