Spinal extradural en plaque meningiomas: clinical features and long-term outcomes of 12 cases.

OBJECT: Extradural en plaque meningiomas are very rare tumors in the spinal canal. Most studies on these lesions have been case reports with literature reviews. In this paper, the authors review their experience in a surgical series of 12 patients with histologically proven, purely extradural en plaque meningiomas and discuss their clinical features, radiological findings, and long-term outcomes.

METHODS: Clinical and imaging data of 12 patients with spinal extradural en plaque meningiomas treated at a single institution were retrospectively analyzed.

RESULTS: There were 5 male and 7 female patients, with a mean age of 39.9 years. The mean follow-up period was 74.8 months. Nine tumors were located in the cervical spine, 1 in the cervicothoracic spine, and 2 in the thoracic spine. All the tumors were confirmed as extradural en plaque meningiomas with sheetlike growth along the dura mater. Gross-total resection of the tumor with a well-demarcated dissection plane was achieved in 4 cases. Subtotal resection was achieved in 8 cases, 2 of whom underwent postoperative low-dose radiation therapy. The symptoms present before the surgery were improved in all cases at the last follow-up evaluation. The postoperative follow-up MRI showed no recurrence or regrowth in 4 cases with gross-total removal and 7 cases with subtotal removal during the mean follow-up periods of 58.0 months and 71.1 months, respectively. One patient experienced recurrence at 88 months after his initial subtotal removal and improved following a revision operation.

CONCLUSIONS: Spinal extradural en plaque meningiomas are amenable to surgery if complete removal can be achieved. Because of the encirclement of the dura that is characteristic of the tumors, complete resection is usually difficult, subtotal removal for spinal cord decompression is advised, and follow-up imaging is needed. The risk of long-term recurrence/regrowth of the lesions is low, and a good clinical outcome after total or subtotal removal can be expected.