Dementia is an umbrella term for a progressive neuro-degenerative illness. Here we look at different forms of dementia, identifying those that may occur early (before the age of 65) and describe the symptoms of each.
Within the dementia umbrella the majority (approximately 60%) have Alzheimer’s disease.
Alzheimer’s disease is typified by memory impairment followed by impairment to cognitive thinking. Cognitive thinking is “the mental action or process of acquiring knowledge and understanding through thought, experience, and the senses”. It encompasses processes such as knowledge, attention, memory and working memory, judgment and evaluation, reasoning and “computation”, problem solving and decision making, comprehension and production of language.
Loss of cognitive function is caused by shrinking of parts of the brain, which leads to neuro degeneration and loss of brain function.
Familial Alzheimer’s Disease
Very rare cases of Familial Alzheimer’s Disease account for less than 1% of all dementia cases.
This is an early-onset disease characterised by many members of the family developing dementia before the age of 65.
The good news is that scientists have identified the 3 genes which cause the disease. The bad news is that if it is present in the family, family members have a very high probability (50%) of inheriting the faulty gene.
Trials are taking place to remove the abnormal protein plaques from the brain to see whether this will slow, or even stop, Alzheimer’s from developing.
Vascular dementia happens when narrowing of the blood vessels inside the brain limits blood supply to the brain, leading to the death of parts of the brain and impaired brain function.
This form of dementia accounts for approximately 19% of dementia cases.
There are 4 main causes of Vascular dementia;
- Stroke-related dementia
- Post-stroke dementia
- Single-infarct/multi-infarct dementia (one or more smaller strokes or TIAs cause impairment to brain function)
- Subcortical dementia, characterised by diseases of the very small blood vessels that lie deep in the brain.
Each type of Vascular dementia shares some symptoms, has some that are peculiar to its type and develop differently.
Frontal Temporal Dementia (FTD)
In this form of dementia it is the two lobes positioned right at the front of the brain which are affected; these control behaviour and language (patients with language problems often show greater loss of brain tissue on the left side of the brain).
This disease typically starts between the ages of 50 and 60, which may mean that is more difficult to get a definite diagnosis.
About 10% of patients with FTD may develop disorders which affect movement – e.g. Motor Neurone Disease (affecting motor function), Corticobasal Syndrome (stiffness and slowness of movement on one side of the body) or Progressive Supranuclear Palsy (balance problems, falls, difficulty in moving eyes up and down).
Within the FTD diagnosis there are several overlapping syndromes, including:
Behavioural Variant Frontotemporal Dementia (BVFD) – also known as Pick’s Disease
In BVFD changes in behaviour and personality are the first symptoms. This type of dementia accounts for just under 5% of all dementia cases.
This is an early onset disease, which means that patients presenting with symptoms are likely to be aged under 65.
Symptoms may include behavioural changes such as:
- Inappropriate social behaviour and disinhibition
- Obsessive-compulsive tendencies such as sticking to routines
- Loss of empathy
- Changes in appetite
- Loss of control over decision-making and planning brain function.
Dementia with Lewy Bodies (DLB)
DLB is present in 5% of all dementia diagnoses. Again, this is an early onset form of dementia which is more prevalent in patients aged 65 or under.
Lewy Bodies are abnormal collections of protein that develop inside brain cells.
DLB is particularly associated with cognitive fluctuations which would not be seen in other forms of dementia and which are particularly difficult to deal with for family and carers.
Hallucinations are very much a part of the illness – it is as if the person is really seeing something, it is absolutely real to them. Hallucinations may be non-threatening or absolutely terrifying.
Delusions (false but fixed beliefs that the person cannot be argued out of) are also typical of DLB.
This form of dementia is linked to Parkinson’s Disease. The difference between actual Parkinson’s Disease and Dementia with Lewy Bodies is defined by which symptoms appear first and which are more prevalent:
- Parkinson’s Disease Dementia – dementia symptoms appear at least 12 months after the Parkinson’s Disease diagnosis;
- Dementia with Lewy Bodies – cognitive fluctuations followed by Parkinson-like motor issues
Primary Progressive Aphasias
These are types of Frontal Temporal Dementia which affect language and the ability to find words or to understand what is being said. These include Semantic Dementia, characterised by a loss of understanding of concepts and facts, and problems in finding the right words.
Progressive Non-Fluent Aphasia is characterised by difficulty speaking or understanding language. People living with this type of dementia find it hard to connect words and thoughts. Background noise and distractions become a problem. Talking takes concentration. Social situations can become difficult, leading to isolation.
Logopenic Aphasia is characterised by problems making words, structuring a sentence or understanding what words mean. Reading becomes impossible. This type of dementia often has an Alzheimer’s pathology, but with specific Logopenic Aphasia symptoms.
Posterior Cortical Atrophy (PCA)
This type of dementia is caused by shrinkage at the back of the brain, the part which deals with visual messages. In essence, what the eye sees and what the brain processes are different.
This is an early onset form of dementia which accounts for 5% of dementia cases.
Primary symptoms are visual, initially with driving or reading. Spelling and calculation may also be affected.
The visual impairments typical of PCA have been described as “Like looking through a cracked mirror and seeing only parts of the whole.”
There is a typically a very slow route to diagnosis of PCA because people often think it’s a vision or eye problem. As an early onset disease people are younger when symptoms start, so that also contributes to difficulties in diagnosis. Neurologists are usually the only people who are able to make a definitive diagnosis.
The link between all the diseases described above is that they are all caused by degeneration in part of the brain. It is the part of the brain that is initially affected that determines the diagnosis and specific symptoms.
Unfortunately, whichever type of dementia is originally diagnosed all dementia seems to eventually spread either forwards/backwards/sideways resulting in total cognitive impairment.
Let’s hope that some of the new research projects will bring hope of treatment or, better still, a cure.
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