Rarer causes and types of dementia

Expert reviewers, Dr Pravir Sharma, Consultant in Mental Health and Old Age Psychiatry and Dr Adrian Raby, General Practitioner
Next review due December 2024

Dementia is a term used to describe a set of symptoms that can include problems with memory and thinking. There are four common causes or types of dementia. These are:

But there are also rarer forms of dementia symptoms, some of which we describe in more detail here.

Holding hands

Parkinson's disease

Around two to three out of every 10 people with Parkinson’s disease will develop some symptoms of dementia or will slow down mentally. This is more common when Parkinson’s is more advanced than in the early stages.

Parkinson’s dementia is similar to a type of dementia called dementia with Lewy bodies. The main difference is that in Parkinson’s dementia, problems with physical movement usually start years before any problems with thinking and memory. In both conditions, protein deposits called Lewy bodies are found in brain cells. These may be harmful to the brain cells and cause dementia, but doctors don’t know this for sure.

A typical symptom of dementia with Lewy bodies is seeing things that aren’t there (hallucinations). This also happens in Parkinson’s dementia but less commonly than in dementia with Lewy bodies, and the hallucinations are less severe.

Other symptoms of dementia in Parkinson’s can include:

  • slowed thinking, poor concentration and difficulty planning
  • feeling sleepy during the day
  • personality changes, such as loss of usual interests (apathy) and feeling agitated
  • memory loss
  • difficulty making sense of surroundings – this can increase the risk of falls


As well as dementia, many people with Parkinson’s disease develop depression.

There are medicines that can help to treat the symptoms of Parkinson’s dementia. The first type of medicine a doctor will prescribe a person with mild-to-moderate dementia is an acetylcholinesterase inhibitor such as rivastigmine. If this type of medicine isn’t suitable, another option may be a NMDA

Normal pressure hydrocephalus (NPH)

Hydrocephalus is a condition in which fluid builds up in the brain and increases pressure. Normal pressure hydrocephalus (NPH) has some of the same symptoms (for example, difficulty walking) but the pressure in the brain isn’t significantly high.

Doctors aren’t quite sure what causes NPH. It may be to do with reduced flow of blood leaving the brain if the circulation is blocked due to vascular disease. It may also be caused by problems with the circulation of fluid in the brain (cerebrospinal fluid). And if a person has a head injury or bleeding in the brain, that may contribute to NPH developing.

Symptoms of dementia caused by NPH include:

  • a general mental slowing down
  • poor attention span
  • loss of or reduced short-term memory


Memory problems may show up later than problems with thinking and managing. As well as dementia, people with NPH have difficulty walking. They may become slow and cautious, unsteady, or have difficulty changing direction. People with NPH may also have trouble controlling their bladder (urinary incontinence) later on in the disease.

A specialist doctor may try medicines for Parkinson’s disease. If these don’t help, it can help to rule out Parkinson’s disease and diagnose NPH. Doctors might be able to see if a person has NPH by scanning the brain. In NPH, some of the fluid-filled chambers in the brain (the ventricles) may appear to be bigger than usual.

If there’s a build-up of fluid in the brain, some can be drained off by doing a lumbar puncture (also called a spinal tap). If this helps, it can be followed by putting in a tube to drain away the excess cerebrospinal fluid. This is called a shunt and drains the excess fluid to another part of the body, usually the tummy (abdomen). The fluid is then absorbed into the blood.

The doctor may also suggest treatment to help stop any circulatory problems from getting worse. This may include stopping smoking, and medicines to reduce high blood pressure or cholesterol.

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Multiple sclerosis

Multiple sclerosis (MS) is a condition where the insulation around nerve fibres is lost. This means the electrical signals that travel along the nerves are slowed down. There are different types of MS that develop at different rates. Memory problems and other dementia symptoms are most common if MS develops more rapidly.

Around half of people with MS will have some difficulties with thinking and remembering at some stage of their illness. This depends on the areas of the brain MS affects and the effect can vary in severity. In some people, the effects will only be slight. They may have:

  • memory problems
  • difficulty learning new information
  • difficulty planning
  • poor concentration


Up to one in 10 people with MS will develop dementia. People with MS are also more likely to have depression. This should be treated with antidepressants as it can make these as it can make these other dementia-like symptoms worse.

Treatment will generally be aimed at managing symptoms. As well as antidepressants, doctors may suggest short-term medicines to help with anxiety if this is a problem.

