Meningioma is a derivative of the meninges and meningeal space. It is the second most common intracranial tumor, accounting for 19.2% of all tumors, with a female:male ratio of 2:1. All intracranial areas rich in arachnoid granules and arachnoid villi are good sites for meningioma. Parasagittal sinus, cerebral convexity, and pars falcae are common, followed by pterygoid crest, saddle node, olfactory groove, pontocerebellar horn and cerebellar curtain, etc. Growth in the ventricles is rare and can also be seen in the epidural. Other sites are occasionally seen.
Clinical symptoms
Benign meningioma grows slowly and has a long course, with early symptoms lasting about 2.5 years on average and as long as 6 years in the longest cases. In elderly patients, epilepsy is the first symptom.
If the tumor grows to both sides, bilateral limb weakness and urinary disorder, epilepsy and intracranial pressure increase may occur.
Etiology and pathology
The occurrence of meningioma may be related to certain internal environmental changes and genetic mutations. It is not caused by a single factor, but may be related to cranial trauma, radiation exposure, viral infection and combined with bilateral auditory neuroma.
Meningiomas are spherical in shape and have clear borders with brain tissue. The tumor is a dense gray or dark red tissue, sometimes containing sand granules. Intratumoral necrosis is seen in malignant meningiomas. Meningiomas can sometimes thicken or thin the adjacent skull by invasion. Tumors can range in size from 1 cm to more than 10 cm in diameter. Most tumors are spherical, conical, flat, or dumbbell-shaped.
Common meningiomas are of the following types.
1.Endothelial type
2.Fibroblastic type
3.Vascular type
4.Grit type
5.Mixed or migratory type
6.Malignant meningioma
7.Meningeal sarcoma.
The susceptible sites are, in order of prevalence
1.Sagittal sinus accounts for about 50%
2.Saddle node
3.Sieve sinus
4.Cavernous sinus
5.Pontocerebellar horn
6.Cerebellar curtain, etc.
Classification
According to their pathological characteristics, they are classified into the following types: endothelial or fibrous, vascular, granular, mixed or migratory, malignant meningioma, and meningeal sarcoma. The first five types are generally classified as benign meningioma, and malignant changes occur most frequently in vascular meningioma.
Growth characteristics of malignant meningioma
The cell morphology is characteristic of malignant tumors, with rapid growth into the surrounding tissues and metastasis.
Ectopic meningioma
There are still ectopic meningiomas, occasionally seen in the skull plate barrier, frontal sinus, subscalp of nasal cavity or neck, which are from ectopic arachnoid tissue, not metastasis. Meningiomas are multiple, accounting for about 1% to 2%, and can be as many as dozens, scattered in the same area, with a large nodule and small tumors, as large as a walnut or as small as a corn, and there are far more supratentorial meningiomas than infratentorial meningiomas. In addition, meningiomas can coexist with gliomas and neurofibromas in the skull, or with hemangiomas.
Meningeal sarcoma
Meningiosarcoma is a rapidly developing, infiltrative, irregularly shaped and poorly defined tumor that develops rapidly after surgery and is associated with distant metastases.
The specific clinical manifestations of meningiomas vary according to the location, and are briefly described below.
Meningioma of the convex surface of the brain, with a generally long history, mainly manifests as varying degrees of headache, mental disorders, limb movement disorders and changes in vision and visual field. About 60% of patients may develop symptoms of increased cranial pressure after six months, and some patients may develop localized epilepsy, facial and hand convulsions, and grand mal seizures are uncommon.
Parasagittal sinus meningioma
Epilepsy is the first symptom of the disease, which is partial or grand mal seizures. Mental disorders are manifested as dementia, emotional indifference or euphoria, and personality changes.
Pterygoid crest meningioma
Tumor originating from the anterior bed projection may present with vision loss or even blindness; invasion to the orbit or supraorbital area may present with protrusion of the eye, eye movement disorders, dilated pupils; epilepsy, psychiatric symptoms, olfactory disorders, etc.
Saddle node meningioma
Visual field disorders, more than 80% of patients have visual impairment as the first symptom; headache, a few patients may develop drowsiness, memory loss, anxiety and other psychiatric symptoms; some patients may develop endocrine dysfunction, such as loss of libido, impotence, amenorrhea, etc.; some patients also present with loss of sense of smell, epilepsy, and actinic nerve palsy as the first symptom.
Olfactory meningioma
Early symptoms include gradual loss of sense of smell, increased intracranial pressure may cause visual impairment, excitement, hallucinations, delusions, sluggishness, mental indifference when the tumor affects frontal lobe function, and epilepsy in a few patients. It often causes ipsilateral optic nerve atrophy and becomes Foster-kenydy sign due to increased intracranial pressure and contralateral optic nerve edema.
