Introduction
Spinal cord tumors are uncommon causes of back pain, radicular pain, and sensorimotor deficits in adults and pediatric patients. Primary spinal tumors are less common than intracranial tumors and represent approximately 2–4% of primary central nervous system (CNS) tumors.
Classification of spinal cord tumors
Spinal cord tumors are classified as either (1) intradural intramedullary, (2) intradural extramedullary, or (3) extradural depending on the relationship to the spinal cord and dura.
Extradural tumors . The majority of spinal tumors are extradural, accounting for 60% of spinal cord tumors and are frequently compressive osseous metastatic lesions. Intradural spine tumors can originate adjacent to the spinal cord (e.g., extramedullary) or within the cord (e.g., intramedullary). The differential diagnosis can be narrowed by recognizing where the tumor is located relative to the thecal sac and spinal cord.
Intramedullary tumors . Intradural intramedullary spinal cord tumors (IMSCTs) comprise 8–10% of primary spinal cord tumors, of which 60–70% are ependymomas and 30–40% are astrocytomas. The third most common IMSCT is hemangioblastoma, which represents 3–8% of all IMSCT. Hemangioblastomas are associated with von Hippel-Lindau (VHL) syndrome in 15–25% of cases. The clinical presentation of primary spinal cord tumors depends on the location of the lesion. In a recent series of IMSCTs, pain was the most common presenting symptom (72%) and can manifest as back pain (27%), radicular pain (25%), or central pain (20%). Motor disturbance was next most common (55%), followed by sensory problems (39%).
Intradural extramedullary tumors . Intradural extramedullary spinal tumors are usually benign lesions with a few exceptions and can be cured with preserved neurologic function with surgery alone in the majority of cases. Intradural extramedullary tumors comprise more than 70% of intradural spinal cord tumors in adults and are only slightly less common in pediatric patients. The most common intradural extramedullary tumors are derived from nerve sheath cells (schwannomas and neurofibromas) or meningeal cells (meningiomas). Myxopapillary ependymoma is an extramedullary lesion arising from the conus medullaris and filum terminalis. Other rare extramedullary tumors include hemangiopericytomas, paragangliomas, malignant peripheral nerve sheath tumors, epidermoid cysts, and dermoid cysts.
Clinical cases
Case . A 5-year-old boy presented to the pediatric orthopedic clinic with complaints of worsening back pain and scoliosis. He had been previously evaluated for his scoliosis with a plan to conservatively manage and observe clinical symptoms. Due to the progressive nature of his complaints, an MRI of the thoracic and lumbar spine were obtained, which demonstrated a 21-mm enhancing intramedullary lesion with a distal cystic component at the thoracolumbar region of the spinal cord with an associated syrinx proximally ( Fig. 8.1 ). On examination, he maintained a kyphotic posture due to pain and had dysesthesias throughout his bilateral lower extremities but no appreciable strength deficits. Reflexes in the lower extremities were symmetrically absent. Surgical resection was recommended, and the patient underwent laminectomy and gross total resection of the tumor. The surgery and his postoperative course were uneventful, and he was discharged to a rehabilitation facility 1 week later. Final pathology was consistent with a pilocytic astrocytoma. His follow-up imaging demonstrated complete tumor removal without residual enhancement and improvement in his syrinx. He continues to do well without functional imitations on serial follow-up.
Teaching Points: Imaging of Spinal Cord Astrocytoma. Astrocytomas account for 80–90% of IMSCT in childhood and approximately 60% in adolescence. The peak incidence of astrocytomas is in the third decade of life, but they are not as common as intramedullary ependymomas in this age group. In adults, astrocytomas make up almost 25% of IMSCT with equal incidence in men and women. Intramedullary astrocytomas are predominantly located in the cervicothoracic or thoracic region in pediatric patients, but cervical involvement is more common in the adult population. , Astrocytomas can span multiple vertebral levels and can have associated cyst formation. , Low-grade astrocytomas and fibrillary astrocytomas account for almost two-thirds of intramedullary astrocytomas in adults and almost 90% of intramedullary astrocytomas in children. High-grade lesions are rarer and account for about 10% of intramedullary astrocytomas.
