case_images: PMC10858758_01
case_images: Computed tomography head without contrast (a) sagittal (b) and two axial views with evidence of occipitoatlantal assimilation
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case_images: F1
case_images: Furthermore, there was evidence on CT of partial occipitoatlantal assimilation as well as basilar invagination [Figure 1].
case_images: Preoperative magnetic resonance imaging (a) sagittal T2-weighted, (b) T1-weighted , (c) T1 post-contrast, and (d) axial T1 post-contrast views. There is a Chiari I malformation, with inferior descent of the cerebellar tonsils below the level of the foramen magnum by approximately 8 mm.
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case_images: F2
case_images: Magnetic resonance imaging (MRI) with and without contrast confirmed inferior descent of the cerebellar tonsils below the level of the foramen magnum by approximately 8 mm [Figure 2], consistent with a Chiari malformation. A well-delineated cystic dilation was also noted in the upper cervical cord, approximately 3.5 cm in the vertical dimension, with some subjacent T2 hyperintensity within the cord parenchyma, suggesting associated cord edema or gliosis [Figure 2].
case_images: (a) Immediate postoperative magnetic resonance imaging (MRI) sagittal post-contrast sequence demonstrating no visible lesion in the cervicomedullary junction and (b) delayed 4-month postoperative T2-weighted MRI sagittal view with a significant reduction in the size of the cervical syringomyelia.
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case_images: F3
case_images: A postoperative MRI of the brain soon after surgery demonstrated decompression of the suboccipital region and expected postoperative changes [Figure 3]. A delayed MRI four months after surgery showed a significant decrease in size of the cervical syringomyelia [Figure 3].
case_images: (a) Hematoxylin and eosin stain permanent block demonstrating pseudo-lumen rosettes, (b) glial brillary acidic protein positivity, (c) K167 proliferation index of <1% (c), and (d) P53 negativity.
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case_images: F4
case_images: Health Organization (WHO) Grade 1 subependymoma. Histopathological review demonstrated pseudo-lumen rosettes and a nodular pattern [Figure 4]. Immunohistochemistry stained positive for glial fibrillary acidic protein and negative for P53 [Figure 4]. Ki67 positivity was less than one percent [Figure 4].