Anatomy & Tumour types
Let’s deal with brain anatomy first. brainstrust asked Paul Grundy, a consultant neurosurgeon and our Patron, for his take on how the brain is structured and what the consequences would be if damage happened. It is the most complex organ and is the organ about which we know the least. Heart surgery? It’s not rocket science. Brain surgery, on the other hand, is – to the lay person. This page is to help you have a better understanding of how the brain is structured.
Basic brain anatomy
The brain is a complex structure. It contains millions of nerve cells (neurones) and their processes (axons and dendrites) in a highly organised manner. These are supported by many other cell types (astrocytes, oligodendrocytes, etc). The brain is divided into several regions that have different functions: the cerebrum is the largest area and is the source of conscious activity. It is divided into 2 cerebral hemispheres. The cerebellum is situated beneath the cerebral hemispheres and is connected to the brainstem, which in turn runs into the spinal cord.
The left and right cerebral hemispheres control functions for the opposite side of the body. In addition, certain important functions (particularly speech and language) are located in only one hemisphere, called the dominant hemisphere. In right-handed patients this is virtually always the left hemisphere and in left-handed patients it may be either hemisphere (but is still often the left).
Each hemisphere is divided into 4 principal lobes (see the diagram) and a hidden small lobe called the insula. The surface of the brain is folded with each crest being termed a gyrus and each groove between them a sulcus. The central sulcus separates the frontal from the parietal lobe and on each side of this sulcus lie the pre-central gyrus (in front) and the post-central gyrus (behind). The pre-central gyrus (motor cortex) is responsible for movement on the opposite side of the body and the post-central gyrus (sensory cortex) is responsible for sensations.
Brainstem All nerve fibres connecting the cerebral hemispheres with the cerebellum and spinal cord pass through the brainstem, controlling all functions in the limbs and body. There are also collections of neurones (nuclei) in the brainstem that control many functions in the head and neck, particularly eye movements, facial sensation and movement, swallowing and coughing. Areas within the brainstem also control consciousness, breathing, heart rate and blood pressure. So it’s an important area!
As these vital nerves all lie very close together in the brainstem, even a small area of damage might produce multiple severe deficits.
Here is a description of what we know about the functions of different parts of the brain. However it’s important to understand that each lobe of the brain does not function alone. There are very complex relationships between the lobes of the brain and between the right and left hemispheres. But this does give you further indication of what might be affected by the position of a brain tumour:
- Personality, behaviour, emotions
- Judgment, planning, problem solving
- Motivation, initiation
- Speech: speaking and writing (Broca’s area)
- Body movement (motor strip)
- Intelligence, concentration, self-awareness
- Interprets language, words
- Sense of touch, pain, temperature (sensory strip)
- Interprets signals from vision, hearing, motor, sensory and memory
- Spatial and visual perception
- Interprets vision (colour, light, movement)
- Understanding language (Wernicke’s area)
- Sequencing and organisation
Messages within the brain are carried along pathways. Messages can travel from one gyrus to another, from one lobe to another, from one side of the brain to the other, and to structures found deep in the brain (e.g. thalamus, hypothalamus).
Other brain words you might hear include:
Cranium – just a more interesting word for skull
Skull base – the bones at the bottom of the skull
Blood brain barrier – the mechanism by which the blood vessels of the brain prevent substances in the blood (such as bacteria) from reaching the brain. This is good, but can also work against the patient if vital anticancer drugs need to pass through this.
Glia – most of the brain tissue is composed of glial cells. Most brain tumours originate from glial cells.
And if you have some brain words to add please get in touch! or for more words visit our glossary.
Brain tumour types
Basic question – what is a brain tumour?
A brain tumour is a mass of abnormal cells growing in the brain. The cells can come from the brain itself or from its lining (primary brain tumours) or from other places in the body (secondary or metastatic brain tumours). Primary brain tumours can be benign or malignant. Secondary brain tumours are always malignant.
