All About Glioblastoma
By: Sahasra Pokkunuri
Tags: Brain, Glioblastoma, Cancer

(Image by Getty Images)

A splitting headache that continues non-stop. A weakness in the muscles and being unable to walk a small distance. Feeling abnormally sleepy at random periods of the day.

For many individuals with glioblastoma (a type of brain tumor), these symptoms were generally dismissed as the body feeling generally unwell. Even when non-cancer patients think of these symptoms, a condition as deadly as glioma would not be the first thing to come to mind. Unfortunately, these subtle symptoms can transform into a rapidly-progressing disease with minimal chance of survival.

52% of all primary brain tumors are glioblastoma, and 17% of all tumors in the brain are a glioblastoma (whether the tumor is primary or metastatic doesn’t matter). Despite the tumor more commonly occurring in individuals between ages 45–70, the median survival rate for brain cancers is around age 64, which is devastating. GBM is evidently becoming a larger problem, and research is imperative to reduce the progression of this disease.

As scary as this sounds, recent breakthroughs are beginning to change the way we look at glioblastoma. Interested to learn more? Let’s take a look at this seemingly deadly cancer and recent studies about it.

A Brief Introduction to the Brain

To understand the nature of glioblastoma, we require a general understanding of the different regions in the brain. Despite the brain being known for being overly complex, the two most important sections to note are the cerebrum and the cerebellum.

A general diagram of the brain (Image by Colorbox).

Cerebrum

The cerebrum refers to the anterior part of the brain that’s located towards the front of the skull, and is much larger compared to the cerebellum. The cerebrum can be divided into many subsections with varied function, but the purpose of the cerebrum includes recognizing external surroundings, problem-solving, and coordinating movement.

With regards to a brain tumor, most cases (regardless of whether it’s benign or malignant) will occur in the cerebrum. Tumors in the cerebrum are also referred to as supratentorial since they are present above the tentorium, which is a fissure that divides the cerebrum from the cerebellum. The cerebrum also contains ventricles with cerebrospinal fluid, which is responsible for protecting the brain while providing bouyancy.

The sections of the cerebrum (Image by Depositphotos).

Cerebellum

While the cerebrum is above the tentorial line, the cerebellum is below this fissure and also neighbors the brain stem. While the cerebrum is split into several sections, the cerebellum has two important subsets to note: the cerebellar cortex and cerebellar nuclei.

The cerebellar cortex consists of three layers:

The outermost layer is made of the axons and dendrites of cerebellar neurons, indicating it contains a majority of the cerebellum’s neurons.

The middle layer contains Purkinje cells , which are a type of flask-shaped neuron native to the cerebellum. The primary function of these cells is the emission of GABA ( gamma-aminobutyric acid ), a neurotransmitter that regulates nerve impulses throughout the brain and controls motor function.

, which are a type of flask-shaped neuron native to the cerebellum. The primary function of these cells is the emission of ( ), a neurotransmitter that regulates nerve impulses throughout the brain and controls motor function. The innermost layer has granular cells, which are the smallest type of neuron in the brain. These cells send impulses to the Purkinje cells in the cerebellum, which move into the outermost molecular layer throughout the cerebellar cortex. These granule-cell — Purkinje-cell synapses are super important for the brain, and they use glutamate as a neurotransmitter.

On the other hand, the cerebellar nuclei is the innermost section of white matter of the cerebellum. This subsection will receive inhibitory signals from Purkinje cells (usually from the cerebellar cortex) and is responsible for communicating such signals throughout the brain. Within this inner white matter, the four types of deep cerebellar nuclei are:

Dentate

Emboliform

Globase

Fastigii

Tumors are rarely found in the cerebellum, but these infratentorial tumors (since the cerebellum is below the tentorium) can also be located in the brain stem and other neighboring structures.

A more complex diagram of the brain (Image by diagramchartspedia.com).

Where and How Glioblastoma Starts

Now that we have a general understanding of the brain’s anatomy, let’s look at the nature of a glioblastoma. More often than not, GBMs are supratentorial tumors and are also a type of astrocytoma, which is a brain tumor originating from astrocyte cells in the brain.

In the central nervous system (CNS), astrocytes are a type of glial cell that perform a number of functions throughout the brain and spinal cord. Some of their key purposes are supporting synapses (which relay electrical signals between neurons), controlling the blood-brain barrier, and regulating blood flow throughout the brain. Depending on the type of astrocyte, they will either be located throughout the CNS or primarily in white matter, a characteristic of more fibrous glia.

An image of an astrocyte (Image by iStock).

Though astrocytes are the primary cause of glioblastoma, the reason behind their sudden abnormality remains a mystery. Scientists have discovered that a number of mutations within astrocytes have likely caused the development of cancerous cells in the brain, but the cause of these mutations isn’t well-known either.