The sellar septum is an extension of the dura mater and a barrier between the contents of the saddle and the suprasellar region [11]. The suprasellar extension will mechanically destroy the structure of the sellar septum. Once the suprasellar extension of pituitary adenomas is located in the dura mater and connected with the skull cavity, it will increase the incidence of surgical complications [12].
Intracranial infection is one of the complications after endoscopic transsphenoidal pituitary adenoma resection. Previous studies have shown that cerebrospinal fluid leakage is one of the independent risk factors [13,14,15], which is consistent with the results of this study. The incidence of cerebrospinal fluid leakage after endoscopic treatment of pituitary adenomas is between 0.5% and 14% [16], and the incidence of leakage in this study was 12.8%, and is therefore, placed in the high range, because the extension of pituitary adenomas to the saddle will increase the risk of cerebrospinal fluid leakage [8]. Gongyumin et al. [17] found that the pathogenic mechanism of postoperative cerebrospinal fluid leakage leading to intracranial infection may be that this leakage causes the brain tissue to connect with the outside world, providing a channel for bacteria to invade the brain, resulting in intracranial infection. In addition, studies have shown that postoperative intracranial pneumatosis (maximum pneumatosis cavity diameter ≥ 1cm) is also an independent risk factor for intracranial infection after endoscopic transsphenoidal pituitary adenoma resection [18].
However, in the multifactorial model from this study, intracranial pneumatosis did not reach statistical significance. Among the 12 patients with intracranial infection after operation, seven patients had cerebrospinal fluid leakage and intracranial pneumatosis at the same time after operation, two patients had no cerebrospinal fluid leakage but had intracranial pneumatosis after CT Reexamination, and both of the two patients were found to have cerebrospinal fluid leakage during operation. The remaining thee patients did not have cerebrospinal fluid leakage and intracranial pneumatosis after operation, This indicates that postoperative intracranial pneumatosis is not equal to the presence of cerebrospinal fluid leakage at the same time. We believe that the formation of postoperative intracranial gas accumulation may be due to the channel presence between the brain and the outside world caused by cerebrospinal fluid leakage during the operation, causing gas enter the brain. However, this channel is transient and after the operator reconstructs and repairs the skull base, the brain can become a closed space again, thus reducing the incidence of postoperative cerebrospinal fluid leakage.
In addition, pituitary adenomas can invade the suprasellar region through the sellar septal foramen during the growth process [11]. For pituitary adenomas with Hardy grade ≥ 2, studies have reported that patients with adenomas extending to the suprasellar region are more likely to have complications such as visual field defect, pituitary dysfunction, cerebrospinal fluid leakage, when compared to patients with adenomas extending in other directions [17,19]. However, there are relatively few studies investigating complications of postoperative intracranial infection. In our study, tumor features were described quantitatively, and pituitary adenomas were measured quantitatively from sagittal and coronal MRI images. Of course, the tumor can also extend to the parasellar and infrasellar regions, but we believe that the extension distance above the sellar region is more important. However, the extension of the tumor to the infrasellar region will reduce the pressure in the sellar region to a certain extent. If the tumor invades into the parasellar cavernous sinus, the internal carotid arteries on both sides will be pushed and displaced, and the positions measured on the coronal images will change accordingly. The suprasellar distance is measured based on bone structure in the sagittal position. Therefore, SSE in the sagittal position is relatively constant and more reliable [20].
In our study, preoperative sagittal SSE ≥ 15.6mm and tumor toughness were independent risk factors for postoperative intracranial infection in patients with suprasellar extended pituitary adenomas. The sellar septum is the dura extension of the skull base, covering the pituitary fossa. The extension and invasion of pituitary adenomas to the sellar septum will break through the sellar septal foramen and destroy the original structure of the sellar septum. For pituitary adenomas with suprasellar extension, the operator needs to remove the tumor to the suprasellar region, which may damage the sellar septum structure again, causing intracranial communication with the outside world, leading to the occurrence of postoperative intracranial infection. The tumor texture will affect the incidence of postoperative foramen leakage [16], further increasing the incidence of postoperative intracranial infection.
During surgery, soft tumors can be easily removed by suction, while tough tumors, require difficult surgical procedures, which increases damage to normal tissue. In this study, cerebrospinal fluid leakage during operation was also included, but there was no correlation between this factor and postoperative intracranial infection. We believe that in some cases of postoperative cerebrospinal fluid leakage without intraoperative cerebrospinal fluid leakage, the operator needs to evaluate whether there is clearly visible leakage during the operation, which may cause some low flow cerebrospinal fluid leakage to be ignored, or the sellar septum to collapse due to sneezing after the operation, resulting in leakage. Therefore, some studies suggest that even if cerebrospinal fluid leakage is not found, if there is obvious subarachnoid hernia, sellar floor reconstruction can be performed [21].