21 Surgery of Intramedullary Spinal Cord Tumors BENNETT M. STEIN, M.D.
Only one-third of all primary intraspinal neoplasms are intrinsic to the spinal cord, attesting to their rarity. Although the histological variation of these tumors is broad, the most common types are astrocytomas and ependymomas. The tumors are generally low grade and extend over many segments of the spinal cord. In some instances, especially accompanying astrocytomas, cysts may be present, further extending the intramedullary span of these lesions. Remarkably, many of these tumors have a welldefined plane with adjacent gliotic tissue of the spinal cord. A gratifying recovery and a useful life may be expected in many patients who are operated on in the early stages of tumor growth before severe neurological deterioration has developed. Since the majority of these tumors are benign, a cure may be anticipated in cases in which a total removal has been accomplished. In spite of the small size of the spinal cord and the critical function mediated by its substance, it is astonishing to see advanced tumor growth, occupying the majority of the intramedullary space, which causes minimal symptomatology. However, a phase in the tumor expansion is reached when the spinal cord can no longer accomodate and a marked deterioration in neurological function will occur. Persistent pain involving the dorsal root dermatomes in the area of the tumor involvement is often the signature of an intramedullary neoplasm. Subsequently, posterior column symptomatology develops in a progressive fashion with sensory dysesthesias in the arms, torso, and legs, depending upon the site of the intraspinal neoplasm. Sacral sparing mayor may not be present and is not an invariable finding with intramedullary neoplasms. Occasionally, lower motor neurone symptomatology and signs will be present in the area of the tumor. Well-defined central cord syndromes, as seen in syringomyelia, with disassociated sensory loss and the classic signs of anterior horn cell involvement are often lacking with intramedullary neoplasms. The symptomatology is usually progressive with few remissions and exacerbations. Symptoms are usually bilateral, but rarely, neurological abnormalities may be confined to 1 extremity. The duration 529
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of symptoms is generally measured in years, although some neoplasms may present with histories of 6 months or less. Intramedullary tumors occur most commonly in adults (1-4), although large series of intramedullary tumors in children have been reported (6, 7). The symptomatology in both age groups is similar. Almost every type of tumor seen in the brain can occur in the spinal cord; however, astrocytomas and ependymomas comprise the largest group of intramedullary tumors, occurring with about equal frequency. Astrocytomas are most commonly located in the cervical and thoracic regions, whereas the ependymomas have a higher incidence in the caudal regions of the spinal cord due to their prevalence in the conus medullaris and filum terminale. Intramedullary ependymomas often have a distinct plane between neoplasm and spinal cord tissue. These tumors are soft generally and solid and have a pseudocapsule. They are not highly vascular tumors and may have areas of necrosis. Astrocytomas are usually infiltrative with an illdefined margin between neoplasm and normal spinal cord tissue. Where a well-defined plane between neoplasm and spinal cord exists, a pseudocapsule is encountered. This variety is similar to the cerebellar astrocytoma with uniformly soft consistency and minimal vascularity and is sometimes associated with cysts containing yellow fluid of high protein content. The teratomatous and dermoid tumors have a varying amount of grumous material in their central portions, are frequently variegated in nature, and have a capsule that is adherent to the surrounding spinal cord tissue, often with a pedicle involving the dura and overlying soft tissues. Tumors which occur less frequently include dermoids, epidermoids, teratomas, oligodendrogliomas, hemangioblastomas, and either primary or metastatic malignant tumors. Lipomas, common in children, have different growth patterns and implications as regards therapy and will not be included in this discussion. Commonly, astrocytomas and ependymomas produce a fusiform enlargement of the spinal cord and often leave no indication of their presence on the surface of the spinal cord other than an occasional dilated vein at the caudal end of the tumor. In some cases, the dorsal surface of the cord will be so thin that it will be transparent. Teratomas and dermoid or epidermoid tumors are often associated with fibrous tracts bridging the dorsal surface of the cord to the dura and in some instances the overlying bone and soft tissues. Glioblastomas produce a distinct discoloration of the cord and are associated with a plethora of enlarged arterialized veins and obvious feeding arteries. Ependymomas of the conus or filum terminale region often grow in an exophytic fashion from the intramedullary locus, into the cauda equina, displacing and sometimes adhering to the nerve roots. Because of the expanding nature of these
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neoplasms, structural changes in the osseous spinal canal may. be produced. In instances where the tumor is associated with a fibrous tract, radiographic defects may be present in the overlying bone. Intramedullary tumors receive their blood supply from perforating branches of the anterior spinal artery which enter the ventral aspect of the tumor with a fibrous band, probably representing the central canal or the depths of the anterior longitudinal fissure. These vessels are small and are not associated with a high degree of vascularity within the tumor. Small vessels also enter the tumor from the dorsal and immediate circumferential portions of the spinal cord. The tumors tend to be eccentric and located in the more dorsal portion of the spinal cord. Invariably there is a thin layer of compressed spinal cord tissue overlying the dorsal surface of these tumors, and they rarely present directly on the surface of the spinal cord. In 1907 von Eiselsberg totally excised a neurofibrosarcoma from the cord while in 1924 Cushing operated on an 8-year-old child and completely removed an intramedullary ependymoma extending from Cl to T2 (9). However, the first well-documented surgical effort directed towards removal of intramedullary tumors was published by Elsberg (1) in 1925, when he reported 13 cases. Three of these tumors were totally removed, and the remainder were partially removed. He stressed that some of these tumors were infiltrating and thereby defied removal, but emphasized that the surgeon must search out those tumors with well-defined cleavage planes which might permit total removal of the neoplasm. These results were remarkable, considering the lack of magnification techniques and previous surgical experience with such tumors at that time. When a definitive plane between tumor and spinal cord was not visible at the first operation, Elsberg suggested a second operation, at which time the tumor would possibly present through the myelotomy and total removal would be feasible. Later, Matson (6) also advocated this technique. Other than these reports, little experience with 2-stage removal has been published. Subsequent to the early reports of Elsberg, others (2-5, 6, 9, 12) have reported successful removal of intramedullary tumors. Greenwood (3) placed the successful surgical therapy of these tumors on a firm foundation when he presented his experience with 10 intramedullary tumors, primarily ependymomas, in which a total removal was accomplished without mortality. These results, with useful survival, justified his enthusiasm for an aggressive surgical approach to these lesions. He emphasized the use of magnification techniques and microsurgical instrumentation in the performance of this surgery. Guidetti (4) published his experience with a large group of intramedullary tumors and emphasized the difficulty in totally removing astrocytomas. However, in the presence of intramedullary ependymomas and other tumors he felt that every
