Spinal tumors are to be classified as extradural, intradural-extramedullary or intramedullary. The most prevalent intradural lesions comprise schwannomas, neurofibromas, and meningiomas, while the most common metastatic lesions occur in the epidural space¹⁴⁾.

Spinal meningiomas are typically considered primary spinal tumors, accounting for up to 20% to 30% of all primary spinal tumors³⁾. These tumors are predominantly located in the intradural and extramedullary compartments of the thoracic region¹³⁾; however, extradural meningiomas are extremely rare^2,26). Spinal extradural meningiomas account for only 2.5% to 3.5% of all spinal meningiomas^15,21,25). In this report, we present a case of an extradural meningioma in the upper thoracic spine and review existing literature on epidural meningiomas.

A 58-year-old female presented with progressive motor weakness and paresthesia in both legs over the course of two months. She exhibited paraparesis with a motor grade of 4 in both legs and experienced gait disturbances. Nonetheless, she reported no symptoms of sphincter dysfunction.

A spinal magnetic resonance imaging (MRI) of the thoracic vertebrae revealed an 8.8 cm mass in the left and posterior extradural space at the T1-5 level, showing high signal intensity and homogeneous, avid enhancement on T1 and T2 images. The mass compressed the thecal sac and displaced the spinal cord to the right, causing spinal cord edema at levels T1-3 (Fig. 1). A subsequent computed tomography scan of the thoracic spine identified calcification on the right side of the mass without any evidence of bony erosion (Fig. 2). Preoperatively, endovascular embolization was performed on the feeding artery of the mass, which originated from the right subclavian artery, to reduce the risk of bleeding during surgery. The following day, the patient underwent excision involving a total laminectomy at T2 and T3 and a partial hemilaminectomy at T1 and T4. The laminectomy revealed a reddish-yellow tumor compressing the spinal cord (Fig. 3). A biopsy of the T1-4 epidural lesion identified a meningothelial meningioma, classified as World Health Organization (WHO) grade 1, showing mild cellular atypia and mitotic activity (Fig. 4). Post-surgery, the patient did not receive additional treatments such as postoperative radiotherapy and was discharged on the 12th day after the surgery. She was advised to return for follow-up visits in the 1st, 2nd, 3rd, and 5th months postoperatively. One month later, a follow-up spinal MRI revealed a residual enhancing lesion at the left neural foramina of T2-3 and T3-4 levels, as well as enhancement at the posterior epidural space and laminectomy site at T3-5. Additionally, we observed postoperative fluid collection in the soft tissue from T1-5. Despite these findings, the patient's neurological symptoms had improved, and she returned to work without further complaints (Fig. 5).

Using an operative microscope, the patient underwent a radical surgical excision of the lesions through a total laminectomy at T2 and T3, and a left partial hemilaminectomy at T1 and T4. An extradural tumor was discovered intraoperatively. The lesion, characterized by its reddish-yellow color, hard consistency, and calcifications, had severely compressed the spinal cord to the right. Intra-operative monitoring was used, and there were no special abnormalities during surgery. The extradural mass was completely removed.

A study reported that lamia replacement using a titanium plate improved spinal stability¹⁸⁾. In this surgery, lamina replacement was not performed and no instability or dead space occurred. However, if there is a possibility of instability during the surgical procedure, posterolateral fusion or laminoplasty can be considered. In order to reduce dead space, in this surgery, suture was performed densely, as if sutured the fascia, rather than approximately sutured the muscle.

Spinal meningiomas primarily occur within the dura of the thoracic spine. These tumors are believed to originate from the dentate ligament, with over 95% pathologically classified as WHO grade I¹⁹⁾. Although pure epidural meningiomas are rare, it is crucial to differentiate these extradural lesions from metastatic tumors preoperatively and intraoperatively, as they can be easily misidentified¹⁹⁾. Extradural spinal meningiomas typically exhibit the same histologic features, are most frequently diagnosed in individuals in their 50s and 60s, predominantly occur in the thoracic spine, and are more common in females compared to intracranial meningiomas¹⁵⁾.

Clinically, the symptoms of extradural meningiomas resemble those of intradural meningiomas, including back pain, sensory and motor changes, and, in some cases, sphincter dysfunction¹⁾.

Surgical resection of extradural meningiomas can be challenging and often necessitates a second surgical approach^11,13). In our case, the patient underwent a T2-3 total laminectomy and a left partial hemilaminectomy at T1 and T4. The tumor, which had severely compressed the spinal cord, was nearly completely resected. To prevent cord injury, a safe surgical field where surgical instruments can enter and exit was secured through a total laminectomy. Additionally, a cottonoid was inserted between the capsule membrane to ensure a continuous margin. In addition, sufficient saline application was performed when using bipolar coagulation forceps. Eighteen months post-surgery, the patient has shown no signs of recurrence. According to the WHO classification, meningiomas are categorized into three grades, with meningothelial, fibrous, and transitional subtypes being the most common in Grade I⁹⁾. Our patient’s pathology report indicated a meningothelial meningioma, classified as WHO grade 1, with mild cellular atypia.

Since 2018, we have reviewed 12 cases of spinal extradural masses, as summarized in Table 1. Hong et al.⁹⁾ analyzed 12 cases of spinal epidural meningioma reported from 2002 to 2017. Extradural meningiomas were most commonly located in the thoracic spine, followed by the cervical spine, and predominantly affected female patients. Imaging studies typically showed intraspinal extradural masses with mostly homogeneous enhancement. Most masses exhibited an extradural en plaque lesion, indicative of a dural-based origin, also known as the dural tail sign, resulting in a dumbbell-shaped appearance⁹⁾. Among the 12 cases listed in Table 1, there were 2 cases of atypical meningioma and 1 case of choroid meningioma; the remaining cases were classified as Grade 1 meningiomas. Thus, the majority of the pathology in extradural meningioma was WHO grade 1, consistent with previous research and a 2018 study published in the Journal of Radiology⁹⁾.

Previous literature reviews of major spinal meningioma series, including both intra- and extradural subtypes, report surgical recurrence rates of 3% to 7%¹⁾. However, the recurrence rate after surgery for extradural meningiomas is four times higher than that for intradural meningiomas^5,12). Among the 12 reviewed cases, no recurrence was reported⁹⁾.

Spinal epidural meningiomas are rare, typically presenting as WHO grade 1 tumors. Surgical intervention often results in favorable outcomes, including symptom relief and a low recurrence rate.