Intradural Spine Tumors: Is There an Advantage to Removing Intradural Spine Tumors Using an MIS Approach?

19 Intradural Spine Tumors: Is There an Advantage to Removing Intradural Spine Tumors Using an MIS Approach?

MIS: Anthony Conte and Trent L. Tredway
Open: Jeremy Fogelson and Michelle J. Clarke

19.1 Introduction

Intradural extramedullary spinal cord tumors (IDEM) are rare but surgically challenging lesions. Intradural spinal cord tumors make up over two-thirds of all spinal cord tumors, occurring with an incidence of 1 to 10 per 100,000 people.1,2,3,4,5,6,7 Intradural tumors exhibit a slight male predominance and most commonly present in the sixth to seventh decades of life.7 The majority of intradural tumors are schwannomas, comprising between 55 and 65% of IDEMs. Approximately 10 to 25% of IDEMs are meningiomas, most commonly found in the thoracic spine. Neurofibromas are also frequently seen. Additionally, intradural ependymomas, hemangioblastomas, paragangliomas, cavernomas, sarcomas, and epidermoid cysts have been reported in the literature.1,2,3,4,5,6,7 The most common presentation of IDEMs is localized back/leg pain, with 40 to 50% of patients also exhibiting sensory or motor symptoms.8,9 Approximately one-fourth of patients will present with symptoms of bowel/bladder incontinence or retention.

Intramedullary spinal cord tumors make up approximately 2% of all central nervous system tumors and 5 to 10% of all spinal tumors.10,11,12,13,14,15,16,17 Ependymomas are the most common intramedullary tumor type in adults, accounting for 60% of lesions. Approximately 40% of ependymomas originate from the filum terminale, the majority of which are myxopapillary ependymomas.14,17,18 Astrocytomas make up 90% of intramedullary spinal cord tumors (IMSCT) in patients younger than 10 years but decrease in frequency with age to become the second most common intramedullary tumor in adults.14,17,18 Hemangioblastomas are the third most frequent IMSCT encountered in the adult population comprising 2 to 5% of all IMSCT19 with 25% of lesions occurring in patients with von Hippel–Lindau (VHL) disease.20,21 Other neoplastic lesions including gangliogliomas, metastases, lipomas, and lymphomas and nonneoplastic lesions such as cavernomas, cysts, and dysembryogenic lesions may also be observed as are intramedullary spinal cord masses.

Surgical treatment of IMSCT is pathology dependent, yet maximizing treatment while preserving neurologic function is the common primary aim. Gross total resection is the primary treatment for an ependymoma to achieve cure or long-term tumor control.15,22,23,24 Often these lesions have a reasonable surgical plane and smaller lesions can be removed en bloc. Occasionally, internal debulking to lessen the traction on the spinal cord is performed. This allows the surgeon to confirm pathology, given the goals for the surgical treatment of astrocytomas are different. The main surgical goal in treating astrocytomas is to obtain tissue for histopathologic diagnosis, given that many of these lesions are unresectable. Unlike ependymomas, astrocytomas are infiltrative, and the risk of neurologic injury must be balanced with the desire for a subtotal debulking or gross total resection. Although extent of resection may correlate with outcome, usually intraoperative pathologic confirmation of high-grade astrocytomas dampens the enthusiasm for further resection.15,25,26,27 Dural tube expansion through patch grafting may be employed to provide space for tumor growth and delay neurologic deficit.

Hemangioblastomas are well circumscribed, highly vascular lesions. Due to their vascularity, dissecting around the tumor capsule, cauterizing feeding vessels, and removing the mass without disruption of the capsule are preferred.19,28,29,30

Intradural tumors of 2 to 3 cm in size have been reported (range: 1–6 cm).1,2 Often these tumors span multiple vertebral levels. Depending on tumor size, internal debulking with ultrasonic aspiration may need to be employed prior to resection. However, most intradural extramedullary tumors can often be readily dissected from the neural elements with minimal risk of cord or nerve root injury. This chapter explores the ability of a surgeon to achieve these major surgical goals through minimally invasive surgical (MIS) techniques versus the more traditional open surgical approaches.

19.2 Advantages of Minimally Invasive Surgery

Since intradural spinal cord tumors are quite rare, there is a paucity in the literature regarding MIS techniques for tumor resection. In fact, to the authors’ knowledge, there have been only three published reports. However, extrapolating from the literature in regard to minimally invasive treatment of various types of spinal pathology, the potential advantages may include decreased perioperative pain, lower blood loss, lower infection rate, decreased risk of dead space leading to pseudomeningocele formation, as well as decreased bone removal and tissue destruction which theoretically will decrease the rate of postoperative deformity.

19.3 Advantages of Open Surgery

Open techniques allow a wider exposure of the surgical field and familiar techniques can be employed by the neurosurgeon. The traditional midline laminectomy approach is common and does not require special retractors or suturing tools.

