|Year : 2022 | Volume
| Issue : 2 | Page : 247-255
Spinal intramedullary tumors
Girish Menon1, Siddharth Srinivasan1, Rajesh Nair1, Ajay Hegde1, Suresh Nair2
1 Department of Neurosurgery, Kasturba Medical College, Manipal Academy of Higher Education, Manipal, Karnataka, India
2 Department of Neurosurgery, SCTIMST, Thiruvananthapuram, Kerala, India
|Date of Submission||09-Nov-2022|
|Date of Acceptance||12-Nov-2022|
|Date of Web Publication||23-Dec-2022|
Prof. Girish Menon
Department of Neurosurgery, Kasturba Medical College, Manipal Academy of Higher Education, Manipal - 576 104, Karnataka
Source of Support: None, Conflict of Interest: None
Intramedullary spinal cord tumors constitute an uncommon group of central nervous system neoplasms which pose considerable diagnostic and management challenges. Often low grade, these tumors have an insidious onset and slow progression, which makes early diagnosis a challenge. Advances in magnetic resonance imaging technology have greatly aided the diagnosis and preoperative planning of intramedullary tumors. Yet, radiological diagnosis can be difficult in the presence of several tumor mimics. The introduction and advancement of microsurgical techniques have made surgery the preferred treatment modality. Timing of intervention, however, is contentious. Eloquence of the surrounding tissue and the unforgiving nature of the spinal cord adds to the surgical challenge. Their treatment and prognosis is largely dependent on tumor histology and patient functionality. Well-demarcated tumors like ependymomas and hemangioblastomas can be resected completely with good outcome. Infiltrative tumors such as high-grade astrocytomas are best managed with biopsies or limited resections. Postoperative deficits can be crippling and the use of intraoperative neurophysiologic monitoring and other adjuncts is mandatory. Subtotal resection carry a high risk of recurrence and gross total resection carries a high risk of operative morbidity. With the availability of newer imaging modalities and intraoperative adjuncts, the earlier pessimistic conservative approach has been replaced by an aggressive surgical approach. This review provides an overview on the entire spectra of spinal intramedullary tumors with particular focus on management strategies.
Keywords: Astrocytoma, ependymoma, intramedullary, spinal cord
|How to cite this article:|
Menon G, Srinivasan S, Nair R, Hegde A, Nair S. Spinal intramedullary tumors. Arch Med Health Sci 2022;10:247-55
| Introduction|| |
Intramedullary spinal cord tumors constitute an uncommon group of central nervous system neoplasms which pose considerable diagnostic and management challenges. Intramedullary spinal cord tumors are most often low-grade malignant tumors and their insidious onset and slow progression of symptoms make early diagnosis a challenge. Surgery is the preferred treatment modality, but the timing of intervention is contentious. Postoperative deficits can be crippling, but safe maximal resection can be curative. Subtotal resection carries a high risk of recurrence and gross total resection (GTR) carries a high risk of operative morbidity. With the availability of newer imaging modalities and intraoperative adjuncts, the earlier pessimistic conservative approach has been replaced by an aggressive surgical approach. This review provides an overview on the entire spectra of spinal intramedullary tumors with particular focus on management strategies.
| Epidemiology|| |
Primary spinal intradural tumors are rare and intramedullary neoplasms are even less frequent. Overall, intradural tumors present with an age-adjusted incidence of 0.97 per 100,000 patients per year. Spinal intramedullary tumors account for 4%–10% of all central nervous system tumors and nearly 20%–35% of all intraspinal tumors.,, Primary glial neoplasms account for majority of spinal intramedullary tumors, of which ependymomas and astrocytomas account for 80%–90%. Among glial neoplasms, ependymomas account for 21% of all spinal tumors and up to 80% of all spinal gliomas., Hemangioblastomas are the most common nonglial primary intramedullary neoplasms representing 3%–8% of all intramedullary spinal cord tumors. Other intramedullary neoplasms include less common tumors such as dermoids, metastases, lymphoma, germinomas, epidermoids, lipomas, intramedullary meningiomas, and nerve sheath tumors.,
Ependymomas arise from the ependymal cells lining the ventricles in the brain and the central canal in the spinal cord. Ependymomas are commonly seen either in the conus medullaris ependymomas (40%) or cervical intramedullary (25%–42%) region, especially in young men.,,,, Astrocytomas are the second most common intramedullary tumors and are more commonly seen in children and adolescents where they account for nearly 60% of all spinal cord tumors. In one of the largest series reported from India, Nair et al. observed astrocytomas to be the most common tumors closely followed by ependymomas.