Pontocerebellar horn meningioma
Tumors in this area are most common with auditory neuroma, accounting for 70-80% of meningiomas and only 6-8% of cholesteatomas and 4-5% of cholesteatomas. Clinical manifestations are hearing loss, tinnitus, facial numbness, and hypesthesia. Damage is manifested by unsteady walking, gross horizontal tremor, and ataxia of the affected side.
Rock-bone – slope meningioma
Often presents as headache, but often goes unnoticed, with significant symptoms of III-X cranial nerve damage.
Intracerebroventricular meningioma
Because of intracerebroventricular growth, early neurological impairment is not obvious, but the tumor is usually large by the time of consultation. It often presents with headache, optic papilledema, epilepsy, isotropic hemianopia, and contralateral limb hemiparesis.
Middle cranial fossa meningioma
They present with trigeminal neuralgia, eye movement disorders, eyelid ptosis, diplopia, decreased visual acuity, and isotropic hemianopia.
Meningioma of the cerebellar curtain
It presents with coarse horizontal tremor and ataxia on the affected side, visual field disorder, etc.
Paraneoplastic meningioma of the spongy sinus
Headache, visual field changes, eye muscle paralysis, and pain in the area of the first and second branches of the trigeminal nerve.
Occipital foramen magnum meningioma
Early manifestations include neck pain, numbness in the hands and upper extremities, which can be easily misdiagnosed.
Meningioma of the orbit and cranio-orbital communication
Protrusion of the eye, eye movement disorders, and loss of vision
Clinical diagnosis
Meningiomas are characterized clinically by slow onset and long duration of disease. Meningioma may have different clinical manifestations in different parts of the body. Because of the high incidence in adults, the possibility of meningioma should be considered in adults with chronic headache, mental changes, epilepsy, loss of vision or even blindness on one or both sides, ataxia or limited cranial masses, especially when accompanied by progressively increasing symptoms of intracranial pressure. Funduscopic examination often reveals chronic optic nerve papillary edema or has shown secondary atrophy.
Confirmation of tumor diagnosis also relies on ancillary diagnostic tests. Tests that are important for the diagnosis of meningioma include cranial plain films, CT scans and cerebral angiograms. They can not only achieve localization, but also understand the size and characterization of the tumor.
1.Cranial plain film: Intracranial meningioma requires routine cranial plain film, about 75% of cases can show signs of intracranial tumor on plain film, while 30% to 60% of cases can make diagnosis of meningioma based on the signs on plain film. displacement, 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 scan: In the diagnosis of meningioma, CT scan has replaced isotope brain scan, pneumoencephalography and ventriculography. Meningioma is mostly substantial and rich in blood flow, which is most suitable for CT examination, and its accuracy can reach the detection of 1cm size meningioma. On CT scan images, meningioma has its own special signs, showing a limited round uniform density contrast-enhanced image in the skull, which may be accompanied by osteophytes, a hypodense cerebral edema band around the tumor, corresponding brain displacement, and signs of hydrocephalus caused by cerebrospinal fluid circulation obstruction.
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 blood flow and the distribution of adjacent blood vessels, which are of great value to the development of surgical plan and the study of surgical access and surgical methods. If selective external carotid artery, internal carotid artery and vertebral artery angiography can be performed, especially by digital subtraction angiography, the signs of vascular changes will be clearer and more definite.
In addition, lumbar puncture can reflect the increased intracranial pressure and increased protein content of cerebrospinal fluid, which still has some reference significance in diagnosis and differential diagnosis.
Treatment
The treatment of meningioma is mainly surgical resection. In principle, complete resection and removal of the meninges and bone invaded by the tumor should be strived for, with a view to radical cure. Meningioma is a tumor growing outside the parenchyma and most of them are benign. If early diagnosis can be made and surgery is performed before the tumor damages the surrounding brain tissues, important cranial nerves and blood vessels, total resection should be achieved.
However, there are some advanced tumors, especially deep meningioma, which are huge and adhere to the nerves, blood vessels, brainstem and lower thalamus, or the nerves and blood vessels are not easy to be separated, in this case, total resection should not be performed reluctantly to avoid aggravating brain and cranial nerve damage and the risk of intraoperative hemorrhage, or even death or serious disability.
It is advisable to limit the tumor to subtotal resection, reduce the volume of the tumor, supplemented by decompression surgery to reduce the pressure of the tumor on the brain, relieve the intracranial pressure and protect the vision. Or to be treated by staged surgery. For advanced tumors that cannot be removed surgically, after biopsy of tumor tissue, only decompressive surgery can be performed to prolong life. For malignant cases, radiotherapy can be used as a supplement.
According to the growth location and growth characteristics, meningioma resection needs to cut off the surrounding meninges together in order to cure completely and prevent recurrence, but about 50% of the parts of skull base and meninges that cannot be resected can not be completely cut.