Imaging and histology. MRI of low-grade spinal astrocytomas reveals an enlarged homogeneous mass with hypointense to isointense signal on T1-weighted images and hyperintense signal on T2-weighted images. There is very little edema and no hemorrhage in low-grade astrocytomas. Most intramedullary astrocytomas enhance, and calcifications are rare. While pilocytic astrocytomas can have well-defined borders, fibrillary astrocytomas are poorly defined with irregular tumor margins. High-grade anaplastic astrocytoma or glioblastoma account for only about 10% of intramedullary astrocytomas. These higher grade lesions display heterogeneous enhancement associated with necrosis, edema, and cyst formation. Microscopically, low-grade astrocytomas show a low degree of cellularity, low mitotic activity, and absence of necrosis and microvascular proliferation. Anaplastic astrocytoma and glioblastoma show moderate to high cellularity and an increased mitotic index. Glioblastoma specifically exhibits a high degree of necrosis and microvascular proliferation.
Clinical features. Presentation of intramedullary spinal cord astrocytoma is variable and typically progresses over months to years. Pain is the earliest and most frequent presenting complaint and can be local or radicular. Sensory disturbance is also common and may consist of dysesthesias or loss of sensation unilaterally or bilaterally. Spasticity and weakness follow with loss of bowel and bladder function occurring late with the exception of tumors involving the conus medullaris. , Due to the centrally located nature of the tumor, motor deficits present with weakness in the upper extremities preceding the lower extremity. In children, pain is the most common first symptom, but gait deterioration, motor regression, torticollis, and kyphoscoliosis are also significant presenting findings. In malignant tumors, pain is followed by rapid neurological deterioration resulting in significant disability in 3 to 5 months. ,
Patient management . Treatment is directed at total surgical resection, particularly for low-grade gliomas. There is no evidence that the degree of resection affects outcome in high-grade gliomas, and the goal of surgery for these patients should be a less extensive resection in order to reduce postsurgical morbidity.
Electrophysiologic monitoring is frequently used intraoperatively during the resection of IMSCT with motor-evoked and somatosensory-evoked potentials being the most common modalities. Gross total resection is achievable with pilocytic astrocytomas due to its well-circumscribed nature. However, the infiltrative nature of even low-grade astrocytomas make gross total resection difficult without risking postoperative morbidity. The rate of gross total resection is reported to be between 30% and 70%. , ,
Subtotal resection of fibrillary astrocytomas is appropriate in many cases, and there does not seem to be any significant difference in survival between total and subtotal resection techniques in long-term survival when controlled for tumor grades. Intramedullary fibrillary astrocytomas have a high recurrence rate that ranges from 25% in low-grade tumors to almost 100% in high-grade tumors. , Adjuvant radiotherapy at diagnosis of high-grade astrocytoma or with tumor recurrence is frequently utilized. The utility of concomitant chemotherapy is uncertain due to systemic toxicity and inability of large molecules to bypass the blood-spinal cord barrier. In low-grade astrocytomas, 5-year survival ranges from 80–100%. Patients with intramedullary anaplastic astrocytomas or glioblastoma have an average life expectancy of 15 months. ,
Clinical Pearls
- 1.
Intramedullary spinal cord tumors account for ∼10% of primary spinal cord tumors and are most often ependymomas, which are slightly favored over astrocytomas.
- 2.
Most intramedullary WHO grade 1 pilocytic astrocytomas enhance on neuroimaging and may be confused with higher-grade lesions without a tissue diagnosis.
Case . A 53-year-old man was admitted after a cycling accident in which he sustained a displaced left C7 transverse process fracture in addition to a left clavicular fracture. He noted some numbness and mild weakness in his left hand. He was initially treated conservatively in a hard collar for his fractures and returned with plain x-rays at 3 months. He received an MRI to evaluate his persistent pain, which demonstrated an intramedullary enhancing lesion from C7 to T3 causing expansion of the cord and surrounding edema. There was susceptibility artifact associated with the lesion suggestive of microhemorrhage consistent with ependymoma ( Fig. 8.2 ). Thoracic laminectomy for removal of the tumor was performed. The patient awoke with new-onset right greater than left leg weakness, of which the left leg improved more rapidly. He was discharged to a rehabilitation facility and continued to recover strength. His postoperative course was further complicated by a deep vein thrombosis managed with warfarin before developing a subdural hematoma, which required cessation of anticoagulation. His final pathology was consistent with grade II ependymoma. He was referred to radiation oncology. He underwent 50 Gy in 28 fractions of intensity modulated radiation therapy (IMRT) to the tumor bed. He continues to have some right lower extremity weakness on examination but was able to ambulate without assistance.
