Overview of frontotemporal lobe dementia

Frontotemporal lobe dementia (FTD) is a neurodegenerative condition that slowly takes away an individual's ability to perform everyday tasks - moving, speaking, socialising and thinking - and subsequently damages their ability to continue living independently. Generally, FTD onset is relatively young in comparison to other forms of dementia. The majority of cases are diagnosed between the ages of 45-65 years old. For many people, the disease strikes at a pivotal time in their lives when they are busy working and raising families. 

Damage to neurons in the frontal and temporal lobes of the brain leads to atrophy of this region and the symptoms associated with FTD.¹ The frontal lobes are the largest lobes in the human brain and are situated directly behind the forehead.² They are involved in a variety of motor functions as well as cognitive functions, including:

• Executive function 
• Attention
• Memory 
• Language 

The temporal lobes are located posteriorly and inferiorly to the frontal lobes.³ This region in the brain plays a significant role in language, memory and emotional regulation.³ Degeneration of this area can result in difficulty decoding words and sentences, recognising people and objects and recognising and responding to different emotions. 

Types of FTD and symptoms

FTD is divided into three subtypes based on the primary symptoms displayed: behavioural frontotemporal dementia, primary progressive aphasia (PPA) and movement disorders. 

Symptoms associated with the behavioural variant are:¹

• Difficulty in planning and sequencing events
• Inability to prioritise tasks and activities 
• Repetition of activities and words when speaking
• Acting impulsively and inappropriately 
• Disinterest in previous hobbies 
• Improper emotions in situations
• Lack of empathy
• Compulsive eating 

PPA affects your ability to communicate and is further divided into three subtypes: 

• Semantic PPA: Gradual decline in the ability to understand single words
• Agrammatic PPA: Lack of fluency and production of grammatically incorrect sentences
• Logopenic PPA: Difficulty finding the correct word in conversation.  

Corticobasal syndrome and progressive supranuclear palsy are two movement disorders associated with FTD. Corticobasal syndrome is caused by the loss of neurons in the corticobasal region of the brain and leads to a gradual decline in an individual's ability to control movement. Progressive supranuclear palsy generally affects balance and walking.

FTD is rare and is often misdiagnosed as other disorders, which will be discussed here.   

Differential diagnoses for frontotemporal lobe dementia

Dementia is an umbrella term that encompasses a range of progressive neurodegenerative conditions. Many neurodegenerative conditions have overlapping symptoms, so many people may receive differential diagnoses. FTD is a relatively rare form of dementia, so it is often misdiagnosed as a more commonly seen disorder. 

Alzheimer's disease

Alzheimer’s disease (AD) is the most common form of dementia globally.⁴ It is characterised by the formation and abnormal accumulation of a protein called beta-amyloid, which leads to significant damage and loss of surrounding neurons.⁵ There are several risk factors that can increase an individual's likelihood of developing the disease:

• Age: The prevalence of AD increases with age
• Gender: Some studies have shown a higher prevalence in women than men⁵
• Genetics and a family history
• Lifestyle factors: diet, physical activity, smoking

There is no cure for AD, but there are drug treatments available to help manage some of the symptoms. 

Alzheimer’s disease vs FTD

We can compare AD to FTD and identify differences between these two forms of dementia. 

The risk of AD increases with age and is most commonly diagnosed in individuals over the age of 65 years old. On the contrary, FTD is often diagnosed at an earlier age (~45 years), and the chances of an FTD diagnosis decrease the older you get. Early studies demonstrated that in AD, whole brain and hippocampal atrophy occurs, whilst in FTD, atrophy is localised to the frontal and temporal lobes.⁶ In AD, memory loss is often the first symptom reported, whilst in FTD, distinct behaviour and language changes are often first noted.  

Vascular dementia

Vascular dementia is associated with brain ischemic events or haemorrhages, causing reduced perfusion to the brain and subsequent damage and death of neurons.⁷ There are risk factors linked to the development of cerebrovascular disease, including:

• Age
• Smoking
• An unhealthy diet 
• Diabetes
• High blood pressure 
• Obesity 
• Atherosclerosis (hardening of the arteries)
• Lack of physical activity 

Vascular dementia is the disruption of cognitive pathways caused by the damaged neurons that give rise to the symptoms of vascular dementia.

Clinically, vascular dementia presents like AD, with problems with memory being the most common symptom. Others may experience changes in behaviour and difficulty organising and carrying out simple everyday tasks.⁸  

Although there is no way to recover the damaged neurons, lifestyle changes can help slow down the loss of neurons and subsequent disease progression. Changes may include losing weight, increasing exercise, a healthy diet or medicine to control blood pressure, reduce cholesterol and prevent blood clots.⁹ 

Vascular dementia vs FTD

Vascular dementia typically occurs in older patients, whilst we know that FTD is usually associated with early-onset dementia. Neuroimaging techniques will observe evidence of damage caused by stroke in vascular dementia. Whereas in FTD abnormalities in the frontal and temporal lobes will be reported. 

Psychiatric disorders

In FTD, if the primary symptoms displayed are of the behavioural variant, individuals are often confused with patients suffering from psychiatric conditions.⁸ Depression is a common symptom of FTD and is often one of the earliest presentations of dementia. 

Common symptoms of depression are:

• Social withdrawal 
• Poor hygiene
• Loss of interest in hobbies
• Tearfulness
• Lack of motivation 

Due to the early onset of FTD, changes in personality and behaviour can be perceived to be caused by schizophrenia or bipolar disorder. 

Obsessive-compulsive disorder may also need to be distinguished from FTD. Repetitive and compulsive behaviours are often seen in the behavioural subtype of FTD.⁸ 

Brain imaging and thorough neuropsychological testing should be able to distinguish FTD from psychiatric conditions.

Conclusion

In conclusion, FTD is a form of dementia that generally has an early age of onset. It is divided into three types based on the primary symptoms: behavioural, primary progressive aphasia and movement disorders. Due to the rarity of FTD, it can often be diagnosed for other conditions such as Alzheimer's disease, vascular dementia or depression. Brain imaging is a helpful tool to distinguish other conditions from FTD. 

Frequently asked questions (FAQs)

What is dementia?

Dementia is an umbrella term that encompasses a variety of disorders that gradually lead to a decline in brain function. 

What are the most common forms of dementia?

Alzheimer's disease and vascular dementia are the most common types of dementia. 

How is FTD different from other types of dementia?

A: The primary symptoms of FTD usually affect behaviour and language, whilst problems with memory are commonly the primary symptom of other forms of dementia. FTD has a relatively early age of onset. Loss of neurons in the frontal and temporal lobes of the brain is what causes the symptoms of FTD. 

Why is it important to distinguish between the different types of dementia?

A: Although there is no cure for dementia, understanding what type of dementia will enable clinicians to offer the appropriate support and guidance to manage the condition. 

How can different forms of dementia be diagnosed?

A thorough history can be taken, and extensive cognitive tests may be performed as part of the diagnosis. A CT scan or MRI is a helpful tool to visualise any changes in the brain.