Glioma

What glial cells are

Glial cells surround and support nerve cells. The main types are astrocytes, oligodendrocytes (which make the myelin insulation around nerves) and ependymal cells (which line the brain's fluid spaces). Gliomas are named after the cell type they most resemble.

Types and grades of glioma

Since 2021, the World Health Organization classifies gliomas using both their appearance under the microscope and their molecular markers, which predict behavior and response to treatment.

"Low-grade" usually refers to grades 1 and 2, and "high-grade" to grades 3 and 4.

Symptoms

Symptoms depend on the tumor's location, size and speed of growth.

• Seizures: the first symptom in many low-grade gliomas
• Headaches: often worse in the morning or with coughing or bending, sometimes with nausea and vomiting, from raised pressure inside the skull
• Personality, mood or behavior changes, especially frontal lobe tumors
• Memory, concentration and thinking problems
• Weakness or numbness on one side of the body
• Speech and language difficulties
• Vision changes, including loss of part of the visual field
• Balance and coordination problems, with tumors in the cerebellum
• Fatigue and drowsiness

Causes and risk factors

The cause of most gliomas is unknown. Known risk factors include:

• previous radiation to the head, such as childhood radiotherapy
• inherited syndromes: neurofibromatosis type 1, Li-Fraumeni syndrome, Lynch syndrome, tuberous sclerosis
• age: glioblastoma becomes more common with age
• sex: slightly more common in men

There is no consistent evidence that mobile phones, head injury or diet cause gliomas.

Diagnosis

• Neurological examination
• MRI of the brain with contrast, the main imaging test. Advanced MRI (perfusion, spectroscopy) helps assess grade and plan surgery
• Biopsy or surgical removal to confirm the diagnosis, grade and molecular markers: IDH mutation, 1p/19q codeletion, MGMT promoter methylation (which predicts response to temozolomide), and others
• Functional MRI and mapping before surgery near speech or movement areas

Treatment

Treatment is planned by a specialist neuro-oncology team and tailored to the tumor type, grade, markers, location and the person's health.

Surgery

The goal is maximal safe resection: removing as much tumor as possible without causing new deficits. Surgeons may use awake surgery and brain mapping for tumors near critical areas. Surgery also relieves pressure and provides tissue for diagnosis.

Radiation therapy

Usually given over several weeks after surgery for high-grade gliomas, and for many grade 2 tumors, sometimes delayed while the tumor is monitored.

Chemotherapy

• Temozolomide with and after radiation is standard for glioblastoma.
• PCV (procarbazine, lomustine, vincristine) or temozolomide for oligodendroglioma and IDH-mutant astrocytoma.

Targeted and other therapies

• Vorasidenib, an IDH inhibitor, for grade 2 IDH-mutant astrocytoma or oligodendroglioma after surgery, which can delay the need for radiation and chemotherapy
• BRAF and MEK inhibitors for tumors with BRAF changes
• Tumor treating fields: a wearable device delivering electric fields to the scalp, used with temozolomide for glioblastoma
• Bevacizumab for recurrent glioblastoma, mainly to reduce swelling
• Clinical trials of new drugs, vaccines and immunotherapies

Supportive care

• steroids such as dexamethasone to reduce brain swelling
• anti-seizure medicines
• rehabilitation, palliative care and psychological support from diagnosis onward

Outlook

Outlook varies greatly by type and grade:

• Pilocytic astrocytoma (grade 1): often cured by surgery.
• Oligodendroglioma: many people live 10 to 15 years or longer.
• IDH-mutant astrocytoma: median survival is often many years for grade 2 and less for grade 4.
• Glioblastoma: median survival is about 15 to 18 months with standard treatment, though some people live much longer, especially those with MGMT-methylated tumors.

Regular MRI scans monitor for recurrence. Many people continue working and living independently for long periods with low-grade gliomas.

Frequently asked questions

What is a glioma?

A glioma is a tumor that begins in the glial cells that support nerve cells in the brain or spinal cord. It is the most common type of primary brain tumor and ranges from slow-growing low-grade tumors to aggressive glioblastoma.

Is a glioma always cancer?

Gliomas are considered brain tumors that can be benign-behaving or malignant. Grade 1 tumors such as pilocytic astrocytoma are often curable. Most diffuse gliomas in adults, even low-grade ones, infiltrate the brain and eventually progress, so they are treated as cancers.

What are the first signs of a glioma?

Common early signs include a first seizure, new persistent headaches (often worse in the morning), personality or memory changes, weakness or numbness on one side, and speech or vision problems. Symptoms depend on where the tumor is.

What is the survival rate for glioma?

It depends on the type and grade. Grade 1 gliomas are often cured. People with oligodendroglioma frequently live more than 10 years. Glioblastoma has a median survival of about 15 to 18 months with treatment, though some people live much longer.

What causes gliomas?

Most have no known cause. Risk factors include previous radiation to the head and inherited conditions such as neurofibromatosis type 1 and Li-Fraumeni syndrome. Gliomas are not caused by head injuries, and evidence does not link them to mobile phone use.