Introduction and Objective: The use of expanded endoscopic endonasal approaches (EEA) is an increasingly popular and effective technique for the treatment of skull base tumors.1,2 There is an expected risk of temporary post-operative pneumocephalus due to the nature of intradural and subarachnoid dissection. The degree of pneumocephalus can be exacerbated by lumbar drainage; a known modality to aid in skull base reconstruction. This is due to the increased pressure gradient from the CSF flow diversion, leading to increased air accumulation from the skull base defect.2 Meanwhile, oxygen therapy has been previously described as a therapy to expedite the improvement in pneumocephalus, often monitored with serial CT scans.3,4 To date, no published research explores the efficacy of skull x-rays for monitoring pneumocephalus resolution in the postoperative period. The purpose of this proof-of-concept study is 1) to show the efficacy of bedside skull x-rays to monitor for worsening of pneumocephalus in patients requiring postoperative lumbar drainage, 2) show the reliability of high fraction inspired oxygen (FIO2) as an effective method of relieving pneumocephalus, and 3) compare the reduction in hospital costs and radiation exposure by using this method instead of repeat CT scans.
Method: Patients from a single surgeon and institution between September 2022 and June 2023 who underwent expanded EEA for skull base pathologies. Inclusion criteria included patients who underwent intradural dissection, required lumbar drain placement postoperatively, experienced moderate to severe postoperative pneumocephalus shown on post-op CT head which was treated with high FIO2 (delivered via a non-rebreather facemask) and monitored with serial skull x-rays. Hospital costs of inpatient x-ray and CT scans were also examined. Radiation dose delivery of a skull x-ray and head CT were explored.
Results: 9 patients who underwent expanded EEA requiring lumbar drain postoperatively had moderate to severe postoperative pneumocephalus, four men and four women between ages 37-68. Of these tumors, three were pituitary adenomas, four meningiomas, one tuberoinfundibular pilocytic astrocytoma, and one esthesioneuroblastoma. One patient developed significant agitation and was found to have worsening postoperative pneumocephalus after starting lumbar drainage of CSF as confirmed on bedside skull x-rays. The other patients were treated with post-operative oxygen via non-rebreather mask, and improvement of pneumocephalus was seen in all patients with bedside skull x-rays while undergoing lumbar drainage. An inpatient skull x-ray at this institution cost roughly $203 compared to a CT head costing roughly $1,071, a five-fold increase in cost. Radiation of skull x-ray is 0.1mSv, which is 20 times less than the 2.0mSv dose of a head CT.
Conclusion: Bedside skull x-rays can aid in monitoring post-operative pneumocephalus status when there is a concern for over drainage and subsequent air being drawn through the surgical defect. Meanwhile, high FIO2 can aid in accelerating the resorption of trapped gaseous content within the intracranial cavity. The use of bedside x-rays supplants the need for patient transfer to the CT scanner while significantly reducing cost and radiation exposure.
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