Meningiomas are a common type of tumor that primarily affects the meninges, which are the protective layers surrounding the brain. These tumors are generally non-glial neoplasms that originate from the arachnoid cap cells of the meninges and can be found anywhere these protective layers are present. Meningiomas are typically easy to diagnose and are often slow-growing. However, there are various subtypes of meningiomas, each with unique characteristics.
Types of Meningiomas
In the 5th Edition (2021) of the WHO classification of CNS tumors, 15 subtypes of meningioma are recognized. These subtypes include:
- Angiomatous Meningioma
- Atypical Meningioma (Grade 2)
- Anaplastic (Malignant) Meningioma (Grade 3)
- Chordoid Meningioma (Grade 2)
- Clear Cell Meningioma (Grade 2)
- Fibrous Meningioma
- Lymphoplasmacytic-Rich Meningioma
- Meningothelial Meningioma (17%)
- Metaplastic Meningioma
- Microcystic Meningioma
- Papillary Meningioma (Usually more aggressive)
- Psammomatous Meningioma
- Rhabdoid Meningioma (Usually more aggressive)
- Secretory Meningioma
- Transitional Meningioma (40%) – Contains mixed histology, typically meningothelial and fibrous components.
Meningiomas are more common in elderly women. Atypical and malignant meningiomas are slightly more common in males. When meningiomas are diagnosed in individuals under the age of 40, it may raise suspicion of neurofibromatosis type 2, especially in young patients.
Clinical Presentation
The clinical presentation of meningiomas depends on their location and size. Small meningiomas are often asymptomatic and discovered incidentally. Larger tumors, especially those near sensitive brain structures, can cause various symptoms, including:
- Headaches
- Muscle weakness (paresis)
- Changes in mental status
Most meningiomas are found in supratentorial locations, with common sites being parasagittal areas, convexities, sphenoid ridge, olfactory groove/planum sphenoidale, and juxtasellar regions. Some are infratentorial and may appear in miscellaneous locations, such as intraventricular meningiomas, optic nerve meningiomas, and the pineal gland.
Radiography
The best imaging method for diagnosing meningiomas is MRI with contrast, as it provides the most accurate visualization of the tumor, its extensions, and its relationship with the surrounding brain tissue. CT scans are useful when bony anatomy information is needed or when MRI is contraindicated. They are also valuable in cases of entirely ossified or calcified meningiomas, often referred to as “burnt out meningiomas.”
A Case Report of Calcified Meningioma
One illustrative example is the case of a calcified meningioma, which presents as a well-defined extradural mass with extensive calcification. The mass measures approximately 5.5 x 4.8 x 4.2 cm and is located in the left fronto-parietal region. This mass exhibits both rim and intralesional calcifications, causing significant perilesional edema and mass effect on adjacent sulcal spaces, the left basal ganglia, and the left lateral ventricle. This results in a midline shift towards the right by 10 mm.
In conclusion, meningiomas are a diverse group of tumors originating from the meninges. Understanding their various subtypes, clinical presentations, and the role of radiography in their diagnosis is crucial for effective management and treatment.