19.4 Case Illustration

A 32-year-old woman with a history of neurofibromatosis type 2 presented to the neurosurgical clinic with worsening back pain. The patient stated that this pain has increased in severity over the past 3 months, without radiation into the lower extremities, preventing her from participating in running and other fitness classes. Over the past 3 weeks, she has complained of a generalized numbness sensation throughout bilateral feet. She states that during this time period, she had stumbled a number of times and even fallen to the ground twice. Patient currently denies bowel or bladder incontinence, retention, or saddle anesthesia. Preoperative exam is significant for 4 +/5 strength in the right quadriceps muscle and 4 +/5 strength with dorsiflexion and plantarflexion bilaterally. There is no Hoffman’s reflex, but patient does exhibit clonus and 3 + patellar reflexes bilaterally. Rectal tone and sensation are normal. Imaging studies included an MRI with and without contrast and revealed an intradural extramedullary tumor at the level of T7 (images Fig. 19.1 and images Fig. 19.2).

19.5 Surgical Technique in Minimally Invasive Surgery

After obtaining consent, the patient underwent a minimally invasive approach using a tubular retractor and microscope. The patient was placed prone on a Jackson’s table with Wilson’s frame. A 2-cm right paramedian incision, 1.5-cm off midline, was made. Employing a muscle-splitting approach, serial dilators were used to aid in the docking of an expandable tubular retractor on the right T7 lamina and base of the spinous process. A hemilaminectomy with undercutting of the spinous process was performed to gain exposure for the intradural exploration. Upon midline opening the dura, the extramedullary tumor was internally debulked with an ultrasonic aspirator and meticulously resected off the spinal cord (images Fig. 19.3). After resection of the tumor, the dura was closed using a Castro-Viejo needle driver, knot pusher, and bayoneted forceps (images Fig. 19.4). The dura closure was reinforced with a dural substitute and dural sealant.

19.6 Surgical Technique in Open Surgery

The patient is taken to the operating room, placed under general anesthesia, and carefully positioned. Somatosensoryevoked potential and motor-evoked potential monitoring is used throughout the case. Standard open complete laminectomy (T6–T9) and medial facetectomy through a midline bilateral exposure is performed. Ultrasound is brought in to verify that the bone work provides adequate exposure for the tumor resection. A midline durotomy is completed just beyond the suspected margins of the tumor, tacking the dural leaves to the paraspinal muscles to maximize exposure and prevent blood from obscuring the field.

Attention is then turned to obtaining a pathologic diagnosis and maximizing tumor resection. Under the operating microscope, the arachnoid layer is sharply dissected off the tumor surface. The tumor capsule is then entered, and the tumor is internally debulked using an ultrasonic aspirator, allowing further delivery of tumor margins into the surgical bed. Once margins are clearly identified, the tumor is carefully dissected off the spinal cord. The subarachnoid space is then irrigated, hemostasis is achieved, and the dura is closed with 4–0 Nurolon sutures. A Valsalva maneuver is used to confirm watertight closure. The patient is kept on bedrest with head of bed flat for the next 48 hours. Consideration for an instrumented fusion is given in a delayed manner after confirming a gross total resection on postoperative MRI.

19.7 Discussion of Minimally Invasive Surgery

19.7.1 Level I/II Evidence in Minimally Invasive Surgery

There is no level I or level II evidence available.

19.7.2 Level III/IV Evidence in Minimally Invasive Surgery

To the author’s knowledge, there are five patients (images Table 19.1) reported in the neurosurgical literature who received minimally invasive resection of intramedullary spinal cord tumors.31,32,33

In the case report by Ogden and Fessler,31 a tubular muscle-splitting retractor system was used to limit trauma to the ipsilateral paraspinal muscles and their insertions. The decreased trauma to the paraspinal muscles may reduce the risk of late postoperative kyphotic deformity. In some series of conventional open approaches to IMSCTs, the rate of postoperative kyphotic deformity varies from 10 to 100%,34,35,36 but this is more common in the pediatric population compared to adults. It is notable that pediatric IMSCT patients are at higher risk of deformity as evidenced by the literature demonstrating deformity as a presenting feature of IMSCT in children.37 Thus, sparing the paraspinal muscle’s further trauma may be advantageous. The second major difference in exposure in this case report is the use of a modified hemilaminar approach. Exposure was increased through the resection of the ventral spinous process and contralateral lamina which provided a view of the entire dorsal surface of the spinal cord. The disadvantage to this is a “slightly oblique working angle and a deeper operating field.”31 Additionally, Ogden and Fessler noted that the additional bone work required to extend the hemilaminar approach for adequate visualization is not biomechanically detrimental. This assertion may be supported by the study conducted by Lee et al that compared traditional open versus muscle-sparing hemilaminotomies in a biomechanical cadaveric dissection model. This study demonstrated a significantly more stable spine when hemilaminotomies were employed.38 It should be noted that this study was performed on the lumbar spine and not on the more rigid thoracic spine.

Because this is a relatively new extension of the MIS technique, it is unclear what the surgical limitations are in regard to location, size, and characteristics of candidate lesions. Ogden and Fessler noted that large tumors more than two spinal segments, or those with difficult dissection planes, may best be approached through a traditional open approach. It is also notable in this case that a small area of enhancement was seen in the resection cavity on the postoperative MRI. Most likely this is granulation tissue, although residual tumor is a possibility.

The case series published by Haji et al included 20 patients with spinal tumors, 2 of which were intramedullary.32

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Jan 15, 2020 | Posted by in ORTHOPEDIC | Comments Off on Intradural Spine Tumors: Is There an Advantage to Removing Intradural Spine Tumors Using an MIS Approach?

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