22 Intramedullary Spinal Cord Tumors

Intramedullary spinal cord tumors comprise about 4 to 10% of primary central nervous system tumors.¹ These rare neoplasms can cause severe pain, dysfunction, and deformity, all of which further contribute to poor quality of life for patients.^2,3,4 About 35% of all spinal tumors in children are classified as intramedullary tumors, in contrast to 10% in adults.⁵ Ependymomas are the most common subtype, comprising 60% of all spinal cord tumors, followed by astrocytomas at 30% and hemangioblastomas at 2 to 15%.^5,6,7

Intramedullary spinal cord tumors are often benign and slow growing.⁸ In most patients, back pain is the predominant presenting symptom, followed by motor or sensory disturbances and urinary incontinence.^2,4 Some studies show an association between intramedullary tumors with syringomyelia and even scoliosis in advanced cases.^3,4 Magnetic resonance imaging (MRI) has become the recommended imaging modality for identification and evaluation of intramedullary tumors.² The presence of spinal cord edema and high signal intensity on T2-weighted MRIs is common to all intramedullary tumors.⁹ Despite studies elucidating the differentiating characteristics among the most common subtypes, the diagnosis nonetheless remains an area of focused research.⁹

The recommended initial treatment modality for intramedullary spinal cord tumors is microsurgical resection, followed by adjuvant therapy in certain cases. Although gross total resection is associated with better survival and better long-term neurologic function,^8,10,11 it can be challenging to accomplish safely, with surgery carrying a risk of clinically significant neurologic deficit and a potentially negative impact on the patient’s quality of life.^8,11,12 Several variables influence outcome, with preoperative functional status and neurologic status as well as tumor histology being the best predictors.^4,12,13 Given the proximity of vital neurologic structures to these tumors, proper surgical planning and technique are key to successful neurologic outcomes.¹²

22.2 Incidence and Epidemiology

Extradural, intradural extramedullary, and intradural intramedullary tumors make up the three main groups of spinal cord tumors. The vast majority of spinal cord neoplasms are classified as extradural, with intramedullary tumors being the least common at approximately 10% of all spinal tumors.^5,6,7,14,15 The intracranial counterparts are more common than those in the spinal cord, occurring at about a 4:1 ratio. Although intramedullary tumors are infrequent, the incidence is greater in children than in adults, accounting for 35% and 10% of spinal cord tumors, respectively.⁵ Interestingly, neuroepithelial types are the primary type of intramedullary tumor.^4,15 Syringomyelia occurs in about 25 to 58% of people with intramedullary spinal tumors, most commonly in the lower cervical region.^16,17

The main subtypes of spinal cord tumors are astrocytomas, ependymomas, and hemangioblastomas.^18,19 Ependymomas are the most common intramedullary spinal cord tumor in adults and are often found in the cervical or thoracic region.^2,6 Myxopapillary ependymomas are World Health Organization grade I and commonly originate from the filum terminale.²⁰ Making up about 60% of spinal cord tumors, ependymomas typically carry a good prognosis^2,7 and are frequently associated with the presence of syringomyelia as well as neurofibromatosis type 2 (NF2).^17,21 In most cases, these tumors are considered benign, and they occur equally in both sexes.¹⁶

Astrocytomas are the second most common intramedullary spinal cord neoplasm, comprising about 30% of spinal cord tumors.^5,6 Most of these tumors are low grade, with a 5-year survival rate of more than 70%, although the higher-grade ependymomas carry a much lower survival rate.⁶ These tumors have an established association with neurofibromatosis type 1 due to a germline mutation in chromosome 17q11, which codes for the tumor suppressor neurofibromin.^{17,21,22,23,24} Similar to ependymomas, astrocytomas most commonly affect the cervical level and are strongly associated with syrinx formation.² In terms of age disparity, adults usually present with high-grade tumors, whereas children typically present with low-grade tumors.²⁵

Hemangioblastomas are the third most common intramedullary spinal tumor, making up about 2 to 10% of all intramedullary neoplasms.^16,26,27,28 They are considered benign mesenchymal tumors most likely originating from vascular endothelial growth factor-secreting cells.^2,5,16 Commonly found in the cervical spine, these tumors carry an excellent prognosis.² Hemangioblastomas often occur as a solitary tumor, mainly in the posterior portion of the spinal cord, and most occur in patients younger than 40 years of age.^5,16 As many as one-fourth of these patients have signs of von Hippel–Lindau syndrome, an inherited cancer syndrome affecting many systems with visceral and central nervous system manifestations.^15,29 This syndrome, caused by a deletion in chromosome 3q, is also associated with retinal hemangiomas, renal and pancreatic cysts, and renal cell carcinoma.²⁹

Cancer metastasis to the intramedullary spinal cord is relatively rare, affecting only about 1 to 3% of patients with intramedullary neoplasms; however, with improving survival of patients with metastatic disease, this disease entity is more frequently encountered.^30,31 Lung cancer is responsible for approximately one-half of the primary tumor metastases to the spinal cord, which is particularly significant because lung cancer is associated with the highest mortality rate of any cancer type.^30,32 Unfortunately, the prognosis of patients with this diagnosis is dismal, and the median survival time is about 4 months.²

Lipomas comprise about 1% of intraspinal tumors and usually occur in the extramedullary region, although they are also found in the intramedullary location. These neoplasms are associated with spinal dysraphism and are associated with an excellent long-term prognosis with gross total resection.^5,16 Various other types of intramedullary spinal neoplasms can be found as well, but because the incidence is low, the literature on these pathologies is scarce. Gangliogliomas are slow growing and rare in the adult population.⁶ Dermoid and epidermoid tumors, as well as teratomas ( Fig. 22.1), are other neoplasms that can present in this location; sacrococcygeal teratomas are the most commonly diagnosed tumors among newborns, with an incidence of approximately 1 case per 14,000 live births.³³

