Meningiomas are the most common type of brain tumours that develop from the meninges, which are the layers of tissuea group of cells that work together to perform a function that cover the brain and the spinal cord in the central nervous system (CNS). These tumours are often benignnot cancerous, can grow but will not spread to other body parts, however in rare cases they may become malignantcancerous, may grow and spread to other areas of the body. Meningiomas are most commonly found in the cerebrum or cerebellum portions of the brain, but can develop anywhere in the CNS.
The brain is a complex organ that is responsible for controlling all functions of the body. It has five main portions: the cerebrum, cerebellum, brainstem, pituitary gland, and hypothalamus. The cerebrum is the biggest part of the brain, and consists of the frontal, parietal, temporal, and occipital lobes. This part of the brain is responsible for voluntary movement, intelligence, and memory. The cerebellum is a small part of the brain located at the back of the head, and regulates posture and balance. The brainstem is a small, stalk-like structure towards the bottom of the brain that connects the brain to the spinal cord. It regulates many vital bodily processes, such as swallowing, breathing, and heart rate. The pituitary gland is a pea sized organ located behind the eyes, and is responsible for the production and secretion of hormones in the body. The hypothalamus is located deep within the brain, and has many important functions, such as producing and secreting different hormones, regulating temperature, and controlling appetite.
The spinal cord is a long, thin, tubular structure that extends down from the brainstem to the lower back. It is made of nerve tissue, and is surrounded by the bones of the spine (vertebrae). The spinal cord is responsible for transmitting nerve signals from the brain to the body, and vice versa. It has motor functions (such as voluntary movement), sensory functions (such as pressure, touch, temperature, and pain), and autonomous functions (such as regulating digestion, heart rate, and bloodthe red bodily fluid that transports oxygen and other nutrients around the body pressure).
Meningiomas are more common in women, and are generally diagnosed in people over the age of 60. However, anyone can develop this disease.
Types of Meningiomas
There are several types of meningiomas, which are often categorised by their location within the CNS, and their cellular appearance under the microscope.
Meningioma Subtypes Based on Location
Meningiomas can be classified by their location within the CNS.
Convexity Meningioma
Convexity meningiomas are one of the most common subtypes of meningioma, and are generally found on the surface of the brain under the skull. It is found in an area known as the convexity, which connects the frontal and parietal lobes of the cerebrum. In many cases, convexity meningiomas are benign, and develop slowly over time.
Parasagittal/Falx Meningioma
Parasagittal meningiomas, also known as falx or falcine meningiomas, are tumours that develop in the falx cerebri, which is a sickle-shaped structure of dura mater (connective tissue that makes up part of the meninges). It is found between the two cerebral hemispheres of the brain. In many cases, parasagittal meningiomas are benign, and develop slowly over time.
Intraventricular Meningioma
Intraventricular meningiomas are a rare subtype of meningioma that often develops within the ventricles of the brain. The ventricles of the brain are large, open and complex structures that are responsible for the production and secretion of cerebrospinal fluid (CSF) in the body. In many cases, intraventricular meningiomas are benign, and develop slowly over time.
Skull Base Meningioma
Skull base meningiomas are a common subtype of meningioma that develop on the bones that form the base of the skull. These tumours are generally found beneath the brain and behind the eyes, and are often more difficult to surgically remove due to their location. In many cases, skull base meningiomas are benign, and develop slowly over time.
Sphenoid Wing Meningioma
Sphenoid wing meningioma is one of the most common types of meningioma, and is found on the sphenoid bone in the skull. The sphenoid bone is a wasp shaped structure that lies behind the top of the nasal cavity, and extends to the left and right side of the skull. In many cases, sphenoid wing meningiomas are benign, and develop slowly over time.
Olfactory Groove Meningioma
Olfactory groove meningiomas are a rare subtype of meningioma that develops in the nerves enabling our sense of smell. These nerves are partially contained in depressions of the ethmoid bone of the skull, known as olfactory grooves. In many cases, olfactory groove meningiomas are benign, and develop slowly over time.
