Brain stem gliomas are classified according to:
- Location
- Extent of spread (radiographic appearance)
- Histology
There are two main categories of brain stem glioma.
Each has a very different natural history and prognosis.
1. Diffusely infiltrating:
- 70-80% of all brain stem gliomas
- primarily arise in the pons
- tend to be high grade gliomas
- have an extremely poor prognosis
2. Focal:
- More commonly seen in the medulla or midbrain rather than the pons
- Element of exophytic growth is seen commonly
- Tend to be low grade tumors (pilocytic)
- Associated with NF-1
- Prognosis is much better - related to:
- Tumor biology
- Degree of surgical accessibility
Comparison of diffuse and focal brain stem tumors:
Diffuse |
Focal |
|
Proportion of brainstem tumors |
70-80% |
20% |
Prognosis |
Poor |
Good |
Density |
Regions of hypodensity |
Lack of hypodensity |
Symptoms |
Short duration prior to diagnosis (weeks to months) |
Prolonged duration prior to diagnosis (months to years) |
Pathology |
Fibrillary astrocytoma Anaplastic astrocytoma Glioblastoma multiforme |
Pilocytic astrocytoma Ganglioma |
Extent |
Diffuse, may spread to medulla or midbrain |
Circumscribed, focal |
Common site of origin |
Pons |
Midbrain or medulla |
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