Proposal of a new radiological classification system for spinal meningiomas as a descriptive tool and surgical guide

- SM can be radiologically classified accurately based on preoperative axial post contrast MRI.
- Staging and subtyping depend on the cross sectional surface area of the tumor and relation to spinal cord, respectively.
- Despite rarity, small ventrally located SM may require additional bone resection or non-conventional surgical approach.
- Surgical treatment selection is mainly based on the location of the bulk of the tumor rather than site of dural attachment.

Objectives1) To provide neurosurgeons and radiologists with a new quantitative and anatomical method to describe spinal meningiomas (SM) consistently.2) To provide a guide to the surgical approach needed and amount of bony resection required based on the proposed classification.3) To report the distribution of our 58 cases of SM over different Stages and Subtypes in correlation to the surgical treatment needed for each case.4) To briefly review the literature on the rare non-conventional surgical corridors to resect SM.Patients and methodsWe reviewed the literature to report on previously published cohorts and classifications used to describe the location of the tumor inside the spinal canal. We reviewed the cases that were published prior showing non-conventional surgical approaches to resect spinal meningiomas. We proposed our classification system composed of Staging based on maximal cross-sectional surface area of tumor inside canal, Typing based on number of quadrants occupied by tumor and Subtyping based on location of the tumor bulk to spinal cord. Extradural and extra-spinal growth were also covered by our classification. We then applied it retrospectively on our 58 cases.Results12 articles were published illustrating overlapping terms to describe spinal meningiomas. Another 7 articles were published reporting on 23 cases of anteriorly located spinal meningiomas treated with approaches other than laminectomies/laminoplasties. 4 Types, 9 Subtypes and 4 Stages were described in our Classification System. In our series of 58 patients, no midline anterior type was represented. Therefore, all our cases were treated by laminectomies or laminoplasties (with/without facetectomies) except a case with a paraspinal component where a costotransversectomy was needed.ConclusionSpinal meningiomas can be radiologically described in a precise fashion. Selection of surgical corridor depends mainly on location of tumor bulk inside canal.