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effort should be made to accomplish total removal, although this would only be possible in the presence of a line of cleavage between the normal spinal cord and tumor. He suggested that once a cleavage was established the tumor be separated by gentle dissection from the normal spinal cord on each side and then lifted carefully by one end or the other and slowly removed from its bed. Blood vessels should be severed close to the tumor by bipolar cautery with irrigation. His operative mortality was 10%, with an overall total removal of 24 of the 71 tumors representing a wide variety of histological types. The famous case of Horrax and Henderson (5) should be mentioned in which an intramedullary ependymoma extended the entire length of the spinal cord and was totally enucleated during a series of operations with recovery and long-term survival. Our series comprises 13 cases of intramedullary tumor, in which 11 total removals were accomplished (Table 21.1). The tumors represent a range of histology, with astrocytoma and ependymoma being the most common tumor and with lesser frequency, teratomatous types of tumors. No lipomas are included in this group. Some patients had undergone previous treatment which included decompressive laminectomy, tapping of cysts associated with the tumors, and radiotherapy. This gave us an opportunity to study both the natural course of the disease and the effects of treatment on some of these tumors. Unfortunately, the series is small, and the natural course of these tumors, which spans many years, makes the evaluation of any therapy, other than total removal, difficult. The postoperative result was often dependent upon the degree of neurological deficit as a result of the disease process prior to definitive surgical treatment of the tumor. The radiological confirmation of intramedullary tumors hinges upon myelography. Prior to the advent of water-soluble dyes, Pantopaque (Pantopaque-Iophendylate, Lafayette Pharmacological, Inc., Lafayette, Ind.) myelography has been the procedure of choice. Myelography demonstrates a fusiform dilation of the cord in the region of the tumor. A band between the tumor and the dura may be visualized in cases of teratomatous tumors. A complete block is generally not present. When present, the dye should be instilled from the opposite end of the spinal canal to make a definitive evaluation of the length of the tumor. Increased use of water-soluble contrast agents should significantly improve the radiological definition of these tumors. When dilated venous channels at the caudal aspect of small intramedullary tumors are present, the differential diagnosis of a vascular malformation may be raised. This differential is rarely a problem, and spinal angiography has not been of diagnostic value except for the identification of an intramedullary hemangioblastoma. In some instances the differential diagnosis between
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40 24 49 28 38 17 13 4mo 60 13 3 48 38
1 2 3 4 5 6 7 8 9 10 11 12 13
Conus Conus C C-D C D Conus Conus D-C D-L C-D C C
Location
Epend Epend Epend Epend Epend Teratoma Dermoid Epidermoid Astroc Astroc Astroc Astroc Astroc
Histology
0 0 + + + + 0 0 + + 0 0 +
Prior surgery
T T T T T T T T 90% T 95% T T
Removal
1+ 2+ 3+ 4+ 3+ 4+ 2+ 2+ 4+ 2+ 1+ 1+/pain 2+
Pre op neurological defects
D, dorsal; C, cervical; T, total; 1+, mild defect; 2+, paresis; 3+, moderate deficit; 4+, para- or quadriplegia.
Age
No.
TABLE 21.1 Intramedullary Spinal Cord Tumors
Improved Improved Improved Static Static Improved Improved Improved Static Static Improved Improved Improved
Result
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syringomyelia and intramedullary tumor presents a perplexing problem. Air myelography has been a useful technique in distinguishing these 2 conditions. In the case of syringomyelia, a "collapsing cord" sign may be demonstrated, whereas in intramedullary neoplasms the cord will remain of uniform width regardless of the position of the patient (Fig. 21.1). Routine computed tomography (CT) scanning of the spinal canal has not been of practical use in the diagnosis of these neoplasms. We have
FIG. 21.1. Air myelogram demonstrating the "collapsing cord" sign of syringomyelia. (A) Head-down position with cervical cord enlarged (arrows). (B) Head-up position with cervical cord narrow (arrows).
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retrospectively scanned a number of patients in which large tumors were present, with failure to definitively visualize the tumors. CT scanning of the spinal canal with water-soluble contrast agents promises to assist in the definitive diagnosis of these tumors.
Surgical Technique (Fig. 21.2, A-C) We quite agree with Turnbull (9), who stated: "A surgeon exploring a spinal cord for a suspected intramedullary tumor must be prepared to face a formidable problem and also have the courage of conviction to make every attempt to remove that tumor. Anything less than this, with a cursory inspection of the spinal cord or aspiration thereof, can only create problems of a more complex nature for the subsequent surgical effort to remove such tumors." When these tumors are located in the cervical region, either a sitting or prone position may be utilized. We prefer the prone position for 2 reasons. First, the potential for vasomotor collapse abetted by compromise of the autonomic pathways by tumor is minimized. Second, we have found it of benefit to have the assistant actively involved in the operation on these tumors, providing traction on the tumor or assisting other aspects of the surgery. It is important that the full extent of the tumor be known prior to the operative intervention. A wide laminectomy is then carried out over the entire extent of the tumor and to a level above and below. The dura must then be carefully opened since the pia-arachnoid of the enlarged spinal cord is often adherent to the underside of the dura. It is important to prevent any injury to the subarachnoid vasculature since hemorrhage during this phase of the operation will obscure all landmarks and significantly compromise the surgical effort. Facing a widened spinal cord, the surgeon must not be misled in those rare instances of an anterior extramedullary lesion in which the cord is splayed out over the lesion (8). Having ruled out this possibility, a site for posterior myelotomy should be selected. The most avascular route on the dorsal surface of the cord is followed and need not be along the midline; it may be expeditious to go paramedian. Obviously, some of the traversing vasculature will be sacrificed during this myelotomy. An initial myelotomy of approximately 1 to 2 em is carried out over the greatest enlargement of the spinal eord. This allows the operator to evaluate the plane between the tumor and the spinal cord tissue. In some instances the presence of a cyst associated with the tumor may be readily apparent and, if so, additional room may be gained by aspiration of some of the cystic contents by a small-bore needle. To facilitate dissection, these cysts should not be completely evacuated. If it is determined that the neoplasm is cystic or has welldefined planes, then the myelotomy is lengthened over the extent of the
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FIG.
