Surgical strategies for managing foraminal nerve sheath tumors: the emerging role of CyberKnife ablation

Abstract

Sixteen Stanford University Medical Center (SUMC) patients with foraminal nerve sheath tumors had charts reviewed. CyberKnife radiosurgery was innovative in management. Parameters were evaluated for 16 foraminal nerve sheath tumors undergoing surgery, some with CyberKnife. Three neurofibromas had associated neurofibromatosis type 1 (NF1). Eleven patients had one resection; others had CyberKnife after one (two) and two (three) operations. The malignant peripheral nerve sheath tumor (MPNST) had prior field-radiation and adds another case. Approaches included laminotomy and laminectomies with partial (three) or total (two) facetectomies/fusions. Two cases each had supraclavicular, lateral extracavitary, retroperitoneal and Wiltze and costotransversectomy/thoracotomy procedures. Two underwent a laminectomy/partial facetectomy, then CyberKnife. Pre-CyberKnife, one of two others had a laminectomy/partial facetectomy, then total facetectomy/fusion and the other, two supraclavicular approaches. The MPNST had a hemi-laminotomy then laminectomy/total facetectomy/fusion, followed by CyberKnife. Roots were preserved, except in two. Of 11 single-operation-peripheral nerve sheath tumors, the asymptomatic case remained stable, nine (92%) improved and one (9%) worsened. Examinations remained intact in three (27%) and improved in seven (64%). Two having a single operation then CyberKnife had improvement after both. Of two undergoing two operations, one had symptom resolution post-operatively, worsened 4 years post-CyberKnife then has remained unchanged after re-operation. The other such patient improved post-operatively, had no change after re-operation and improved post-CyberKnife. The MPNST had presentation improvement after the first operation, worsened and after the second surgery \and CyberKnife, the patient expired from tumor spread. In conclusion, surgery is beneficial for pain relief and function preservation in foraminal nerve sheath tumors. Open surgery with CyberKnife is an innovation in these tumors' management.

Fig. 1

Asazume et al.’s cervical dumbbell tumor classification system was used to categorize tumors. Type I represents intraspinal intra- and extradural tumors which constrict the dura and do not involve the foramen. Type IIa, lesions are extradural, show foraminal constriction, but are not extraforaminal. Types IIb and IIc tumors are extradural/paravertebral and foraminal/paravertebral, respectively. Type III tumors have both dural and foraminal constrictions: type IIIa tumors include intra- and extradural foraminal tumors with dural and foraminal constructions and IIIb are intra- and extradural paravertebral. Type IV tumors are extra- and intravertebral and invade the vertebral body; type V lesions are extradural and extralaminal with laminar invasion and type VI tumors show multi-directional bone erosion (Reprinted with permission from Lippincott, Williams & Wilkins, Spine, vol 49, number 1, 2003, p. e11, Figure 1)

Fig. 2

An 87-year-old female (Case 8) presented initially with shortness of breath (SOB), back and right lower extremity (LE) pain and bilateral LE weakness. Five years earlier, a 2.0 × 3.0 cm right posterior mediastinal mass had been found on chest X-ray, however, the patient did not wish to have surgery. At a subsequent admission, a chest X-ray revealed the tumor to be 9.5 × 10.5 cm (a). On MRI, the tumor extended through the right T5–T6 foramen into the T5 vertebral body and resulted in T5 extradural cord compression. Due to increasing SOB and worsening of her other symptoms, the tumor was removed in two separate stages. A T5 laminectomy with costotransversectomy and an extracavitary approach with a partial T5 vertebrectomy and T4–T7 instrumentation and fusion were performed (b, c). Two months later, a right thoracotomy and resection of her posterior mediastinal mass was carried out (d). The patient’s SOB, back and right LE pain and bilateral LE weakness were markedly improved 2 months after the second-stage of the two operations

Fig. 3

Foraminal nerve sheath tumor management algorithm