PMC9512490_01
Preoperative radiological images show a meningoencephalocele in the lateral sphenoid sinus and a bony defect in the left middle skull base.
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A: MR angiography images show an arteriovenous malformation in the right parietal lobe. B: CT image reveals a bony defect in the left middle skull base and a continuous structure that protrudes into the left lateral sphenoid sinus. C: Three-dimensional bone computed tomography image reveals a large bony defect outside the foramen rotundum (black arrow). D: Coronal CT image with multiple arachnoid pits in the greater wing of the sphenoid bone (white arrowheads). E: Axial magnetic resonance imaging (MRI) reveals a trabecular structure with a low signal on a T1-weighted image (not shown) and a high signal on a T2-weighted image. F: Sagittal constructive interference in the steady-state sequence shows the empty sella. G-I: Retrospective MRI on T2-weighted images shows how the mass gradually increased (G: 12 years before surgery, H: 9 years before surgery, I: 2 years before surgery).
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A 72-year-old female with no previous history of trauma was diagnosed with a right parietal lobe cerebral AVM 23 years ago (Fig. 1A). Plain computed tomography (CT) of the head revealed a bony defect in the left middle skull base and a continuous structure extending into the left lateral SS (Fig. 1B). Three-dimensional CT revealed a bony defect that was integrated into the foramen rotundum (Fig. 1C), whereas coronal CT images showed multiple small bony defects (Fig. 1D). Magnetic resonance imaging (MRI) revealed a trabecular structure with low signal on T1-weighted images and high signal on T2-weighted images, and the trabecular structure was noted to be continuous from the tip of the temporal lobe to the lateral SS (Fig. 1E). MRI constructive interference in the steady-state sequence showed an empty sella (Fig. 1F). The mass gradually increased for over 12 years (Fig. 1G-I).
Intraoperative images.
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A: Multiple arachnoid pits (white arrowheads) in the middle fossa exposed after a left frontotemporal craniotomy. B: Partially removed brain tissue covered with dura. Asterisk (*) indicates the V2 root through the medial bone defect. C: Double asterisks (**) indicate the large bony defect and arachnoid pit. D: 70-degree endonasal endoscopic view. Brain tissue covered with mucosa was revealed in the sphenoid sinus. E: The dural defect was patched with temporal fascia after resection of the meningoencephalocele. F: The large bony defect and multiple bone pits in the middle fossa were repaired with the pedunculated temporalis fascia and a bone fragment made of the inner plate of the frontotemporal bone.
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After performing a left frontotemporal craniotomy, we separated the middle fossa dura from the skull base, and the V2 and V3 nerve roots and several arachnoid pits that invaginated into bone were thereafter identified (Fig. 2A-C). We then observed the pulsatile mass through the enlarged natural ostium in the SS (Fig. 2D), and the incised brain tissue was removed from the nasal cavity. The dural defect was closed using a galeal patch with sutures (Fig. 2E). The defects of the middle fossa, enlarged foramen rotundum, and several caves by arachnoid pits were covered with the bone fragment consisting of the inner plate of the frontotemporal bone and pedunculated temporalis fascia (Fig. 2F).
Histological findings of the resected specimen.
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A: The mass consists of brain tissue with a cyst partially covered with epithelium and a thick connective tissue membrane. H&E. B-D: Higher magnification of the area indicated by an arrow in A. Glial tissue immunolabeled with glial fibrillary acidic protein (GFAP) is intermixed with fibrocollagenous tissue, whose surface was stained green with Elastica-Goldner staining (El-Gold). B, H&E; C, GFAP; D, El-Gold. E-G: Higher magnification images taken from the consecutive section of A. The area indicated by the dotted square shows an irregular surface of gliotic cortical tissue covered with ciliated columnar epithelium lined with a dense fibrocollagenous band and sparse fibrous tissue. Inset: Sparse fibrous tissue indicated by a square in E includes epithelial membrane antigen (EMA)-labeled cells that are meningothelial in nature. E, H&E; F, GFAP; G, El-Gold; inset in E, EMA. H: A higher magnification image taken from the area indicated by H in A shows cortical tissue with fibrillary gliosis and a dysmorphic large neuron (arrow) and scattered Rosenthal fibers (arrowheads). H&E. I: A higher magnification image taken from the area indicated by I in A shows uneven neuronal distribution with a dysmorphic neuron (arrow) and closely adjacent small neurons (arrowheads). Inset: A binuclear dysmorphic neuron. Kluver-Barrera staining. J: A higher magnification image taken from the area indicated by the square in A exhibits abnormal clustered arterioles and venules with thickened fibrous adventitia. El-Gold. Bar = 800 mum for A, 30 mum for B, and inset in E, 50 mum for C, D, and H, 100 mum in E-G, 75 mum for I, 115 mum for J, and 10 mum for inset in I.
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Histological examination of the resected mass revealed that it consisted of brain tissue and a cyst partially covered with ciliated columnar epithelium and a thick fibrocollagenous tissue membrane (Fig. 3A). Elastica-Goldner staining (El-Gold) (Fig. 3B-D); the gliotic cortical tissue was noted to be irregularly extended under the fibrocollagenous tissue (Fig. 3E-G). Epithelial membrane antigen-labeled cells that were meningothelial in nature were evident in the sparse fibrous tissue covering the cortex (Fig. 3E inset). The resected cortex exhibited severe cortical laminar disorganization accompanied by large dysmorphic neurons (arrows in Fig. 3H and I) including binuclear neurons (Fig. 3I inset). Fig. 3H). Furthermore, abnormal clustered arterioles and venules with thickened fibrous adventitia were also observed to be evident on the cortical surface (Fig. 3J).