Presentation
Dizziness, ataxia, tinnitus, and right hearing loss.
Patient Data
MRI shows a rounded, well-defined, heterogeneous lesion, iso-intense on T1-weighted sequences, hyperintense on T2-weighted sequences and FLAIR, with foci of magnetic susceptibility artifact, partial restriction to diffusion, and vivid enhancement after the application of gadolinium. The mass demonstrates fairly low ADC values only slightly higher than adjacent brain.
Case Discussion
This case most likely is of a grade 1, typical meningioma, which constitutes 89-94% of meningiomas and has a 3-7% recurrence in 5 years.
The absence of a substantial IAC component, dural tail and marked alanine peak makes a schwannoma a far less likely possibility.
Meningiomas are the most frequent non-glial intracranial primary tumors, of which posterior fossa meningiomas constitute up to 20%, just below Schannomas.
MRI is the choice technique for typical meningiomas. They are seen as iso- or hypointense in T1-weighted sequences (most of them are hypointense) and with variable signal on T2-weighted sequences based on histologic type. Tumors that are T2 hypointense are composed of fibroblastic or transitional elements, while those that are hyperintense are angioblastic or syncytial. They show intense and homogeneous enhancement after Gadolinium administration. Also, spectroscopy is a great aid for the diagnosis of meningiomas since this neoplasm generally shows a decrease in the concentration of NAA and creatinine and an increase in peaks of lactate, lipids, and specifically alanine, which is seen in this case.
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