| Presentation|| |
The clinical presentation of intramedullary tumors is highly variable. Owing to their insidious nature of growth, the signs and symptoms may remain dormant for a long time before diagnosis is made. Diagnosis is especially difficult in children, where these tumors may remain asymptomatic for a long period of time or may cause nonspecific complaints.,, Quite often, an intramedullary tumor is diagnosed on investigation for an “idiopathic” scoliosis. The most common presenting symptom seen in nearly half of the patients is a deep boring type of pain along the spine with worsening at night. Other common presenting symptoms include sensory disturbance in the form of hyperesthesia (in nearly 82% of patients) followed by dysesthesia (in nearly 63% patients). Motor weakness, ataxia, and autonomic dysfunction succeed pain and sensory symptoms and is generally found in two-thirds of the of patients., Sphincter dysfunction is seen in only half of the patients. Bladder symptoms tend to occur rather late stage and is seldom seen as a presenting symptom., In view of the wide spectrum of manifestation, accurate grading of deficits often becomes a challenge for objective evaluation. The modified McCormick scale is the most commonly used tool to quantify the pre- and postoperative functional status for patients with intramedullary tumors and has gained universal acceptance [Table 1].
| Imaging|| |
Imaging diagnosis of an intramedullary spinal tumor can be challenging and radiological findings need to be always interpreted along with the clinical background. Diffuse cord swelling is the most consistent observation seen in all imaging sequences. If the swelling is confined to a single segment or short segment, it is less likely to be neoplastic. Diffuse cord swelling spread over long segments along with high signal intensity changes on T2-weighted images is highly suggestive of a neoplastic pathology [Figure 1] and [Figure 2]. Both astrocytomas and ependymomas are usually hypo- or isointense on T1-weighted images and hyperintense on T2-weighted images and show heterogeneous contrast enhancement. On axial sections, astrocytomas may be seen to be eccentrically located in comparison to ependymomas which are more centrally located [Figure 2]. Ependymomas characteristically have a “cap sign” – a syrinx cavity either in the rostral or caudal pole or both [Figure 1]. Strong homogenous enhancement and an eccentric subpial location strongly suggests a diagnosis of hemangioblastoma, [Figure 3]. An infiltrative pattern of growth suggests high-grade glioblastomas which are relatively uncommon. Uncommon lesions such as dermoids, melanomas, and metastasis have varied appearances on magnetic resonance imaging (MRI). Melanomas appear hyperintense on T1 due to the melanin content and are seen as hypo- or isointense on T2. Germ cell tumors (GCTs) usually occur in the lower thoracic level, show good contrast enhancement, and may have associated focal spinal cord atrophy. Lymphomas appear as diffusion restricted contrast enhancing lesions. MRI characteristics of a dermoids vary, depending on cystic content. Fluid and fat appear hyperintense on T-1 weighted and the solid portion of the tumor is slightly hypointense. Fat hyperintensity is most specific for dermoids [Figure 4].
