A Novel Classification and Its Clinical Significance in Spinal Schwannoma Based on the Membranous Hierarchy

Background: Spinal schwannoma is a common benign tumor. However, the high recurrence rate and incidence of surgical complications are unsolved problems.

Objective: To propose a morphological classification of spinal schwannoma based on tumor-membrane relationships to increase the gross total resection (GTR) rate and to decrease the incidence of surgical complications.

Methods: Histological techniques were used to study 7 adult cadavers. Following picrosirius staining, the membranes around the nerve root were observed under a microscope. Data from 101 patients with spinal schwannoma were also collected for clinical analysis.

Results: The sleeve around the spinal nerve root consisted of dura and arachnoid tissues. The space between them gradually narrowed and fused at the proximal pole of the nerve root ganglion. Spinal schwannomas were divided into 4 types based on membranous structure: intrapial (type I), subarachnoidal (type II), intra- and extradural (type III), and extradural growth (type IV). Types II and III were further subdivided into 2 subtypes. GTR was achieved in all patients (100%), with no tumor recurrence during follow-up. Overall functional status significantly improved postoperatively. A total of 59 patients (92%) showed improvement or significant improvement postoperatively. There was no difference in surgical outcomes among the tumor classifications (P = .618). No intraoperative vertebral artery injuries or postoperative cerebrospinal fluid fistula occurred.

Conclusion: Spinal schwannoma classification based on a membranous hierarchy provides an intuitive platform for preoperative planning and intraoperative safety. This classification scheme may help surgeons better define surgical goals and anticipate or even avoid complications from resection.