case_images: PMC6652055_01
case_images: Preoperative thoracic MRI. Heterogeneous epidural posterior mass compressing the thoracic cord between Th6 and Th9 was revealed at the admission. Sagittal view of heterogeneous isointense mass of T1-weighted image (a), heterogeneous isointense mass of T2-weighted image (b), and nonenhancing mass of Gd-enhanced T1-weighted image (c). Axial view of epidural mass of T2-weighted image in Th6/7 (d), Th7/8 (e), Th8/9 (f), and Th9/10 (g) intervertebral levels. This epidural mass was considered as an old epidural hematoma initially.
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case_images: PMC6652055_01_CRIOR2019-1640485.001.jpg
case_images: fig1
case_images: T1- and T2-weighted images (Figure 1). These clinical courses and radiological findings suggested old epidural hematoma.
case_images: Preoperative thoracic CT. Ossified epidural posterior mass compressing the thoracic cord between Th6 and Th9 was revealed in coronal view (a) and sagittal view (b) of thoracic CT. Ossified lesion reached to extraforamen at Th7/8 intervertebral levels (c). Axial view of epidural ossified mass in Th6/7 (d), Th7 (e), Th8/9 (f), and Th9/10 (g) levels, which occupied about 50-80% of the spinal canal.
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case_images: PMC6652055_01_CRIOR2019-1640485.002.jpg
case_images: fig2
case_images: Th7/8 foramen) or to the extent which integrated the lamina (Th7-Th8 laminas), leading to make the spinal cord compressed severely. These ossification lesions seemed to have the bone marrow inside (Figure 2).
case_images: Surgical excision of ossified lesion under O-arm-based navigation system. After performing Th6-Th10 laminectomy, the posterior epidural space was filled with an ossified mass. To float the adhered ossified mass, pediculectomy of Th7 and Th8 and posterior spinal fusion from Th5 to Th11 were performed. Surgeons can resect or float an enormous contiguous ossified mass safely (arrowhead), confirming the thickness of ossification and the adhesion to circumferential tissues under O-arm-based 3D navigation (sagittal view (a), coronal view (b)).
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case_images: PMC6652055_01_CRIOR2019-1640485.003.jpg
case_images: fig3
case_images: Th7-Th8 levels, where this mass adhered to bilateral pedicles of Th7 and Th8 (Figure 3). To float these lesions, pediculectomy of Th7 and Th8 was performed.
case_images: Thoracic spine radiological findings post Th5-Th11 posterior spinal fusion. Postoperative MRI showed the dura matter swollen (sagittal view (a)), while CT demonstrated the total resection of these extremely ossified components (sagittal view (b), axial view in Th7/8 level (c)).
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case_images: PMC6652055_01_CRIOR2019-1640485.004.jpg
case_images: fig4
case_images: Th6-9 epidural ossified mass. This separated beak lesion was considered as the dynamic factor to mainly cause thoracic myelopathy through the compression of the spinal cord. The resection or floating of these extremely ossified components made compressive dura matter swollen (Figure 4).
case_images: Histopathological analysis of the resected tumors. Macroscopic findings of the resected epidural mass (a). Ossification of the ligament tissue was observed in the resected tumor. This mass was diagnosed as a contiguous multilevel OLF according to microscopic findings (hematoxylin and eosin stained) (b).
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case_images: PMC6652055_01_CRIOR2019-1640485.005.jpg
case_images: fig5
case_images: Contiguous multilevel OLF was diagnosed and confirmed by pathology (Figure 5).