Meningiomas are mostly benign tumours which arise from the dura mater and are usually slow-growing. Meningiomas usually form well-circumscribed lesions but, rarely, can be more diffuse - eg, when they grow next to the sphenoid ridge and are called 'meningioma en plaque'. Meningiomas occur either intracranially or within the spinal canal. Meningiomas can be graded in various ways - eg, site of origin, encroachment of surrounding tissues and histological grading. The most common system used is the World Health Organization (WHO) classification:
- Grade I (generally benign): meningothelial, psammomatous, secretory, fibroblastic, angiomatous, lymphoplasmacyte-rich, transitional, microcystic, metaplastic.
- Grade II (there is a higher rate of recurrence after surgery, especially if a resection is incomplete): clear-cell, chordoid, atypical. Chordoid type has been associated with Castleman's disease (an uncommon lymphoproliferative disorder).
- Grade III (anaplastic): papillary (rare and mostly seen in children), rhabdoid and anaplastic. Grade III meningiomas are malignant with a high rate of local invasion, recurrence and metastases.
- They are the most common tumours in the central nervous system, accounting for about one-third of all adult central nervous system tumours.[3, 4]
- The reported annual incidence of cerebral meningiomas ranges from 1.3/100,000 to 7.8/100,000.
- There is a female:male ratio of 2:1.
- 2-3% of the population have asymptomatic meningiomas and 8% have multiple meningiomas.
Aetiology and risk factors
- Aetiology is not known and most cases are sporadic.
- Some are increased in the presence of certain genetic disorders - eg, loss of chromosome 22 and presence of neurofibromatosis type 2.[1, 6]
- Other risk factors include advanced age, cranial irradiation, head injury and breast cancer (although causality not determined).[2, 3]
Site (the most common first)
- Skull vault.
- Skull base - eg, sphenoid wing and petrous ridge.
- Sites of dural reflection - eg, falx cerebri and tentorium cerebelli.
- Optic nerve sheath.
- Choroid plexus.
- Spine (rarely).
- Outside the craniospinal axis (very rarely) - eg, the ear, temporal bone and foot.
- Proliferation markers provide information on the likelihood of recurrence. For example, MIB-1 and Ki67 are found in higher levels of tumours that are likely to recur.[2, 7] However, further work is needed to clarify the role of proliferation markers and prognosis.
- Meningiomas can also express progesterone receptors.
- Higher levels of progesterone receptors have been reported to be associated with a lower frequency of recurrence and a better prognosis.
- More than 70% of meningiomas express somatostatin receptors which can be used with radiological imaging, especially when looking for local recurrence.[2, 9]
Meningiomas present as a space-occupying lesion.
- Seizures - focal or generalised are common with meningiomas.
- Raised intracranial pressure effects - eg, obstructive hydrocephalus with headache.
- Neuropsychological effects - eg, change in personality and disinhibition in frontal lesions.
- Neurological features - eg, cranial nerve palsies depending on location of a meningioma or language dysfunction.
- Transient ischaemic attack and intracranial haemorrhage may also be seen.
- Meningiomas that compress the visual pathways cause visual field defects.
Other rare presentations include:
- Meningiomas near the sella turcica may produce panhypopituitarism.
- Spinal meningiomas may cause Brown-Séquard's syndrome.
This is as for space-occupying lesions. Meningiomas can be discovered incidentally when patients are investigated for other conditions. Other lesions which may also affect the dura mater include:
- Other primary brain tumours.
- Metastases from lymphoma and adenocarcinoma.
- Inflammatory disorders - eg, sarcoidosis.
- Infections - eg, tuberculosis.
- Imaging - MRI is superior to CT scanning as it shows the dural origin. Meningiomas are well-defined, extra-axial lesions. They may show central cystic degeneration and oedema of nearby white matter.
- Endovascular angiography allows pre-operative assessment of the blood supply of the tumour and its proximity to vital vascular structures.
- Biopsy - stereotactic biopsy via a skull burr-hole or open exploration (craniotomy).
Management will depend on the clinical presentation, age of the patient, site of the tumour and size of the tumour. For example, an elderly patient with multiple comorbidities who is discovered incidentally to have a small, asymptomatic meningioma, can be managed conservatively. This usually consists of yearly MRI scans for three years and then just clinical follow-up if nothing new has developed.
- This involves embolisation of the blood supply to the meningioma - eg, coil or glue applied endovascularly to the meningeal artery.
