Background: Iatrogenic cerebrospinal fluid leak (iCSF-L) is a major complication of endonasal surgeries whose occurrence is always a potential adverse event due to anatomical variation/asymmetry of the skull base (SB). The aim of this manuscript is to provide a topographical map of iCSF-L and to investigate the role of SB asymmetry in iCSF-L occurrence. Methods: In this retrospective study, the location of iCSF-L dural defect was studied and compared to patients affected by spontaneous and post-traumatic CSF-L. Considering only iCSF-L, after having collected the SB asymmetry data, the Keros, Gera, distance of the anterior ethmoidal artery from the SB, frontal sinus pneumatization, and Thailand–Malaysia–Singapore score classifications were compared to a control group of patients. Results: A total of 153 CSF-Ls (103 spontaneous, 37 iatrogenic, and 13 traumatic) were included. A significant association was noted (p < 0.001) between the nature of the CSF-L and the areas involved. Considering iCSF-Ls, only the Gera classification was significantly different (p < 0.05) and the most reliable in predicting the risk of dural transgression (AUC = 0.719). Conclusions: ICSF-Ls present peculiar regional SB involvement with the cribriform plate, with the ethmoidal roof being the most involved. After having assessed the asymmetry of the SB, the Gera classification was the most reliable one.

Introduction: Meningeal metastasis (MM) from naso-ethmoidal malignancies (NEMs) is rare, its metastatic route is still debated, and its prognostic impact remains unclear. Our aim is to analyze a retrospective series of NEMs with non-contiguous MM to study the possible route of spread and the prognostic value of MM. Materials and methods: The institutional database of SNC treated at the University of Brescia between 1995 and 2021 was reviewed. Clinical–pathological data were collected, and survivals were estimated with Kaplan–Meier. Univariate and multivariate logistic regression analysis were run to identify predictors of MM. Results: Among 296 patients, 17 experienced non-contiguous MM, all located along the dura. Intestinal-type adenocarcinoma (10/17) and olfactory neuroblastoma (3/17) were the most frequent histologies. At univariate analysis, brain edema (p < 0.0001), resection (p = 0.026) or invasion (p = 0.006) of brain parenchyma, and local (p = 0.0004) and nodal (p = 0.021) recurrence were predictors of MM. At multivariate analysis, local recurrence was confirmed as an independent factor (odds ratio: 11.88, p = 0.0005). Dural surgical resection was not a risk factor. The five-year disease-specific survival was longer in patients with exclusive MM compared with patients with distant metastasis at other sites (64.3% vs. 30.1% p = 0.046). Conclusions: Dural venous shunt is the most likely pathway of spread of MM. Local recurrence is the only independent risk factor. Exclusive MM has a better prognosis than extrameningeal metastasis.