Brain Gliomas

Tumori Cerebrali

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Definition and Etiology

Gliomas are brain tumors that originate from the glial cells, which provide support and trophism for neurons.

Glial cells can be distinguished as follows:

astrocytes: they protect the neuronal structure
oligodendrocytes: they produce myelin which surrounds the axons (neuronal structures that ensure connectivity between the neurons themselves)
ependymal cells: they cover the ventricles where the cerebrospinal fluid is contained

Histological benignity or malignancy depend on the degree of differentiation of the cells: they can be well differentiated (i.e. similar to the healthy tissue) and therefore benign, or more undifferentiated (i.e. presenting more alterations compared to the normal brain tissue) and therefore more malignant (also called anaplastic).

Grade I is well differentiated and therefore presents characteristics of benignity.
Grade II presents areas of undifferentiation which have not yet resulted in anaplasia.
Grade III presents important anaplastic tissue alterations.
Grade IV is an undifferentiated tumor with characteristics of absolute malignity.

PILOCYTIC ASTROCYTOMA (WHO GRADE I)

The pilocytic astrocytoma is a very frequent tumor in children and represents about 10% of all gliomas.

The most frequent site for its development is the cerebellum, but it can also affect the hypothalamus and the optic chiasm.

LOW-GRADE EPENDYMOMA (WHO GRADE II)

The low-grade ependymoma is also a tumor typical of the paediatric age.

It originates from the ependymal cells that cover the ventricular brain cavities. In particular, it develops in the ependymal of the IV ventricle, in the posterior cranial fossa, but can also emerge in the lateral ventricles.

LOW-GRADE GLIOMAS (WHO GRADE II)

Low-grade gliomas can be divided into:

Astrocytomas: tumors originating in the astrocytes
Oligodendrogliomas: tumors originating in the oligodendrocytes
Oligoastrocytoma: tumors constituted by a mixed form of pathological astrocytes and oligodendrocytes

These are tumors that primarily affect young adults.

ANAPLASTIC GLIOMAS (WHO GRADE III)

Anaplastic gliomas can be divided into:

Anaplastic astrocytomas
Anaplastic oligodendrogliomas
Anaplastic oligoastrocytomas
Anaplastic ependymomas

These tumors can arise as a consequence of the malignant transformation of a low-grade glioma or they can directly appear.

They usually affect middle-aged subjects and are more frequent in the male gender.

GLIOBLASTOMA MULTIFORME (WHO GRADE IV)

The glioblastoma multiforme is by far the most aggressive brain tumor and one of the most lethal tumors in general.

It generally affects subjects in their 60s, but can appear at any age.

Symptoms

PILOCYTIC ASTROCYTOMA (WHO GRADE I)

Since it is a slow-growing tumor, the symptoms can be silent for long periods of time.

When they do occur, they are related to the fact that the tumor is frequently located in the posterior cranial fossa, and include balance disorders and disfunctions in motor coordination, symptoms related to hydrocephalus caused by the tumor’s obstruction of the regular flow of cerebrospinal fluid.

Also, visual dysfunctions may occur.

LOW-GRADE EPENDYMOMA (WHO GRADE II)

Precisely because it is often located inside the IV ventricle, the symptoms are related both to the direct compression of the cerebellar structures (balance and motor coordination disorders) and to the emergence of hydrocephalus due to the obstruction of the of cerebrospinal fluid flow.

LOW-GRADE GLIOMAS (WHO GRADE II)

The symptoms depend on the site where the tumor is located; they often begin with a seizure.

The symptoms may be:

headache
nausea and vomiting
language disorders
visual impairment
balance disorders

ANAPLASTIC GLIOMAS (WHO GRADE III)

Also in this case the symptoms depend on the tumor location and are:

headache
nausea and vomiting
language disorders
visual impairment
balance disorders
seizures

GLIOBLASTOMA MULTIFORME (WHO GRADE IV)

The glioblastoma is a fast-growing tumor, therefore often the symptoms are connected to the increase in intracranial pressure caused by the mass effect of the neoplasm. There can be symptoms like headache, nausea, cognitive-motor slowing, and may go as far as compromising the state of consciousness.

