This is a rare case of an enormous contiguous multilevel OLF in a 20-year-old female’s thoracic spine after mild back trauma, to the extent that it was misdiagnosed as an old epidural hematoma initially. This female with obesity presented with a 6-month history of progressively worsening dorsal cord disorders. Resection or floating of the enormous OLF could be successfully achieved using O-arm-based navigation, and sensory loss, numbness, and gait disturbance were improved after the operation.
A 20-year-old female with obesity (body mass index: 33.3 kg/m2) presented with a 6-month history of progressively worsening paresthesia of the lower limbs and gait disturbance. Moderate muscle weakness, severe spasticity in the lower limbs, superficial hypoesthesia below the Th6 level, and severe dorsal cord disorders were noted on the first physical examination. There was a history of a contusion in the back following the drop from 2 meters height, treated with conservative therapy 2 years previously. She showed no feature of skeletal dysplasia. Laboratory data revealed no abnormality.
Magnetic resonance imaging (MRI) showed a dorsally located epidural lesion (Th6-Th9) which seemed a heterogeneous mass hypointense on both T1- and T2-weighted images. These clinical courses and radiological findings suggested old epidural hematoma. Computerized tomography (CT) scans revealed that this dorsally located epidural lesion consisted of ossified components, which occupied about 50-80% of the spinal canal, and partially developed even to extraforaminal regions (bilateral Th7/8 foramen) or to the extent which integrated the lamina (Th7-Th8 laminas), leading to making the spinal cord compressed severely. These ossification lesions seemed to have the bone marrow inside.
Thoracic pedicle screw insertions in Th5, 6, 10, and 11 levels preceding thoracic cord decompression and the surgical excision of ossified lesion or floating of ossified lesion with the slight adhesion to dura matter were performed under O-arm-based navigation system (O-arm Surgical Imaging System and StealthStation; Medtronic, Inc., Minneapolis, MN, USA). When Th6-Th10 laminectomy was performed, the posterior epidural space was filled with an ossified mass. Between Th6-Th9 laminas and the ossified mass, there was a part of denatured flavum with abundant blood vessels. In particular, these ossified lesions developed in Th7-Th8 levels, where this mass adhered to bilateral pedicles of Th7 and Th8. To float these lesions, pediculectomy of Th7 and Th8 was performed. We found bilateral OLF in Th9/10 level, separated from 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. After the resection of ossified lesions, an autologous local bone graft harvested during decompressive laminectomy was placed between decorticated transverse processes or remained laminas as posterolateral spinal fusion from Th5 to Th11. The operation took 303 minutes. In spite of denatured enormous lesions, the intraoperative blood loss was no more than 420 mL, by repeating vigorous hemostasis by electrocoagulation, bone wax, and FLOSEAL hemostatic matrix (Baxter Healthcare Corp, Fremont, CA, USA).
Ossification of the ligament tissue was observed in the resected tumor. Contiguous multilevel OLF was diagnosed and confirmed by pathology. After the operation, sensory loss, numbness, and gait disturbance were improved. Her Japanese Orthopaedic Association (JOA) score for thoracic myelopathy recovered from preoperative 5.0 points to 8.0 points out of 11 points. Following examinations indicated the absence of recurrence or neurological deterioration.