What is Meningioma?
Define meningioma: It is a primary brain tumor that originates from the meninges, the thin protective layers covering the brain and spinal cord, and represents one of the most frequently diagnosed intracranial tumors. Representing approximately 30% of all intracranial tumors, meningiomas are usually benign and slow-growing, but depending on their size and location, they can cause significant neurological deficits.
Meningiomas most commonly develop intracranially but can also originate in the spinal canal, where they account for about 25-30% of spinal tumors.
Causes and Risk Factors
The precise meningioma causes remain incompletely understood, but several risk factors have been identified:
Genetic mutations: Particularly alterations in the NF2 gene are strongly linked to tumor development.
Exposure to ionizing radiation: Prior radiation therapy to the head or spine increases risk.
Hormonal influences: The higher incidence in women, along with detection of estrogen and progesterone receptors in many tumors, suggests hormonal involvement.
Age and gender: Most diagnoses occur between ages 40 and 70, with a female predominance.
Pathology and Classification
1. Histopathological Features
Meningiomas derive from arachnoid cap cells and typically consist of spindle-shaped cells arranged in whorls or sheets. Psammoma bodies—calcified, concentric microscopic structures—are commonly observed. The degree of cellular atypia and mitotic activity varies by tumor grade.
2. WHO Classification (2021 Update)
Based on histological and clinical behavior, meningiomas are categorized into three grades:
Grade | Description | Characteristics |
|---|---|---|
I | Benign | Well-differentiated, slow-growing, low recurrence risk |
II | Atypical | Elevated mitotic activity, brain invasion, increased recurrence risk |
III | Anaplastic/Malignant | Marked atypia, rapid growth, aggressive, poor prognosis |
3. Common Histological Subtypes
Grade I: Meningothelial, Fibrous (Fibroblastic), Psammomatous, Angiomatous, Microcystic, Secretory
Grade II: Atypical, Clear Cell, Chordoid
Grade III: Anaplastic, Papillary, Rhabdoid
Clinical Presentation
1. Intracranial Meningiomas
Symptoms vary by tumor size and location, often developing gradually:
Persistent or worsening headaches
Seizures (new onset or poorly controlled)
Focal neurological deficits such as weakness, sensory loss, or speech impairment
Visual disturbances if tumors compress the optic nerves or chiasm
Hearing loss or tinnitus with temporal lobe involvement
Signs of increased intracranial pressure including nausea, vomiting, and papilledema
Cognitive or behavioral changes, especially in frontal lobe tumors
2. Spinal Meningiomas
Though less common, spinal meningiomas comprise 25-30% of spinal tumors and primarily affect the thoracic spine:
Gradual onset of back pain and radicular pain radiating along nerve roots
Motor weakness, sensory deficits, and gait disturbances
In advanced cases, myelopathy resulting from spinal cord compression
Diagnostic Approach
1. Neurological Examination
Comprehensive evaluation of motor, sensory, cranial nerve, and reflex functions is essential.
2. Imaging Studies
Magnetic Resonance Imaging (MRI): The gold standard for both cranial and spinal meningiomas. MRI delineates tumor size, dural attachment (notably the “dural tail sign”), involvement of adjacent structures, and provides excellent soft tissue contrast. Contrast-enhanced T1-weighted sequences typically reveal intense homogeneous enhancement.
Computed Tomography (CT): Useful for detecting calcifications and bone changes, especially skull hyperostosis or erosion in cranial meningiomas.
Dotatate PET MR: Functional imaging modality detecting somatostatin receptor expression in meningiomas. It is especially useful for identifying residual or recurrent disease after surgery or radiotherapy, thereby guiding targeted medical therapies.
3. Histopathological Confirmation
Definitive diagnosis is confirmed via biopsy or resected tumor tissue examination.
Treatment Modalities
1. Microsurgical Resection
The primary and often curative treatment for meningiomas is surgical removal. The extent of resection is graded by the Simpson scale, which correlates with recurrence risk:
Complete resection including affected dura and bone offers the lowest recurrence risk.
2. Radiotherapy
Indicated when complete surgical resection is not feasible or for higher-grade tumors:
Stereotactic radiosurgery (GammaKnife, CyberKnife) is preferred for small, well-circumscribed lesions or residual lesions.
Fractionated external beam radiotherapy is utilized for larger, invasive, or recurrent tumors.
3. Medical Therapy: Somatostatin Analogs
Many meningiomas express somatostatin receptors, making somatostatin analogs like Octreotide (Sandostatin) a valuable adjunct, particularly in recurrent, unresectable, or radiotherapy-resistant tumors. Treatment decisions are informed by DOTATATE PET/MR receptor imaging to optimize targeted therapy and disease control.
Prognosis
Overall prognosis depends on tumor grade, location, size, extent of resection, and patient factors. Benign meningiomas have excellent long-term survival, while atypical and anaplastic variants necessitate vigilant management.