21.2. (A) drawing of myelotomy over intramedullary tumor.
tumor. With teratomatous tumors, the stalk between the cord and the dura should be removed as an integral part of the lesion. In the case of ependymomas extending from the conus, the extra-axial portion in the cauda equina may be removed first to afford adequate decompression and visualization of the residual tumor involving the intramedullary portion of the conus. The draining veins of intramedullary hemangioblastomas must also be left to the latter part of the surgical resection. Having performed an adequate myelotomy, 6-0 sutures are placed through the pial margin of the myelotomy on either side in order to provide gentle retraction of the spinal cord and open it in the fashion of opening a book. With the operating microscope and microsurgical techniques, utilizing bipolar cautery, small suction tubes, and various dissectors, a plane is developed around the margin of the tumor, taking care to retract primarily on the tumor and not on the spinal cord. The surgeon works to one or the other end of the tumor, and at this point where the tumor is the narrowest it may be possible to grasp the end and gently extract it from the interior of the cord. All the fine vascular adhesions to the spinal cord, especially on the ventral aspect of the tumor, should be cauterized with bipolar cautery and divided sharply. No blunt dissection should be carried out in areas in which vascular channels connect the tumor to the spinal cord. These tumors are amazingly avascular and present no problems in terms of hemorrhage or the control of large blood vessels. It is important to keep the operative. field scrupulously dry so that the plane between the tumor and the spinal cord may be readily
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FIG. 21.2. (B) drawing of removal of intramedullary tumor. (C) drawing of open cord after the removal of an intramedullary tumor.
identified. If the tumor is too large to remove in toto or necessitates too much retraction on the spinal cord, its interior may be decompressed. Cystic collections at the margins of the tumor, as in the case of astrocytomas, facilitate the tumor resection. However, we make no attempt to
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remove the thin-walled cyst associated with these tumors, as we do not feel this is a portion of the neoplasm. If there is any question about the totality of removal, small biopsies may be obtained from the margin of the resection and evaluated by frozen section during operation. In most instances the margins are well-defined, and there is no question about the removal of the tumor. When the margins of the cord are allowed to fall back into position, the remarkable decompressive effect of tumor removal is quite apparent. The dorsal columns often are thin to the point of transparency. If retraction on the cord has been minimal, these fiber tracts function in a satisfactory fashion and will show progressive recovery of function. Gentleness of dissection may be gauged by the vascular pattern on the dorsal surface of the cord at the completion of tumor resection. Distended veins which were present prior to removal, usually at the caudal end of the tumor on the surface of the spinal cord, will now be less prominent. No attempt has been made to sew the pial surfaces of the spinal cord together. When the dura is closed in a watertight fashion, it is rarely necessary to utilize a fascial graft other than in those cases which had been previously operated on and the dura left open. If the surgery has involved extensive areas of the cervical region, the endotracheal tube is left in place at least 24 hours, regardless of the patient's condition at the termination of operation. Steroids are used pre- and postoperatively on a routine basis. In cases which have had prior surgery and/or radiotherapy, intense scarring has been noted between the overlying tissues and the spinal cord, especially when the dura has been left open. This scarring compromises a definitive surgical endeavor. If total removal of an intramedullary tumor is not feasible, the dura should be reconstructed) preferably with a fascial graft, so that subsequent surgical endeavors may be facilitated. In cases in which radiation had been previously given, we have noted intense intramedullary gliosis, by biopsy, separate from the margin of the tumor, usually at the caudal or rostral interface. It is assumed that this is an adverse effect of preoperative radiation. In those cases which have had previous surgery with aspiration of a cyst but without definitive removal of the intramedullary tumor, benefits have been transient with rapid reaccumulation of the cyst fluid. In tumors of teratomatous origin, the border of the tumor, although well-defined, may be densely adherent to the surrounding spinal cord. Every attempt should be made to remove this capsule, as it is a potential source of regrowth. These tumors may involve extensive central areas of the spinal cord and may extend from posterior to anterior surface. Teratomatous tumors may also have a dumbbell configuration within the substance of the spinal cord, and the surgeon must be wary not to miss satellite portions of the primary tumor.
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The results of this small series were gratifying in that no patient was made worse by the surgery and those patients with marked neurological deficits prior to surgery were helped in some instances. Those with only mild-to-moderate neurological deficit prior to the surgery did extremely well and returned to normal activity, regardless of tumor size. The followup (Table 21.1) ranges from years to a few months. During this period there has been no evidence of recurrence. Case History. This 38-year-old male had symptoms of severe pain of 1 year's duration in the low cervical region radiating into both shoulders. Coincident with diminution of the pain, he noted progressive stiffness and weakness of his shoulder muscles so that it became impossible for him to reach over his head or button his collar. He also noted numbness and strange feelings in the fingers of both hands and he was unable to appreciate the temperature of objects held in his hands. Although the process continued unrelentingly, it was asymmetrical, the left side being more affected than the right. He noted no abnormalities in his legs. The neurological examination showed atrophy and weakness of the shoulder girdle muscles. Muscles below the C61evel showed good strength. There was loss of pain sensation from C2 to C6 which was more prominent on the left side. The lower extremities showed slight hyperactivity of reflexes with a Babinski on the left side. There was a slight disturbance of position sense in the toes bilaterally. A myelogram demonstrated a wide cervical spinal cord from CI to C6 compatible with an intramedullary tumor. Subsequently, a cervical laminectomy was carried out with total removal of an intramedullary solid ependymoma (Figs. 21.3-21.5). Postoperatively the patient showed progressive improvement, and at a 2-year follow-up
FIG. 21.3. Appearance of spinal cord with intramedullary ependymoma.
