Meningioma of the frontal lobe

Among intracranial tumors there is a neoplasm of the brain membranes (meninges) originating from meningothelial cells of its spider web, which is adjacent to the frontal lobe (lobus frontalis) of the large hemispheres - meningioma of the frontal lobe. As a rule, such a tumor is benign. [1]

Epidemiology

Meningiomas are common tumors of the brain membranes and statistically account for 15-18% of all intracranial tumors. Meningiomas are more likely to occur around the age of 60, and their risk increases with age.

Benign meningiomas are identified in 80-81% of cases; 17-18% of cases are grade II meningiomas and 1-1.7% are grade III meningiomas.

The recurrence rate of meningioma ten years after its removal is 7-25% for benign tumors and 30-52% for atypical tumors. Recurrence of anaplastic meningiomas is observed in 50-94% of patients.

While benign tumors of the brain membranes are more common in women, grade II and III meningiomas are more common in men. [2]

Causes of the meningiomas of the frontal lobe

Like the other two brain shells (hard and soft), the spider web (arachnoidea mater) between them protects the brain from mechanical damage and provides support for its homeostasis.

The arachnoid sheath is formed from the mesectoderm of the neural crest of the embryo; it has no blood vessels or nerves; it is attached to the underlying soft cerebral sheath by connective tissue protrusions. Between these membranes is the subarachnoid space with liquor (cerebrospinal fluid), which circulates in a network of trabeculae, and enters the venous sinuses of the brain through the spider villi - microscopic outgrowths of the spider sheath into the dura.

Meningiomas form along and attach to the dura mater, but can also grow outward (causing localized thickening of the skull). The exact causes of their occurrence are unknown despite much research into the biology of the dura mater. In most cases, meningiomas are considered sporadic neoplasms, although their etiologic association with chromosome abnormalities and gene mutations has been suggested.

Differentiating from mesenchymal cells of the primary dura mater, arachnoidea mater cells can be inside the brain, where they cover the spaces surrounding some blood vessels (so-called Virchow-Robin spaces). Therefore, some meningiomas are intracerebral and can affect the frontal lobes of the brain.

Based on histologic features, meningiomas are classified into slow-growing benign (grade I), atypical (grade II) - intermediate malignancy, and anaplastic (grade III) - fast-growing malignant tumors.

Risk factors

Specialists consider risk factors for the formation of meningiomas (including frontal lobe):

• increased radioactive background and direct exposure of the brain to ionizing radiation;
• obesity;
• alcoholism;
• exposure to exogenous hormones (estrogens, progesterone, androgens);
• Having a history of diseases such as genetically determined neurofibromatosis type 2; Hippel-Lindau disease (caused by mutations in one of the tumor suppressor genes); multiple endocrine neoplasia type 1 (MEN 1); Li-Fraumeni syndrome, hereditary syndrome, or Cowden disease.

Pathogenesis

Usually meningiomas form on the surface of the brain and grow slowly. The mechanism of formation of these tumors lies in pathological mitosis (uncontrolled multiplication) of healthy meningothelial cells of the spider web and cytoplasmic processes occurring in them. But the pathogenesis of meningiomas is not fully understood.

The meningothelial cells of the tumor are sometimes separated by thin fibrous septa and have partial phenotypic features of epithelial cells, and their classical histological features visible under the microscope include polygonal or spindle-shaped cells with oval monomorphic nuclei, psammomatous corpuscles (round accumulations of calcium), nuclear pores (perforation of the shells of the nuclei), intracytoplasmic inclusions of eosinophilic character, etc.

Grade II and III frontal lobe meningiomas usually appear as an enlarging mass on the outer covering of brain tissue and are characterized by invasion of the brain (may penetrate the brain tissue). [3]

Symptoms of the meningiomas of the frontal lobe

Most meningiomas are asymptomatic. It is not uncommon for a slowly growing frontal meningioma to be silent, and the first signs - when the tumor compresses the frontal lobes - may be headaches, weakness and impaired coordination of movements, difficulty walking, absent-mindedness, episodes of confusion, nausea and vomiting.

In later stages, symptoms depend on the specific area of tumor localization in the frontal lobe, which controls acquired motor skills and gestures, planning of purposeful actions, thinking, attention, speech, mood, etc.

For example, a frontal lobe meningioma on the left side may manifest with muscle seizures (clonic and tonic-clonic) on the right side of the face and limbs. The same focal convulsive seizures, but in the left side of the face and left limbs, are often manifested by frontal lobe meningioma on the right side. In addition, with right-sided tumor localization, there is bipolar affective disorder and visual hallucinations.

Frontal meningiomas may manifest with mental disorders: anxiety; schizophrenia-like pseudodepression - with apathy, slowness and difficulty in expressing thoughts; pseudomanic syndrome - with euphoria and talkativeness. Behavioral abnormalities may also be observed: disinhibition, increased irritability, aggressiveness.

In general, frontal lobe syndrome develops, more in the publication - Symptoms of frontal lobe lesions

Some tumors have calcified deposits and when these are found, calcified frontal lobe meningioma/obstructed meningioma is diagnosed. [4]

Complications and consequences

When a frontal menigioma is present, complications and consequences such as:

• increased intracranial pressure (due to impaired circulation of cerebrospinal fluid);
• edema of peritumoral brain tissue (which develops due to the secretion of the vascular endothelial growth factor VEGF-A by tumor cells);
• Hyperostosis of the cranial vault (in cases of primary extradural meningiomas);
• limb weakness to the point of paralysis;
• vision, memory and attention problems;
• loss of sense of smell;
• Motor aphasia;
• progressive neurological deficits.

Tumor cells can spread to other areas of the brain through the liquor, and grade III meningiomas can spread to other organs.

Diagnostics of the meningiomas of the frontal lobe

Diagnosis begins with a neurologic examination of patients, but only instrumental diagnostics can detect meningiomas. The gold standard for imaging intracranial tumors is magnetic resonance imaging (MRI) of the brain. Specialists may also use computed tomography with contrast and positron emission tomography.

After removal of the neoplasm, a biopsy and histologic analysis of a tissue sample of the tumor is required to determine its type, grade, and stage.

Differential diagnosis

Differential diagnosis is made with arachnoid cyst, meningothelial hyperplasia, glioma and astrocytoma, meningeal carcinomatosis, Lennox-Gasto syndrome, etc.

Treatment of the meningiomas of the frontal lobe

Benign frontal lobe meningioma grows slowly, and if it does not cause symptoms, it is best to monitor its growth with periodic MRI scans.

Conservative treatment with antineoplastic and immunomodulatory drugs is possible; these are drugs such as Hydroxyurea, Sandostatin, Interferon alfa-2a, Interferon alfa-2b.

But in case of rapidly growing tumors, large meningiomas and presence of symptoms, surgical treatment by subtotal resection of the tumor is necessary.

Radiation therapy or stereotactic radiosurgery is used for recurrences or residual tumor whose continued growth is detected by another MRI scan.

Adjuvant radiation or chemotherapy (with the monoclonal IgG1 antibody-containing Bevacizumab) may be required to reduce recurrence rates in partially removed meningiomas and in atypical or anaplastic tumors.

Prevention

Prevention of the formation of primary central nervous system tumors such as frontal lobe meningioma has not been developed.

Forecast

The outcome for patients with benign meningioma is favorable. The prognosis for atypical or anaplastic meningioma depends on timely detection of the tumor (preferably at an early stage) and adequate treatment. Currently, the 5-year survival rate after meningioma removal exceeds 80%, and the 10-year survival rate is 70%.