Transparaspinal exposure of dumbbell tumors of the spine

Transcription

1 J Neurosurg 88: , 1998 Transparaspinal exposure of dumbbell tumors of the spine Report of two cases STEPHEN T. ONESTI, M.D., ELY ASHKENAZI, M.D., AND W. JOST MICHELSEN, M.D. Department of Neurological Surgery, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, New York The authors present a surgical technique for resection of dumbbell tumors of the spine. The transparaspinal exposure combines laminectomy and sectioning of the paraspinal muscles through a transverse incision. The procedure allows total tumor resection by means of a single posterior approach in selected patients, thus obviating the need for a combined anteroposterior operation. The advantages and disadvantages of the transparaspinal approach compared with the more extensive lateral extracavitary approach are discussed. KEY WORDS spine neurofibroma paraspinal muscles surgical approach S 106 PINAL tumors with both intracanalicular and extracanalicular extension remain challenging surgical lesions to resect. These dumbbell tumors may grow within the spinal canal and neural foramen, producing compression of the spinal cord and nerve root of origin. In addition, the tumors may grow extensively outside the spinal canal. Often the tumor will compress the paraspinal and iliopsoas muscle complexes as well as the adnexal structures (Fig. 1). These include the aorta, vena cava, and azygous vein in the thoracic spine and the iliac vessels, kidneys, ureters, and lumbosacral plexus in the lumbar spine. Proximity of the tumor capsule to these structures can make resection difficult. A variety of techniques have been developed to treat dumbbell tumors. Large tumors with significant extraspinal involvement frequently require combined anterior and posterior exposures for complete removal. 1,5 The posterior approach is undertaken first, providing neural decompression and initial resection of the tumor cavity. The anterior approach then permits separation of the tumor from the perispinal vascular and neural structures, allowing complete removal. This combined approach has the disadvantage of a two-stage operation with transthoracic or retroperitoneal dissection. The resurgence of the lateral extracavitary approach has permitted singlestage removal via a posterolateral approach in selected cases. 2 4,8 10 This approach provides extensive exposure, but remains a time-consuming and technically demanding procedure. The lateral extracavitary technique was originally developed by Capener 3 for the treatment of tuberculosis of the spine. In his report, the paraspinal muscles were transected on one side at the level of the gibbus to expose the lateral spinal elements. Complete or partial paraspinal muscle sectioning has subsequently been used in the treatment of a variety of other spinal diseases. In 1975, Jefferson 6 described a T-shaped incision with sectioning of the paraspinal muscles for the treatment of thoracic disc herniations. This type of incision has also been incorporated into the lateral extracavitary technique to enhance exposure. 9 Unilateral paraspinal transection has been found to be well tolerated by the patient and produces no adverse biomechanical effects. In this report we describe a technique for resection of dumbbell tumors by means of a posterior exposure developed by the senior author (W.J.M.) that we call the FIG. 1. Axial cross-section illustration demonstrating relationship of tumor to paraspinal and psoas muscles, bony elements, kidney, and ureter. Note dumbbell extension of tumor into spinal canal through the neural foramen.