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21.4. Initial myelotomy with visualization of intramedullary ependymoma (arrow).
FIG. 21.5. Cavity remaining in spinal cord after removal of intramedullary ependymoma. Note fine stay sutures in pial margin of the cord (arrows).
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was working full time with minimal weakness and atrophy of his shoulder .muscles, His other neurological functions were normal.
Discussion It would appear from our experience (2) and that of others (3, 4) that a decompressive laminectomy, whether or not a tumor cyst has been evacuated, with or without radiotherapy, has been of little beneficial effect in the treatment of the majority of intramedullary spinal cord tumors. Reviews (4, 10, 11, 12) of the effects of radiation on these tumors are clouded by lack of knowledge of the natural course of these tumors and the number of variables involved which include decompression and partial surgical removals. Publications by Guidetti (4), Woltman et ale (10), and Woods and Pimenta (12) suggest that even with partial removal, long-term survival with static neurological deficit may be expected. Radiation has apparently yielded beneficial effects (11), but this report has a high percentage of histologically unverified tumors. There has been little objective follow-up of reduction in tumor size following radiation therapy. A significant number of reports would indicate that the best treatment is surgical removal (2-4, 6, 7, 12). This may be accomplished in the majority of cases with anticipated improvement in the patient's condition or at least an arrest of the neurological deterioration. Postoperative result is predicated upon the degree of neurological involvement prior to operation. Many surgeons have reported difficulty in total removal of astrocytomas. In our small series we have been able to totally remove 3 of 5 astrocytomas which presented no more significant problem than encountered in the removal of ependymomas. In the other 2 cases, near total removals were carried out with a definitive plane being observed around most of the tumor. Through the use of microsurgical techniques, careful anesthesia, and strict attention to the postoperative pulmonary function, negligible mortality and morbidity rates can be expected, even with removal of extensive tumors in the cervical region. Similar experiences have been reported by Greenwood (3). Guidetti (4) supports radical removal of these tumors, except where ill-defined planes do not permit this to be accomplished. In such cases he feels that subtotal resection produces no better result than biopsy. In those cases of astrocytoma in which biopsy only was performed and presumably postoperative radiation was given, average survival rate was 5 years. His feeling is that a significant number of the astrocytomas may be totally removed and at that least an attempt with microsurgical techniques should be made to accomplish this. We have not used postoperative radiation for intramedullary tumors which have been totally removed and do not advocate postoperative radiation for benign intramedullary tumors that
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have been incompletely removed. The patient's course should be followed carefully, facilitated by the use of water-soluble contrast agents and CT scanning. A second surgical attempt should be made to remove the tumor at the time of recurrence. Following this, radiation may be considered. Experience with a significant number of cases confirms that recurrence should not be a problem. Greenwood's (3) series comprised almost exclusively ependymomas, and his long-term survivals, as well as those of Guidetti (4) and others (5, 10, 12), have been gratifying. Radicular pain in the distribution of the nerve roots associated with the tumor has been a distressing postoperative problem. This pain has a burning quality, severely disturbing to the patient and extremely difficult to control. One may surmise that it is due to the derangement of the physiological pathways for pain at the dorsal route entry zone. Unfortunately, we have not had satisfactory results in the treatment of these postoperative dysesthetic or pain syndromes. REFERENCES 1. Elsberg, C. A. Tumors of the Spinal Cord and the Symptoms of Irritation and Compression of the Spinal Cord and Nerve Roots: Pathology, Symptomatology, Diagnosis, and Treatment. Paul B. Hoeber, New York, 1925. 2. Garrido, E., and Stein, B. M. Microsurgical removal of intramedullary spinal cord tumors. Surg. Neurol., 7: 215-219,1977. 3. Greenwood, J., Jr. Surgical removal of intramedullary tumors. J. Neurosurg., 26: 276282,1967. 4. Guidetti, B. Intramedullary tumours of the spinal cord. Acta Neurochir. (Wien), 17: 723,1967. 5. Horrax, G., and Henderson, D. G. Encapsulated intramedullary tumor involving whole spinal cord from medulla to conus: complete enucleation with recovery. Surg. Gynecol. Obstet., 68: 814-819, 1939. 6. Matson, D. D. Neurosurgery of Infancy and Childhood, pp. 647-688. Charles C Thomas, Springfield, Ill., 1969. 7. Rand, R. W., and Rand, C. W. Intraspinal Tumors of Childhood. Charles C Thomas, Springfield, Ill., 1960. 8. Stein, B. M. Case Records of the Massachusetts General Hospital-Case 26. N. Engl. J. Med., 293: 33-38, 1975. 9. Turnbull, F. Intramedullary tumors of the spinal cord. In Clinical Neurosurgery, pp. 237-247. Williams & Wilkins, Baltimore, 1962. 10. Woltman, H. W., Kernohan, J. W., Adson, A. W., and Craig, W. M. Intramedullary tumors of spinal cord and gliomas of intradural portion of filum terminale: fate of these patients who have these tumors. Arch. Neurol. Psychiatry, 65: 378-395, 1951. 11. Wood, E. H., Berne, A. S., and Taveras, J. M. The value of radiation therapy in the management of intrinsic tumors of the spinal cord. Radiology, 63: 11-24, 1954. 12. Woods, W. W., and Pimenta, A. M. Intramedullary lesions of the spinal cord: a study of 68 consecutive cases. Arch. Neurol. Psychiatry, 52: 383-399, 1944.
