case_images: PMC6744738_01
case_images: Preoperative magnetic resonance imaging showing T1- weighted (a), T2-weighted (b), and fluid-attenuated inversion recovery (c) images. The cyst content demonstrates slightly higher intensity than regular cerebrospinal fluid on fluid-attenuated inversion recovery images, containing a mucous-like nodule with isointensity on T1WI and mild high intensity on T2WI. Uncal herniation is observed at the level of the mesencephalon (d).
case_images: SNI-10-141-g001.jpg
case_images: PMC6744738_01_SNI-10-141-g001.jpg
case_images: F1
case_images: T2- weighted images [Figure 1b], with no diffusion restriction. The cyst fluid showed a cerebrospinal fluid (CSF)-like pattern in most sequences, other than in fluid-attenuated inversion recovery images, where the content showed slightly higher intensity than regular CSF [Figure 1c]. There was a mucous- like nodule with isointensity on T1-weighted images and mild high intensity on T2-weighted images. The lesion was not enhanced the following gadolinium injection.
case_images: Intraoperative presentation of the cyst. The cyst is covered by a thin whitish membrane and contains white turbid fluid.
case_images: SNI-10-141-g002.jpg
case_images: PMC6744738_01_SNI-10-141-g002.jpg
case_images: F2
case_images: As the dura mater was opened, a large extra- axial cyst was seen, covered with a thin whitish membrane and containing white turbid fluid [Figure 2].
case_images: Postoperative course is organized as a timeline. The patient experienced a tonic-clonic seizure 9 h after surgery. Lumbar puncture and electroencephalogram were performed on postoperative day 1. The seizure was finally controlled with levetiracetam 4000 mg, Fosphenytoin 7.5 mg/kg, Lacosamide 200 mg, and propofol 0.3 mg/kg/h.
case_images: SNI-10-141-g003.jpg
case_images: PMC6744738_01_SNI-10-141-g003.jpg
case_images: F3
case_images: Postoperative course shown above is organized as a timeline [Figure 3].
case_images: (a and b) Postoperative magnetic resonance imaging shows cyst shrinkage and disappearance of the mass effect.
case_images: SNI-10-141-g004.jpg
case_images: PMC6744738_01_SNI-10-141-g004.jpg
case_images: F4
case_images: On postoperative MRI performed 2 weeks after the surgery, the cyst shrank dramatically with satisfactory decompression [Figure 4].
case_images: Histopathological features of the cyst wall. Hematoxylin and eosin staining shows pseudostratified ciliated columnar epithelium with a basement membrane (a). The presence of goblet cells is shown by periodic acid-Schiff staining (b). Carcinoembryonic antigen is also positive in the cytoplasm in a few epithelial cells, suggesting carcinoembryonic antigen secretory capacity (c).
case_images: SNI-10-141-g005.jpg
case_images: PMC6744738_01_SNI-10-141-g005.jpg
case_images: F5
case_images: On histopathological examination, the cyst wall contained pseudostratified ciliated columnar epithelium with a basement membrane on hematoxylin and eosin staining [Figure 5a]. A few goblet cells were also present on staining with periodic acid-Schiff [Figure 5b], mucicarmine, and Alcian blue stains. CAM5.2 and epithelial membrane antigen were positive, which supported the diagnosis of an endodermal cyst. Carcinoembryonic antigen (CEA) was also positive in the cytoplasm in a few epithelial cells [Figure 5c].