Gliomas are primary brain tumors of the Central Nervous System originating from neuroglial stem cells or progenitor cells. They are rare, with an annual incidence of approximately 6 cases per 100,000 individuals worldwide. Men are 1.6 times more likely to be diagnosed with gliomas than women.
The evolution of neurologic symptoms and signs related to tumors allows estimating the growth dynamics of gliomas: tumors that cause symptoms only weeks before diagnosis usually grow fast, while those that cause symptoms years before being diagnosed usually grow slower.
Types of glioma
Based on their histological appearance, gliomas are divided into the following subtypes: astrocytomas, ependiomas, and oligodendrogliomas. Understand them.
Astrocytomas are the most common gliomas and, based on the presence of specific genetic markers, are organized as follows according to the WHO (World Health Organization) classification, which indicates different degrees of malignancy from I to IV:
- Grade 1: pilocytic astrocytomas;
- Grade II: low-grade astrocytomas;
- Grade III: anaplastic astrocytomas (and anaplastic oligoastrocytomas);
- Grade IV: glioblastomas and diffuse midline gliomas.
Ependymomas represent 3% to 5% of brain gliomas in adults, while in children they represent the third most common brain tumor, corresponding to 10% to 12% of all pediatric brain tumors. Although 50% to 60% of ependymomas in adults are located in the spinal cord, only 20% are found there in children. Most tumors occur sporadically, but some cases may be associated with Neurofibromatosis type 2.
According to the WHO classification, they are organized as follows:
- Grade I: subependymoma;
- Grade II: ependymoma;
- Grade III: anaplastic ependymoma;
- Grade IV: ependymoblastoma (which is rare and occurs mainly in infants).
Oligodendrogliomas are tumors that infiltrate the brain in a diffuse way. They have slower growth and are more common in the forebrain, especially in the frontal lobes. In the WHO classification, they are located in grade II. If they evolve into more aggressive forms, such as anaplastic oligodendroma, they go to grade III in this classification.
In most individuals, glioma symptoms are non-specific, meaning they are common to other illnesses and health conditions – such as fatigue or a headache.
Symptoms more directly related to the clinical presentation of this group of tumors may include:
- New onset of seizures;
- Focal deficits, such as loss of movement of arms or legs;
- Neurocognitive impairment (such as memory changes);
- Headache, nausea and/or vomiting (caused by increased intracranial pressure).
At the patient’s first visit, in addition to evaluating disease-related signs and symptoms, adequate history taking may reveal familial risk and/or rare exogenous risk factors (such as previous exposure to radiation therapy) associated with the development of brain tumors.
After medical consultation, with a detailed physical and neurological examination, some imaging tests may be requested, such as computed tomography and magnetic resonance imaging.
The diagnosis of glioma is closed after biopsy or surgery, when a sample of tumor tissue is obtained for proper evaluation by a neuropathologist.
Treatment of a brain tumor depends on its nature, how quickly it grows, symptoms, and location. Often, several approaches are used. The potential benefits and risks of different treatment options are also taken into account. In the case of gliomas, the following can be used:
- Surgery – most common initial treatment for gliomas. It requires a craniotomy (opening of the skull). The purpose of surgery is diagnostic and therapeutic, aiming at the best possible surgical resection, which does not leave permanent sequelae to the patient;
- Radiotherapy – usually used as a complement to surgery, depending on the age of the patient, the type of tumor and its location. It can be performed alone or combined with chemotherapy;
- Chemotherapy – can be used as a complement to surgery and radiotherapy, depending on the histological type of the tumor, age of the patient, molecular characteristics present in the tumor, degree of surgical resection and in cases of recurrent disease.
There are no related causes or well-established and preventable risk factors for the emergence of these types of tumors. Therefore, it is currently not possible to prevent or avoid gliomas.