Frontotemporal dementia (FTD) is a long-term, progressive condition characterised by perpetual damage to brain cells within specific regions of the brain. When damaged, these regions can no longer carry out their function– causing a range of behavioural, language-based, and motor dysfunctions. Frontotemporal dementia currently does not have a cure, though research is ongoing and available treatments can be effective at managing and alleviating symptoms. Frontotemporal disease is relatively rare; however, it has a big impact on the lives of patients, their families, friends, and caregivers.
Introduction to frontotemporal dementia
Frontotemporal dementia is a term used for a group of progressive neurodegenerative conditions. Over time, people with FTD sustain increasing damage to the neurons in the frontal and temporal lobes of the brain.1 In healthy brains, the frontal lobes control aspects of movement, language, and executive function- a term used to describe your ability to plan, organise and self-monitor.2 The temporal lobes are involved in processing verbal information, visual perception, and learning.3 As FTD progresses, the neuron damage in the frontal and temporal lobes makes it harder for an individual to control the functions associated with both regions. Therefore, people with FTD find it increasingly difficult to regulate their behaviour, understand language, and form speech. FTD is classified into three groups depending on the early clinical presentation (symptoms) of the disease: Behavioural Variant Frontotemporal Dementia, Nonfluent Variant Primary Progressive Aphasia, and Semantic Variant Primary Progressive Aphasia.1 FTD is the second most common form of dementia in people under the age of 65 and the third most common form for those 65 and older, with an individual being most likely to develop FTD between the ages of 45 and 64.4 The behavioural variant is the most common form of FTD diagnosed in the clinic.1
What are the variants of frontotemporal dementia?
The three variants of FTD, Behavioural Variant Frontotemporal Dementia, Nonfluent Primary Progressive Aphasia, and Semantic Variant Primary Progressive Aphasia, are distinguishable early on in disease progression. A variant-specific diagnosis is made after clinical assessments, brain imaging, and genetic testing. In later stages of disease progression, the systemic damage to the frontal and temporal lobes causes the symptoms of the three variants to converge. Across the variants, people with end-stage FTD present with global cognitive impairment and motor deficits.1
Behavioural variant frontotemporal dementia (bvFTD)
In bvFTD, the damage to the brain originates in the paralimbic regions of the inner brain. People with bvFTD have behavioural changes and a loss of executive function early in disease progression, which is associated with the dysfunction of the paralimbic regions.5
Semantic variant primary progressive aphasia (svPPA)
People with svPPA can have a primary involvement of the left or right temporal lobe. If the left temporal lobe is affected, the first symptoms will be language-based. Behavioural symptoms dominate if it is the right temporal lobe svPPA.5
Nonfluent variant primary progressive aphasia (nfvPPA)
In nfvPPA, difficulty with speech production is the primary symptom. This is due to damage in Broca’s region in the brain, which is involved in verbal output.5
Related FTD syndromes
The main FTD disorders are bvFTD, svPPA, and nfvPPA. However, other related disorders exist on the FTD spectrum. These include frontotemporal dementia with motor neuron disease, corticobasal degeneration, and progressive supranuclear palsy.5
What are the causes and risk factors of frontotemporal dementia?
How and why FTD develops is not yet fully known by scientists. Research has confirmed that the loss of neurons in the brains of people with FTD is associated with abnormal protein deposition. The proteins Tau, TAR-DNA binding Protein (TDP) and Fused in Sarcoma (FUS) have all been implicated in FTD disorders.1 Tau, TDP and FUS are all produced naturally by the body and assist cellular processes.6, 7, 8 In FTD, Tau, TDP, and/or FUS malfunction leads to the formation of protein clumps. The protein aggregates interfere with normal brain cell function, causing them to die. In the regions affected, there is a loss of cellular volume (the brain area shrinks) and function.1 The exact biological mechanism that leads to abnormal protein deposition and aggregation is still being investigated.
In over half of all FTD cases, the cause is unknown (idiopathic). In 40% of FTD cases, there is a family history of dementia. Scientists have discovered that heritable mutations in the DNA that encodes specific genes can cause the abnormal protein production associated with FTD. The mutated forms of the C90RF72, MAPT and GRN genes have all shown that once mutated, the resulting variants can lead to dysregulated protein production and degradation.1 Other than a family history of dementia, head trauma and thyroid disease have both been found to be a risk factor for FTD.9
How does frontotemporal dementia present clinically, and what are the symptoms?
How FTD presents itself initially is dependent on which regions of the brain are affected. As the disease progresses, the number and severity of symptoms will change. A healthcare provider will provide support to an individual and their caregivers to manage each new symptom.
For bvFTD, there are six groups of symptoms; individuals may present with a select combination or all of the following:1
- Behavioural Disinhibition: This means that you no longer receive a neuronal signal to not say or do something. It can cause people with FTD to lose their ‘filter’ and make inappropriate comments, stop them from respecting other people's personal space, or engage in impulsive, reckless actions such as gambling or shoplifting.
- Apathy: If a person has apathy, they will present with a loss of motivation; they may socially isolate and stop properly looking after themselves.
- Lack of Sympathy/Empathy: People with FTD can lose their ability to read the emotions of others. They, therefore, may be perceived as acting cold or harsh.
- Compulsive Behaviours: In FTD, compulsive behaviour can mean simple repetitions of movements or phrases to more complex compulsive ritualistic behaviour.
- Dietary Changes: Binge eating and increasing consumption of sweets or alcohol is common in FTD, along with the examination of food or other objects by putting them in their mouth (hyperorality).
- Deficit in Executive Function: When a person with FTD loses their executive function, they may become inflexible, disorganised or display bad judgement.
