Incidence of and risk factors for chronic subdural hematoma after endoscopic endonasal surgery: quantitative analysis of pneumocephalus.

Objective: Chronic subdural hematoma (CSDH) is known to occur after endoscopic endonasal surgery (EES); however, the detailed clinical picture remains unclear. In this study, the authors aimed to examine the incidence of and risk factors for post-EES CSDH, with a focus on the quantitative evaluation of postoperative pneumocephalus.
Methods: The authors retrospectively collected data on consecutive patients who, between November 2016 and December 2022, had undergone EES during which intraoperative cerebrospinal fluid (CSF) leakage occurred. Using CT images obtained immediately after surgery (CT0), the authors measured the extent of pneumocephalus in detail. The locations of pneumocephalus were divided into two groups: remote and local. Remote pneumocephalus was further subdivided into convexity and ventricular. The incidence of post-EES CSDH was calculated, and its risk factors were analyzed.
Results: Among the 159 EES patients included in the study, Esposito grade 1, 2, and 3 intraoperative CSF leakage was confirmed in 22 (14%), 27 (17%), and 110 (69%) patients, respectively. CSDH occurred in 6 patients (3.8%). One patient (0.6%) required unilateral burr hole surgery, whereas the hematomas spontaneously disappeared in the others. All CSDHs occurred in patients with Esposito grade 3 CSF leakage and convexity pneumocephalus on CT0. In the multivariate analysis of 149 sides with convexity pneumocephalus on CT0, the product of the diameter and the thickness of convexity pneumocephalus on CT0 was significantly associated with subsequent CSDH (OR 1.21, 95% CI 1.06-1.38, p = 0.004). Using a cutoff value of 10 cm2, CSDH development could be predicted with a sensitivity of 0.82 and specificity of 0.74.
Conclusions: The incidence of post-EES CSDH is acceptably low, and surgery is rarely required. Patients with extensive convexity pneumocephalus on immediate postoperative CT are prone to develop CSDH and thus should be carefully monitored.