Meningioma Brain Tumors

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Definition and Etiology

Meningiomas are prevalently benign tumors originating in the meninges, i.e. the membranes covering the brain and the spinal cord.

They represent about 25% of all brain tumors.

They generally affect adults from 40 to 65 years of age, and are more frequent in women than in men with a 2:1 ratio. 25% of all cases are related to neurofibromatosis 2, which is a genetic syndrome.

Depending on where the meningiomas are located, they are classified as one of the following:

convexity meningiomas
skull base meningiomas
posterior fossa meningiomas

The World Health Organization (WHO) has classified meningiomas according to their degree of biological aggression as follows:

Benign meningiomas (Grade I): they represent about 80% of all cases. They are benign tumors, do not infiltrate the parenchyma, and have a low recurrence rate.
Atypical meningiomas (Grade II): about 10-15% of all cases. They are tumors with an intermediate degree of biological aggression, which tend to recur after some time.
Anaplastic meningioma (Grade III): this is the rarest form representing about 2-3% of all cases. They are characterised by a high biological aggressiveness, so much so that they are considered malignant tumors. As opposed to benign meningiomas, they can present areas of infiltration into the parenchyma and bone structures, and they frequently recur.

The etiology of these tumors is unknown; a certain correlation between the alterations caused by hormonal regulation in women and the genesis of meningiomas in these subjects has been pointed out. In women, there is a certain correlation between the development of breast cancer and meningiomas.

Symptoms

The majority of meningiomas are asymptomatic, since they are small in size and are usually diagnosed incidentally as a consequence of tests performed for other reasons.

The symptoms are caused by the direct compression of the adjacent neural structures by the meningioma and by the edema that is often associated to it. There can be various types of disorders depending on where the meningioma is located.

In convexity meningiomas the most frequent symptoms are:

headache
seizures
mental confusion
behavioural alterations
language disorders
weakness of the arms and legs on the side of the body opposite to where the meningioma is located

In skull base meningiomas the most frequent symptoms are:

visual impairment
impaired smell
eye movement disorders

These symptoms are due to direct cranial nerve compression.

In posterior fossa meningiomas the most frequent symptoms are:

balance disorders
alteration of motor coordination
symptoms related to from intracranial hypertension (headache, vomiting, drowsiness, sluggishness) due to the meningioma’s compression of the structures in which the cerebrospinal fluid flows causing it to accumulate (hydrocephalus).

Meningiomas generally grow at a slow pace and do not infiltrate the neural structures. For this reason, they can reach a rather considerable size before becoming symptomatic

Diagnosis

A radiological diagnosis of meningioma can be obtained by means of contrast-enhanced brain CT and MRI. These tests make it possible to identify the morphological characteristics of the lesions, which appear as rounded shapes with a regular outline.

The brain MR study can furthermore define the relationship between the tumor and the adjacent neural structures.

Treatment

The treatment of meningiomas is microsurgical removal, which, in the majority of cases, can be total and lead to full recovery.

In cases in which the tumor cannot be entirely removed due to its proximity to delicate vascular and neural structures, the patient can later be subjected to radiosurgery, which can arrest tumor growth.

In cases of anaplastic meningioma post-surgical radiotherapy is advisable.

Depending on where the meningiomas are located, they are classified as one of the following: posterior fossa meningiomas (1), convexity meningiomas (2), skull base meningiomas (3).

The picture shows a convexity meningioma: the tumor arises from the meninges that cover the brain

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