MRI findings in low-grade astrocytoma
Low-grade astrocytoma (Low-Grade Astrocytoma) on magnetic resonance imaging is visualized as a mass lesion with indistinct margins. The tumor causes marked thickening, or expansion, of the upper cervical spinal cord. In some cases, the pathological process extends cranially, involving the medulla oblongata, the bulbomedullary junction, and the posterior parts of the brainstem.
The signal characteristics of this neoplasm are not strictly specific, but they present typical patterns:
- On T1-weighted images (T1WI), a diffuse hypointense signal is determined.
- On T2-weighted images (T2WI), the signal becomes hyperintense.
- Upon administration of a paramagnetic contrast agent (on contrast-enhanced T1WI), there is no contrast enhancement within the lesion, which is a characteristic feature of low-grade tumors.
Differential diagnosis: Haemangioblastoma
Haemangioblastoma (Haemangioblastoma) is a rare, benign tumor with abundant blood supply, accounting for 2% to 10% of all spinal neoplasms. The peak incidence occurs in the fourth decade of life. In 75–85% of cases, these are purely intramedullary tumors. Extradural variants are extremely rare.
Morphologically, two typical variants are distinguished:
- A small subpial nodular lesion surrounded by an extensive zone of intramedullary edema.
- A small nodule accompanied by massive syringomyelic (cystic) cavities.
The pathogenesis of cyst formation is interstitial in nature. Vascular endothelial growth factor (VEGF) and hydrodynamic forces cause plasma leakage into the tissues. When absorption reserves are depleted, edema forms, followed by a cyst. Digital subtraction angiography (DSA) is used for diagnosis, allowing the identification of feeding arteries prior to embolization.
Association of haemangioblastoma with von Hippel-Lindau syndrome
Von Hippel-Lindau syndrome (VHLs) is an autosomal dominant disorder manifested by multiple tumors, including retinal angiomatosis, renal cell carcinoma, and phaeochromocytoma.
Unlike sporadic cases where a single lesion is detected in the cervical or thoracic region, in VHLs the lesions are multiple and located at all levels of the spinal cord. Tumors manifest on average 10 years earlier, and neurological symptoms are less pronounced. Up to a third of patients develop new lesions every two years, necessitating regular MRI screening.
Differential diagnosis: Ganglioglioma
Ganglioglioma (Ganglioglioma) is a neoplasm composed of a mixture of neoplastic ganglion cells and glial elements. In adults, this is a rare pathology (1–2%), whereas in children it is significantly more common (up to 15%), with a peak age incidence from 1 to 5 years.
The tumor typically has a low grade of malignancy (WHO grades 1 and 2). Despite the low malignant potential, gangliogliomas have a significant propensity for local recurrence. The glial component may undergo malignant transformation to a high grade. The primary treatment method is surgical resection, providing a five-year survival rate of 89%.
Briefly: answers to topical questions
What MRI features allow differentiation of intramedullary astrocytoma from spinal cord ependymoma?
The main criteria for differential diagnosis are the growth pattern and margins of the tumor, as well as the presence of characteristic MRI features.
| MRI feature | Astrocytoma | Ependymoma |
|---|---|---|
| Margins and growth | Infiltrative growth, poorly defined borders | Relatively well-demarcated tumor |
| Specific features | Specific symptom not specified | Cap sign (cap sign), satellite cysts, syringomyelia (syrinx) |
| Contrast enhancement | In low-grade astrocytoma, contrast enhancement may be absent | Focal nodular contrast enhancement in the center of the spinal cord |
Which spinal arteries most frequently act as feeding vessels for haemangioblastomas during angiography?
In the described case of cervical haemangioblastoma, the afferent branches feeding the tumor originated from the right vertebral artery and the right thyrocervical trunk.
Which neoplasms, in addition to spinal haemangioblastomas, are characteristic of von Hippel-Lindau syndrome?
In von Hippel-Lindau syndrome, besides spinal haemangioblastomas, cerebellar haemangioblastomas, retinal angiomatosis, renal cell carcinoma, and phaeochromocytoma are characteristic. Serous cystic neoplasms and neuroendocrine tumors of the pancreas may also occur in this syndrome.
Class and exam questions
How does a low-grade spinal cord astrocytoma respond to contrast on MRI?
On contrast-enhanced T1WI, contrast enhancement within the lesion is entirely absent.
How to distinguish a symptomatic haemangioblastoma from an asymptomatic one on MRI?
Symptomatic small haemangioblastomas are often accompanied by large concurrent syringomyelic cysts, whereas asymptomatic nodules lack such cysts.
What is the localization feature of haemangioblastomas in von Hippel-Lindau syndrome?
Unlike sporadic single lesions, VHL syndrome reveals multiple tumors located at any level of the spinal cord.
Which age group is most prone to the development of spinal ganglioglioma?
The peak incidence occurs in early childhood — predominantly from 1 to 5 years, which is similar to the epidemiology of pilocytic astrocytomas.
What else to study on this topic
- MRI semiotics of cystic lesions in haemangioblastomas
- The role of VEGF in plasma extravasation and the formation of syringomyelic cavities
- Genetic aspects and screening protocols in von Hippel-Lindau syndrome
- Indications for preoperative angiography (DSA) in vascular tumors
- Histological picture of ganglioglioma and mechanisms of its local recurrence
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