2 Transparaspinal exposure FIG. 2. Case 1. A: Plain anteroposterior radiograph demonstrating extensive bony destruction of the sacrum and L-5 vertebral body. Note the enlargement of the neural foramen by the tumor. B: Noncontrast-enhanced axial CT scan demonstrating bone involvement by tumor. C: Sagittal T 1 -weighted MR image demonstrating intraspinal and extraspinal components of tumor. Note relation of tumor anterior to the iliac vessels. D: Axial T 1 -weighted MR image demonstrating large intraspinal and extraspinal tumor with destruction of the vetebral body and displacement of the psoas muscle and lumbosacral plexus. transparaspinal approach. The approach combines laminectomy and transverse sectioning of the paraspinal muscles through a horizontal incision. This approach provides excellent exposure of the lateral aspects of the spine and permits complete removal of many paraspinal tumors without the need for subsequent anterior surgery. Our experience using this technique has demonstrated that the capsule of most dumbbell tumors can be mobilized from the adnexal structures, including major vessels and peripheral nerve plexuses. In selected cases, the transparaspinal approach provides a simpler and quicker alternative to the lateral extracavitary technique. Indications and Contraindications The transparaspinal approach may be successfully used throughout the spinal axis. There is no upper limit of tumor size that precludes the approach. The transparaspinal approach does not provide adequate visualization of the anterior dural margin and therefore is contraindicated in cases of significant anterior spinal cord compression. In addition, it is not possible to provide anterior column reconstruction by using this approach in cases of spinal instability. Case Reports Two illustrative cases of dumbbell schwannomas resected via the transparaspinal approach are presented. A case involving a thoracic dumbbell tumor as well as one of a lumbar dumbbell are presented to demonstrate the versatility of the technique. Case 1. This 54-year-old woman presented with radicular symptoms and localized pain. Radiographic studies revealed a neurofibroma at L-5 (Fig. 2). Gross-total removal was achieved via the transparaspinal approach. Postoperatively, the radicular symptoms resolved and the patient returned to work full time. Case 2. This 37-year-old woman also presented with radicular symptoms and pain. Magnetic resonance imaging (Fig. 3) showed a neurofibroma located at T-2. Fol- FIG. 3. Case 2. Left: Coronal MR image demonstrating cystic schwannoma with erosion of the vertebral body and proximity to the pleura. Right: Axial MR image showing intracanalicular extension and proximity to the pleura. FIG. 4. Schematic illustration demonstrating horizontal skin incision in relation to tumor. This may be combined with a vertical incision if needed. 107

3 S. T. Onesti, E. Ashkenazi, and W. J. Michelsen FIG. 5. Illustration showing sectioning of the paraspinal muscles with electrocautery. The tumor is just starting to come into view between the transverse processes. lowing gross-total removal her symptoms resolved and the patient returned to work full time after normal postoperative rehabilitation. As in Case 1, there were no complications related to sectioning of the paraspinal muscles. Operative Procedure The patient is positioned prone on the operating table. A Foley catheter and arterial line are placed. We favor use of spinal cord monitoring with evoked potentials in cases in which there is intraspinal extension of the tumor. Two types of skin incision may be used. A traditional vertical midline skin incision may be used, supplemented by a transverse T-shaped extension at the level of the tumor. This incision provides initial midline exposure, which is familiar to all neurosurgeons. Once the paraspinal muscle dissection has been accomplished and the level of the tumor has been identified, the lateral portion of the incision may be made. Alternatively, a single transverse skin incision may be used (Fig. 4), which begins a few centimeters from the midline on the side contralateral to the tumor and extends just beyond the lateral border of the paraspinal musculature ipsilateral to the tumor. In cases in which posterior stabilization is required following tumor resection, use of the vertical skin incision is mandatory. The fascia is opened vertically over the spinous processes. In general, the fascia will need to be opened two levels above and two levels below the tumor to permit adequate exposure. A subperiosteal exposure of the spinous processes, laminae, and facet complex is obtained. This is usually performed bilaterally to permit ease of retraction and adequate exposure of the bony elements, although in purely unilateral tumors dissection may be restricted to one side. The tumor will usually appear first, either eroding through the bony elements or embedded in the paraspinal muscles