PMC8053460_01
Preoperative nonenhanced computed tomography (CT) scan demonstrating a paramedian right occipital well-circumscribed, inhomogeneously hyperdense, lesion with sharply demarcated erosion of both tables of the skull in axial (a) and sagittal view (b); preoperative 3D CT scan showing the bone defect (c).
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F1
A noncontrast-enhanced CT scan demonstrated a paramedian right occipital well-circumscribed, inhomogeneously hyperdense, lesion with sharply demarcated erosion of both tables of the skull and scalloping of sclerotic bony margins [Figures 1a and b]; the 3D CT reconstruction clearly showed the bone defect [Figure 1c].
Preoperative contrast-enhanced T1-weighted magnetic resonance imaging in sagittal (a) and coronal (b) view demonstrating the hypointense lesion obstructing the confluence of the superior longitudinal and transverse sinuses, confirmed by MRV (c).
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F2
MRI confirmed the presence of the intradiploic, almost spherical, lesion with a diameter of about 2.6 cm; on T1-weighted images, the lesion appeared hypointense to the brain and slightly hyperintense to the CSF; on T2-weighted images, it appeared inhomogeneously hyperintense to the brain and almost isointense to CSF; diffusion-weighted images were hyperintense with a high value on apparent diffusion coefficient; contrast-enhanced T1-weighted images revealed almost complete occlusion of the venous flow at the confluence of sinuses (torcular herophili) by the lesion itself, which resulted nonenhanced [Figures 2a and b]; MRI venogram confirmed the occlusion of the torcular [Figure 2c].
Intraoperative images: the lesion, exposed through a longitudinal median parieto-occipital incision and skeletonization, bulged from the eroded outer bone table, harvested by a fibrous capsule (a); under microscopic magnification, the capsule was incised evidentiating the cyst content, which had a variegated appearance with some dark areas suggestive for previous subacute intralesional hemorrhage and other areas with the classical pearly aspect of epidermoid cysts (b); the lesion was removed piecemeal (c and d); after evacuation of the cystic contents, the fibrous capsule was separated from the borders of the bone and dissected from the intact dura mater (e); the sclerotic and thickened bony borders were drilled away, highlighting blood flow restoration in the confluence of sinuses (f and g); the bony defect was reconstructed by acrylic resin cranioplasty (h).
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F3
A longitudinal median parieto-occipital incision of 8 cm, centered on the inion, allowed skeletonization of the region and exposure of the lesion, which bulged from the eroded outer bone table, harvested by a fibrotic capsule; incision of the capsule gave rise to a small amount of brownish fluid (collected for analysis) exposing the cyst content, which had a variegated appearance with some dark areas suggestive for previous subacute intralesional hemorrhage and other areas with the classical pearly aspect of epidermoid cysts; under microscopic vision, the lesion was removed piecemeal; the fibrotic capsule was separated from the sclerotic borders of the bone and dissected away from the intact dura mater, with evident blood flow restoration in the confluence of sinuses; thereafter, the sclerotic scalloped bone margins were drilled to reduce their thickness, for a better reconstruction, which was performed by acrylic resin cranioplasty [Figure 3a-h].
Postoperative CT scan showing complete removal of the lesion and reconstruction of the bone defect by acrylic resin material cranioplasty in axial (a) and sagittal view (b) and in 3D CT scan (c).
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F4
Postoperative CT scan with 3D reconstruction and MRI with MR venogram, performed during hospitalization, demonstrated the radical exeresis of the lesion, the optimal result of cranioplasty, and the restoration of flow in the torcular herophili and transverse sinuses [Figures 4 and 5].
Postoperative contrast-enhanced T1-weighted MRI in sagittal (a) and coronal (b) view, demonstrating the complete exeresis of the lesion with resolution of venous sinuses obstruction, as confirmed by MRV (c).
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F5
Postoperative CT scan with 3D reconstruction and MRI with MR venogram, performed during hospitalization, demonstrated the radical exeresis of the lesion, the optimal result of cranioplasty, and the restoration of flow in the torcular herophili and transverse sinuses [Figures 4 and 5].
Photomicrograph of the specimen shows a cystic formation with a fibrous wall, outlined by squamous epithelium and containing keratinic material arranged in lamellae (a: HE, x100); foreign body granulations with moderate vascularity and intralesional hemorrhage can be observed at higher magnification (b: HE, x200; foreign body granulation in the circle).
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F6
Histology of specimen revealed features consistent with a cystic formation with a fibrous wall, outlined by squamous epithelium and containing keratinic material arranged in lamellae, consistent with the diagnosis of epidermoid cyst [Figure 6].