Characteristics and Types of Meningiomas

Characteristics and Types of Meningiomas

Meningiomas are one of the most prevalent types of primary brain tumors, accounting for approximately 30% of all intracranial tumors. These tumors originate from the meninges, the protective membranes covering the brain and spinal cord. Meningiomas can vary significantly in their clinical behavior, ranging from benign to malignant forms. According to the World Health Organization (WHO), meningiomas are classified into three grades based on their histological features:

• Grade I (Benign): These tumors are characterized by slow growth, a low rate of recurrence, and include subtypes such as meningothelial, psammomatous, transitional, and fibrous meningiomas.
• Grade II (Atypical): These tumors exhibit increased cellularity, a higher mitotic activity, and a greater potential for recurrence compared to benign tumors.
• Grade III (Anaplastic): These are aggressive tumors with a high growth rate and significant recurrence risk, necessitating aggressive treatment strategies.

It is crucial to identify the molecular characteristics of meningiomas for tailored treatment strategies. Molecular classification has revealed distinct subgroups with varying prognostic implications, and understanding these can significantly impact treatment planning (Nassiri et al., 2021).

Implications of Skull Invasion in Meningiomas

Meningiomas can occasionally invade the skull, leading to complications and increased surgical challenges. Skull invasion is noted in about 4.5-17% of cases, with hyperostosis indicating tumor infiltration into the skull bone occurring at a consistently high rate of 96% (Kim et al., 2025). This phenomenon is associated with worse prognosis, as patients with skull-invading meningiomas often face higher recurrence rates and mortality (Weller et al., 2021).

The presence of skull invasion complicates surgical resection, as complete removal of both the tumor and the affected bone is necessary to minimize the risk of recurrence. Patients typically require comprehensive imaging studies, such as MRI or CT scans, to assess the extent of skull involvement before surgery (Zadeh et al., 2022). Understanding the implications of skull invasion is vital for preoperative planning and managing patient expectations regarding recovery and prognosis.

Surgical Approaches for Meningioma Resection

The surgical management of meningiomas with skull invasion requires a multidisciplinary approach and careful planning. The primary goal is total resection of the tumor while preserving neurological function. Various surgical techniques may be employed depending on tumor location, size, and extent of invasion.

1. Craniotomy: This technique allows direct access to the tumor, facilitating complete resection. The craniotomy approach is tailored based on the tumor’s location, with lateral or posterior approaches being common for skull base meningiomas.

2. Craniectomy: In cases where the tumor has infiltrated the skull, a more extensive craniectomy may be performed. This involves removing the affected bone to ensure complete tumor excision.

3. Endoscopic Techniques: For select lesions, minimally invasive endoscopic approaches may be considered. These techniques are less traumatic and can lead to quicker recovery times, although they may not be suitable for all skull-invading meningiomas.

4. Adjuvant Therapies: In cases where complete resection is not possible, adjuvant therapies such as radiation therapy may be utilized to reduce the risk of recurrence (Capper et al., 2018).

Surgical approaches must be individualized, taking into account factors such as tumor size, anatomical location, and patient health status. The use of intraoperative imaging and neuromonitoring techniques can further enhance surgical safety and outcomes.

Techniques for Skull Reconstruction Post-Resection

Once a meningioma with skull invasion has been surgically resected, reconstruction of the skull is essential to restore structural integrity and protect underlying tissues. The techniques for skull reconstruction vary based on the extent of the resection and the characteristics of the tumor.

1. Bone Flap Replacement: In cases of mild hyperostosis, the removed bone flap can often be replaced after drilling down any hyperostotic areas. This technique helps preserve the patient’s native bone structure.

2. Alloplastic Cranioplasty: For extensive bone loss or significant invasion, alloplastic materials, such as titanium mesh or acrylic cement, can be used to reconstruct the skull. These materials are biocompatible and can provide effective support for the surrounding tissues.

3. Autologous Bone Grafts: Autologous grafts from the patient’s own body may also be employed, particularly in cases where the tumor has necessitated large resections. This technique minimizes the risk of rejection and promotes better integration with existing bone.

4. Tissue Engineering Approaches: Emerging techniques utilizing scaffolding and bioactive materials are being explored and may offer promising outcomes for complex cranial defects in the future (Liu et al., 2024).

The choice of reconstruction strategy should be made collaboratively by the surgical team, considering patient-specific factors and the potential for complications.

Prognostic Factors and Recurrence Rates in Meningioma Cases

The prognosis for patients with meningiomas, particularly those with skull invasion, can be influenced by various factors. Key prognostic indicators include:

• Tumor Grade: Higher-grade meningiomas (Grade II or III) are associated with increased rates of recurrence and reduced overall survival (Zadeh et al., 2022).
• Extent of Resection: Complete resection of the tumor is critical for improving outcomes. Studies indicate that gross total resection significantly reduces recurrence rates compared to subtotal resection (Nassiri et al., 2021).
• Patient Age and Health: Older patients or those with significant comorbidities may experience worse outcomes, necessitating a tailored approach to treatment planning (Kim et al., 2025).

Recurrence rates for skull-invading meningiomas can vary but are generally higher than for benign forms. The management plan should include regular follow-up imaging and assessment to monitor for recurrence, particularly in high-risk patients.

Table 1: Key Prognostic Factors Associated with Meningiomas

FAQ

What are meningiomas?
Meningiomas are tumors that arise from the meninges, the protective layers surrounding the brain and spinal cord. They can be benign or malignant and vary in behavior.

How are meningiomas diagnosed?
Diagnosis typically involves imaging studies like MRI or CT scans, along with clinical evaluations to assess symptoms and tumor characteristics.

What treatment options are available for meningiomas?
Treatment may include surgical resection, radiation therapy, and monitoring for smaller, asymptomatic tumors. The approach depends on tumor size, location, and patient health.

What is the prognosis for patients with skull-invading meningiomas?
The prognosis can vary significantly based on tumor grade, extent of resection, and individual patient factors. Higher-grade tumors and incomplete resections are associated with poorer outcomes.

What are the risks associated with meningioma surgery?
Risks include infection, bleeding, neurological deficits, and potential complications related to anesthesiThe specific risks depend on tumor location and the patient’s overall health.

References

1. Nassiri, F., Liu, J., Patil, V., et al. (2021). A clinically applicable integrative molecular classification of meningiomas. Nature, 597(7874), 119-125. https://doi.org/10.1038/s41586-021-03850-3

2. Kim, C. H., Kang, Y., et al. (2025). Association Between Preoperative Frailty Using Frailty Index‐Laboratory Test and Clinical Outcomes in Older Adults Undergoing Brain Tumor Surgery. Nursing & Health Sciences, 27(2), e70168

3. Weller, M., van den Bent, M., et al. (2021). EANO Guidelines on the Diagnosis and Treatment of Diffuse Gliomas of Adulthood. Nature Reviews Clinical Oncology, 18(3), 170-186. https://doi.org/10.1038/s41571-020-00447-z

4. Zadeh, G., et al. (2022). Development and validation of a molecular classifier of meningiomas. Neuro-Oncology, 24(7), 1087-1096

5. Liu, F., et al. (2024). Identification of intracranial solitary fibrous tumor and atypical meningioma by multi-parameter MRI-based radiomics model. Discover Oncology, 14(1). https://doi.org/10.1007/s12672-025-02988-0