Meningioma overview

# Overview
Meningioma is a relatively common neoplasm of the central nervous system that arises from arachnoidal cells which are normally involved in the protection of the brain and spinal cord by forming a thick envelope of meninges around them. Meningioma is the most common benign tumors of the brain. About 90% of meningiomas are benign with about 2% being malignant. Meningioma was first discovered by Dr Felix Platter, a Swiss physician, in the 16th century. Meningioma may be classified according to the histological criteria of the WHO. It is classified into 3 groups: benign classic meningioma (WHO grade 1), atypical meningioma (WHO grade 2), and anaplastic malignant meningioma (WHO grade 3). Neurofibromatosis type II, cowden syndrome, and multiple endocrine neoplasia 1 are among a few conditions that are associated with meningioma. There are no established direct causes for meningioma. Meningioma must be differentiated from other diseases that cause similar presentation such as schwannoma, hemangiopericytoma, and solitary fibrous tumor. The incidence of meningioma is approximately 7.62 per 100,000 individuals in the United States. The prevalence of meningioma was estimated to be 97.5 cases per 100,000 individuals in the United States. Common risk factors in the development of meningioma are history of radiation treatment, increasing age, and female gender. There is insufficient evidence to recommend routine screening for meningioma. Meningioma could present with complications such as peritumoral brain edema, stroke, and increased intracranial pressure. The hallmark symptom of meningioma is headache. Other common symptoms of meningioma include visual impairment, hearing loss/tinnitus, focal neurological deficits, behavioral changes. Head CT scan may be diagnostic of meningioma. Some of the findings on CT scan suggestive of meningioma include edema, CSF attenuation cleft, round/elongated extraaxial mass, and hyperostosis of the adjacent skull.  MRI with gadolinium is the investigation of choice for the diagnosis of meningioma. On MRI, meningioma is characterized by a homogeneous, well circumscribed, and extra-axial mass with a broad dural base. Other findings on MRI suggestive of meningioma include CSF vascular cleft sign, dural tail sign, and central necrosis or calcification that do not enhance. In asymptomatic meningiomas, the decision of surgical resection must be weighed against the possibility of conservative management according to the patient's age, clinical presentation, and the anatomical location of the tumor. The predominant therapy for meningioma is surgical resection. Current data suggest that both external beam radiotherapy and radiosurgery play an important role in the management of grade II and III meningiomas.

# Historical Perspective
Meningioma was first discovered by Dr Felix Platter, a Swiss physician, in the 16th century. He described the tumor as having the shape of an acorn, fleshy, and full of holes.

# Classification
Meningioma may be classified according to the histological criteria of the WHO into 3 groups: benign classic meningioma (WHO grade 1) which is made up of nine variants, atypical meningioma (WHO grade 2) which is made up of three, and anaplastic malignant meningioma (WHO grade 3) made up of three variants.

# Pathophysiology
Meningioma arises from the arachnoid "cap" cells, which are normally involved in the protection of the central nervous system by forming a thick envelope of meninges around the brain and spinal cord. Because of the abundance of arachnoid cap cells in the skull base and perivenous sinuses, meningiomas are commonly found in these sites. Some meningiomas may have progesterone receptors which could make the tumor grow in size during pregnancy and in the luteal phase of the menstrual cycle. Meningiomas could be found in various locations such as sphenoid ridge, olfactory grove, falx cerebri, cerebellopontine angle, foramen magnum, ventricles, etc. Though most meningiomas are benign in nature, some may be malignant and this characterization is usually based on brain invasion, frank anaplasia, and distant metastasis. NF2, MEG2, TERT, AKT1, and NDRG2 are some of the genes that may be involved in the pathogenesis of meningioma. Some conditions could be associated with meningioma, they include neurofibromatosis type 2, cowden syndrome, nevoid basal cell carcinoma, multiple endocrine neoplasia 1 (MEN1), etc. On gross pathology, a gray, well-circumscribed, dome-shaped mass is a characteristic finding of meningioma. On microscopic histopathological analysis, meningiomas may have different characeteristics, they include mitotic figures, interdigitating processes and intercellular junctions, prominent nucleoli, necrosis, and increased cellularity.

# Causes
There are no established direct causes for meningioma.

# Differentiating Meningioma from other Diseases
Meningioma must be differentiated from other diseases that have similar presentation such as schwannoma, oligodendroglioma, pituitary adenoma, hemangioblastoma, etc

# Epidemiology and Demographics
The prevalence of meningioma was estimated to be 97.5 cases per 100,000 individuals in the United States. The incidence of meningioma is approximately 7.62 per 100,000 individuals in the United States. Meningiomas may appear at any age, but occur most commonly among patients between 40 to 60 years. Females are more commonly affected with meningiomas than males, with the ratio being 2:1. Meningioma usually affects individuals of the African American race. Caucasian and Latin American individuals are less likely to develop meningioma.