Posterior Fossa/Petrous Meningioma
Posterior fossa meningiomas, also known as petrous meningiomas, are a rare subtype of meningioma that grow in the posterior fossa. This area of the brain is adjacent to the brainstem and cerebellum, and can cause problems with movement, hearing, and other important bodily functions. In some cases, this tumoura tissue mass that forms from groups of unhealthy cells can result in a condition called trigeminal neuralgia, which causes painful sensations (similar to an electric shock) on one side of the face. In many cases, posterior fossa meningiomas are benign, and develop slowly over time.
Suprasellar Meningioma
Suprasellar meningiomas are a rare subtype of meningioma that develops in the suprasellar regions of the brain. This area is near many important structures, such as the pituitary gland (gland primarily responsible for hormonea chemical substance produced by glands in the endocrine system that regulates various functions in the body secretion) and the optic nerve (nerves enabling our vision). In many cases, suprasellar meningiomas are benign, and develop slowly over time.
Meningioma Subtypes Based on Cellular Appearance
In addition to their location, meningiomas can also be classified by how the cancera disease where abnormal cells split without control and spread to other nearby body tissue and/or organs cellsthe basic structural and functional unit of all living things look under the microscope.
Angiomatous Meningioma
Angiomatous meningiomas are a rare subtype of meningioma that are often classified as a benign or gradea description of how abnormal cancer cells and tissue look under a microscope when compared to healthy cells I tumour. These tumours are categorised by an abnormal abundance of blood vessels that make up over 50% of the tumour. These tumours are generally non-aggressive, slow growing, and can have a good prognosisto predict how a disease/condition may progress and what the outcome might be.
Cystic Meningioma
Cystic meningiomas are a rare subtype of meningioma that are often classified as benign or grade I tumours. These tumours are categorised by the presence of a few, large cystsabnormal growths that are usually filled with liquid or air within the tumour, and are commonly confused with microcystic meningiomas. There are five classifications of cystic meningiomas, which are classified by location:
- Type 1: cyst(s) are located centrally within the meningioma.
- Type 2: cyst(s) are located within the meningioma, but not in the centre.
- Type 3: cyst wall contains an area of tumour cells.
- Type 4 (most common): cyst(s) are located in a separate portion of the brain adjacent to the meningioma.
- Type 5 (arachnoid cyst): cyst is located between the meningioma and the adjacent brain.
Cystic meningiomas are generally non-aggressive, slow growing, and can have a good prognosis.
Fibroblastic Meningioma
Fibroblastic meningiomas, also known as fibrous meningiomas, are one of the most common types of meningioma that are often classified as a benign or grade I tumour. These tumours are categorised by spindle-shaped tumour cells, and are the most common variant of intraventricular meningiomas. These tumours are generally non-aggressive, slow growing, and can have a good prognosis.
Lymphoplasmacyte-rich Meningioma
Lymphoplasmacyte-rich meningiomas are a very rare subtype of meningioma that are often classified as benign or grade I tumours. These tumours are categorised by the presence of excess lymphocytes and plasma cells (types of white blood cells) within the tumour. Unlike most other types of meningiomas, lymphoplasmacytic-rich meningiomas are more common in children and young adults. These tumours are generally non-aggressive, slow growing, and can have a good prognosis.
Meningothelial Meningioma
Meningothelial meningioma, also known as syncytial or endothelial meningioma, is the most common type of meningioma that are often classified as a benign or grade I tumour. These tumours are categorised by the presence of syncytial cells, which are infected cells that have fused together with healthy cells resulting in an infected cell with multiple nuclei. These tumours are generally non-aggressive, slow growing, and can have a good prognosis.
Metaplastic Meningioma
Metaplastic meningioma is a very rare subtype of meningioma that is often classified as a benign or grade I tumour. There are several types of metaplastic meningiomas, including:
- Cartilaginous meningiomas (tumour contains cells found in cartilage).
- Lipomatous meningiomas (tumour contains cells found in adipose tissue/fat).
