Surgical Treatment of Spinal Intradural Extramedullary Tumors

Surgical resection is the mainstay of treatment for intradural extramedullary (IDEM) spinal tumors such as meningiomas and nerve sheath tumors. ¹ The goal of surgery is complete tumor removal, thereby decompressing the spinal cord and obtaining tissue for pathological study. Meticulous surgical technique is essential to the safe, complete resection of these lesions.

24.2 Patient Selection and Preoperative Imaging

Patients with IDEM spinal tumors may manifest with pain or a variety of neurologic deficits, depending on tumor size, location, and relationship to the spinal cord and exiting nerve roots. A high-quality magnetic resonance imaging (MRI) with and without gadolinium is the primary imaging study necessary for planning the resection of extramedullary spinal tumors. The spinal cord, nerve roots, and the tumor are usually readily distinguished with multiplanar MRI. Most IDEM tumors enhance at least partially with gadolinium, further improving the resolution of the imaging.

Myelography followed by computed tomography (CT) may help the surgeon determine the bony removal necessary to achieve an exposure that allows for safe and complete tumor removal. In some cases, particularly those involving dumbbell-shaped tumors, there may be significant bony destruction that is most clearly seen on axial CT images. In these circumstances, a CT myelogram is informative; the test is not otherwise routinely obtained.

24.3 Preoperative Preparation

Intraoperative neurophysiologic monitoring of both motor and sensory tracts has been shown to be sensitive and specific for iatrogenic neurologic injury during resection of IDEM lesions ² and should be available for the surgeon planning to resect an IDEM tumor. An arterial line for blood pressure monitoring may be indicated, particularly if spinal cord perfusion is of concern because of significant spinal cord compression.

A Foley catheter and sequential compression devices are routinely used. Preoperative antibiotics are selected for their gram-positive coverage. Steroids are given preoperatively and at appropriate intervals during the operation. Postoperatively, the steroids usually may be stopped or rapidly tapered off over a period of a few doses.

24.4 Operative Procedure

The typical IDEM tumor is approached posteriorly through a posterior midline incision and a multilevel laminectomy. This approach allows the surgeon to extend the exposure rostrally and caudally as far as needed for resection of the tumor. Although it is occasionally necessary to use an anterior approach to safely resect an intradural extramedullary lesion, these cases are rare. ³ The patient is positioned in the prone position on chest bolsters, a Wilson frame, or an open-frame spine table. For tumors at or above the T4 level, the head is held in a Mayfield device or in Gardner–Wells tongs with approximately 15 pounds (5-7 kilograms) of traction. The arms are tucked alongside the patient for cervical and thoracic lesions at or above T6; for more caudally located lesions, the shoulders are abducted 90 degrees and the arms placed on arm boards.

A standard laminectomy extending approximately one-half to one level rostral and caudal to the lesion usually provides sufficient exposure. The cancellous edges of the laminae should be waxed thoroughly. Occasionally a facetectomy or pedicle resection may be necessary to establish a ventrolateral operative corridor. Meticulous hemostasis must be achieved before performing the durotomy; particular attention should be given to the epidural veins. Collagen sponges (Gelfoam), oxidized cellulose strips (Surgicel), and collagen/thrombin suspension (Floseal) are all used to ensure a dry surgical field before opening the dura.

A midline, linear dural opening is made. Cotton strips are placed on the dura lateral to the durotomy to absorb any run-down into the field; 4–0 silk sutures are used to retract the dural leaves by suturing them to the paraspinal muscles just dorsal to the laminae. Cotton wall-offs are placed on the exposed muscle to absorb the small amount of blood that may accumulate during the operation ( ▶ Fig. 24.1).

Fig. 24.1 The dural leaves are retracted with silk sutures secured to the paraspinal muscles. Cotton wall-offs are placed on the muscle to maintain a dry surgical field.

After the dura is opened, a careful inspection of the spinal cord and tumor is made. The arachnoid membrane is carefully opened over the entire extent of the tumor ( ▶ Fig. 24.2). In cases of ventral or ventrolateral tumors, division of the dentate ligaments may be necessary. The spinal cord may be carefully rotated and retracted to improve access to a ventrally located tumor by placing a 6–0 Prolene suture through the remnant of a divided dentate ligament and applying gentle traction ( ▶ Fig. 24.3).