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Only one-third of all primary intraspinal neoplasms are intrinsic to the spinal cord, attesting to their rarity. Although the histological variation of these tumors is broad, the most common types are astrocytomas and ependymomas. The tumors are generally low grade and extend over many segments of the spinal cord. In some instances, especially accompanying astrocytomas, cysts may be present, further extending the intramedullary span of these lesions. Remarkably, many of these tumors have a welldefined plane with adjacent gliotic tissue of the spinal cord. A gratifying recovery and a useful life may be expected in many patients who are operated on in the early stages of tumor growth before severe neurological deterioration has developed. Since the majority of these tumors are benign, a cure may be anticipated in cases in which a total removal has been accomplished. In spite of the small size of the spinal cord and the critical function mediated by its substance, it is astonishing to see advanced tumor growth, occupying the majority of the intramedullary space, which causes minimal symptomatology. However, a phase in the tumor expansion is reached when the spinal cord can no longer accomodate and a marked deterioration in neurological function will occur. Persistent pain involving the dorsal root dermatomes in the area of the tumor involvement is often the signature of an intramedullary neoplasm. Subsequently, posterior column symptomatology develops in a progressive fashion with sensory dysesthesias in the arms, torso, and legs, depending upon the site of the intraspinal neoplasm. Sacral sparing mayor may not be present and is not an invariable finding with intramedullary neoplasms. Occasionally, lower motor neurone symptomatology and signs will be present in the area of the tumor. Well-defined central cord syndromes, as seen in syringomyelia, with disassociated sensory loss and the classic signs of anterior horn cell involvement are often lacking with intramedullary neoplasms. The symptomatology is usually progressive with few remissions and exacerbations. Symptoms are usually bilateral, but rarely, neurological abnormalities may be confined to 1 extremity. The duration 529
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of symptoms is generally measured in years, although some neoplasms may present with histories of 6 months or less. Intramedullary tumors occur most commonly in adults (1-4), although large series of intramedullary tumors in children have been reported (6, 7). The symptomatology in both age groups is similar. Almost every type of tumor seen in the brain can occur in the spinal cord; however, astrocytomas and ependymomas comprise the largest group of intramedullary tumors, occurring with about equal frequency. Astrocytomas are most commonly located in the cervical and thoracic regions, whereas the ependymomas have a higher incidence in the caudal regions of the spinal cord due to their prevalence in the conus medullaris and filum terminale. Intramedullary ependymomas often have a distinct plane between neoplasm and spinal cord tissue. These tumors are soft generally and solid and have a pseudocapsule. They are not highly vascular tumors and may have areas of necrosis. Astrocytomas are usually infiltrative with an illdefined margin between neoplasm and normal spinal cord tissue. Where a well-defined plane between neoplasm and spinal cord exists, a pseudocapsule is encountered. This variety is similar to the cerebellar astrocytoma with uniformly soft consistency and minimal vascularity and is sometimes associated with cysts containing yellow fluid of high protein content. The teratomatous and dermoid tumors have a varying amount of grumous material in their central portions, are frequently variegated in nature, and have a capsule that is adherent to the surrounding spinal cord tissue, often with a pedicle involving the dura and overlying soft tissues. Tumors which occur less frequently include dermoids, epidermoids, teratomas, oligodendrogliomas, hemangioblastomas, and either primary or metastatic malignant tumors. Lipomas, common in children, have different growth patterns and implications as regards therapy and will not be included in this discussion. Commonly, astrocytomas and ependymomas produce a fusiform enlargement of the spinal cord and often leave no indication of their presence on the surface of the spinal cord other than an occasional dilated vein at the caudal end of the tumor. In some cases, the dorsal surface of the cord will be so thin that it will be transparent. Teratomas and dermoid or epidermoid tumors are often associated with fibrous tracts bridging the dorsal surface of the cord to the dura and in some instances the overlying bone and soft tissues. Glioblastomas produce a distinct discoloration of the cord and are associated with a plethora of enlarged arterialized veins and obvious feeding arteries. Ependymomas of the conus or filum terminale region often grow in an exophytic fashion from the intramedullary locus, into the cauda equina, displacing and sometimes adhering to the nerve roots. Because of the expanding nature of these
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neoplasms, structural changes in the osseous spinal canal may. be produced. In instances where the tumor is associated with a fibrous tract, radiographic defects may be present in the overlying bone. Intramedullary tumors receive their blood supply from perforating branches of the anterior spinal artery which enter the ventral aspect of the tumor with a fibrous band, probably representing the central canal or the depths of the anterior longitudinal fissure. These vessels are small and are not associated with a high degree of vascularity within the tumor. Small vessels also enter the tumor from the dorsal and immediate circumferential portions of the spinal cord. The tumors tend to be eccentric and located in the more dorsal portion of the spinal cord. Invariably there is a thin layer of compressed spinal cord tissue overlying the dorsal surface of these tumors, and they rarely present directly on the surface of the spinal cord. In 1907 von Eiselsberg totally excised a neurofibrosarcoma from the cord while in 1924 Cushing operated on an 8-year-old child and completely removed an intramedullary ependymoma extending from Cl to T2 (9). However, the first well-documented surgical effort directed towards removal of intramedullary tumors was published by Elsberg (1) in 1925, when he reported 13 cases. Three of these tumors were totally removed, and the remainder were partially removed. He stressed that some of these tumors were infiltrating and thereby defied removal, but emphasized that the surgeon must search out those tumors with well-defined cleavage planes which might permit total removal of the neoplasm. These results were remarkable, considering the lack of magnification techniques and previous surgical experience with such tumors at that time. When a definitive plane between tumor and spinal cord was not visible at the first operation, Elsberg suggested a second operation, at which time the tumor would possibly present through the myelotomy and total removal would be feasible. Later, Matson (6) also advocated this technique. Other than these reports, little experience with 2-stage removal has been published. Subsequent to the early reports of Elsberg, others (2-5, 6, 9, 12) have reported successful removal of intramedullary tumors. Greenwood (3) placed the successful surgical therapy of these tumors on a firm foundation when he presented his experience with 10 intramedullary tumors, primarily ependymomas, in which a total removal was accomplished without mortality. These results, with useful survival, justified his enthusiasm for an aggressive surgical approach to these lesions. He emphasized the use of magnification techniques and microsurgical instrumentation in the performance of this surgery. Guidetti (4) published his experience with a large group of intramedullary tumors and emphasized the difficulty in totally removing astrocytomas. However, in the presence of intramedullary ependymomas and other tumors he felt that every