Progressive supranuclear palsy (PSP)

Progressive supranuclear palsy (PSP) is a rare condition that affects movement. It gradually gets worse over a number of years. PSP can also cause difficulties with thinking and memory.

PSP affects the nervous system and usually starts in late middle age. Some of the symptoms can be similar to Parkinson’s disease. People may have difficulty moving the eyes to look up or down. They may also become unsteady with a tendency to have falls.

Symptoms can include:

  • memory problems
  • slowed thinking
  • personality changes, such as becoming more emotional


There are also physical symptoms. Muscles become rigid and movements slow down.

There’s no cure for PSP – treatment aims to control symptoms. The doctor may suggest medicines to help with muscle stiffness. Physiotherapy and occupational therapy may help with movement and reduce the risk of falls.

Huntington’s disease

Huntington’s disease (HD) is an inherited (genetic) condition. Symptoms usually start when people are in their 30s and 40s. HD affects the nervous system and causes characteristic jerky movements.

A first sign that a person has HD is their personality or behaviour changes. This can develop or happen at the same time as jerky movements. Over a number of years, people become less mobile and begin to develop severe dementia. Symptoms include:

  • slowed thinking and poor concentration
  • anxiety
  • depression
  • loss of interest in life (apathy)
  • aggression
  • irritability and agitation
  • developing obsessions or compulsive behaviour (later in the illness)


There’s no cure for HD – treatment aims to control symptoms. The doctor may suggest medicines for depression or anxiety. If agitation or compulsive behaviour is a problem, they may prescribe medicines called anti-psychotics.

Members of the family of a person affected with HD can have genetic testing for Huntington’s disease if they wish. It can be a difficult decision whether or not to have this. It’s entirely your choice and you can take as long as you need. Counsellors are available who can talk to you about the testing and answer any questions you may have before you decide. You can have the tests at a genetic clinic.

Creutzfeldt–Jakob disease (CJD)

Creutzfeldt–Jakob disease (CJD) is a type of prion disease. This is a disease where a brain protein is folded wrongly, so it doesn’t work properly.

CJD is very rare. In the years from 1985 to 2020, 2,494 people in the UK people were diagnosed with sporadic CJD (the most common type of CJD). There are different types which are even less common, including a type linked to eating meat from cattle infected with BSE (bovine spongiform encephalopathy – sometimes called ‘mad cow disease’.

CJD is a condition that gets worse over time and this can be very quick. One of the main features of CJD is memory loss and confusion. Other symptoms include:

  • early signs of difficulty with organising, planning and multi-tasking
  • problems with sight, such as double vision or hallucinations
  • poor coordination and loss of control of body movements
  • jerking muscle movements
  • agitation and depression


There’s no cure for CJD. Treatment is aimed at managing symptoms and keeping people as comfortable as possible. Doctors may prescribe anti-depressants and medicines for anxiety and agitation. People with CJD may also have medicines for difficulty sleeping and to try to control muscle spasms.

Wilson’s disease

Wilson’s disease is a condition where the body doesn’t deal properly with copper from your diet. This copper builds up in the liver, brain and other organs, where it causes damage.

Wilson’s disease is a genetic condition that can be hard to spot. Sometimes it’s picked up because of early signs, including greenish-gold rings around the iris (the coloured part of your eye), blood in the urine or periods stopping or having repeated miscarriage. But not everybody gets these early signs (only about five to 10 people in 100 do).

If Wilson’s disease isn’t diagnosed early, it may cause dementia-like symptoms, including changes in the ability to focus on tasks, memory loss, behaviour and mood changes, and problems with coordination. As well as these, someone may have:

  • liver problems such as hepatitis and cirrhosis
  • slow or slurred speech
  • tremor
  • muscle spasms and twitches
  • excessive saliva (drooling)


Wilson’s disease is usually diagnosed between the ages of 10 and 40 but, in theory, it can develop at any age

Wilson’s disease is treatable with medicines called chelating agents. These remove copper from the body. A doctor may also prescribe zinc because this stops the body from absorbing any more copper but it won’t get rid of the excess. Once a person has been diagnosed, they take these medicines for life, to prevent high levels of copper from collecting.

Some symptoms that have developed before treatment started may remain permanently, but others will improve. If Wilson’s disease isn’t treated, it’s usually fatal.

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  • Reviewed by Rachael Mayfield-Blake, Freelance Health Editor, December 2021

    Expert reviewers, Dr Pravir Sharma, Consultant in Mental Health and Old Age Psychiatry and Dr Adrian Raby, General Practitionert

    Next review due December 2024