- This is usually performed before surgical removal, as it reduces the amount of blood loss.
- It has also been performed as the primary therapy in those unsuitable for surgery.
- Embolisation usually causes necrosis of the meningioma, which can cause some histological doubt when specimens are examined postoperatively.
- The tumour and its dural base are removed. Total excision is the aim but this is not always technically possible.
- Surgery may be complicated by invasion into local structures - eg, parasagittal tumours invading into the cerebral dural sinus.
- Stereotactic radiosurgery can provide excellent local tumour control.
- Radiotherapy is used in the following:
- Incomplete resection.
- Following recurrence of meningioma.
- High-grade meningiomas with atypia or anaplasia on histology.
- In these clinical scenarios the use of radiotherapy is associated with a better outcome. For example, in one study stereotactic radiosurgery was associated with better tumour control (approximately 10%) and fewer complications. However, a recent paper has shed some doubt on how useful radiotherapy is in meningiomas.
- Stereotactic application of radiotherapy has further benefits compared with traditional radiotherapy. This includes less damage to undiseased tissue and better five-year control rates.[2, 14, 15]
- Radiotherapy is successful and may be used as the primary therapy for tumours, especially inaccessible meningiomas - eg, optic nerve lesions.
Chemotherapy and molecular agents
- Chemotherapy has so far shown disappointing results and has been reserved for when surgery and radiotherapy have failed to control the disease.
- Chemotherapeutic regimens involving hydroxyurea have been used but with little success.[16, 17]
- Other drugs studied include temozolomide, RU-486 and interferon alfa, which have also shown disappointing results.
- More novel molecular targets are being researched.[18, 19]
- Atypical and anaplastic types of meningiomas can rarely metastasise.
- Completely resected meningiomas usually have an excellent prognosis. The five-year survival for typical meningiomas is more than 80%; however, this falls to below 60% in malignant and atypical meningiomas.
Further reading and references
; Histological classification and molecular genetics of meningiomas. Lancet Neurol. 2006 Dec5(12):1045-54.
; Meningiomas. Lancet. 2004 May 8363(9420):1535-43.
; Update on meningiomas. Oncologist. 201116(11):1604-13. doi: 10.1634/theoncologist.2011-0193. Epub 2011 Oct 25.
; Epigenetics of Meningiomas. Biomed Res Int. 20152015:532451. doi: 10.1155/2015/532451. Epub 2015 May 25.
; Epidemiology of meningiomas. Neurochirurgie. 2014 Sep 20. pii: S0028-3770(14)00112-X. doi: 10.1016/j.neuchi.2014.05.006.
; Molecular genetics of meningiomas: from basic research to potential clinical applications. Neurosurgery. 2007 May60(5):787-98
; Molecular signatures define two main classes of meningiomas. Mol Cancer. 2007 Oct 156:64.
; Immunohistochemical expression of progesterone and estrogen receptors in meningiomas. Folia Neuropathol. 200644(2):111-5.
; Expression of c-Myc, neurofibromatosis Type 2, somatostatin receptor 2 and erb-B2 in human meningiomas: relation to grades or histotypes. Clin Neuropathol. 2008 Sep-Oct27(5):334-45.
; Endovascular treatment of cerebrovascular diseases and intracranial neoplasms. Lancet. 2004 Mar 6363(9411):804-13.
; Preoperative embolization of intracranial meningiomas with Embosphere microspheres. Minim Invasive Neurosurg. 2004 Oct47(5):299-305.
; Central nervous system tumors. Mayo Clin Proc. 2007 Oct82(10):1271-86.
; Radiotherapy as an adjuvant in the management of intracranial meningiomas: are we practising evidence-based medicine? Br J Neurosurg. 2008 Aug22(4):520-8.
; Stereotactic radiation treatment for benign meningiomas. Neurosurg Focus. 200723(4):E5.
; The application of stereotactic radiosurgery to disorders of the brain. Neurosurgery. 2008 Feb62 Suppl 2:707-19
; Diagnosis and treatment of atypical and anaplastic meningiomas: a review. Neurosurgery. 2005 Sep57(3):538-50
; Meningioma. Crit Rev Oncol Hematol. 2008 Aug67(2):153-71. Epub 2008 Mar 14.
; Novel therapies for meningiomas. Expert Rev Neurother. 2006 Oct6(10):1447-64.
; Targeted drug therapy for meningiomas. Neurosurg Focus. 200723(4):E12.
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