Meningioma
The most common brain tumor, usually slow-growing and benign, arising from the coverings of the brain and causing symptoms by pressing on brain tissue.
Emergency Management: Brain herniation secondary to massive peritumoral edema, requiring emergency intubation, hyperventilation, IV Mannitol, and emergent craniotomy.
A meningioma is a typically slow-growing, benign central nervous system tumor that arises from the meningothelial cells of the arachnoid mater, the middle layer of the meninges covering the brain and spinal cord.
Detailed Overview
Meningiomas are the most common primary intracranial tumors in adults, accounting for over 30% of cases. Because they grow slowly inward from the meninges, they do not invade the brain parenchyma but rather compress it. Many are discovered incidentally on imaging and remain asymptomatic. When symptoms do occur, they are insidious and depend entirely on the tumors location (e.g., frontal lobe compression causing personality changes, optic nerve compression causing vision loss). While >80% are benign (WHO Grade 1), their location can make surgical removal challenging. Complete resection is often curative.
Epidemiology & Demographics
Incidence increases with age, peaking in the 6th and 7th decades. They are approximately twice as common in women as in men, likely due to hormone receptor expression. More common in African Americans.
Etiological Mechanism
Most are sporadic, driven by somatic mutations, most frequently the loss of the NF2 tumor suppressor gene on chromosome 22q. Prior ionizing radiation to the head is a strong environmental trigger.
Primary Causes
Genetic mutations in arachnoid cap cells. Can be induced by prior therapeutic radiation (e.g., for childhood leukemia or tinea capitis).
Arachnoid cap cells, located in the arachnoid villi, undergo neoplastic transformation following chromosomal deletions (notably 22q loss). The tumor grows slowly, firmly attached to the dura mater (causing a dural tail on MRI). It forms a well-circumscribed, lobulated mass that pushes the underlying brain tissue, inciting reactive vasogenic edema in the white matter. Histologically, they show a whorled pattern of spindle cells and calcified concentric concretions called psammoma bodies. They can invade the adjacent skull bone, causing hyperostosis, but rarely break the pia mater to invade the brain.
Diagnostic Criteria & Guidelines
Diagnosis is strongly suspected based on characteristic MRI findings (homogeneously enhancing extra-axial mass with a dural tail) and confirmed by histopathological examination following resection or biopsy.
For asymptomatic, small (<3 cm) meningiomas: Active surveillance with serial MRIs. For symptomatic or growing tumors: Maximal safe surgical resection (craniotomy). The Simpson Grade of resection determines recurrence risk.
Second-Line & Adjunctive Therapy
Stereotactic Radiosurgery (e.g., Gamma Knife) is used for small, symptomatic tumors in deep, surgically inaccessible areas (e.g., cavernous sinus), or for remnants left behind after surgery.
Surgical & Procedural Management
Craniotomy and tumor resection. The goal is complete removal of the tumor, its dural attachment, and any involved bone (Simpson Grade I), though functional preservation takes priority over complete resection near eloquent brain areas.
Patient Counseling & Advice
Provide reassurance that "brain tumor" in this context usually means a benign, curable growth, not cancer. Explain that even benign tumors can cause serious damage if they press on vital structures, making surgery necessary.
Follow-Up & Monitoring Schedule
Post-operative MRI at 3 months, then annually for 5 years, then every 2-3 years, as late recurrences can happen even 10 years out.
Preventive Strategies
Avoidance of unnecessary ionizing radiation to the head.
Excellent for fully resected WHO Grade 1 tumors (10-year survival >90%). Atypical and Anaplastic grades have higher recurrence rates and lower survival.