What causes dementia?

Dementia is a neurodegenerative condition. These type of conditions cause damage to the nerve cells of the brain.  The condition affects people in different ways and each case is unique. The symptoms are dependent on the area of the brain that is affected.

The term 'degenerative' in the word neurodegenerative refers to the gradual decline in the functioning of the nerve cells (neurons) of the brain. As neurons become damaged they gradually stop functioning correctly and die. This has an impact on the connections between the nerve cells, known as synapses. The causes a disruption in the brain's communication network and the 'messages' that the brain sends to the rest of the body which tell it how to function. This disconnect often results in a number of dysfunctions.

There are several different types of dementia, the types are grouped by their similarities, such as their progressive traits or the part of the brain impacted. There are some dementias, for example, those that have been caused by an onset reaction to vitamin deficiencies or medications, that are occasionally reversible and improve ment occurs through treatment. Dementia is also often reversible in cases where the underlying cause is alcohol, drugs, hormonal, medication, depression or even due to hospitalisation (this may occur in the elderly). However, the condition is irreversible when the cause is that of trauma or a degenerative disease.

Progressive dementias

There are certain dementia types that are not reversible and progress over time, these include:

• Alzheimer’s disease – Alzheimer’s disease is known to be the most prevalent cause of dementia in those who are 65 years old or older. The exact cause of Alzheimer’s disease is still unknown, however, those who are diagnosed with the condition, have tangles and plaques found in their brain. These are accumulations of abnormal proteins known as amyloid plaques. The fibrous tangles are made of abnormal tau proteins which cause microtubules that facilitate the transport of vital chemicals and nutrients in the brain, to collapse, causing damage of the nerve cells. Alzheimer’s usually occurs in patients over the age of 65, although some cases may even develop in patients who are just 40 or 50 years old. The condition is also referred to as Alzheimer’s dementia.

• Vascular dementia – The second most well known cause or type of dementia is vascular dementia. It is the result of blood vessels supplying blood to the brain being damaged. Issues with the blood vessels can be the result of conditions related to blockages or damage to the blood vessels such as a stroke. Vascular dementia is often the case when a person has multiple strokes that go unnoticed as they do not show the typical symptoms of visions loss, numbness or weakness associated with a stroke. Patients who have heart disease or hypertension (high blood pressure) that is not treated, have a higher risk of developing vascular dementia.

• Lewy body dementia – Clumps of specific proteins in the brain that are abnormal are known as Lewy bodies, these are found in those who suffer from Lewy body dementia. These proteins accumulate inside the neurons in the brain. Memory issues and forgetfulness are signs of cognitive decline, these are some of the key features associated with this condition. Sufferers may also have intesnse hallucinations, these hallucinations will seem very realistic to the person experiencing them. In some cases, those suffering from Lewy body disease may also develop symptoms similar to those experienced in Parkinson’s disease, these symptoms will include slowed movement and/or tremors. Lewy body disease is a common form of progressive dementia.
• Frontotemporal dementia – There is a certain group of degenerative diseases that break down the nerve cells found in the temporal and frontal lobes of the brain, these areas are associated with the patient’s behaviour, personality and their language. Frontotemporal dementia is generally associated with shrinkage or pronounced atrophy of these lobes. Sufferers may experience forgetfulness as well as personality changes, poor judgment and even impulsivity. Some people with this form of dementia may even suffer from stiffness in their muscles or develop incoordination. The cause of frontotemporal dementia is still unknown.
• Mixed dementia -  Autopsies done on the brains of those who are 80 years old or older, who suffered from dementia, show that many of these people exhibited a combination Lewy body dementia, Alzheimer’s disease and vascular dementia. There are still ongoing studies being conducted to determine how suffering from mixed dementia affects the symptoms experienced as well as the treatment of the condition.

Other disorders that have been linked to dementia

• Huntington's disease – This is a condition that is the result of a genetic mutation and causes specific nerve cells in the spinal cord and brain to progressively degenerate. The signs and symptoms of Huntington’s disease include a severe decline in the sufferer's cognitive abilities, these symptoms typically show up around the ages of 30 and 40 years old.   
• Traumatic injury to the brain – This is a condition that is the result of repetitive head traumas. This type of injury is often sustained by football players, soldiers and boxers. The signs of dementia that are exhibited dependent on the area of the brain that is injured. Depression, memory loss, explosiveness, tremors, slow movement, and even rigidity (parkinsonism) have been known to develop. Symptoms may only appear years after the incident or brain injury and sometimes are only accurately diagnosed during a post-mortem.  
• Creutzfeldt-Jakob disease – A rare brain disorder, this condition typically develops in those who do not have any know risk factors present. It is believed that this disease may be the result of abnormal forms of protein within the brain or it can be inherited. It is a fatal condition and the signs and symptoms only tend to appear when the sufferer is around 60 years old. The abnormal protein results in the destruction of the brain cells as well as dementia. Most of the cases appear without an exact cause. In very rare cases, the sufferer may have been exposed to an abnormal protein such as prions found in Mad cow disease. This disease normally progresses rapidly over a couple of years and tends to be associated with muscle movements that are abnormal.
• Parkinson's disease – A lot of people who suffer from this disease have been known to develop the symptoms of dementia, this is known as Parkinson's disease dementia.  Parkinson’s is a central nervous system disorder which affects the movement of the patient and often includes tremors.

Conditions that are similar to dementia that are able to be reversed

Some of the causes of symptoms that are similar to those of dementia and that are able to be reversed with treatment include:

• Immune disorders and infections – Symptoms that are dementia-like may be a result of fever as well as other side effects of the body attempting to fight off possible infection. 

• Nutritional deficiencies – Being dehydrated due to a lack of liquid intake or not getting enough of the vitamins B-1, B-6 and B-12, are issues that are often experienced by those who have an addiction to alcohol, and as a result, may develop symptoms that are similar to dementia.
• Subdural hematomas – These occur if there is bleeding between the covering of the brain and the surface of the brain, which is common when an elderly person falls, this can lead to symptoms similar to those of dementia.

• Endocrine abnormalities and metabolic issues – People who suffer from thyroid issues, have low blood sugar, which is known as hypoglycaemia, have too much or too little calcium or sodium, or struggle to absorb the vitamin B-12, can often develop symptoms that are similar to those of dementia, along with changes to their personality.

• Reactions to medications – Medication that causes a reaction or the interaction of several medications, may often result in symptoms of dementia.
• Poisoning – Being exposed to lead, pesticides, and other heavy metals and poisons, as well as the abuse of recreational drugs and alcohol, can often result in dementia-like symptoms.
• Brain tumours – In rare cases, dementia may be a result of damage from a brain tumour.
• Anoxia – This is a condition, which is also known as hypoxia, that occurs due to the organ tissues not receiving enough oxygen. Anoxia can be a result of severe asthma, carbon monoxide poisoning, heart attack or other causes.  
• Normal-pressure hydrocephalus – Also known as NPH, this is an accumulation of the cerebrospinal fluid, also known as CSF, which causes the enlargement of the ventricles in the brain that may cause walking issues, memory loss and urinary difficulties.