Meningiomas account for over 30% of central nervous system tumors in adults, making them the most common tumors in this category. Within the central nervous system, most meningiomas arise on the intracranial or spinal dural surface and rarely from an intraventricular position. They originate from a protective layer around the central nervous system, called meninges, and specifically from cells in the outer layer of the arachnoid mater. The incidence of meningioma increases with age. They are often diagnosed by chance. A widely mentioned risk factor is ionizing radiation. Other associated risk factors such as head injury, smoking, and cell phone use have not been proved. Another established risk factor is neurofibromatosis type 2.
Types
There are 3 types of meningiomas:
Benign meningioma: It is the most common type of meningioma. Benign meningiomas do not invade the surrounding brain tissue. It is also called grade I meningioma.
Malignant meningioma: Also called grade III meningiomas, these tumors make up only 1% of all meningiomas. They can either happen in this malignant form or progress from benign meningioma. This type of meningioma can invade surrounding brain tissue and, in rare cases, spread to other organs such as the lungs.
Atypical meningioma: It is recently recognized as the 3rd type of meningioma by the WHO. Histological and clinical features of this type are in between those of benign and malignant meningioma.
Global perspective
The overall incidence of meningiomas is 8.3 per 100,000 persons-year. Benign meningioma is often diagnosed during the mid-years of life. Around 300 malignant meningiomas are diagnosed in the US every year. Malignant meningioma is mostly diagnosed between the ages of 75 and 84 years. Their overall survival is 2–3 years. Benign meningiomas are more common in females with a male to female ratio of 1:2. Whereas malignant meningiomas are equally prevalent in males and females.
Indian perspective
Similar to the rest of the world, meningioma is the most common primary brain tumor in India. It is being effectively treated in India with a success rate of 95%. Patients can choose from a variety of available hospitals.
Signs and symptoms
Most meningiomas are benign but when they are aggressive, they cause focal neurological deficits such as seizures that greatly affect the quality of life. The specific signs and symptoms of a meningioma depend upon its location in the central nervous system. Meningiomas usually do not spread to other parts of the body hence, the symptoms are mostly focal.
In many patients, the growing tumor causes increased intracranial pressure which manifests itself as a headache.
Other common symptoms arise due to the compression of the tumor against a cranial nerve. In this case, the symptoms are highly related to the functions of that particular cranial nerve.
Meningiomas growing near the anterior portion of the brain cause personality changes, confusion, and an altered level of consciousness.