Concept
Meningiomas are common intracranial benign tumors in adults, often benign, extracerebral, and slow growing. It often causes adjacent bone proliferation and is second only to glioma in incidence. Meningiomas are associated with the arachnoid membrane, especially because their preferred site of origin coincides with the distribution of arachnoid granules. It can occur anywhere where arachnoid cells are present (between the brain and skull, within the brain ventricles, along the spinal cord). This section discusses only intracranial meningiomas.
They are usually slow-growing, well-defined (non-invasive) benign lesions. Tumors that are pathologically malignant (incidence of approximately 1.7%) and/or rapidly growing are also presented here. They can be asymptomatic and actually originate from the arachnoid cells. 8% of patients have multiple tumors, which are particularly common in patients with neurofibromatosis. Occasionally, the tumor grows in a large prostrate pattern (plaque-like meningioma).
Epidemiology
They account for 14.3-19% of primary intracranial tumors, with a high incidence age of 45 years and 1?s1.8 in males?s1.8 in females. 1.5% occur in children and adolescents, usually between 10-20 years of age, and 19-24% of adolescent meningiomas occur in neurofibromatosis type I (von Recklinghausen’s).
Location
Common sites are listed in Table 3-1. Other sites include the CPA, slope, and foramen magnum, and approximately 60-70% grow along the falx (including parsagittal sinus), pterygoid (including saddle node), or convex surface. Meningiomas are rare in children, with 28% occurring intracerebroventricularly and the posterior cranial fossa being another common site.
Pterygoid pterygoid (or crestal) meningioma
Three basic types.
1, lateral pterygoid wing type (or wing point): presentation and treatment are similar to meningioma of the convex side of the brain
2.Middle 1/3 (or wing)
3, medial type (bed protrusion type): mostly encircling the ICA, MCA, cranial nerve and optic nerve in the supraorbital fissure area, may compress the brainstem, and total excision is usually not possible
Sagittal sinus and parafalcine meningioma
Half of them invade the superior sagittal sinus and are divided into the following categories.
1. Anterior: from the septal plateau to the front of the coronal suture, accounting for 33% of cases. The most common symptoms are headache and psychiatric changes.
2.Middle: between the coronal suture and the herringbone suture, accounting for 50% of cases. The most common symptoms are Jacksonian epilepsy and progressive paralysis of a single limb.
3.Posterior: from the herringbone suture to the sinus sink, accounting for 20%, the most common symptoms are headache, visual disturbance, focal epilepsy or
psychiatric changes. Parasagittal sinus meningiomas can grow in the motor area, and the most common first symptom is contralateral foot drop.
Olfactory groove meningioma
Clinical manifestations (most grow to a large size before symptoms appear) include.
1. Foster-Kennedy syndrome: loss of smell (often unrecognized by the patient), ipsilateral optic nerve atrophy, contralateral optic papillary edema
2, mental changes: frontal lobe symptoms are common (apathy, lack of will, etc.)
3.Urinary incontinence
4.Posteriorly located tumor may compress visual structures and cause visual field defects.
5. Epilepsy
Table 3-1 Adult meningioma sites (336 cases)
Site %
Parasagittal sinus 20.8
convex surface 15.2
Saddle node 12.8
Pterygoid crest 11.9
Olfactory groove 9.8
Fossa cerebri 8
Lateral ventricles 4.2
Cerebellar curtain 3.6
Middle cranial fossa 3
Orbit 1.2
Spinal cord 1.2
Lateral fissure 0.3
Extracranial 0.3
Multiple 0.9
Pathology
There are various pathologic classifications, with transitional types between the major types and more than one pathologic feature seen in the same tumor, including
1. 3 main types of “typical meningiomas”
A. Endothelial meningioma, also known as syncytiotrophoblastic: the most common, with a large number of polygonal cells. Some people refer to endothelial meningiomas with dense blood vessels as angiomatous meningiomas.
B. Fibrous or fibroblast type: cells are separated by connective tissue and have a tougher texture than endothelial and transitional meningiomas.