The most prominent symptoms of Primary Progressive Aphasia are all language-based due to the brain regions affected. The exact clinical presentation of svPPA and nfvPPA are different. People with svPPA experience an impaired ability to name objects or actions and comprehend single words. They do retain the ability to repeat words/phrases and produce speech. In nfvPPA, people find it difficult to make sentences with the correct grammatical structure, make the right movements with their mouth and tongue to produce comprehensible speech or comprehend complex sentences. People with nfvPPA do retain single-word comprehension and can name objects/actions.1
What is the diagnostic process for frontotemporal dementia?
If you experience any of the symptoms of FTD, it is important that you discuss them with your healthcare provider. Due to the nature of FTD, it may be someone you know (a friend or relative) who is able to identify that something is wrong. If you do notice symptoms of FTD in someone else, talk to them about how they are feeling and support them in accessing the help they need. Once your healthcare provider discusses the symptoms, they will refer you to a neurologist if they suspect you have FTD. The neurologist will conduct a full clinical assessment and take a medical history. Further tests then ensure that you receive an accurate diagnosis. These include:4
- Neuropsychological Testing
- Brain Imaging (MRI, PET, CT)
- Cerebrospinal Fluid Analysis
- Genetic Testing
- Neurocognitive Testing
The testing process may be difficult and frustrating; however, it is essential to ensure that you receive the correct diagnosis. The symptoms of FTD can be similar to Alzheimer’s disease, other dementia types and some psychological conditions.1
How is frontotemporal dementia treated and managed?
There is currently no cure available for FTD. The therapies available focus on the specific symptoms experienced by an individual. A healthcare provider can give symptomatic and supportive care, medications for specific behavioural and cognitive symptoms, and non-pharmacological interventions for general well-being. As the later stages of the disease are reached, it is likely that long-term care will be needed. Your healthcare provider will talk to you and any caregivers through the services available so that you can receive the support you need.4
Scientists are continuing to work towards finding a cure for FTD. If you have FTD, you may be asked if you would like to take part in a clinical trial for a potential cure or new management strategy.
What is the prognosis of frontotemporal dementia?
FTD is a progressive, life-long condition. The disease can progress at different rates depending on a person’s medical history and the treatments they receive.10
How does frontotemporal dementia impact patients and caregivers?
The complexities and prognosis of FTD bring many emotional and psychological challenges to both the patient and caregiver. There can also be social and financial burdens associated with a patient’s behaviours and the cost of care. If you are feeling overwhelmed either emotionally, physically, or financially, there are many different resources and support services available for patients and caregivers; contact your healthcare provider, and they can refer you to the relevant local organisations.
Frontotemporal dementia is a progressive condition that starts as damage to the brain cells in the frontal and temporal lobes of the brain. The onset of FTD in different areas of the brain dictates the initial symptoms a person experiences; these may be behavioural-based symptoms or language-based symptoms. Frontotemporal dementia does not yet have a cure, which means early detection and treatment intervention are important for symptom management, patient longevity, and maintained quality of life. Research into frontotemporal dementia is ongoing; the information gathered from patients and carers is critical for the continued development of the treatment of the condition.
- Bang J, Spina S, Miller BL. Non-Alzheimer’s dementia 1. Lancet [Internet]. 2015 Oct 24 [cited 2023 Aug 7];386(10004):1672–82. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5970949/
- Queensland Health. Brain map frontal lobes [Internet]. [cited 2023 Aug 7]. Available from: https://www.health.qld.gov.au/abios/asp/bfrontal
- Queensland Health. Brain map: temporal lobes [Internet]. [cited 2023 Aug 7]. Available from: https://www.health.qld.gov.au/abios/asp/btemporal_lobes
- Bott NT, Radke A, Stephens ML, Kramer JH. Frontotemporal dementia: diagnosis, deficits and management. Neurodegener Dis Manag [Internet]. 2014 [cited 2023 Aug 8];4(6):439–54. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4824317/
- Olney NT, Spina S, Miller BL. Frontotemporal dementia. Neurol Clin [Internet]. 2017 May [cited 2023 Aug 8];35(2):339–74. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5472209/
- Mandelkow EM, Mandelkow E. Biochemistry and cell biology of tau protein in neurofibrillary degeneration. Cold Spring Harb Perspect Med [Internet]. 2012 Jul [cited 2023 Aug 9];2(7):a006247. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3385935/
- Jo M, Lee S, Jeon YM, Kim S, Kwon Y, Kim HJ. The role of TDP-43 propagation in neurodegenerative diseases: integrating insights from clinical and experimental studies. Exp Mol Med [Internet]. 2020 Oct [cited 2023 Aug 9];52(10):1652–62. Available from: https://www.nature.com/articles/s12276-020-00513-7
- Ishigaki S, Sobue G. Importance of functional loss of fus in ftld/als. Frontiers in Molecular Biosciences [Internet]. 2018 [cited 2023 Aug 9];5. Available from: https://www.frontiersin.org/articles/10.3389/fmolb.2018.00044
- Rosso SM, Landweer EJ, Houterman M, Kaat LD, Duijn CM van, Swieten JC van. Medical and environmental risk factors for sporadic frontotemporal dementia: a retrospective case–control study. Journal of Neurology, Neurosurgery & Psychiatry [Internet]. 2003 Nov 1 [cited 2023 Aug 9];74(11):1574–6. Available from: https://jnnp.bmj.com/content/74/11/1574
- Moore KM, Nicholas J, Grossman M, McMillan CT, Irwin DJ, Massimo L, et al. Age at symptom onset and death and disease duration in genetic frontotemporal dementia: an international retrospective cohort study. Lancet Neurol [Internet]. 2020 Feb [cited 2023 Aug 10];19(2):145–56. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7007771/