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effort should be made to accomplish total removal, although this would only be possible in the presence of a line of cleavage between the normal spinal cord and tumor. He suggested that once a cleavage was established the tumor be separated by gentle dissection from the normal spinal cord on each side and then lifted carefully by one end or the other and slowly removed from its bed. Blood vessels should be severed close to the tumor by bipolar cautery with irrigation. His operative mortality was 10%, with an overall total removal of 24 of the 71 tumors representing a wide variety of histological types. The famous case of Horrax and Henderson (5) should be mentioned in which an intramedullary ependymoma extended the entire length of the spinal cord and was totally enucleated during a series of operations with recovery and long-term survival. Our series comprises 13 cases of intramedullary tumor, in which 11 total removals were accomplished (Table 21.1). The tumors represent a range of histology, with astrocytoma and ependymoma being the most common tumor and with lesser frequency, teratomatous types of tumors. No lipomas are included in this group. Some patients had undergone previous treatment which included decompressive laminectomy, tapping of cysts associated with the tumors, and radiotherapy. This gave us an opportunity to study both the natural course of the disease and the effects of treatment on some of these tumors. Unfortunately, the series is small, and the natural course of these tumors, which spans many years, makes the evaluation of any therapy, other than total removal, difficult. The postoperative result was often dependent upon the degree of neurological deficit as a result of the disease process prior to definitive surgical treatment of the tumor. The radiological confirmation of intramedullary tumors hinges upon myelography. Prior to the advent of water-soluble dyes, Pantopaque (Pantopaque-Iophendylate, Lafayette Pharmacological, Inc., Lafayette, Ind.) myelography has been the procedure of choice. Myelography demonstrates a fusiform dilation of the cord in the region of the tumor. A band between the tumor and the dura may be visualized in cases of teratomatous tumors. A complete block is generally not present. When present, the dye should be instilled from the opposite end of the spinal canal to make a definitive evaluation of the length of the tumor. Increased use of water-soluble contrast agents should significantly improve the radiological definition of these tumors. When dilated venous channels at the caudal aspect of small intramedullary tumors are present, the differential diagnosis of a vascular malformation may be raised. This differential is rarely a problem, and spinal angiography has not been of diagnostic value except for the identification of an intramedullary hemangioblastoma. In some instances the differential diagnosis between
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40 24 49 28 38 17 13 4mo 60 13 3 48 38
1 2 3 4 5 6 7 8 9 10 11 12 13
Conus Conus C C-D C D Conus Conus D-C D-L C-D C C
Location
Epend Epend Epend Epend Epend Teratoma Dermoid Epidermoid Astroc Astroc Astroc Astroc Astroc
Histology
0 0 + + + + 0 0 + + 0 0 +
Prior surgery
T T T T T T T T 90% T 95% T T
Removal
1+ 2+ 3+ 4+ 3+ 4+ 2+ 2+ 4+ 2+ 1+ 1+/pain 2+
Pre op neurological defects
D, dorsal; C, cervical; T, total; 1+, mild defect; 2+, paresis; 3+, moderate deficit; 4+, para- or quadriplegia.
Age
No.
TABLE 21.1 Intramedullary Spinal Cord Tumors
Improved Improved Improved Static Static Improved Improved Improved Static Static Improved Improved Improved
Result
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CLINICAL NEUROSURGERY
syringomyelia and intramedullary tumor presents a perplexing problem. Air myelography has been a useful technique in distinguishing these 2 conditions. In the case of syringomyelia, a "collapsing cord" sign may be demonstrated, whereas in intramedullary neoplasms the cord will remain of uniform width regardless of the position of the patient (Fig. 21.1). Routine computed tomography (CT) scanning of the spinal canal has not been of practical use in the diagnosis of these neoplasms. We have
FIG. 21.1. Air myelogram demonstrating the "collapsing cord" sign of syringomyelia. (A) Head-down position with cervical cord enlarged (arrows). (B) Head-up position with cervical cord narrow (arrows).
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retrospectively scanned a number of patients in which large tumors were present, with failure to definitively visualize the tumors. CT scanning of the spinal canal with water-soluble contrast agents promises to assist in the definitive diagnosis of these tumors.
Surgical Technique (Fig. 21.2, A-C) We quite agree with Turnbull (9), who stated: "A surgeon exploring a spinal cord for a suspected intramedullary tumor must be prepared to face a formidable problem and also have the courage of conviction to make every attempt to remove that tumor. Anything less than this, with a cursory inspection of the spinal cord or aspiration thereof, can only create problems of a more complex nature for the subsequent surgical effort to remove such tumors." When these tumors are located in the cervical region, either a sitting or prone position may be utilized. We prefer the prone position for 2 reasons. First, the potential for vasomotor collapse abetted by compromise of the autonomic pathways by tumor is minimized. Second, we have found it of benefit to have the assistant actively involved in the operation on these tumors, providing traction on the tumor or assisting other aspects of the surgery. It is important that the full extent of the tumor be known prior to the operative intervention. A wide laminectomy is then carried out over the entire extent of the tumor and to a level above and below. The dura must then be carefully opened since the pia-arachnoid of the enlarged spinal cord is often adherent to the underside of the dura. It is important to prevent any injury to the subarachnoid vasculature since hemorrhage during this phase of the operation will obscure all landmarks and significantly compromise the surgical effort. Facing a widened spinal cord, the surgeon must not be misled in those rare instances of an anterior extramedullary lesion in which the cord is splayed out over the lesion (8). Having ruled out this possibility, a site for posterior myelotomy should be selected. The most avascular route on the dorsal surface of the cord is followed and need not be along the midline; it may be expeditious to go paramedian. Obviously, some of the traversing vasculature will be sacrificed during this myelotomy. An initial myelotomy of approximately 1 to 2 em is carried out over the greatest enlargement of the spinal eord. This allows the operator to evaluate the plane between the tumor and the spinal cord tissue. In some instances the presence of a cyst associated with the tumor may be readily apparent and, if so, additional room may be gained by aspiration of some of the cystic contents by a small-bore needle. To facilitate dissection, these cysts should not be completely evacuated. If it is determined that the neoplasm is cystic or has welldefined planes, then the myelotomy is lengthened over the extent of the
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FIG.
