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Posterior fossa glioblastoma multiforme: MR findings
T Kuroiwa1, Y Numaguchi, M I Rothman
1Department of Diagnostic Radiology, University of Maryland Medical System, Baltimore 21201, USA.
Purpose:
To characterize the MR findings of glioblastoma multiforme in the posterior fossa.
Methods:
MR studies of nine patients with surgically proved posterior fossa glioblastoma multiforme were retrospectively evaluated. MR characteristics studied included tumor location, signal intensity, enhancement pattern, and presence of intratumoral hemorrhage, as well as presence of secondary hydrocephalus or metastatic spread.
Results:
The tumors were located in the median portion of the cerebellum or brain stem in eight cases. Six extended into the fourth ventricle. Hydrocephalus was seen in four cases. Six cases demonstrated decreased T1- and increased T2-weighted signal intensities. Three cases demonstrated mixed signal intensities suggesting intratumoral hemorrhage. All of the eight patients who received contrast showed moderate to marked heterogeneous ringlike enhancement suggesting intratumoral necrosis. Multicentric/multifocal lesions or extraaxial metastases were identified in three of the nine cases, and there was extracranial extension into the cervical region in one case.
Conclusion:
Glioblastoma multiforme is a rare tumor in the posterior fossa. Differentiating it from metastatic tumor or malignant astrocytoma was difficult. However, combination of heterogeneous and ringlike enhancement, midline location, poorly defined margin, tumoral hemorrhage, concomitant multicentric/multifocal lesions, and extraaxial or extracranial metastasis may be clues for the prospective diagnosis of glioblastoma multiforme.
Insights
Glioblastoma multiforme in the posterior fossa is rare and challenging to diagnose. Key MR imaging findings include heterogeneous ringlike enhancement, midline location, and potential for hemorrhage or metastasis.
Area of Science:
- Neuroradiology
- Oncology
- Neuro-oncology
Background:
- Glioblastoma multiforme (GBM) is a primary malignant brain tumor.
- Posterior fossa GBM is exceptionally rare, posing diagnostic challenges.
Purpose of the Study:
- To define the characteristic magnetic resonance (MR) imaging features of posterior fossa glioblastoma multiforme.
- To aid in differentiating posterior fossa GBM from other pathologies.
Main Methods:
- Retrospective analysis of MR studies from nine patients with surgically confirmed posterior fossa GBM.
- Evaluation of tumor location, signal intensity, enhancement patterns, hemorrhage, hydrocephalus, and metastatic spread.
Main Results:
- Tumors predominantly located in the midline cerebellum or brainstem (8/9 cases), often extending into the fourth ventricle (6/9).
- Common MR findings included decreased T1 and increased T2 signal intensity (6/9), intratumoral hemorrhage (3/9), and heterogeneous ringlike enhancement (8/8 contrast-enhanced cases).
- Metastatic spread (extraaxial or extracranial) was observed in 3/9 cases.
Conclusions:
- Posterior fossa GBM presents unique diagnostic difficulties, often mimicking metastatic disease or other high-grade astrocytomas.
- A combination of specific MR findings—heterogeneous ringlike enhancement, midline location, ill-defined margins, hemorrhage, and associated lesions—suggests GBM.