lateral to the facet joint. The fascia is then opened laterally directly over the tumor to the lateral edge of the paraspinal muscle complex. The paraspinal muscles are transected using electrocautery (Fig. 5). Lateral dissection proceeds through the muscles until the entire tumor is exposed. The spinous process and lamina are removed with rongeurs. In addition, the facet complex may have to be removed to gain full exposure of the tumor. The intracanalicular as well as extracanalicular components of the tumor are completely exposed to view in the surgical field (Fig. 6 upper left). The neural elements are decompressed first. The interface between the capsule of the tumor and the dura is developed. The dura is opened if intradural extension of the tumor has taken place. Internal decompression is accomplished with suction or ultrasonic aspiration if required at this point. The nerve root associated with the tumor is identified. The nerve root is located in most instances within the capsule of the tumor. If a neurofibroma rather than a schwannoma is present, the rootlets will be embedded in the substance of the tumor and are dissected free from the tumor capsule. If the root is severely attenuated from the mass effect of the tumor, it may not be possible to preserve its functioning. Sacrifice of the root may have to be made at this point (Fig. 6 upper right). This rarely produces a neurological deficit, presumably because the long-standing root compression leads to development of alternative pathways of innervation. 7,11 The extracanalicular component of the tumor is now internally decompressed with suction or ultrasonic aspiration, allowing the capsule of the tumor to be mobilized. There is usually a well-defined surgical plane between the tumor and adnexal structures (Fig. 6 lower left). The capsule is gently infolded into the decompressed central cavity of the tumor, allowing further capsular dissection. The most difficult part of the dissection occurs at the anterior portion of the tumor capsule. This is the last part to be exposed through the transparaspinal approach. In addition, this portion of the capsule is closest to the adnexal structures. These include the aorta, vena cava, and azygous vein in the thoracic spine; and the iliac vessels, kidneys, ureters, and lumbosacral plexus in the lumbar spine (Fig. 6 lower right). If the capsule of the tumor is densely adherent to the surrounding tissue, a decision must be made whether to leave a portion of the capsule behind. Because the risk of tumor recurrence is low, we recommend subtotal resection of the capsule when total resection poses a significant risk of neurological or vascular injury. After resection of the tumor, the spine is stabilized if necessary. It is mandatory that a vertical skin incision be used if stabilization is performed. The incision and subperiosteal dissection may need to be extended at this point. The technique is compatible with placement of essentially all types of posterior instrumentation throughout the spinal axis. Following hemostasis and irrigation, the wound is closed. The paraspinal muscles are reapproximated with 108

4 Transparaspinal exposure FIG. 6. Artist s drawings demonstrating operative process. Upper Left: Complete exposure of tumor after sectioning of the paraspinal muscles and laminectomy. The cut edges of the ligamentum flavum are visible. Upper Right: The intracanalicular portion of the tumor has been decompressed, and the capsule is being retracted away from the dura. The nerve root has been ligated and divided. Lower Left: A generous internal decompression of the extracanalicular tumor has been performed. The dissection of the soft tissue plane between the tumor and kidney is demonstrated. Note placement of bookmark cottonoid patties. These define the limits of dissection and protect the adnexal structures. Lower Right: The dissection has been completed. The psoas muscle, kidney, renal vessels, and ureter have come into view. Note a small scrap of tumor capsule, which remains adherent to the kidney. large interrupted sutures (Fig. 7). We use absorbable No. 0 Vicryl sutures, but nonabsorbable ones may also be used. The fascia is closed in a similar fashion. The subcutaneous layers and the skin are closed in routine fashion. We use closed drainage for 24 hours, although this may not be necessary if the operative field is dry. Discussion Capener 3 described transverse sectioning of the paraspinal muscles as part of the lateral extracavitary exposure developed for the treatment of Pott s disease. Sectioning of the paraspinal muscles has subsequently been incorporated into a variety of posterior spinal exposures; however, the technique has not gained general acceptance because of concern that complete sectioning of the paraspinal musculature will produce unacceptable postoperative disabili- ty. Our experience as well as that of previous authors indicates that unilateral complete sectioning of the paraspinal muscles does not result in noticeable postoperative defects. 