|Figure 1: A large intramedullary altered signal intensity solid cystic lesion is noted causing cord expansion extending from medulla, abutting the floor of 4th ventricle to D3 level measuring (a-d) with solid component extending from C2-C5 vertebra (c) and another nodules noted at C7 and D3 vertebra (d). The lesion appears isointense on T1 (a) and heterogeneous on T2 (b) and shows heterogeneous postcontrast enhancement. Intramedullary dilated syrinx cavities are noted both caudal and cranial to the lesion (b)|
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|Figure 2: Long segment intramedullary altered signal intensity lesion is seen involving the cervical cord from the level of midportion of C2 till midportion of C7 vertebra. The lesion is isointense on T1WI (a and c) and hyperintense on T2WI (b) and shows heterogeneous postcontrast enhancement. Ill-defined T2 hypointense areas showing hypointensity on GRE (d) is noted at the inferior aspect of the lesion suggestive of hemorrhage. Multiple small T2/STIR (b and d) hyperintense perilesional cyst-like lesions are noted superior to the aforementioned lesion. T2WI: Type 2-weighted image|
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|Figure 3: An enhancing exophytic solid cystic nodule measuring is noted in the posterior aspect of cervicomedullary junction (red arrow, a and b) Few small peritumoral cysts are noted in cord at the C1-C2 level (c). Another intramedullary predominantly cystic lesion with enhancing mural nodule is noted extending from the lower border of C3 vertebra extending up to the lower border of C5 vertebra. A vividly enhancing solid intramedullary lesion causing cord expansion measuring is noted at the D6-D7 vertebral level (d)|
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|Figure 4: Well-defined lobulated intramedullary altered signal lesion is seen in the lower dorsal spinal cord, extending from D11 to L2 vertebrae. The lesion has both cystic/solid components and is hypointense on T1WI (a) hyperintense on T2WI/STIR sequences (b). The fat component appears hyperintense on T1WI/T2WI and hypointense on STIR sequence (c) and shows suppression on T1FS sequence (d). There is associated scalloping of D12, L1, and L2 vertebrae. Small syrinx noted at D11 vertebral level, just proximal to the mass lesion. The spinal cord appears to extend anteriorly L4-5 disk level suggestive of possible tethered cord. T2WI: Type 2-weighted image|
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Intramedullary tumors need to be differentiated from other vascular lesions, inflammatory conditions, infections, and syrinx. MRI findings of a hemosiderin rim are characteristic of a cavernoma. Dural arteriovenous fistulas, multiple sclerosis, transverse myelitis, spinal cord abscesses, and neurosarcoidosis are some of the other lesions which need to be considered in the differential diagnosis for an intramedullary mass lesion.
| Management Philosophy|| |
The first successful removal of an intramedullary tumor was done by Von Eiselberg. The high risk of postoperative morbidity was, however, a deterrent and the management philosophy for long revolved around biopsy, lax duroplasty, and adjuvant radiotherapy (RT). Later, Greenwood, and Epstein et al. proved that morbidity could be reduced through meticulous surgical techniques.,, Since the introduction of microsurgical techniques, surgery has become the mainstay of treatment for most intramedullary tumors.,, The current standard of care is GTR wherever possible while minimizing neurological injury.,, Ependymomas particularly have excellent results with this approach of maximal safe resection and so do low-grade astrocytomas and hemangioblastomas. With high-grade lesions and infiltrative astrocytomas, the role of aggressive surgery is controversial, although few recent studies have reported a significant advantage of resection over biopsy.,
One major management dilemma is the decision to intervene in asymptomatic or mildly symptomatic patients. Radiological evidence of a lesion does not necessarily mandate operative removal. Behmanesh et al. studied the natural history of ependymomas and observed a wait and watch policy can be safely adopted in some patients. They reported that tumor progression mostly appears after many years and may not be debilitating in most cases. Nair et al. strongly concur with the above approach and recommend that the decision for surgery should be guided by progression of symptoms rather than the radiological detection of the lesion.
