Neurosurgical Techniques

Transcription

1 Neurosurgical Techniques

2 Neurosurgical Techniques Laminectomy for the Removal of Spinal Cord Tumors J. GRAFTON LOVE, M.D. Section of Neurologic Surgery, Mayo Clinic and Mayo Foundation, Rochester, Minnesota AMINECTOMY is a surgical procedure consisting of the removal of part or all of one or more laminae for the exposure of the spinal meninges, spinal cord, nerve roots, and intraspinal lesions. Fig. 1 depicts 6 steps in the performance of a classic bilateral laminectomy consisting of the removal of 3 spinous processes and 3 pairs of laminae. Often a tumor is removed with the sacrifice of only 1 spinous process and 1 pair of laminae. On the other hand, large and extensive tumors may require the removal of many spines and laminae. Adequate exposure is essential and everything possible should be done to avoid further damage to the vital spinal cord. The first step in laminectomy is incision of the skin and subcutaneous tissues down to the dorsal fascia through which the tips of the spinous processes can be seen and easily palpated. The dorsal fascia and supraspinous ligament are incised in the midline. In order to minimize bleeding and postoperative atrophy of the muscles, it is important to reflect the periosteum with the muscles. The muscles and ligaments are therefore stripped subperiosteally and reflected laterally with the help of an Adson laminectomy chisel. As the muscles are stripped from the spinous processes and laminae, gauze sponges should be packed in the gutter. This maneuver is usually sufficient to control any except arterial bleeding; and further, it "irons out" the muscles and facilitates the introduction of the self-retaining retractor and the exposure of the laminae and ligamenta tiara. When the soft tissues have been reflected laterally to the articulating facets and the retractor has been inserted, bone removal begins. If the surgeon knows the exact loca- 116 tion of the tumor, he may remove bone overlying the tumor (with or without x-ray control) and then work above and below the lesion until adequate exposure is obtained. When a normal amount of extradural fat is encountered above and below the lesion, the extent of the tumor is usually revealed. Pulsations may be seen in the dural sac above the obstructing lesion but not below it. The mass has a muting effect on the dural pulsations. If there is a question regarding the location of the tumor, a minimal amount of bone and ligameutum flavum should be removed, and intraspinal extradural exploration with a silver probe or a size 8 F catheter utilized to estimate the presence or absence of an abnormal mass. When sufficient bone has been removed to expose the tumor, careful hemostasis should be accomplished before beginning the actual tumor removal. If the tumor is extradural and there is no need to open or sacrifice dura, the problem of hemostasis is much simpler. If the hydrostatic effect of the cerebrospinal fluid within an intact arachnoid and dura mater can be maintained, electrocoagulation, silver clips, muscle pledgers, or gelfoam can be employed to control bleeding. If the tumor is intradural or a part of the dura has to be resected because of tumorous involvement, the dura should be opened widely enough to expose the lesion and the nutrient vessels; if possible, these vessels should be secured before removing the tumor from its bed. The first opening in the dura and arachnoid should always be rostral to or above the lesion in order to avoid the additional spinal cord damage which may accompany sudden initial release of fluid caudal to or below the tumor. Another reason for

3 Laminectomy for Removal of Spinal Cord Tumors Fro. 1. Classic bilateral laminectomy. 117

4 118 J. Grafton Love FIG. ~. Exposure for the removal of intradural meningioma. opening the meninges rostral to the lesion is to avoid the risk of damaging a posteriorly displaced spinal cord through an incision made right over the site )f compression. The dural edges usually are hdd up by silk sutures which pass out of the wound and are held taut by artery forceps. A~; times it is better to stitch the dural edges to the soft tissues lateral to the resected laminae. Figs. ~ and 3 represent the removal of an intradural meningioma. The division of an overlying nerve root facistated the removal. A generous piece of dura surrounding the tumor must be removed to prevent recurrence. In Fig. ~ the tumor mass can be seen stretching the dura and sufficient bone has been removed to get wel] around the tumor. In Fig. ~, the dura is incised around the superior surface of the meningioma. After clipping and dividing the nerve root, the dura to which the tumor is attached is resected. Silver clips are applied to the dura below the tumor to occlude the feeding vessels and then the dura beyond the tumor is incised. The tumor and attached dura are then removed. The sacrificed dura may be replaced with a dural substitute or the defect may be left open if the remainder of the wound is closed watertight. It is my practice to leave the dural defect. Neodura will form and I have not had any trouble in this regard. Figs. 4, 5 and 6 show the exposure and removal of an intramedullary astrocytoma of the spinal cord. Fig. 4B illustrates aspiration of the neoplasm with a fine needle. Often there is some fluid in or around the tumor

5 Laminectomy for Removal of Spinal Cord Tumors 119 FIo. S. Excision of intradural meningioma.

6 FIG. 4. Exposure of intramedullary astrocytoma of spinal cord (A) and aspiration of fluid (B). FIG. 5. Incision of cord (C) and removal of intramedullary tumor with ethmoid curet (D).

7 Laminectomy for Removal of Spinal Cord Tumors 121 FIG. 6. Removal of intramedullary tumor with Love-Gruenwald forceps (E) and fixation of dura to laminectomy margins (F). and aspiration of the fluid will help delineate the mass. Fig. 5C illustrates a dorsal slit with a small sharp blade through the thinnest least vascular portion of the cord covering the intramedullary tumor. Fig. 5D shows removal of tumor tissue with an ethmoid curet. At times the tumor can be scraped away from the compressed spinal cord substance. Fig. 6E shows removal of tumor tissue with Love- Gruenwald forceps. Fig. 6F shows the collapsed cord after removal of the intramedullary tumor. Also, the dural edges are shown sutured to the laminectomy margins to prevent constriction of the cord from postoperative edema and to provide prolonged decompression of the spinal cord if the tumor recurs.