What is Brain Disease?

There are many different brain diseases, disorders, and injuries that can affect your day-to-day life and neurological function. Read this article to learn about common conditions in Australia, different types of brain disease, risk factors, and when to see a doctor.

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Medically reviewed by Professor David Burke AC. Last updated August 9, 2022.

What is brain disease?

The human brain is the centre of the body’s nervous system and the locus of your cognition. It is responsible for everything that you do, feel, and perceive. So when this system is damaged by brain disease, disorder, or injury, it can affect many aspects of your daily life.

Graphic with possible symptoms of brain disease (personality, motor function, senses, cognition, organ function, memory)

There are many causes of neurological conditions. For example:

There is no one answer to the question ‘what is brain disease’ because many different conditions can affect the brain, and different conditions vary greatly in symptoms, severity, diagnosis and treatment. There are over 600 diseases that can affect the nervous system

Keep reading to learn about some of the most common types of brain disease, risk factors, and when to see a doctor.

Common brain diseases

The most common brain diseases and disorders in Australia include:

  1. Migraine & tension-type headache (4.5 and 7.9 million people respectively)
  2. Stroke (387,000 people)
  3. Alzheimer’s disease and other dementias (250,000 people)
  4. Epilepsy (151,000 people)
  5. Parkinson’s disease (110,000 people)
  6. Cerebral palsy (34,000 people)
  7. Multiple sclerosis (25,600 people)

Sources: Mindgardens Neuroscience Network (2019 report); Australian Institute of Health and Welfare (2022 report; 2018 report), Parkinsons ACT (2018 estimate), MS Research Australia (2017 report), Cerebral Palsy Alliance (updated 2015). 

Traumatic brain injury and concussion are also very common but statistics are less concrete. Many people will make a full recovery in 3-6 months. However, many others will not seek medical attention after a head injury. A spokesperson from Brain Injury Australia said that “more than 3,000 people are hospitalised [each year] after being concussed, just from playing sport … but triple that number won’t seek medical attention”.

Estimating the prevalence of any neurological condition can be difficult, but at the end of the day the prevalence is not what’s important. No matter how rare a condition may be, it will have a profound impact on any person living with it, as well as their loved ones. Rare diseases can also be extremely isolating to live with because it is harder to connect with other patients suffering from the same disorder.

What is brain disease - generic prevalence image

There is often also less research into rare conditions and fewer treatments available. This is why the Brain Foundation accepts research grant applications for any neurological disease, disorder, or injury. We want to provide much-needed opportunities for any projects that might not have access to widespread funding sources. You can read more about our funding process here >

Types of brain disease

In addition to the most common neurological conditions, there are hundreds of others that can affect people. Rather than describing each one, it can help to understand the broad categories used to classify these conditions.

There are a few different ways that neurologists classify brain disease, and sometimes there is overlap between the categories. The table below uses the categories as defined by the Brain Foundation Scientific Committee.

CategoryWhat is it?Examples
Neurodegenerative diseaseNeurodegenerative disease is a broad category including any condition in which neurons lose function and eventually die. This category encompasses movement disorders (such as Parkinson’s disease), neuromuscular disorders, and most types of dementia. The clinical presentation depends on which neurons are first affected, e.g., motor neurons in motor neurone disease; neurons in the “substantia nigra” in Parkinson’s disease.Motor neurone disease
Amyotrophic lateral sclerosis
DementiasNeurodegenerative diseases affecting higher cortical function and causing the loss of cognitive function to the point that it interferes with daily life. It affects skills such as memory, problem-solving, language, and other thinking abilities.Alzheimer’s disease
Fronto-temporal dementia
Lewy body disease
Movement disordersBrain disorders that impair your ability to move in some way. A movement disorder could impair your voluntary movements (hypermobility, reduced, or slowed movement) or cause involuntary movements.Parkinson’s disease
Huntington’s disease
Neuromuscular disordersDisorders that affect your muscles, the nerves that control them, and communication between your nerves and muscles. Symptoms vary depending on the severity of the disease but can range from numbness (with involvement of sensory nerve fibre) to muscle weakness and wasting (with involvement of motor nerve fibres or muscle).Muscular dystrophies
Peripheral neuropathy
Charcot-Marie-Tooth disorder
Brain tumoursBrain tumours may involve growths of brain tissue or secondary deposits that have spread to the brain from cancer elsewhere in the body. Primary brain tumours may be benign, as in a meningioma and acoustic neuroma, or malignant as in many forms of glioma). There are many types of brain tumours which vary in cause and severity. Gliomas
Acoustic Neuroma
Cerebrovascular diseaseConditions that affect blood flow or the blood vessels in your brain. These diseases can cause clots or ruptured blood vessels, which can result in brain damage or stroke.Stroke
Arteriovenous malformations (AVM)
Concussion & traumatic brain injury (TBI)Injury caused by external forces, such as falls, car crashes, sports injuries, or domestic violence incidents. TBIs vary in severity from concussion (‘bruising’ of the brain) to bleeding in the brain or coma.Concussion
Traumatic Brain Injury
EpilepsyA long-term neurological disorder in which groups of neurons become spontaneously active, leading to seizures or ‘fits’. A seizure can affect your consciousness and can cause convulsions or involuntary movements.Epilepsy
Migraine & headache disordersHeadache can be a symptom of an underlying medical condition, but headache disorders (or primary headache) more commonly occur without a significant underlying abnormality of the brain. Some headache disorders can significantly impact a person’s quality of life.Migraine
Tension-type headache
Cluster headache
InfectionsNeurological infections occur when viruses or bacteria get into your brain or spinal cord. Meningitis is the infection of the outer covering of your brain and spinal cord, and encephalitis is the infection of the brain itself.Meningitis
Inflammatory diseasesNeuroinflammatory diseases happen when the immune system misfires and attacks healthy cells. This can occur in various parts of the central nervous system, including the brain, spinal cord, optic nerves (e.g., MS, transverse myelitis), peripheral nerve (Guillain-Barré syndrome), and neuromuscular junction (e.g., myasthenia gravis).Multiple Sclerosis
Transverse Myelitis
Guillain-Barré syndrome
Paediatric neurologyPaediatric neurology is the study of brain diseases, disorders, and injuries in children and adolescents. These conditions could also fall into other categories, but the causes, symptoms and treatments are often different for children.Cerebral palsy