6,9 This may be explained by the segmental innervation, blood supply, and attachments of the paraspinal muscles. As a result, cutting the muscles at a single level does not produce noticeable weakness of the erector spinae group. Prior to refinements in the lateral extracavitary technique, complete removal of many dumbbell tumors of the spine required both anterior and posterior exposures. 1,5 The lateral extracavitary technique makes possible extensive lateral spinal dissection, allowing, in many instances, complete tumor removal through a single posterior exposure. 2,4,8,10 However, even in experienced hands, this approach remains technically demanding and time-consuming. 109

5 S. T. Onesti, E. Ashkenazi, and W. J. Michelsen Conclusions The transparaspinal approach provides rapid, simple, and direct exposure of dumbbell tumors of the spine. A transverse skin incision with sectioning of the paraspinal muscles is used to provide lateral exposure. The approach is sufficient to allow complete removal of most dumbbell tumors of the spine without necessitating a subsequent anterior operation. The transparaspinal approach provides a simpler and less time-consuming alternative to the lateral extracavitary approach in selected cases. The transparaspinal approach does not permit anterior decompression or stabilization. The technique does permit posterior spinal stabilization with minor modification. References FIG. 7. Drawing showing operative closure. The paraspinal muscles have been closed, and the fascia is now reapproximated. Hemostatic material has been placed over the exposed dura. The transparaspinal approach offers a simpler and more direct exposure of the lesion in selected cases. The skin incision and fascial opening are considerably smaller than those necessary in the lateral extracavitary approach. Sectioning of the paraspinal muscles by using electrocautery is extremely rapid and virtually bloodless. In addition, the transparaspinal approach provides better exposure of the lateral aspect of the tumor. In our experience, most dumbbell tumors are easy to separate from the adjacent adnexal structures. This is analogous to the mobilization of the capsule of an intracranial meningioma from surrounding neural and vascular structures. Although there is no formal tissue plane analogous to the arachnoidal plane of a meningioma, most tumors will be quite easily mobilized. However, in rare cases in which the tumor cannot be moved easily, a decision must be made whether to leave a portion of the tumor capsule behind. Depending on the volume of tumor that remains, a subsequent anterior approach may be indicated. The transparaspinal approach is not appropriate for lesions with significant anterior spinal column involvement. The exposure of the anterior column is not sufficient to decompress the neural elements safely. In addition, anterior column stabilization and instrumentation are impossible through this approach. As a result, the transparaspinal approach is not indicated in the treatment of spinal trauma or epidural metastases with anterior column involvement or in other cases in which internal fixation is required. 1. Abernathey CD, Onofrio BM, Scheithauer B, et al: Surgical management of giant sacral schwannomas. J Neurosurg 65: , Benzel EC: The lateral extracavitary approach to the spine using the three-quarter prone position. J Neurosurg 71: , Capener N: The evolution of lateral rhachotomy. J Bone Joint Surg (Br) 36: , Fessler RG, Dietze DD Jr, Mac Millan M, et al: Lateral parascapular extrapleural approach to the upper thoracic spine. J Neurosurg 75: , Grillo HC, Ojemann RG, Scannell JG, et al: Combined approach to dumbbell intrathoracic and intraspinal neurogenic tumors. Ann Thorac Surg 36: , Jefferson A: The treatment of thoracic intervertebral disk protrusions. Clin Neurol Neurosurg 78:1 9, Kim P, Ebersold MJ, Onofrio BM, et al: Surgery of spinal nerve schwannoma. Risk of neurological deficit after resection of involved root. J Neurosurg 71: , Larson SJ, Holst RA, Hemmy DC, et al: Lateral extracavitary approach to traumatic lesions of the thoracic and lumbar spine. J Neurosurg 45: , Martin NA, Khanna RK, Batzdorf U: Posterolateral cervical or thoracic approach with spinal cord rotation for vascular malformations or tumors of the ventrolateral spinal cord. J Neurosurg 83: , McCormick PC: Surgical management of dumbbell and paraspinal tumors of the thoracic and lumbar spine. Neurosurgery 38:67 75, Schultheiss R, Gullotta G: Resection of relevant nerve roots in surgery of spinal neurinomas without persisting neurological deficit. Acta Neurochir 122:91 96, 1993 Manuscript received May 1, Accepted in final form August 18, Address reprint requests to: Stephen T. Onesti, M.D., Department of Neurosurgery, Montefiore Medical Center, 111 East 210th Street, Bronx, New York