21.2. (A) drawing of myelotomy over intramedullary tumor.
tumor. With teratomatous tumors, the stalk between the cord and the dura should be removed as an integral part of the lesion. In the case of ependymomas extending from the conus, the extra-axial portion in the cauda equina may be removed first to afford adequate decompression and visualization of the residual tumor involving the intramedullary portion of the conus. The draining veins of intramedullary hemangioblastomas must also be left to the latter part of the surgical resection. Having performed an adequate myelotomy, 6-0 sutures are placed through the pial margin of the myelotomy on either side in order to provide gentle retraction of the spinal cord and open it in the fashion of opening a book. With the operating microscope and microsurgical techniques, utilizing bipolar cautery, small suction tubes, and various dissectors, a plane is developed around the margin of the tumor, taking care to retract primarily on the tumor and not on the spinal cord. The surgeon works to one or the other end of the tumor, and at this point where the tumor is the narrowest it may be possible to grasp the end and gently extract it from the interior of the cord. All the fine vascular adhesions to the spinal cord, especially on the ventral aspect of the tumor, should be cauterized with bipolar cautery and divided sharply. No blunt dissection should be carried out in areas in which vascular channels connect the tumor to the spinal cord. These tumors are amazingly avascular and present no problems in terms of hemorrhage or the control of large blood vessels. It is important to keep the operative. field scrupulously dry so that the plane between the tumor and the spinal cord may be readily
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FIG. 21.2. (B) drawing of removal of intramedullary tumor. (C) drawing of open cord after the removal of an intramedullary tumor.
identified. If the tumor is too large to remove in toto or necessitates too much retraction on the spinal cord, its interior may be decompressed. Cystic collections at the margins of the tumor, as in the case of astrocytomas, facilitate the tumor resection. However, we make no attempt to
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remove the thin-walled cyst associated with these tumors, as we do not feel this is a portion of the neoplasm. If there is any question about the totality of removal, small biopsies may be obtained from the margin of the resection and evaluated by frozen section during operation. In most instances the margins are well-defined, and there is no question about the removal of the tumor. When the margins of the cord are allowed to fall back into position, the remarkable decompressive effect of tumor removal is quite apparent. The dorsal columns often are thin to the point of transparency. If retraction on the cord has been minimal, these fiber tracts function in a satisfactory fashion and will show progressive recovery of function. Gentleness of dissection may be gauged by the vascular pattern on the dorsal surface of the cord at the completion of tumor resection. Distended veins which were present prior to removal, usually at the caudal end of the tumor on the surface of the spinal cord, will now be less prominent. No attempt has been made to sew the pial surfaces of the spinal cord together. When the dura is closed in a watertight fashion, it is rarely necessary to utilize a fascial graft other than in those cases which had been previously operated on and the dura left open. If the surgery has involved extensive areas of the cervical region, the endotracheal tube is left in place at least 24 hours, regardless of the patient's condition at the termination of operation. Steroids are used pre- and postoperatively on a routine basis. In cases which have had prior surgery and/or radiotherapy, intense scarring has been noted between the overlying tissues and the spinal cord, especially when the dura has been left open. This scarring compromises a definitive surgical endeavor. If total removal of an intramedullary tumor is not feasible, the dura should be reconstructed) preferably with a fascial graft, so that subsequent surgical endeavors may be facilitated. In cases in which radiation had been previously given, we have noted intense intramedullary gliosis, by biopsy, separate from the margin of the tumor, usually at the caudal or rostral interface. It is assumed that this is an adverse effect of preoperative radiation. In those cases which have had previous surgery with aspiration of a cyst but without definitive removal of the intramedullary tumor, benefits have been transient with rapid reaccumulation of the cyst fluid. In tumors of teratomatous origin, the border of the tumor, although well-defined, may be densely adherent to the surrounding spinal cord. Every attempt should be made to remove this capsule, as it is a potential source of regrowth. These tumors may involve extensive central areas of the spinal cord and may extend from posterior to anterior surface. Teratomatous tumors may also have a dumbbell configuration within the substance of the spinal cord, and the surgeon must be wary not to miss satellite portions of the primary tumor.
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The results of this small series were gratifying in that no patient was made worse by the surgery and those patients with marked neurological deficits prior to surgery were helped in some instances. Those with only mild-to-moderate neurological deficit prior to the surgery did extremely well and returned to normal activity, regardless of tumor size. The followup (Table 21.1) ranges from years to a few months. During this period there has been no evidence of recurrence. Case History. This 38-year-old male had symptoms of severe pain of 1 year's duration in the low cervical region radiating into both shoulders. Coincident with diminution of the pain, he noted progressive stiffness and weakness of his shoulder muscles so that it became impossible for him to reach over his head or button his collar. He also noted numbness and strange feelings in the fingers of both hands and he was unable to appreciate the temperature of objects held in his hands. Although the process continued unrelentingly, it was asymmetrical, the left side being more affected than the right. He noted no abnormalities in his legs. The neurological examination showed atrophy and weakness of the shoulder girdle muscles. Muscles below the C61evel showed good strength. There was loss of pain sensation from C2 to C6 which was more prominent on the left side. The lower extremities showed slight hyperactivity of reflexes with a Babinski on the left side. There was a slight disturbance of position sense in the toes bilaterally. A myelogram demonstrated a wide cervical spinal cord from CI to C6 compatible with an intramedullary tumor. Subsequently, a cervical laminectomy was carried out with total removal of an intramedullary solid ependymoma (Figs. 21.3-21.5). Postoperatively the patient showed progressive improvement, and at a 2-year follow-up
FIG. 21.3. Appearance of spinal cord with intramedullary ependymoma.
