by Clarissa Giebel,The Conversation

Credit: Pixabay/CC0 Public Domain

What most people think of when they hear the word "dementia" is memory problems and forgetfulness. But what people often don't know is that dementia can cause many different symptoms—affecting speech, behavior, sleep, motor function and more.

In fact,dementiais an umbrella term. There are estimated to be more than100 types of dementia.Alzheimer's diseaseis the most common subtype of dementia, affecting approximately 60% of all cases. Memory loss is one of the most common symptoms of this type of dementia.

Butapproximately 40%of all dementia cases are considered to be different, rarer types. Unfortunately, having a rarer subtype of dementia often makes diagnosismore difficult and requires more complex care.

Although most people might be aware of some types of dementia—including Lewy Body, Parkinson's disease dementia and frontotemporal dementia—awareness of other rarer types is low.

Knowing how to spot the signs of these rarer types of dementia early could be crucial in ensuring loved ones get the support they need.

Posterior cortical atrophy

Posterior cortical atrophy(PCA) affects mostlyvisualand spatial functioning. Memory is not as badly affected early on as it is in Alzheimer's disease.

People with PCA can struggle with visual hallucinations and spatial navigation. This can become apparent when reading or judging depth and space on a staircase—making it difficult to judge where the next step is, for example. Symptoms commonly start appearing between the ages of 55 and 65.

There's still much we don't know about PCA because of how rare it is. Researchers are still trying to figure out whether PCA is adistinct subtype of dementiaor whether it's an atypical form of Alzheimer's disease. This is because the brain changes that occur in people with PCA closely resemble those that occur in people with Alzheimer's disease, although the symptoms are different. It's also estimated that between5% to 15% of people with Alzheimer'shave PCA.

Creutzfeld-Jakob disease

Creutzfeld-Jakob diseaseis a particularly rare form of dementia, affecting about one in 1 million people worldwide.

Creutzfeld-Jakob disease is a prion disease. These diseases involve prion proteins which, for unknown reasons, suddenly change into a three-dimensional shape. The function ofhealthy prionsremains unknown, but they appear to play some role in protecting nerves and brain cells and keeping the body's circadian rhythm functioning (the natural, 24-hour cycle our body follows that controls everything from sleep, digestion and immunity).

Themisfolding of prion proteinsin Creutzfeld-Jakob disease causes a very rapid and severe form of dementia, progressing much more quickly than Alzheimer's disease or Lewy Body dementia, for example. Besides the notably quick nature of progression, people with Creutzfeld-Jakob disease struggle with memory and movement, including sudden jerky movements.

Risk factorsfor this subtype of dementia include old age and genetics (occurring in 10%–15% of cases). In very rare cases, it can also develop as aresult of contamination—such as from eating beef from cattle infected with mad cow disease.

FTD-MND

FTD-MNDis a form of frontotemporal dementia that occurs alongside motor neuron disease.

Frontotemporal dementia refers to subtypes of the disease that cause gradual brain tissue loss in the frontal and temporal lobes of the brain.

Motor neuron disease, on the other hand, is a rapidly progressing neurological condition which can lead to difficulties breathing, movement and paralysis. Although it affects the brain and nerves, it is not itself a form of dementia.

Approximately 10%–15%of people with frontotemporal dementia also develop motor neuron disease. This co-occurence seems to be linked to amutationin theC9orf72 gene. Because of this genetic link, FTD-MND canrun in families.

People with FTD-MND experience several muscle-related issues, including muscle waste, stiffness and problems with swallowing. These are things you would not normally associate with dementia and memory problems.

It's currently not clear whether frontotemporal dementia develops first and then motor neuron disease, or if it's the other way around.

Progressive supranuclear palsy

Progressive supranuclear palsy(PSP) is a rare neurological condition that causes both dementia and problems with movement.

It's estimated to affect approximately4,000 people in the UK. PSP is difficult to diagnose as it overlaps with many other conditions—including Parkinson's disease.

PSP primarily leads to damage in subcortical brain regions, specifically the brainstem and basal ganglia. These areas are linked to vision and movement.

As such, people with PSP struggle using their eyes and can thus often fall and experiencedifficulties moving around. People with PSP can also struggle with concentrating andproblem solving.

Dementia support

As with all dementia subtypes, there isno cure yet. While there are medications that can delay symptoms, these only work in cases ofAlzheimer's disease.

As such, we still need to find ways to support people with other subtypes of dementia as best as possible.

One way of doing this is by properly understanding their condition and their subtype. Knowing that someone might particularly struggle with walking and movement as opposed to memory is important to put the right care in place in advance.

It is just as important to be able to spot the signs early on. Dementia doesn't just affect memory. Changes in behavior, problems seeing or falling more frequently, walking or moving differently or difficulty speaking can all beearly signs of dementia.

Better understanding dementia's many forms will hopefully lead to better ways of managing and treating this complex disease.

This article is republished fromThe Conversationunder a Creative Commons license. Read theoriginal article.

Key medical concepts Creutzfeldt-Jakob Disease Progressive Supranuclear Palsy Alzheimer's Disease