You can find a more detailed article about these categories here >

Risk factors

Brain diseases, disorders and injuries can affect anyone. Many conditions are idiopathic, which means they have no known cause. However, there are some risk factors for specific conditions. 

  • Genetics. The presence of certain genes or genetic mutations can increase the risk of many brain diseases. Sometimes these mutations occur spontaneously and in other cases they are passed on through families. Researchers have identified genes that are linked to brain tumours, neurodegenerative disorders, neurodevelopmental disorders, and epilepsy. Headache disorders are also highly hereditary – if one person in a family has migraine, it is more likely for other family members to have it as well.
  • Environmental toxins & radiation. Long-term exposure to toxic chemicals (e.g. certain pesticides) or radiation can increase the risk of certain brain diseases. Chemicals have been linked to dementias & other neurodegenerative diseases, brain tumours, and multiple sclerosis, to name a few.
  • Infections. Some bacteria, viruses, or fungal infections can spread to the brain and cause meningitis or encephalitis.
  • Injuries. Repeated traumatic brain injuries can increase your risk of developing epilepsy and chronic traumatic encephalopathy (which is often studied in contact sports players).
  • Unhealthy lifestyle choices. Smoking, lack of exercise, poor diet, and alcohol use are linked to dementia and stroke.

Even though many neurological conditions have no clear cause, research will hopefully change this. Researchers are actively investigating specific conditions & how the brain works in general to improve our understanding of what causes brain disease. This could uncover preventive strategies, new treatments, or even cures in the future.

Brain disease researcher photo

When to see a doctor

It is important to seek medical help as soon as possible for many brain diseases, disorders, and injuries. Certain conditions can be slowed or prevented with early diagnosis and treatment. For example, if an unruptured aneurysm is detected, a surgeon could remove it thereby preventing a stroke.

If you are experiencing symptoms of a stroke you should call 000 for emergency medical help immediately. Stroke symptoms usually come on suddenly, and they include:

  • Altered speech, slurring, or difficulty understanding others
  • Weakness in one side of the body (mouth drooping, unable to lift both arms)
  • Loss of vision in one eye, loss of vision in half the visual field of each eye, or double vision
  • Sudden, severe headache with no known cause
  • Sudden dizziness or loss of balance
  • Drowsiness or loss of consciousness.

You should also see your general practitioner if you experience any unusual changes in your:

  • Mood, behaviour or personality
  • Cognition (e.g. memory, ability to focus, problem solving)
  • Physical function (e.g. balance, coordination, walking, limb movement)
  • Speech
  • Vision

They may be able to diagnose and treat you through their practice or they might refer you to a neurologist or other specialist.

Further information & resources

If you want to learn more about brain disorders, diseases, and injuries, you can view the following resources:

Support for people living with brain disorders, diseases or injuries:

If you found this article helpful, please consider donating to support Australian neurological research. Your donation, no matter how small, is greatly appreciated and will help so many. Donate today >

Brain FoundationThe Brain Foundation is the largest, independent funder of brain and spinal injury research in Australia. We believe research is the pathway to recovery.