C. Transitional type: The cells are spindle-shaped and typical meningioma cells can be seen in some areas. The cells are arranged in a whirling pattern, and some of them have calcification (sand-like tumor vesicles)
The following variant types may accompany any of the above 3.
(1). Microcystic type: AKA (also known as) “wet” or vacuole-forming meningioma. Typically, the extracellular space is dilated and devoid of any component, but may sometimes contain PAS-positive staining or fat. Microcysts may fuse to form a large sac or a cystic cavity similar to an astrocytoma that can be seen on imaging.
(2). Sandy tumor type: calcified meningeal endothelial cells arranged in a swirling pattern (some call this the transitional type)
(3). Mucinous tumor
(4). Xanthoma
(5). Lipoma
(6). Granular type
(7). Secretion type
(8). Chondrocyte-forming type
(9). Osteoblast type
(10). Melanosis type
2. Angioblastoma: Different authors use this name differently, some call it extravascular meningioma, while others call it “hemangioblastoma” because of the pathological similarity to angiogenic cells. Angioblastoma or malignant meningioma can metastasize outside the CNS, with common sites of metastasis being the lung, liver, lymph nodes, and heart.
3. Atypical meningioma: includes any of the above meningiomas with more than one of the following features, which include: elevated mitotic activity (1-2 split images/high magnification field), elevated cell density, focal necrosis, and giant cells. Cellular pleomorphism is not uncommon, but is not significant in itself. The literature reports increased aggressiveness of the tumor with elevated atypicality.
4. Malignant meningioma: Also known as mesenchymal, papillary or sarcomatoid meningioma, the characteristic changes are mitotic common, invasive into the cortex, recurring quickly even in the case of total resection, and rarely metastasis. A large number of mitotic images or the presence of papillary changes strongly suggest malignancy. It may be more common in younger patients. Compared to other tumors, angioblastoma meningioma exhibits more malignant clinical features.
Diagnosis
(A) Clinical manifestations
1. Medical history Meningioma is a benign tumor with slow growth and long course. Because of the swelling growth of the tumor, patients often have headache and epilepsy as the first symptoms.
2.Headache The symptoms of increased intracranial pressure may not be obvious. Many patients only have mild headache, or even incidental detection of meningioma by CT scan.
Epilepsy Meningiomas located in the frontal or parietal region can produce irritation symptoms, most often as limited epilepsy.
Localized masses Meningiomas often cause changes in the bone quality of the adjacent skull, manifesting as thinning and destruction of the bone plate by pressure, or even erosion through the bone plate to the subcapsular tendon membrane, and localized elevation of the scalp.
(B) Auxiliary examination
1.Cranial X-ray can show the thickening of skull bone in the tumor area, or bone destruction, and widening of the tortuous meningeal vascular sulcus.
It can show: intra-tumor calcification (about 10%), cranial bone hyperplasia or destruction (including the base of anterior cranial fossa in patients with olfactory meningioma), enlargement of vascular sulcus (especially the middle meningeal artery).
2.MRI
Initially thought not to show meningiomas well, MRI now shows most meningiomas on MRI (>0.5T) T2-weighted images (unless they are almost completely calcified). It provides information on the patency of the dural sinuses (with an accuracy of about 90% for estimating the degree of sinus invasion), and the “dural tail” sign is a common sign.
3.CT
CT non-enhanced scans with values of 60-70 are often associated with calcification of sand-like tumors. There may be no obvious cerebral edema, but there may be obvious cerebral edema, and sometimes the scope may reach the whole cerebral hemisphere.
Intracerebroventricular meningioma: 50% of cases present with extraventricular edema. It is easily mistaken for a malignant tumor on angiography prostate cancer is similar to meningioma (metastases to the brain are rare, but often metastasize to the bones and can metastasize to the skull leading to osteophytes.