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INTRAMEDULLARY SPINAL CORD TUMORS
FIG.
CLINICAL NEUROSURGERY
21.4. Initial myelotomy with visualization of intramedullary ependymoma (arrow).
FIG. 21.5. Cavity remaining in spinal cord after removal of intramedullary ependymoma. Note fine stay sutures in pial margin of the cord (arrows).
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was working full time with minimal weakness and atrophy of his shoulder .muscles, His other neurological functions were normal.
Discussion It would appear from our experience (2) and that of others (3, 4) that a decompressive laminectomy, whether or not a tumor cyst has been evacuated, with or without radiotherapy, has been of little beneficial effect in the treatment of the majority of intramedullary spinal cord tumors. Reviews (4, 10, 11, 12) of the effects of radiation on these tumors are clouded by lack of knowledge of the natural course of these tumors and the number of variables involved which include decompression and partial surgical removals. Publications by Guidetti (4), Woltman et ale (10), and Woods and Pimenta (12) suggest that even with partial removal, long-term survival with static neurological deficit may be expected. Radiation has apparently yielded beneficial effects (11), but this report has a high percentage of histologically unverified tumors. There has been little objective follow-up of reduction in tumor size following radiation therapy. A significant number of reports would indicate that the best treatment is surgical removal (2-4, 6, 7, 12). This may be accomplished in the majority of cases with anticipated improvement in the patient's condition or at least an arrest of the neurological deterioration. Postoperative result is predicated upon the degree of neurological involvement prior to operation. Many surgeons have reported difficulty in total removal of astrocytomas. In our small series we have been able to totally remove 3 of 5 astrocytomas which presented no more significant problem than encountered in the removal of ependymomas. In the other 2 cases, near total removals were carried out with a definitive plane being observed around most of the tumor. Through the use of microsurgical techniques, careful anesthesia, and strict attention to the postoperative pulmonary function, negligible mortality and morbidity rates can be expected, even with removal of extensive tumors in the cervical region. Similar experiences have been reported by Greenwood (3). Guidetti (4) supports radical removal of these tumors, except where ill-defined planes do not permit this to be accomplished. In such cases he feels that subtotal resection produces no better result than biopsy. In those cases of astrocytoma in which biopsy only was performed and presumably postoperative radiation was given, average survival rate was 5 years. His feeling is that a significant number of the astrocytomas may be totally removed and at that least an attempt with microsurgical techniques should be made to accomplish this. We have not used postoperative radiation for intramedullary tumors which have been totally removed and do not advocate postoperative radiation for benign intramedullary tumors that
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have been incompletely removed. The patient's course should be followed carefully, facilitated by the use of water-soluble contrast agents and CT scanning. A second surgical attempt should be made to remove the tumor at the time of recurrence. Following this, radiation may be considered. Experience with a significant number of cases confirms that recurrence should not be a problem. Greenwood's (3) series comprised almost exclusively ependymomas, and his long-term survivals, as well as those of Guidetti (4) and others (5, 10, 12), have been gratifying. Radicular pain in the distribution of the nerve roots associated with the tumor has been a distressing postoperative problem. This pain has a burning quality, severely disturbing to the patient and extremely difficult to control. One may surmise that it is due to the derangement of the physiological pathways for pain at the dorsal route entry zone. Unfortunately, we have not had satisfactory results in the treatment of these postoperative dysesthetic or pain syndromes. REFERENCES 1. Elsberg, C. A. Tumors of the Spinal Cord and the Symptoms of Irritation and Compression of the Spinal Cord and Nerve Roots: Pathology, Symptomatology, Diagnosis, and Treatment. Paul B. Hoeber, New York, 1925. 2. Garrido, E., and Stein, B. M. Microsurgical removal of intramedullary spinal cord tumors. Surg. Neurol., 7: 215-219,1977. 3. Greenwood, J., Jr. Surgical removal of intramedullary tumors. J. Neurosurg., 26: 276282,1967. 4. Guidetti, B. Intramedullary tumours of the spinal cord. Acta Neurochir. (Wien), 17: 723,1967. 5. Horrax, G., and Henderson, D. G. Encapsulated intramedullary tumor involving whole spinal cord from medulla to conus: complete enucleation with recovery. Surg. Gynecol. Obstet., 68: 814-819, 1939. 6. Matson, D. D. Neurosurgery of Infancy and Childhood, pp. 647-688. Charles C Thomas, Springfield, Ill., 1969. 7. Rand, R. W., and Rand, C. W. Intraspinal Tumors of Childhood. Charles C Thomas, Springfield, Ill., 1960. 8. Stein, B. M. Case Records of the Massachusetts General Hospital-Case 26. N. Engl. J. Med., 293: 33-38, 1975. 9. Turnbull, F. Intramedullary tumors of the spinal cord. In Clinical Neurosurgery, pp. 237-247. Williams & Wilkins, Baltimore, 1962. 10. Woltman, H. W., Kernohan, J. W., Adson, A. W., and Craig, W. M. Intramedullary tumors of spinal cord and gliomas of intradural portion of filum terminale: fate of these patients who have these tumors. Arch. Neurol. Psychiatry, 65: 378-395, 1951. 11. Wood, E. H., Berne, A. S., and Taveras, J. M. The value of radiation therapy in the management of intrinsic tumors of the spinal cord. Radiology, 63: 11-24, 1954. 12. Woods, W. W., and Pimenta, A. M. Intramedullary lesions of the spinal cord: a study of 68 consecutive cases. Arch. Neurol. Psychiatry, 52: 383-399, 1944.
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