Outcome following surgery is directly related to the preoperative functional status. Patients with significant preoperative deficits should be warned regarding this possibility as recovery from a significant long-standing deficit rarely occurs. Recovery in such patients is often modest seen only in a minority of patients. Patients with mild deficits are more likely to improve following surgery. Such patients with minor symptoms are often unwilling to risk neurological deterioration as a result of operation. A wait and watch policy and close monitoring with serial imaging is the recommended approach in such patients. Once the symptoms progress, patients frequently are more prepared psychologically to face the risks of surgery.
| Surgical Principles|| |
Intramedullary tumors can be purely intramedullary, subpial, or exophytic. Surgical exposure should be adequate enough to expose the full extent of tumor. Dura is opened sparing the arachnoid to avoid extradural venous bleeding. Myelotomy is carried out either through the midline or through the most widened avascular part of the cord or through the dorsal root entry zone.,, Postmyelotomy, the incision is deepened and both tumor poles identified and pial traction sutures applied. Microsurgical dissection is employed to establish the plane between the tumor and spinal cord and tumor decompression carried out using CUSA under neuromonitoring. Bipolar cautery is to be used sparingly to avoid thermal injury to the spinal cord [Figure 5] and [Figure 6].,,,
|Figure 5: Intraoperative photograph showing a distinct well circumscribed intramedullary lesion in the cervicomedullary junction with a clear distal margin A cottonoid has been placed to mark the normal lower limit. The tumor appears to be yellowish brown with necrotic tissue within (ependymoma)|
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|Figure 6: Intraoperative photograph showing a thoracic intramedullary lesion after midline myelotomy Vascular well circumscribed tumor (hemangioblastoma) can be seen emanating from the spinal cord and can be clearly distinguished from the adjacent normal tissue|
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They appear as a soft red or grayish purple noncapsulated mass with a fairly good plane of cleavage from the normal spinal cord. Grade I (myxopapillary variant) are commonly seen in the conus and filum terminale and have a good plane facilitating gross total removal. Grade II ependymomas (cellular, papillary, clear cell, or tanycytic) and Grade III (anaplastic ependymoma) have poor plane and are infiltrative and radical decompression is difficult. En bloc resection is avoided except in very small lesions. In addition to the histological grade of the tumor, extent of resection is the most important prognostic factor for an ependymoma.,,,,
Astrocytomas are more challenging than ependymomas surgically. Astrocytomas are infiltrating, have poor plane of cleavage, and blend imperceptibly with the spinal cord at the margins. Radical resection of these infiltrative lesions may result in a higher morbidity. A less radical intervention with minimal surgical morbidity is therefore preferred. In children, these tumors behave similarly to low-grade posterior fossa astrocytomas which are amenable for total resection. An “inside-out” removal is recommended based on the color and consistency of the tumor compared to the surrounding spinal cord.,,,
| Intraoperative Monitoring|| |
Intraoperative monitoring is an essential and mandatory intraoperative adjunct to minimize operative morbidity and to maximize resection.,, The integrity of the motor and sensory tracts can be ascertained by meticulous monitoring, especially in infiltrative tumors with poor dissection planes., D-wave monitoring correlates well with long-term motor function and maintaining a D-wave amplitude above 50% of baseline values is considered an optimum target to minimize deficits., MEP morphology is also another predictor and a 50% decrease or more in MEP amplitude is a warning sign for imminent deficits. Predictive roles of SSEP is inferior to MEP and D-wave and neurological deficits are known to occur despite normal SSEP.,, Introduction of newer monitoring techniques such as high-resolution microstimulation motor mapping and dorsal columns stimulation is likely to further improve surgical outcome.,
| Other Adjuncts|| |
Intraoperative ultrasound aids in tumor localization before surgery and in ascertaining the extent of resection after tumor decompression. Preoperative identification and localization of major tracts tumor using diffusion tensor imaging (DTI) is another useful adjunct. However, DTI for spinal lesions is yet to be standardized globally., Intraoperative MRI has limitations and fails to be user-friendly., 5-aminolevulinic acid-induced protoporphyrin IX fluorescence alone or in combination with intraoperative MRI maximizes the extent of safe resection. Video angiography using intraoperative intravenous injections of indocyanine green is particularly useful following vascular tumors such as hemangioblastoma. Use of intraoperative frozen section is limited and surgical resection is often guided by the tumor cord interface rather than histology except in few cases like GCTs. Minimally invasive surgery (MIS) is being increasingly attempted for spinal stabilization surgeries, but its merit in intramedullary tumors needs further confirmation. Small lesions spanning <2 spinal levels, especially in children, are best suited for minimal approach. The main advantage of MIS surgery is minimization of postoperative instability.
