Metastatic meningioma to the eleventh dorsal vertebral body: total en bloc spondylectomy. Case report and review of the literature.

INTRODUCTION One in every thousand intracranial meningiomas metastatize extracranially. Lung and intraabdominal organs are most frequently affected. Only 7% involve vertebrae and just a dozen cases have been reported in the literature. To our knowledge, this is the first description of a total en bloc spondylectomy through a posterior approach for the treatment of an intraosseous metastatic meningioma to the eleventh dorsal vertebra. CASE REPORT In March 1996, a 37 year-old male underwent surgical resection for a left occipital intraventricular benign meningioma (WHO I). He was reoperated in February 2002 due to local recurrence. By the end on 2003 he developed progressively invalidating dorsolumbar pain. MRI studies revealed a T11 intraosseous mass. In March 2004, a percutaneous biopsy and vertebroplasty were performed. The pathological specimen was identified as adenocarcinoma and he initiated chemotherapy. Advice from a second pathologist was seeked, who suggested the diagnosis of intraosseous meningioma. Workup studies failed to reveal any primary tumor. In May 2004 the patient was admitted to our department and a new transpedicular biopsy confirmed the diagnosis. In June 2004 he underwent T11 total en bloc spondylectomy (Tomita's procedure), fusion with bone and calcium substitute-filled stackable carbon-fiber cages, and T9 to L1 transpedicular screw fixation. No postoperative complications ocurred and he is, so far, free from primary and secondary disease. Definite pathology: benign meningioma (WHO I). DISCUSSION Distant metastases from intracranial meningiomas are rare entities, arising from benign lesions in, at least, 60% of cases. Enam et al proposed a specific pathological score to differentiate benign, atypic and malignant meningiomas. Such score correlates with the chance of metastatizing: more than 40% in malignant meningiomas compared to 3.8% of brain tumors overall. The ability to metastatize seems to be linked to vascular or lifatic invasiveness. Metastases ocurr more frequently in angioblastic, papillary and meningothelial variants. Hematogenous (especially venous; Batson's perivertebral plexus), linfatic and cerebrospinal fluid are the main routes involved in the spreading of the tumor. Craniotomy itself may also play a role, for the majority of patients have been previously operated on repeatedly. The interval between the onset of the intracranial disease and the appearance of the metastasis varies from months to many years. The value of transpedicular biopsy is widely recognized (efficacy over 80%) and the suitability of the specimen for pathological examination improves when wide inner caliber trephines are used. In the case presented we applied the oncologic concept of vertebral en bloc resection. We believe this case represents a paradigmatic indication of this technique because it respects the concepts of radical resection and spinal stability, and offers an opportunity for the curation of the disease.