# Risk Factors
Common risk factors in the development of meningioma are history of radiation treatment, increasing age, and female gender.

# Screening
There is insufficient evidence to recommend routine screening for meningioma.

# Natural History, Complications and Prognosis
The median age at diagnosis of meningioma is about 65 years, with incidence increasing with advancing age. A higher annual growth rate may be seen in patients with an initial tumor diameter of greater than 25mm, MR imaging T2 signal hyperintensity, patients presenting with symptoms and edema, and male patients. Most meningiomas are single with about 1-10% being multiple. Common complications of meningioma include increased intracranial pressure, cranial nerve palsies, and hydrocephalus. Prognosis is generally good, and the survival rate of patients with meningioma mainly depends on the histological grade of the tumor and the extent of resection during surgery. A poorer survival rate may be seen in patients of advanced age, male patients, black race, malignant tumors, and patients with no initial treatment.

# Diagnosis

## Diagnostic Study of Choice
MRI is the gold standard test for the diagnosis of meningioma but CT is more widely available and better in urgent settings.

## History and Symptoms
The hallmark symptom of meningioma is headache. Other common symptoms of meningioma include weakness, focal neurological deficits, visual impairement, hearing loss, and confusion. However, the specific clinical presentation of meningioma is determined by the exact anatomical location of the tumor.

## Physical Examination
Common physical examination findings of meningioma include decreased visual acuity, hearing loss, ataxia, muscle weakness, focal neurological deficits, and more. Patients with meningioma present with different signs depending on the location of the tumor, its character, and the structures it may compress. Some patients are asymptomatic and may have not present with sign on physical examination.

## Laboratory Findings
There are no diagnostic lab findings associated with meningioma.

## Electrocardiogram
There are no ECG findings associated with meningioma.

## X Ray
Plain radiography no longer has a role in the diagnosis or management of meningioma.

## Echocardiography and Ultrasound
There are no echocardiography/ultrasound findings associated with meningioma.

## CT
Head CT scan may be diagnostic of meningioma. Some of the findings on CT scan suggestive of meningioma include edema, CSF attenuation cleft, round/elongated extraaxial mass, and hyperostosis of the adjacent skull. Although MRI is the diagnostic study of choice, CT is easier to use and may be used in cases where there is a contraindication to the use of an MRI.

## MRI
MRI with gadolinium is the investigation of choice for the diagnosis of meningioma. On MRI, meningioma is characterized by a homogeneous, well circumscribed, and extra-axial mass with a broad dural base. Other findings on MRI suggestive of meningioma include CSF vascular cleft sign, dural tail sign, and central necrosis or calcification that do not enhance. Meningiomas may appear different on T1 and T2-weighted sequence but with a few similarities.

## Other Imaging Findings
Other imaging studies that may be helpful in the diagnosis of meningioma include magnetic resonance (MR) spectroscopy, perfusion MRI, and diffusion MRI. With MR spectroscopy, elevated levels of alanine, choline, and/or lactate could be seen. MR perfusion study could demonstrate an elevated value of relative cerebral blood volume (rCBV).

## Other Diagnostic Studies
Bromodeoxyuridine labeling study may be helpful in the diagnosis of meningioma. An elevated bromodeoxyuridine labeling index is suggestive of a rapid growth rate of meningioma and a greater incidence of recurrence following surgical resection.

# Treatment

## Medical Therapy
In asymptomatic meningiomas, the decision of surgical resection must be weighed against the possibility of conservative management according to the patient's age, clinical presentation, and the anatomical location of the tumor. Current data suggest that both external beam radiotherapy and radiosurgery play an important role in the management of grade II and III meningiomas. Chemotherapeutic agents are generally not effective against meningioma.

## Interventions
Asymptomatic meningiomas found incidentally are usually treated expectantly. In cases with tissue edema and vascular compromise, another approach can be taken. Radiotherapy is pursued depending on the patient factor and location of the tumor. It can be done after surgery with little advantage over radiotherapy alone.

## Surgery
The predominant therapy for meningioma is surgical resection. Adjunctive radiation therapy may be required among certain patients. The Simpson criteria for meningioma correlates the degree of surgical resection completeness with the probability of post-surgical tumor recurrence. Surgical resection is not recommended among patients with asymptomatic stable meningioma.

## Primary Prevention
There are no established measures for the primary prevention of meningioma.

## Secondary Prevention
There are no established measures for the secondary prevention of meningioma.