| Adjuvant Therapy|| |
RT is not recommended after gross total removal and its role after incomplete resection remains controversial., Oh et al. report a definite advantage of RT following STR on PFS but not on overall OS.11 RT results in gliosis, fibrosis, and disruption of the natural dissection planes making re-exploration difficult. RT, thus, is best reserved for Grade III tumors and those with recurrence following repeat surgery., The use of chemotherapy is even less established, and to date, there is no standard chemotherapy although a variety of drugs have been investigated.,, Chemotherapy may be used on a case-by-case basis as an adjuvant therapy, particularly in the pediatric population. In spinal glioblastomas, temozolomide may help in the standard intracranial dose and few series have reported an additional median survival of 23 months.,, Another option in patients with failed temozolomide therapy is salvage or concurrent therapy with bevacizumab. Intracavitary rhenium-186 irradiation is yet another option especially in recurrent pilocytic astrocytoma. The need for newer effective adjuvant therapies as well studies from centers with large series can never be overemphasized.
| Complications and Surgical Morbidity|| |
In the immediate postoperative period, most patients demonstrate some degree of neurological worsening. These deficits are usually transitory and recover within a few months, particularly the motor deficits. The rate of permanent postoperative deterioration of patients undergoing intramedullary tumor resection differs significantly from 14% to 35% among various studies.,,, Dorsal column dysfunction is the most common complication and is seen in as many as 43% of patients. This posterior column dysfunction tends to improve but not to the preoperative level. Other long-term surgical morbidities include neuropathic and dysesthetic pain, causalgia, and residual persisting myelopathy., Cerebrospinal fluid (CSF) leak with its associated sequelae, wound dehiscence, late onset hydrocephalus, and postoperative spine deformity are other possible complications.
Progressive kyphoscoliosis and other spinal deformities remain an important issue following surgery for intramedullary spinal cord tumors, especially in children where the incidence can be as high as 22%. Several authors advocate the use of laminoplasty over laminectomy to prevent the occurrence of this deformity., McGirt et al. in their series of 238 patients operated did not observe any statistically significant difference between laminectomy and laminoplasty with regard to postoperative deformities. Laminoplasty has an added advantage of reducing the risk of CSF leak and redo surgeries are easier following laminoplasty rather than laminectomy. Preoperative functional status has been reported as the strongest predictor of postoperative neurological outcome. It can be, hence, argued that early surgery can prevent or reduce postoperative morbidity. However, this reasoning is controversial and an expert review on asymptomatic lesions recommended surgery only for those with progressive neurologic decline.
| Prognosis and Long-term Outcome|| |
Postoperative neurological recovery is seldom satisfactory and more surgery helps stabilize the symptoms. In one of the largest series from India, Nair et al. reported an overall mortality rate of 5.37%, 22% improvement in neurological status, 44% remained static, and the rest deteriorated. Patient's age, preoperative neurological status, location, extent of removal, and histology are important prognosticators of overall outcome. Young age, good preoperative neurological grade, gross total removal, and a favorable histology predictably are related to good outcome.,,, Resection rates are better with ependymomas and hemangioblastomas compared to astrocytomas.,,, For ependymomas, in general, gross total removal can be achieved in around 85% and 10 year PFS varies from 80% to 90%., Wong et al. reported a GTR rate of only 23% in their series of 89 cases of spinal cord astrocytoma, while Ardeshiri et al. had a comparatively high GTR rate of more than 72% in their series consisting of 22 cases of spinal cord astrocytoma., Correspondingly, recurrence rates are higher with astrocytomas (47.6%) compared with ependymomas (7.3%) and hemangioblastomas. In Karikari et al.'s series, astrocytomas with subtotal resection STR had a 47.6% recurrence rate compared to 7.3% with ependymomas. Benes et al. have suggested that for intramedullary astrocytomas, every 10% increase in residual tumor volume is associated with a 40% increased risk in mortality. 5-year survival rate has been reported at 73% for low-grade gliomas compared to 30% for high-grade tumors, with an average 5-year progression-free survival of around 58%–61% for all intramedullary gliomas.,,,,
| Special Considerations|| |
Pediatric intramedullary tumors
Pediatric spinal cord tumors occur more commonly in males, typically involve the cervical cord and are mostly astrocytomas. The management philosophy is the same as in adults. Laminoplasty and stabilization with instrumentation are more frequently indicated to minimize the risk of postoperative kyphotic deformity. RT is best avoided in the pediatric age group.