22.3 Clinical Features

Intramedullary spinal cord tumors can manifest in various ways, but because of their location, many cause common symptoms that can make differentiation of tumor type difficult. Most of their clinical features are related to tumor growth rate, location, and degree of invasion. The most common symptom is pain—either back pain, radicular pain, or central pain.²⁹ This pain is often caused by dural distention and is exacerbated in the recumbent position.¹⁶ The next most common symptoms include motor symptoms, which are often bilateral with corresponding upper motor signs such as spasticity.^16,29,34 Sphincter disturbances, such as urinary incontinence, are common, with an incidence as high as 45%,⁴ whereas hydrocephalus occurs about 8% of the time.^4,35 Paresthesias often occur later and at first more distally.³⁴ Interestingly, rapidly progressive scoliosis in an adult can be a sign of an intramedullary tumor, highlighting the importance of a wide differential diagnosis in the evaluation of de novo scoliosis or a rapidly progressive deformity.¹⁶

In addition to the common symptoms, clinical features unique to certain types of tumor can, in certain situations, help elucidate the pathology. More specifically, motor and sensory symptoms initially occur most often in patients with ependymomas and astrocytomas⁶; syringomyelia is also common in patients with these two neoplasms. Children with low-grade ependymomas often present with an inability to meet normal developmental milestones, whereas those with astrocytomas often have marked pain at night, specifically abdominal pain.² Sensory symptoms can occur initially in persons with hemangioblastomas because of the predisposition of the tumor to arise in the dorsal spinal cord, which in rare cases can result in subarachnoid hemorrhage or intramedullary hemorrhage.⁶ Patients with gangliogliomas commonly present with paraparesis and radicular pain, and about 40% present with obvious scoliosis.^2,6,36 Finally, when considering all the patient’s symptoms, it is important to note the factors that contribute to symptom development and severity, such as age, degenerative changes, spinal canal size, and comorbidities.

22.4 Magnetic Resonance Imaging

MRI is the preferred imaging modality for diagnosing and characterizing intramedullary spinal cord tumors. Discerning among spinal ependymomas, astrocytomas, and hemangioblastomas on MRI can be challenging, but several radiologic characteristics allow these tumors to be identified with relatively high accuracy.⁹ Ependymomas appear as a local enlargement with symmetric growth in the central region of the spinal cord. They appear hyperintense on T2-weighted MRIs and hypointense or isointense on T1-weighted MRIs, with enhanced margins on T1-weighted contrast images ( Fig. 22.2).^6,12

Astrocytomas can be challenging to differentiate. They appear as fusiform expansions of the spinal cord with poorly defined margins and asymmetrical growth.² They show hypointensity or isointensity on T1-weighted MRIs and hyperintensity on T2-weighted MRIs.⁶ Both ependymomas and astrocytomas have heterogeneous enhancement with contrast, so differentiation on the basis of MRIs alone can be difficult.²

Hemangioblastomas are extremely vascularized tumors with homogenous enhancement, unlike ependymomas and astrocytomas.^6,37 They appear isointense on T1-weighed MRIs and hyperintense on T2-weighted MRIs, and they are associated with cysts and syringomyelia. Angiography is a useful modality to visualize feeding vessels.⁶

Fig. 22.1 A 20-year-old woman presented with lower back pain after prolonged standing with no abnormalities on physical examination. Imaging demonstrates an intradural, intramedullary heterogeneously enhancing mass at the conus medullaris with associated dysraphism (spina bifida, tethered spinal cord, and vertebral body changes). Sagittal (a) T1-weighted noncontrast, (b) T1-weighted postcontrast, (c) T2-weighted magnetic resonance images (MRIs). Red lines on (c) indicate axial T2-weighted MRIs (d-g) through the lesion. The final pathology findings were consistent with teratoma. (Used with permission from Barrow Neurological Institute, Phoenix, Arizona.)

Gangliogliomas have hypointense characteristics on T1-weighted magnetic resonance images (MRIs) and are hyperintense on T2-weighted MRIs with patchy contrast enhancement.^6,36 Signs of scoliosis and tumor cysts may also be visible. Lymphoma shows homogenous contrast enhancement on T1-weighted MRIs and hyperintensity on diffusion-weighted and T2-weighted MRIs.²

Metastatic intramedullary tumors are often single, encapsulated, and eccentrically located lesions. They have characteristic “rim” and “flame” signs that aid in distinguishing between a metastasis and primary spinal cord neoplasms.³⁸ The rim sign is a complete or partial region of gadolinium enhancement, whereas the flame sign is a poorly defined gadolinium-enhancing region.³⁸ These lesions are isointense on T1-weighted MRIs and hyperintense on T2-weighted MRIs. Although it is a rare entity, a first-time presenting intramedullary glioblastoma has been described in the literature ( Fig. 22.3).^39,40

Fig. 22.2 A 54-year-old woman presented with paresthesias and neck soreness at C3-4. A C3–C4 laminoplasty was performed for resection of an ependymoma. Pathology was consistent with a World Health Organization grade II tumor. Sagittal (a) T2-weighted, (b) T1-weighted noncontrast, and (c) T1-weighted contrast-enhanced magnetic resonance images. (Used with permission from Barrow Neurological Institute, Phoenix, Arizona.)

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