Spinal astrocytoma is a glial-origin intramedullary spinal cord tumor that is the second most common in adults and the most common intramedullary tumor in children. Astrocytes (star-shaped support cells) undergo neoplastic transformation forming an infiltratively growing mass within the spinal cord parenchyma. Low-grade forms (pilocytic astrocytoma WHO grade I, diffuse astrocytoma grade II) are more common, while high-grade forms (anaplastic astrocytoma grade III, glioblastoma grade IV) are rare but aggressive. On MRI, it shows eccentric cord expansion, heterogeneous T2 signal, indistinct tumor-cord boundary, and variable/irregular enhancement. The most critical differences from ependymoma are: (1) eccentric vs central location, (2) infiltrative vs well-defined growth, (3) absence of surgical cleavage plane. Therefore, complete surgical resection is usually not possible and prognosis is worse than ependymoma. NF1 (neurofibromatosis type 1)-associated pilocytic astrocytomas have been reported.
Age Range
5-40
Peak Age
20
Gender
Male predominant
Prevalence
Uncommon
Spinal astrocytoma develops from astrocytes (neuroglial support cells) of the spinal cord. Astrocytes normally perform critical functions including neuronal support, blood-brain barrier maintenance, synaptic transmission regulation, and extracellular ion homeostasis. Neoplastic transformation is usually triggered by genetic mutations (TP53, IDH1/2, BRAF V600E, H3K27M). BRAF-KIAA1549 fusion or BRAF V600E mutation is common in pilocytic astrocytomas and this variant has the best prognosis. IDH mutations and TP53 mutations are seen in diffuse astrocytomas. The infiltrative growth pattern of astrocytoma results from the migration capacity of tumor cells along normal spinal cord parenchyma — cells spread along white matter tracts and no clear boundary forms between normal tissue and tumor. This is reflected on MRI as indistinct tumor margins and eccentric expansion. Eccentric expansion indicates the tumor originates from one side of the cord parenchyma rather than the central canal — this is the fundamental difference from symmetric central expansion in ependymoma. Heterogeneous T2 signal reflects different differentiation grades of tumor cells, peritumoral edema, and microcystic degeneration. Variable enhancement results from non-homogeneous blood-brain barrier disruption — in low-grade astrocytomas, minimal barrier disruption results in little enhancement, while in high-grade ones, neovascularization and increased permeability produce prominent heterogeneous enhancement.
More prominent expansion on one side of the spinal cord — indicates astrocytoma originates from cord parenchyma (not central canal). Key differentiating finding from symmetric central expansion in ependymoma.
T2-weighted sequences show eccentric (asymmetric) cord expansion with a heterogeneously hyperintense mass. Tumor margins are indistinct and no clear differentiation can be made between normal cord parenchyma and tumor. Intratumoral cystic areas and peritumoral edema typically accompany. Involvement is usually 3-7 vertebral segments in length — longer than ependymoma. Syringomyelia may be seen at the cranial and/or caudal tumor ends.
Report Sentence
An intramedullary mass causing eccentric expansion of the cervical/thoracic spinal cord at ...-... vertebral levels, heterogeneously hyperintense on T2 with indistinct margins, consistent with intramedullary astrocytoma.
On contrast-enhanced T1-weighted sequences, astrocytoma shows variable enhancement pattern: minimal or no enhancement in low-grade (grade I-II), while heterogeneous, nodular, or irregular enhancement is seen in high-grade (grade III-IV). Pilocytic astrocytoma may show well-defined mural nodule + large cyst pattern. Enhancement margins do not reliably reflect tumor margins because the infiltrative component may not enhance.
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The intramedullary mass shows minimal/heterogeneous/nodular enhancement on contrast-enhanced sequences, this pattern is consistent with intramedullary astrocytoma.
T1-weighted sequences show an eccentrically located hypointense mass in the spinal cord. Tumor margins are indistinct. Intratumoral hemorrhage (subacute T1 hyperintense methemoglobin) may appear as focal bright foci. Prominent cystic component in pilocytic variant appears as low signal.
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An eccentrically located intramedullary mass at ...-... levels, hypointense on T1 with indistinct margins, is observed in the spinal cord.
Spinal canal widening may be seen on CT but intramedullary mass characterization is limited. CT myelography can demonstrate the intramedullary location. CT plays a complementary role mainly in bone structure and calcification assessment.
Report Sentence
Spinal canal widening at ...-... vertebral levels is observed, consistent with intramedullary mass; further characterization with MRI is recommended.
DWI shows variable diffusion characteristics in astrocytoma. Diffusion restriction is typically not prominent in low-grade astrocytomas (ADC normal or mildly elevated). In high-grade astrocytomas, diffusion restriction may be more prominent due to increased cellularity. DWI alone is not sufficient for astrocytoma-ependymoma differentiation but may assist in grading.
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Prominent/mild/minimal diffusion restriction is observed in the intramedullary lesion on DWI (ADC value: ... × 10⁻³ mm²/s).
Criteria
Best prognosis, common in children. May show mural nodule + cyst pattern. BRAF mutation common.
Distinct Features
May be well-defined (unlike other astrocytomas), intensely enhancing mural nodule, minimal peritumoral edema
Criteria
Most common spinal astrocytoma form. Infiltrative growth, minimal enhancement. IDH mutation may be positive.
Distinct Features
Indistinct margins, long segment involvement, low cellularity, risk of malignant transformation (10-15% over years)
Criteria
High-grade, aggressive growth, prominent heterogeneous enhancement. Necrosis and hemorrhage may accompany.
Distinct Features
Rapid clinical deterioration, ring enhancement possible, poor prognosis (median survival 15-18 months)
Distinguishing Feature
Ependymoma shows central location, symmetric expansion, well-defined margins, homogeneous enhancement and cap sign; astrocytoma is eccentric, ill-defined, heterogeneous enhancement
Distinguishing Feature
Spondylodiscitis involves vertebra and disc (extramedullary), end-plate destruction, disc enhancement, fever/leukocytosis accompanies; astrocytoma is intramedullary
Distinguishing Feature
Spinal TB involves vertebra and paravertebral tissues (extramedullary), cold abscess, disc preserved, subligamentous spread; astrocytoma is intramedullary cord tumor
Urgency
urgentManagement
surgicalBiopsy
NeededFollow-up
3-monthMaximum safe resection is targeted in spinal astrocytoma treatment, but complete resection is usually not possible due to infiltrative growth. More aggressive resection may be possible in pilocytic variant (grade I). Observation after subtotal resection for low-grade, adjuvant radiotherapy and/or chemotherapy (temozolomide) for high-grade. Intraoperative neurophysiological monitoring (MEP/SEP) minimizes neurological damage. Prognosis is worse than ependymoma — 5-year survival 60-80% for grade I-II, 15-30% for grade III-IV.
Spinal astrocytoma is treated with surgical resection, but complete resection is usually not possible due to infiltrative growth pattern — this is the most important difference from ependymoma. Observation after subtotal resection is recommended for low-grade cases (grade I-II). Adjuvant radiotherapy and/or chemotherapy is given for high-grade cases (grade III-IV). Pilocytic astrocytoma (grade I) has better prognosis. NF1-associated cases have been reported.