Acute intraoperative cerebral herniation is more common in brain trauma surgery but can occasionally occur in surgery for brain tumor resection. Based on prior literature search, the etiology of intraoperative acute intraoperative brain bulge encompasses the occurrence of hematoma in a distant location from the surgical site, acute cerebral edema resulting from obstruction of cerebral venous return during surgery in the patient (1). It seriously affects the prognosis of patients and does more harm than the disease itself. To the best of our knowledge, there are no previous descriptions of an acute intraoperative epidural lesions in a glioma patient with syphilis that resulted in acute cerebral herniation.

Acute intraoperative cerebral herniation is an infrequent but catastrophic occurrence. According to previous reports, it often occurs in emergency surgery for severe craniocerebral trauma, and the common cause of intraoperative acute cerebral herniation is epidural or subdural hemorrhage during surgery (1). To date, a case of intraoperative cerebral herniation due to a large amount of colorless and transparent gelatinous substances has not been reported. Based on the patient’s symptoms, serology, and CSF findings, we considered the patient to have neurosyphilis. According to previous reports, neurosyphilis can occur at any time after primary infection (3, 4). At the same time, the pathologic findings of meningovascular syphilis include diffuse thickening and lymphocytic infiltration of the meninges with superimposed arteritis (5, 6). The formation of the epidural gelatinous substance in this patient can be attributed to the following reasons. First, the decrease in intracranial pressure after tumor resection leads to an increase in volemia of the epidural blood vessels (7). Second, patients with neurosyphilis have vasculitic changes on the dural surface and increased vascular permeability (8) (Figure 2A). Glioma can form neovascularization with high defects, resulting in vessels with abnormal morphology and function (9). Third, leakage of plasma-protein-rich fluid accumulates in the epidural space, which is stirred repeatedly as the patient’s cerebral pulsatility to form a gelatin-like substance (Figure 2B). According to the CT imaging and intraoperative images, the epidural collection is not only gelatinous but also has a blood component. Young and middle-aged postoperative patients with postoperative intracranial tumors often suffer from epidural hemorrhage because the dura mater is more loosely combined with the skull, and it is easier to peel off when the intracranial pressure changes. Therefore, epidural hemorrhage in remote sites is more likely to occur. In elderly patients, due to the large gap between the dura mater and the brain tissue and the poor compliance of the brain tissue in elderly patients, the intracranial pressure fluctuates significantly during the operation, which may easily lead to stretching and rupture of the bridging vein. Therefore, subdural hematomas in distant parts are more likely to occur (10, 11). Eventually, the gradually increasing epidural collection causes a malignant intraoperative cerebral herniation.

Our case is the first known case of a malignant bulge of the brain during craniotomy caused by the accumulation of a large amount of gelatinous substances. When cerebral herniation occurred, we intervened promptly and accurately, which ultimately led to the patient’s survival. Despite the efficacy of the treatment for neurosyphilis in this particular patient, the irreversible harm inflicted by treponema pallidum on the blood vessels of the meninges necessitates caution among patients undergoing craniotomy, as cerebral bulges may arise during surgery, regardless of whether it occurs during the active phase of neurosyphilis or subsequent to treatment. In conclusion, it is strongly advised that neurosurgeons exercise utmost caution during craniotomy procedures conducted on patients presenting with treponema pallidum infection or any other medical condition that may potentially induce vasculitis. When these patients require a craniotomy, the likelihood of cerebral herniation during surgery will increase.

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Ethical review and approval was not required for the study on human participants in accordance with the local legislation and institutional requirements. Written informed consent from the patients/ participants or patients/participants' legal guardian/next of kin was not required to participate in this study in accordance with the national legislation and the institutional requirements. Written informed consent was obtained from the individual for the publication of any potentially identifiable images or data included in this article.

All authors listed have made a substantial, direct, and intellectual contribution to the work and approved it for publication.

This work was supported by the Sichuan Province Key R&D Project (22ZDYF1826) and the 2021 hospital-level incubation Project of Yibin Hospital, West China Hospital of Sichuan University (2021FY15).

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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