What is a meningioma?
It is a group of derivatives that originate from the meninges and meningeal spaces and may arise from dural fibroblasts and soft meningeal cells, but mostly from arachnoid cells.
What is the incidence of meningioma?
Meningioma has a population incidence of about 2/100,000, second only to glioma, and accounts for about 20% of intracranial tumors, with a female to male ratio of 2:3. The peak age of onset is 30-50 years.
What is associated with the occurrence of meningioma?
The occurrence of meningioma may be related to certain internal environmental changes and genetic variants, and is not caused by a single factor. It may be associated with factors such as cranial trauma, radiation exposure, viral infections, and the combination of bilateral auditory neuromas. The common feature of these factors is that they have the potential to mutate cell chromosomes or to increase the rate of cell division.
What are the clinical manifestations of meningioma?
Meningiomas are mostly benign, with an intact envelope, compressed and embedded in the brain parenchyma, closely adherent to the dura mater, and forming the tip of the tumor, which receives blood from the external carotid artery. There are signs of hyperplasia or infiltration of the adjacent skull. Meningiomas are spherical or nodular in shape, growing outside the brain parenchyma but often embedded in the cerebral hemisphere. These tumors are very slow growing and have a long course, so sometimes they can grow to a large size without showing symptoms. The clinical manifestations depend on the location of the tumor. If the tumor is located in the cerebral hemisphere, it often causes headache, epilepsy, hemiparesis and mental disorders. In elderly patients, epilepsy is especially common as the first symptom. If the tumor is located at the base of the skull, symptoms of cranial nerve and brain involvement are often seen in the corresponding area. Symptoms of increased intracranial pressure usually appear later. Patients may suffer from long-term chronic intracranial pressure increase resulting in loss of vision or even blindness in both eyes. It is important to note that the tumor in the dumb area grows so large that the brain tissue can no longer compensate for it before the patient shows signs of increased intracranial pressure, which can suddenly worsen and even lead to brain herniation in a short period of time.
What are the special tests related to meningioma?
The EEG is mostly limited abnormal Q waves with slow waves predominating, and the background EEG changes are milder. The richer the meningioma blood supply, the more pronounced the appearance of delta waves. x-ray plain radiographs may show localized thickening of the inner plate of the skull, diffuse hyperplasia of the bone plate, and pin-like radiation of the outer plate of the bone hyperplasia. The cranial meningeal arterial sulcus is thickened and distorted. Among them, the site of cranial hyperplasia suggests the central location of the tumor. Cerebral angiography provides essential details to confirm the vascular structure of the tumor, the extent of tumor enrichment in blood vessels, the displacement of major cerebral vessels, and the relationship between the tumor and the larger dura mater, and the degree of sinus opening (to determine whether to ligate intraoperatively).CT examination shows that the tumor is located outside the brain, with clear borders, uniform density, broad-based contact with the dura mater, and uniform enhancement with the meningeal tail sign visible after strengthening.MRI examination T2 signal can be iso-T1 or slightly low signal, high signal (suggesting the tumor is relatively soft), low signal (suggesting the tumor is relatively hard), and obvious enhancement after reinforcement. The main tests for meningioma are CT and MRI.
What are the treatment options for meningioma?
Since most meningiomas are benign, surgical resection is the main treatment. It can be combined with radiation therapy, cytokine therapy, gene therapy (mainly for meningioma, which is still in the research stage), and chemotherapy (mainly for meningeal sarcoma, which can be considered).
Whether a meningioma requires treatment depends on the location and size of the meningioma, whether there is pressure on the surrounding tissues, and whether there are symptoms of increased intracranial pressure. If the meningioma is relatively small (e.g. 1cm) or less and has no obvious compression symptoms on brain tissues and cranial nerves, it can be observed and it is recommended to review once a year for any changes. Meningioma with diameter less than crn can be treated with x-knife or gamma knife. If the tumor is relatively large and has obvious compression to the surrounding brain tissues and cranial nerves, or has symptoms of increased intracranial pressure, surgical resection is recommended as long as the patient has no contraindications to surgery and can tolerate surgery. Since the tumor receives double blood supply from the internal and external carotid arteries, it will bleed more during surgery.