- Melanotic meningiomas (tumour contains melanocytes, the cells responsible for providing pigment to our skin, hair, and eyes).
- Myxoid meningiomas (tumour contains cells that produce mucus).
- Osseous meningiomas (tumour contains cells found in bone).
- Xanthomatous meningiomas (tumour contains cells with a lipid-filled vacuolated cytoplasm).
These tumours are generally non-aggressive, slow growing, and can have a good prognosis.
Microcystic Meningioma
Microcystic meningiomas are a rare subtype of meningioma that is often classified as a benign or grade I tumour. These tumours are categorised by the presence of microscopic cysts scattered throughout the tumour, and may be confused with cystic meningiomas. These tumours are generally non-aggressive, slow growing, and can have a good prognosis.
Psammomatous Meningioma
Psammomatous meningiomas are a relatively common subtype of meningioma that is often classified as a benign or grade I tumour. These tumours are categorised by excess calcium build-up within the tumour, and are one of the most common meningiomas involving the spine. These tumours are generally non-aggressive, slow growing, and can have a good prognosis.
Secretory Meningioma
Secretory meningiomas are a rare subtype of meningioma that is often classified as a benign or a grade I tumour. These tumours are categorised by the presence of secretory globules (also known as pseudopsammoma bodies) that contain cytokeratin (a protein that helps form epithelial tissue, such hair, skin, and the lining of organs) and carcinoembryonic antigen (CEA) (a protein that acts as a tumour marker). These tumours are generally non-aggressive, slow growing, and can have a good prognosis.
Transitional Meningioma
Transitional meningiomas, also known as mixed meningiomas, is a relatively common type of meningioma that is often classified as a benign or a grade I tumour. These tumours are categorised by components of both meningothelial and fibroblastic (or fibrous) meningiomas. These tumours are generally non-aggressive, slow growing, and can have a good prognosis.
Atypical Meningioma
Atypical meningiomas are a less common group of meningiomas that are often classified as a mid-grade or grade II tumour. These tumours show more cellular abnormality than grade I tumours, and tend to develop more rapidly. Atypical meningiomas are more likely to recur, and may not have as good of a prognosis as grade I tumours. There are two types of atypical meningiomas:
- Choroid meningiomas: a rare subtype categorised by meningioma cells developing within the choroid plexus.
- Clear cell meningiomas: a more common subtype categorised by ‘empty cells’, most notable in the spinal canal or posterior fossa. They tend to be more aggressive and have a higher recurrenceto occur or happen again rate than choroid meningiomas.
Anaplastic Meningioma
Anaplastica term used to describe abnormal cancer cells that grow uncontrollably in the body and have little or no resemblence to regular cells meningiomas are a rare group of meningiomas that are often classified as high-grade or grade III tumours. These tumours show significant cellular abnormality and often develop quickly. Anaplastic meningiomas are generally much more aggressive than other subtypes, and may not have as good of a prognosis as grade I or II meningiomas. There are two types of anaplastic meningiomas:
- Papillary meningiomas: a rare subtype categorised by perivascular pseudopapillary tumour cells. Unlike most meningiomas, these tumours generally affect patients around 40 years of age.
- Rhabdoid meningiomas: a rare subtype characterised by the presence of rhabdoid cells within the tumour. This subtype is often very aggressive.
Treatment
When cancers are detected, they are staged and graded based on size, metastasiswhen the cancer has spread to other parts of the body, also known as mets, and how the cancer cells look under the microscope. Stagingthe process of determining how big the cancer is, where it started and if it has spread to other areas and grading helps your doctors determine the best treatment for you. However, brain cancers are rarely staged, as they rarely spread to other parts of the body. Instead, they are generally graded from I-III.
Meningiomas are generally graded by subtype:
- Grade 1 (benign) tumours: cancer cells present as slightly abnormal and are usually slow growing. Includes angiomatous meningiomas, cystic meningiomas, fibroblastic meningiomas, Lymphoplasmacyte-rich meningiomas, meningothelial meningiomas, microcystic meningiomas, psammomatous meningiomas, secretory meningiomas, and transitional meningiomas.