Intramedullary hemangioblastomas are subpial tumors of mesenchymal origin. Spinal hemangioblastomas may be sporadic or syndromic (10%–30%) as part of the VHL complex. Hemangioblastomas are more commonly seen in the posterior fossa (83%) than in the spinal cord (13%). Within the spinal cord, hemangioblastomas are the third most frequent after ependymomas and astrocytomas and account for 3%−4% of all intramedullary tumors. The tumor cord interface is well defined and meticulous dissection with early control of feeders enables total resection. Antiangiogenic therapy using the VEGF receptor-2 inhibitor SU5416 and the VEGF receptor inhibitor drug bevacizumab have shown promising results in some patients.
Germ cell tumors
Intramedullary GCTs of the CNS present as a contrast-enhancing mass commonly in the lower thoracic level with areas of surrounding focal spinal cord atrophy. Surgery if done is limited to biopsy confirmation as germinomas respond to both chemotherapy and RT. Nongerminomatous GCTs, in contrast, are less sensitive and often need a combination of chemotherapy along with low-dose RT.
Composed of both glial and ganglion cells, gangliogliomas are rare, benign, slow-growing tumors (WHO Grade I or II); malignant transformation is rare but possible. Intramedullary gangliogliomas commonly affect children, are usually located within the cervical level, are comparatively larger tumor with a long duration of symptom, and often diagnosed on investigation for scoliosis. GTR is the primary treatment of choice and GTR can be achieved in over 80% of cases.
Intramedullary spinal cord lymphoma may be primary or part of systemic lymphoma. These lymphomas are usually aggressive non-Hodgkin lymphomas of B-cell origin and the primary treatment is chemotherapy with methotrexate.,
Spinal cord is an extremely uncommon site for primary melanomas (1%). Melanomas have a characteristic radiological appearance and appear hyperintense on T1-weighted images due to melanin and remain hypo- to isointense on T2-weighted images. Surgery is often limited to biopsy confirmation. RT, intrathecal interferon-b, and chemotherapy with dacarbazine are useful adjuncts.
Intramedullary metastases are rare and account for only 1%−3% of intramedullary tumors. Seen in <1% of all cancer patients, presence of intramedullary metastasis often indicates end-stage disease with an average median survival of approximately 4 months from the time of diagnosis. Lungs (49%), breast (15%), and lymphoma (9%) account for majority of the primary sites. Surgery is difficult due to leptomeningeal spread and adjuvant RT and chemotherapy of doubtful benefit.
| Conclusion|| |
Intramedullary tumors are rare and pose considerable diagnostic and management challenges. An astute clinical acumen and a sharp radiological expertise is required for early diagnosis as many neurological ailments often mimic intramedullary tumors. The natural history of many of these tumors is unknown and many of them have a long and indolent course. Timing of surgery is hence crucial. As in any neurosurgical procedure, the goal of surgery is maximal safe resection. Meticulous planning and precise intraoperative monitoring is mandatory as the spinal cord is unforgiving for any surgical misadventures. A surgeon should exercise discretion and his intraoperative identification of a tumor/cord interface is the most important determinant of resectability. Prognosis and long-term outcomes are good in low-grade neoplasms which are excised completely. Role of adjuvant therapy in intramedullary glial tumors is yet to be fully established.
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Conflicts of interest
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]