1. Complete surgical resection of tumor to reduce the incidence of neurological damage: With the in-depth study of microscopic neuroanatomy, various surgical approaches have become more mature, and the key to surgery is how to completely resect the tumor. The following problems plague meningioma resection: (1) the tumor encircles important blood vessels and nerves, which makes total resection difficult; (2) the tumor is tough and cannot be totally resected; (3) the tumor is rich in blood supply, which makes surgery dangerous; (4) the tumor invades the dura mater and its formation, which is not easy to handle intraoperatively. In view of the above problems, we need to develop individualized surgical plan, refine surgical skills, choose convenient and delicate surgical instruments, and strive to achieve Simpson grade I-II tumor resection. In this way, postoperative tumor recurrence can be greatly reduced. Of course, it is also very important to assess the risk of tumor resection and nerve damage, which requires very experienced surgeons to evaluate.
The correct choice of stereotactic radiosurgery or radiotherapy for tumor control: Radiotherapy includes photon beam and proton beam therapy or fractionated external radiation therapy. The vast majority of medical centers use modified linear accelerator systems or gamma knives to treat patients. Radiotherapy can be used as an alternative to surgery for small tumors that are located away from vital structures. These are meningiomas that are relatively deep and small (usually less than 3 cm) with no significant compression of brain tissue or cranial nerves. This approach is mainly used for small residual tumors after meningioma surgery, or for small lesions and elderly patients who are to be considered for timely radiosurgery. For eroded dura mater, dural formations and venous sinuses that fail to be treated, the option of conventional radiotherapy is also an important measure to prevent tumor recurrence.
For radiotherapy, radiation therapy (mainly gamma knife treatment) can be performed after surgery cannot be performed for total resection and adequate decompression, which can control or slow down tumor recurrence; or patients cannot tolerate surgery, radiation therapy can be considered directly (without increased intracranial pressure and pressure on cranial nerves or brain tissue). For patients with sub-total resected WHO grade I meningiomas, postoperative radiotherapy is often required. For patients with WHO grade II and III meningiomas, the current standard of care is postoperative adjuvant radiotherapy, regardless of the extent of surgical resection. This is because of the relatively high rate of postoperative local recurrence of these high-grade tumors.
Gamma knife treatment for meningioma is aimed at controlling the growth of the tumor, and its treatment is based on: (1) meningioma is a benign tumor with slow growth, which can be treated with a lower dose, allowing enough time for slow necrosis of the tumor; (2) meningioma is easily visualized on CT or MRI with clear boundaries, which facilitates dose calculation and can effectively protect the surrounding tissues; (3) meningioma can mostly be diagnosed by imaging, and most of them do not require (3) meningiomas can be diagnosed by imaging and most of them do not require pathology; (4) the incidence of meningiomas in the elderly is high and surgical treatment is not appropriate.
A large amount of treatment experience shows that meningiomas on the convex side of the brain, especially paragangliomas, even if they are small in size, are prone to long-term, severe radiation edema reactions, and surgery should be preferred, with residual parts treated with gamma knife. Skull base meningiomas with milder radiation reactions and larger volumes can be treated with fractionated gamma knife. For elderly patients, due to the slow growth of the tumor itself, low-dose treatment can be used, the purpose of growth control is the main, the so-called “human tumor coexistence.
3. Other treatments: ① cytokine therapy. For example, the application of Suramin can interfere with cell signaling and has been found to reduce the proliferation of meningioma cells. Other treatments include IL-1β, IL-6 and IFN for meningioma. ②Gene therapy. For example, adenovirus genes were introduced into the supply vessels of meningioma, and significant gene expression was observed in the tumor. The main studies have focused on NF-2 and p53 gene, etc. (iii) Chemotherapy, the effect of which needs to be further explored. Chemotherapy can be considered mainly for meningeal sarcoma. ④Hormone therapy. Certain hormones have been associated with meningiosarcoma development and progression. Anti-progestational drugs have been used, but with varying results. Recent studies have found that hydroxyurea analogs can reduce the size of unresectable tumors and recurrent meningiomas, but these need further evaluation.
Meningiosarcoma is a malignant type of meningioma, accounting for approximately 5% of all meningiomas. It is prone to recurrence after tumor resection and has a poor prognosis, and is also seen clinically in cystic and multiple meningiomas.