4.Angiography
Characteristically, except for meningiomas in the medial frontal floor (e.g., olfactory groove) that are supplied by the ICA (septal branch of the ophthalmic artery), the rest of the external carotid arteries are involved in the blood supply. Most of the meningiomas in the parasternal area are also fed by the ICA. Angiography can also show obstruction of the dural sinuses, particularly in sagittal sinus/parsagittal meningiomas. Oblique films are the best option to assess the patency of the superior sagittal sinus (SSS). The distinct and uniformly delayed filling of the tumor vessels helps to confirm the diagnosis.
Treatment
Surgical treatment is preferred for symptomatic meningiomas. Incidental meningiomas or those that present only as seizures and are easily controlled can be followed up with periodic MRI, as meningiomas grow slowly and some can be “burned out” and stop growing.
1.Surgery
Preoperative embolization and autologous blood reserve are beneficial for surgery.
Surgical removal of meningiomas is the most effective treatment. With the development of microsurgical techniques, the surgical results of meningioma have been improved, enabling most patients to be cured, but the possibility of recurrence cannot be ruled out.
2.Surgical principles
1) Position Depending on the location of the tumor, lateral, supine, and prone positions are commonly used.
The key to incision design is to locate the tumor exactly in the center of the bone window.
3) Application of surgical microscope The separation of tumor under surgical microscope makes the operation more detailed and can protect the brain tissue and important neurovascular to the maximum.
4) For tumors rich in blood flow, preoperative embolization of the supplying artery or intraoperative ligation of the vessels supplying the tumor can be performed.
5)
The dura mater and cranial bone eroded by the tumor should be removed together to prevent postoperative recurrence. The venous sinuses that have been occluded by imaging and confirmed intraoperatively can also be resected. The dura and skull should be repaired with fascia or artificial dura and skull bone.
6) Postoperative management Control intracranial pressure, anti-inflammatory and anti-epileptic treatment, and pay attention to the prevention of cerebrospinal fluid leakage.
Recurrence
The degree of tumor resection is the most important factor affecting recurrence. The Simpson classification of meningioma resection is listed in Table 3-2. The recurrence rate of fully resected tumors is 11-15%, 29% for incompletely resected tumors (follow-up time not stated), and 37-85% for partially resected tumors at 5 years. One group reported a 20-year recurrence rate of 19% and another group 50%. Malignant meningiomas have a higher recurrence rate than benign ones.
Table 3-2 Simpson grading system for meningioma resection
Grade Extent of resection
I Total subsarcoid resection with dural attachment and abnormal skull (including invaded dural sinus)
II Total subsarcoid resection with electrocoagulation or laser treatment of the dural attachment
III Total subsurface resection with untreated dural attachments and epidural extensions (e.g. hyperplastic bone)
IV Partial resection of tumor
V Decompression alone (± biopsy)
2.Radiation therapy (XRT)
It is usually considered to be ineffective when used as a primary treatment. The role of XRT in preventing recurrence is variable (see Recurrence later). Some neurosurgeons use XRT only for meningiomas that are malignant (infiltrative), vascular, recurrent (aggressive), or unresectable. For meningiomas that are not fully resectable and for a few malignant meningiomas, radiation therapy is required after surgical resection. Radiotherapy is effective for malignant meningiomas and vascular ependymal meningiomas.
In a retrospective study of 135 benign meningiomas at UCSF with 5-15 years of follow-up, the recurrence rate was 4% for total resection, 60% for partially resected patients without XRT and 32% for partially resected patients with XRT. The mean time to recurrence was greater in the XRT-treated group (125 months) than in the non-XRT-treated group (66 months). The results suggest that XRT may be effective in partially resected patients. However, CT or MRI follow-up is also feasible for those who did not undergo XRT
In addition to the common side effects of XRT, there are reports in the literature that XRT can lead to malignant astrocytomas after treatment of meningiomas.
Hormone therapy is not yet effective in slowing down the growth of tumors, and can be used as palliative therapy for meningiomas that have recurred and are not suitable for reoperation.
Treatment effect
5-year survival rate is 91.3%