**9. Expanding role of MISS management of spine tumors**

There is essentially no role for MISS in primary vertebral body tumors, which require an en bloc spondylectomy for wide marginal resection [35]. There are multiple

### *Minimally Invasive Treatment of Spinal Metastasis DOI: http://dx.doi.org/10.5772/intechopen.102485*

reports of both expandable and nonexpendable tubular retractors [36, 37] for extradural intraforaminal and intradural extramedullary tumors. Most reports use MISS techniques on lesions that span no more than two vertebral levels [38]. Combined approaches with tubular retractors have also be described to resect thoracic dumbbellshaped ganglioneuroma in which tubular retractors were used for intraspinal component and robotic-assisted thoracoscopic resection for the extraforaminal intrathoracic component [39].

An interlaminar approach has been described for resection of intradural extramedullary lesions in the lumbar spine. With this technique, the pathology is approached through the center of the interlaminar space, where the space is the largest. This paramedian, bone-sparing approach theoretically preserves the posterior tension band and decreases postoperative instability [40].

Additionally, reports of flexible endoscopes via mini open incisions have been reported for the resection of intradural schwannomas at the cauda equine [41]. UT southwestern reports using a flexible endoscope through a minimal durotomy for aspiration of a dermoid tumor that spanned from T10-sacrum leading to functional recovery and remained asymptotic at 3 years despite small recurrence [42].

In general, treatment of intramedullary spinal cord tumors is associated with high neurologic morbidity. Given the need for GTR (gross total resection) in many of these tumors compared with metastatic tumors, which may undergo STR with separation surgery, GTR cannot be sacrificed for the previously mentioned benefits of MISS. A review of keyhole approaches for intradural tumors showed that only 5.3% of intramedullary lesions could be accessed [41]. MIS management of intramedullary tumors is limited to mini open approach with hemilaminectomy and laminotomy for which GTR may still be achieved with benefit of smaller incision and preservation of vertebral stability [41, 42]. A retrospective study by Kahyaoglu et al., who treated 168 intramedullary tumors via hemilaminectomy, showed that neurologic complications increased when intramedullary tumors extended greater than three spinal segments, especially in thoracic spine compared with the cervical spine [43].

## **10. Conclusion**

Advances in minimally invasive spine surgery techniques and concomitant advances in highly conformal stereotactic radiosurgery capabilities have revolutionized the approach to symptomatic metastatic disease involving the spine. The role of surgery is to create a safe distance between the tumor and the neural structures for the safe delivery of a tumoricidal radiation dose and to treat mechanical instability of the spine. Versatility in the use of MISS techniques is essential for the modern management of metastatic disease of the spine to protect and restore the patient's quality of life and allow them to resume radiation and systemic treatment when indicated.