Teaching Points: Imaging Differential of Enhancing Spinal Cord Ependymoma . Clinical features of intramedul lary ependymomas are variable. The classic central cord syndrome with suspended sensory loss with descending progression, symmetric upper extremity mixed upper and lower motor neuron weakness, and bilateral spastic lower extremities is infrequently seen. Early symptoms are usually nonspecific and may only subtly progress. Time of onset to symptoms ranges from 3–4 years, although intratumoral hemorrhage may precipitate a rapid decline. , Sensory symptoms, particularly dysesthesias, are the earliest to present in upward of 70% of patients. , Painful aching sensation at the level of the tumor is rarely radicular and can occur early in disease progression. Symptoms mainly depend on the location of the tumor. Upper extremity symptoms predominate in patients with cervical lesions, while lower extremity spasticity and sensory disturbances predominate with thoracic lesions. , Numbness is also a common complaint and typically begins distally in the legs, with proximal progression. Tumors in the lumbar spinal cord/conus can present with back pain and leg pain, with leg pain being radicular in nature. Urogenital and anorectal dysfunction occurs earlier with conus lesions.
Imaging and histology. MRI shows a lesion hypointense on T1-weighted imaging and hyperintense on T2-weighed imaging. Intramedullary ependymomas enhance homogeneously with contrast. Although not encapsulated, intramedullary ependymomas often have a distinct plane between the tumor and adjacent spinal cord, despite its frequent association with cysts, syrinxes, and hemorrhage.
Intramedullary ependymomas are circumscribed lesions of modest vascularity. The tumor is usually soft and somewhat friable, but a firmer, more nodular appearance is occasionally encountered. Hemorrhage is more frequent in intramedullary ependymomas compared to astrocytomas. Microscopically, spinal ependymomas might display ependymal rosettes, but perivascular pseudorosettes are more prominent.
Features and management . Intramedullary ependymomas represent 40–60% of adults with IMSCT, with peak incidence in the fourth to fifth decade of life. , , Intramedullary ependymomas account for only 16–35% of IMSCT in the pediatric population. , Most intramedullary ependymomas arise from the cervical or cervicothoracic region. , , Intramedullary ependymomas are mostly well circumscribed, which helps with total surgical resection in 70–100% of cases. , , Tumor recurrence is reported to be less than 10% but can be unrecognized secondary to the slow growth rate of ependymomas. Tumor recurrence is significantly higher with subtotal resection, with reported rates from 50–70%. , Therefore, prognosis for patients with intramedullary ependymomas is dependent upon the extent of surgical resection. Postoperative radiation is controversial but can increase tumor-free survival rates of adult patients with high-grade or subtotally resected tumors. Radiation is debated in children due to radiation-induced damage to the CNS. In addition, both adult and pediatric patients may have increased postoperative neurological morbidity with prior adjuvant radiotherapy. The 5-year survival rate for low-grade intramedullary ependymoma ranges from 83% to 100% but decline rapidly with higher-grade ependymomas, only reaching 20% 5-year overall survival. , , ,
Clinical Pearls
- 1.
Enhancing spinal cord tumors can mimic inflammatory and infectious lesions in the spinal cord including transverse myelitis, multiple sclerosis, neuromyelitis optic spectrum disorder, infectious myelitis, and other related conditions.
Case . A 36-year-old man with a known family history of VHL and multiple cerebellar mass resections presented for evaluation of increasing cervical pain. On examination, he had mild left-handed weakness and numbness, which had worsened recently. His MRI demonstrated multiple small enhancing lesions throughout the cervical spinal cord, with one associated with an enlarging cyst ( Fig. 8.3 ). Given the progression of symptoms and dorsal location of the cystic lesion, he underwent cervical laminectomy for removal of the dorsal mass and cyst decompression. He did well with no additional postoperative deficits and went home on postoperative day 2. He continues to be followed for his VHL and multiple lesions.
