Glioma

What is glioma?

Glioma is a type of brain tumour that occurs in glial cells, which support nerve cells (neurons) in the brain. These tumours mostly develop in the largest regions of the brain (cerebral hemispheres) responsible for functions such as cognition, emotion, movement and speech. However, gliomas can also occur in other brain areas, including:

• Brain Stem: The lower part of the brain that regulates breathing, blood pressure, and heart rate.
• Optic Nerves: The nerve at the back of each eye which connects to the brain, and helps one see.
• Cerebellum: The back part of the brain that controls balance and other motor functions.

Symptoms will differ depending on the brain area affected.

Gliomas are cancerous (malignant) and can be graded based on the type of glial cells affected and their aggressiveness. Knowing the grade of a glioma helps determine the type of treatment and progression of the tumour.

Types of Gliomas

Gliomas can be graded into three primary types based on the origin and function of the tumour cells. In general, the higher the grade, the more aggressive the tumour:

Astrocytoma

Astrocytomas develop from star-shaped glial cells called astrocytes and are categorised into four grades:

• Grade I (Pilocytic Astrocytomas): These slow-growing tumours have well-defined borders and are typically found in younger individuals.
• Grade II (Low-grade or Diffuse Astrocytomas): These slow-growing tumours have less defined borders and are commonly diagnosed in adults aged 20 to 50 years.
• Grade III (Anaplastic Astrocytomas): Representing about 2% of brain tumours, these tumours grow rapidly and aggressively.
• Grade IV (Glioblastomas): The most aggressive type, comprising 12-15% of adult brain tumours. They have a five-year survival rate of approximately 4%.

Ependymomas

Ependymomas originate from ependymal cells that line the brain ventricles and spinal cord canal. They are less common in adults and account for 2-3% of primary brain tumours. Ependymomas are graded as follows:

• Grade I: (Subependymomas and Myxopapillary Ependymomas). These tumours are typically slow-growing.
• Grade II (Ependymomas): The most common type of tumour, with moderate growth rates.
  
• Grade III (Anaplastic Ependymomas): These tumours are more aggressive and grow rapidly.

Oligodendrogliomas

Oligodendrogliomas arise from oligodendrocytes, cells that produce the layer covering nerve cells (myelin sheath). They are divided into:

• Grade II (Low-grade Oligodendrogliomas): These tumours grow slowly and are less aggressive.
• Grade III (Anaplastic Oligodendrogliomas): These tumours are more aggressive.
  

Knowing the grade of a glioma helps determine the type of treatment and progression of the tumour.