case_images: PMC10840588_01
case_images: Preoperative MRI with arrows demonstrating the PFAC at the left CPA with mass effect on the midbrain, pons, and cerebellum (a) axial T2; (b) coronal T2; (c) axial T1; (d) sagittal T2 with arrow demonstrating syringomyelia
case_images: cureus-0016-00000051750-i01.jpg
case_images: PMC10840588_01_cureus-0016-00000051750-i01.jpg
case_images: FIG1
case_images: T5 and cerebellar tonsillar herniation 6 mm below the foramen magnum (Figure 1). There was no diffusion restriction, as confirmed by a neuroradiologist.
case_images: Postoperative MRI with arrows demonstrating improved PFAC, axial T2 MRIs (a) postoperative day 1; (b) six months postoperative; (c) 12 months postoperative; (d) sagittal T2 cervical MRI at 12 months postoperative, with arrow demonstrating the near-complete resolution of the syringomyelia
case_images: cureus-0016-00000051750-i02.jpg
case_images: PMC10840588_01_cureus-0016-00000051750-i02.jpg
case_images: FIG2
case_images: Immediate postoperative MRI demonstrated a decompressed posterior fossa with some persistent adherent cyst wall, edema in the brainstem, ventriculomegaly, and syringomyelia, all of which continued to improve over further imaging 12 months after surgery (Figure 2).
case_images: Hematoxylin and eosin stain demonstrating fragment consistent with benign arachnoid cyst. Keratin debris was also present (not within slide)
case_images: cureus-0016-00000051750-i03.jpg
case_images: PMC10840588_01_cureus-0016-00000051750-i03.jpg
case_images: FIG3
case_images: Pathology was consistent with an arachnoid cyst, though scattered keratin debris was noted on pathology, representing a possible component of an indolent epidermoid tumor (Figure 3).