Minimally invasive resection of an extradural far lateral lumbar schwannoma with zygapophyseal joint sparing: surgical nuances and literature review

Abstract

Introduction. Spinal schwannomas are benign nerve sheath tumors. Completely extradural schwannomas of the lumbar spine are extremely rare lesions, accounting for only 0,7-4,2% of all spinal NSTs. Standard open approaches have been used to treat these tumors, requiring extensive muscle dissection, laminectomy, radical foraminotomy, and facetectomy. In this paper the authors present the case of a minimally invasive resection of a completely extradural schwannoma. Operative technique literature review is presented. Material & Methods. A 50-year-old woman presented with progressive complains of chronic right leg pain and paresthesia. The magnetic resonance imaging revealed a giant well-encapsulated dumbbell-shaped extradural lesion at the L3-L4 level. The patient underwent a minimally invasive gross total resection of the tumor using a tubular expandable retractor system. Results. The patient had complete resolution of radiculopathy in the immediate postoperative period and she was discharged home, neurologically intact, on the second postoperative day. Postoperative MRI demonstrated no evidence of residual tumor. At latest follow-up (18 months) the patient remains asymptomatic. Conclusion. Although challenging, this minimally invasive procedure is safe and effective, being an appropriate alternative, with many potential advantages, to the open approach.

Figure 1

Preoperative MRI documents a right L3/L4 completely extradural dumbbell-shaped tumor with extraforaminal extension into the right psoas muscle: (a) T1-weighted; (b) axial T2-weighted with gadolinium enhancement; (c) sagittal T1-weighted showing extraforaminal and foraminal tumor components; (d) sagittal T2-weighted with gadolinium enhancement showing extraforaminal and foraminal tumor components; (e) coronal view with gadolinium.

Figure 2

Resection of a completely extradural lumbar schwannoma through a minimally invasive approach using an expandable transmuscular tubular retractor, positioned laterally to the facet joint complex.

Figure 3

(a) Patient positioning and (b) preoperative planned skin incision (arrow).

Figure 4

(a) Intraoperative fluoroscopic localization of L3/L4 extraforaminal space; (b) retractor placement and angulation into the intertransverse space, lateral to the L3/L4 facet complex.

Figure 5

(a) Sequential muscle dilation and (b) expandable tubular retractor fixation to the articulated arm.

Figure 6

Intraoperative microsurgical images showing (a) bone removal allowing tumor exposition; (b) tumor capsule incision; (c) internal debulking with CUSA; (d) piecemeal tumor removal; (e) L3 nerve root preservation after tumor gross total resection.

Figure 7

(a) Three cm long right paramedian longitudinal skin incision 4 to 5 cm off the midline; (b) final cosmetic result.

Figure 8

(a and b) Biphasic pattern with cellular Antoni A and hypocellular Antoni B areas. Compact fascicles of elongated tumor cells with slight nuclear polymorphism. Hyalinized vessels.

Figure 9

Postoperative MRI demonstrates gross total resection of the tumor and postoperative changes with no muscle atrophy: (a) axial T1-weighted with gadolinium enhancement; (b) T2-weighted; (c) sagittal T1-weighted with gadolinium enhancement; (d) T2-weighted.

Figure 10

Postoperative bone window CT scan: (a) axial view demonstrating facet joint integrity (arrow); (b) sagittal view showing widening of the neural foramen (∗) and pars interarticularis sparing (arrow); (c) coronal view also illustrating pars preservation (arrow).