Also in this case, the symptoms depend on the tumor location and are:

language disorders
visual impairment
balance disorders
personality change
memory loss
seizures

Diagnosis

PILOCYTIC ASTROCYTOMA (WHO GRADE I)

The brain MRI will reveal a lesion with a regular outline, formed by a solid lump absorbing contrast medium, which may or may not have calcifications within it, surrounded by a cystic component which, on the other hand, does not absorb contrast medium.

LOW-GRADE EPENDYMOMA (WHO GRADE II)

Brain MRI can reveal the presence of an irregular endoventricular lesion with a cystic-necrotic-haemorrhagic content and calcifications.

A final diagnosis is obtained with a histological examination.

LOW-GRADE GLIOMAS (WHO GRADE II)

Radiological diagnosis is obtained with brain CT and MRI, which reveal non contrast-enhanced lesions, with an irregular and undefined outline and a modest perilesional edema.

Typical of oligodendrogliomas is the presence of calcifications within the lesion.

ANAPLASTIC GLIOMAS (WHO GRADE III)

A radiological diagnosis can be obtained by means of brain CT and MRI, which reveal solid lesions with a blurred outline that intensely absorb contrast medium, with fair perilesional edema.

GLIOBLASTOMA MULTIFORME (WHO GRADE IV)

Radiological diagnosis is obtained by means of brain CT and MR, which reveal uneven lesions with a cystic and necrotic content. These lesions intensely absorb contrast medium, with important perilesional edema, which is responsible for the mass effect on the surrounding structures.

Treatment

PILOCYTIC ASTROCYTOMA (WHO GRADE I)

In general, treatment is limited to surgical removal, which, if completely performed, can lead to total recovery in 95% of all cases.

LOW-GRADE EPENDYMOMA (WHO GRADE II)

Also in this case, surgical operation in most cases makes it possible to remove entirely the lesion with consequent full recovery.

When this should not be possible because the tumor has violated important adjacent structures, radiotherapy is employed in case of relapse.

LOW-GRADE GLIOMAS (WHO GRADE II)

Treatment is micro-surgical excision. It is important that the removal of the tumor be as wide as possible while still preserving the integrity of the surrounding areas of the brain.

Although they are slow-growing tumors, low-grade gliomas tend to recur even after surgical removal. Therefore, several brain MRIs over a period of time shall be necessary to reveal any relapse as early as possible.

In some cases, chemotherapy and radiotherapy are useful.

The prognosis for low-grade gliomas, in view of a complete treatment, is of about 7-10 years.

ANAPLASTIC GLIOMAS (WHO GRADE III)

Treatment is microsurgical. Also in this case, it is important perform an excision of the tumor as wide as possible, while still preserving the integrity of the surrounding areas of the brain.

Whenever it is not possible to remove the lesion due to the critical location of the tumor or due to the patient’s clinical condition, it is advisable to perform a biopsy of the tumor tissue in order to make a histological diagnosis and, if necessary, carry out the adjuvant therapies.

Surgery may be followed by chemotherapy, which has proven to be particularly effective in anaplastic oligodendrogliomas.

Anaplastic gliomas are very aggressive tumors and the prognosis, after appropriate treatment, is of about 3 years.

GLIOBLASTOMA MULTIFORME (WHO GRADE IV)

The glioblastoma multiforme requires an aggressive multidisciplinary treatment.

Treatment is microsurgical excision. Also in this case, it is important to perform a wide excision of the tumor while still preserving the integrity of the surrounding areas of the brain.

Following surgery, both radiotherapy and chemotherapy (temozolamide) should be applied.

The average time for the appearance of a recurrence is about 5-6 months. When the lesion recurs in a location that is surgically accessible, a second surgical operation may be performed.

The prognosis is unfavourable, with an average survival, after appropriate treatment, of about 16 months.

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