Size doesn’t matter… this is true. The size of a brain tumour doesn’t matter nearly so much as where it is located. A large, benign tumour may be easily accessible and therefore easy to remove. Or you can have a pea –sized tumour that is critically placed, and so makes treatment very difficult. However, treatments options are developing all the time and one size doesn’t fit all. Some small tumours, in tricky locations, may be treated by radiosurgery and some large, diffuse tumours crossing the midline of the brain can be difficult to treat with radiation. So each case needs to be reviewed, discussed and options explored. It’s complex!
What causes a brain tumour?
No one knows. If we did, then we would be able to treat them more effectively, or even prevent them occurring at all. Some genetic disorders may mean that some people are predisposed to getting a brain tumour and there is suggestion that some environmental factors may increase our risk. We do know that the incidence of brain tumours is increasing by about 2% a year – and this isn’t down to better diagnostic weaponry.
Classification and grading of brain tumours
All tumours in the brain can pose a threat to health. Benign tumours grow slowly and do not invade tissue, but they may put pressure on areas of the brain and cause problems. Malignant primary brain tumours spread into the healthy tissue and tend to grow more quickly than benign tumours. The World Health Organisation has developed a classification system for brain tumours. Knowing the classification and grade of an individual tumour helps to predict its likely behaviour.
Grading brain tumours
Grade I (low-grade) — the tumour grows slowly, has cells that look a lot like normal cells, and rarely spreads into nearby tissues. It may be possible to remove (resect) the entire tumour by surgery, but tumours in the brain stem cannot be completely resected safely.
Grade II — the tumour grows slowly, but may spread into nearby tissue and may recur (come back). Some tumours may become a higher-grade tumour.
Grade III — the tumour grows quickly, is likely to spread into nearby tissue, and the tumour cells look very different from normal cells.
Grade IV (high-grade) — the tumour grows and spreads very quickly and the cells do not look like normal cells. There may be areas of dead cells in the tumour. Grade IV brain tumours are harder to manage than lower-grade tumours. High- grade tumours can be difficult to treat.
Depending on their make up, tumours can be a mix of grades, so they will be defined by the highest grade.
Primary brain tumours are named according to the type of cells or the part of the brain in which they begin.
Generally benign tumours
The term ‘generally’ is key here. Sometimes brain tumours are classified as benign but in some cases they can recur. This is true of meningiomas. There are other implications too. For example, patients with craniopharyngiomas can go on to have hormonal deficits and need life time supplements. Patients with haemangioblastomas who have VHL syndrome are at risk of developing renal cancer.
Malignant tumours and tumours with uncertain behaviour
Hover your mouse over the name to find out more
Germ cell tumour
Want to see this information on video?
This really useful video explains more about this information, courtesy of Cancer Council, New South Wales. It covers:
- What is cancer
- What are the different parts of the brain
- What is a brain tumour
- What’s the difference between benign and malignant
- What are the different types of brain cells
- What are the different types of grades
Resources used in creating this page:
The 2007 Revised World Health Organization (WHO) Classification of Tumours of the Central Nervous System: Newly Codified Entities Gregory N. Fuller, Bernd W. Scheithauer
Article first published online: 26 JUN 2007 DOI: 10.1111/j.1750-3639.2007.00084.x
Living with a Brain Tumour (Peter Black) 2006
Adult brain tumors (2014) available at: http://www.cancer.gov/cancertopics/pdq/treatment/adultbrain/HealthProfessional
Cancer of the Brain and Brain Tumours (2012) available at: http://www.patient.co.uk/health/cancer-of-the-brain-and-brain-tumours
Benign Brain Tumour, NHS Choices (2013), available at: http://www.nhs.uk/conditions/Brain-tumour/Pages/Introduction.aspx
Malignant Brain Tumour, NHS Choices (2013), available at: http://www.nhs.uk/Conditions/brain-tumour-malignant/Pages/Introduction.aspx
Navigating Life with a Brain Tumour, L. Taylor, F. Alyx B. Porter, D. Richard (2013)
Date published: 17-05-2009
Last edited: 12-08-2015
Due for review: 30-09-2016