Meningioma is a common intracranial tumor that occurs in the parsagittal sinus, cerebral convexity, pars falciformis, followed by the pterygoid crest, saddle node, olfactory groove, cerebellopontine angle and cerebellar curtain, and can also be multiple. The population incidence rate is 2/100,000. It accounts for 19.2% of primary brain tumors in the same period, second only to glioma, and is one of the common intracranial tumors in neurosurgery.
Meningiomas originate from the meninges and interstitial derivatives of the meninges, mostly from arachnoid cells, and thus can occur anywhere that contains an arachnoid component. The cause of meningioma is unclear, and it has been analyzed that it may be related to certain internal environmental changes and genetic variants, including cranial trauma, radiation exposure, viral infection, and combined bilateral auditory neuroma, and is not caused by a single factor.
Nature of meningioma – predominantly benign
Meningiomas are spherical in shape, with clear borders to brain tissue, and are mostly spherical, flat, or dumbbell-shaped. Most meningiomas are benign tumors that grow slowly and have a long course, with an average of about 2.5 years for early symptoms and up to 6 years for the longest. Some meningiomas may become malignant intermittently and recur quickly after removal.
Common clinical symptoms of meningioma
Meningioma may have different clinical manifestations in different parts of the body. Because of the high incidence in adults, all adults have chronic headache, mental changes, epilepsy, loss of vision on one or both sides or even blindness, ataxia or limited cranial masses. In particular, the possibility of meningioma should be considered when accompanied by progressively increasing symptoms of increased intracranial pressure. Funduscopic examination often reveals chronic optic nerve papillary edema or has shown secondary atrophy.
Examination of meningioma
1.Cranial plain film
Intracranial meningioma requires routine cranial plain radiographs, which can show signs of intracranial tumor in about 75% of cases, and the diagnosis of meningioma can be made in 30% to 60% of cases based on the signs on plain radiographs.
Some of the signs on x-ray cranial plain films are indirect signs of intracranial tumor and increased intracranial pressure, such as bone erosion and enlargement of the pterygoid saddle, significant pressure marks in the cerebral gyrus with displacement of pineal calcified patches, and in a few cases, separation of cranial sutures. The other part is the signs directly caused by meningioma, including local bone proliferation and destruction of tumor, widening and increase of meningeal artery sulcus caused by increased blood flow of tumor, tumor calcification, local bone thinning, etc. These points are often reliable diagnostic basis for meningioma.
2.CT and MRI scan
In the diagnosis of meningioma, CT and MRI scans have replaced isotope brain scan, pneumoencephalography and ventriculography. Meningiomas are mostly substantial and rich in blood flow, which are most suitable for CT and MRI examinations, and their accuracy can reach the detection of meningioma of 1cm in size.
On CT scan, meningiomas have specific signs, showing a limited rounded, uniformly dense, contrast-enhanced image within the skull, which may be accompanied by osteophytes, a hypointense hydrocephalic band around the tumor, corresponding brain displacement, and signs of hydrocephalus due to cerebrospinal fluid circulation obstruction.
On MRI scan, the signal of meningioma is similar to that of the adjacent cerebral cortex on T1WI, which is often isosignal, while it is hyposignal compared to the white matter of the brain. On T2WI, it is masked by isosignal. After enhancement, the meningioma has significant and uniform enhancement, and the dura mater at its attachment has significant enhancement due to tumor infiltration, which is called “dural rat tail sign” or “meningeal tail sign”.
3.Cerebral angiography
For some meningiomas, cerebral angiography is still necessary. Especially for deep meningioma, its blood supply is multi-channel, only through cerebral angiography can we understand the source of tumor supply, the degree of tumor blood flow and the distribution of adjacent blood vessels, which are of great value in formulating surgery plan, studying the surgical access and surgical methods.
If selective external carotid artery, internal carotid artery and vertebral artery angiography can be performed, especially with digital subtraction angiography, the signs of vascular changes will be clearer and more definite.
Treatment of meningioma
Surgical resection is the main treatment modality
Surgical resection is the main treatment for meningioma. If early diagnosis is possible, in principle, complete resection should be pursued, and the meninges and bone invaded by the tumor should be removed, with a view to radical cure. For some advanced tumors, especially deep meningioma, total resection should not be forced to engage in, so as not to cause the risk of patient death; instead, it is advisable to limit the tumor to subtotal resection and eliminate tumor symptoms.
Radiotherapy is an effective adjuvant therapy
Radiation therapy, especially gamma knife therapy, is an optional treatment for meningiomas that are difficult to undergo surgery or are residual after surgery. It can effectively stop tumor growth, reduce tumor size and lower recurrence rate.