- Grade II (atypical) tumours: cancer cells present as abnormal and grow faster than grade-I tumours. Includes choroid meningiomas and clear cell meningiomas.
- Grade III (anaplastic) tumours: cancer cells present as very abnormal and grow quickly. Includes papillary meningiomas and rhabdoid meningiomas.
Once your tumour has been graded, your doctor may recommend genetic testinga procedure that analyses DNA to identify changes in genes, chromosomes and proteins, which can be used to analyse tumour DNA to help determine which treatment has the greatest chance of success, which analyses your tumour DNA and can help determine which treatment has the greatest chance of success. They will then discuss the most appropriate treatment option for you.
Treatment is dependent on several factors, including location, age, stage of disease and overall health.
Treatment options for meningiomas may include:
- Surgerytreatment involving removal of cancerous tissue and/or tumours and a margin of healthy tissue around it to reduce recurrence to remove as much of the tumour as possible.
- Watch and waitthe close monitoring of a cancer without giving treatment until symptoms appear or worsen (for low-grade meningiomas).
- Radiation therapya treatment that uses controlled doses of radiation to damage or kill cancer cells.
- Clinical trialsresearch studies performed to test new treatments, tests or procedures and evaluate their effectiveness on various diseases.
- Palliative carea variety of practices and exercises used to provide pain relief and improve quality of life without curing the disease.
Risk factors
While the cause of meningiomas remain unknown, the following factors may increase the riskthe possibility that something bad will happen of you developing the disease:
- Previous radiation exposure, especially radiation therapy.
- Genetic conditions, such as neurofibromatosis type 2 (NF2).
A potential link between elevated female sex hormones and the development of meningiomas has also been identified, however more research would be required to confirm this.
Not everyone with these risk factors will develop the disease, and some people who have the disease may have none of these risk factors. See your general practitioner (GP) if you are concerned.
Symptoms
Meningiomas may appear asymptomatic in the early stages of disease, and often vary based on location within the CNS.
The general symptoms of a meningioma in the brain include:
- Seizures.
- Headaches, often worse in the morning.
- Blurred vision.
- Weakness in your arms and/or legs.
- Numbness.
- Changes in vision, such as blurriness and double vision.
- Personality changes.
- Decreased cognition.
- Lack of emotion and/or interest (apathy).
- Difficulty with balance and/or coordination.
- Involuntary eye movements.
- Hearing loss and/or ringing in the ears.
- Memory loss.
- Loss of smell.
- Hydrocephalusa build up of cerebrospinal fluid (CSF) in the brain, causing pressure and potentially damaging brain tissue.
In rare instances, meningiomas can also develop in the spinal cord. Symptoms of a spinal cord meningioma may include:
- Difficulties walking.
- Leg weakness and/or numbness.
- Difficulties with urination and/or bowelportion of the digestive system that digests food (small bowel) and absorbs salts and water (large bowel); also called intestines movements.
Not everyone with the symptoms above will have cancer, but see your general practitioner (GP) if you are concerned.
Diagnosis
If your doctor suspects you have a meningioma, they may order the following tests to confirm the diagnosisthe process of identifying a disease based on signs and symptoms, patient history and medical test results and refer you to a specialist for treatment:
- Physical examinationan examination of your current symptoms, affected area(s) and overall medical history.
- Neurological examinationan assessment of sensory and motor functions, such as vision, balance and coordination.
- Imagingtests that create detailed images of areas inside the body tests, potentially including:
- MRI (magnetic resonance imaging)a type of medical imaging that uses radiowaves, a strong magnet and computer technology to create detailed images of the body.
- CT (computed tomography) scana type of medical imaging that uses x-rays and computer technology to create detailed images of the body.
- Blood teststesting done to measure the levels of certain substances in the blood.
- Biopsyremoval of a section of tissue to analyse for cancer cells.
