The 5 Subtypes of Frontotemporal Dementia (FTD)

Frontotemporal dementia (FTD), also known as frontotemporal degeneration, is a group of brain disorders caused by degeneration of the frontal or temporal lobes of the brain and is the most common form of dementia after Alzheimer’s for people under 65. These degeneration disorders can often lead to significant changes in personality, behavior, and language based on the regions of the brain they affect. If you or a loved one has been diagnosed with FTD, it can be helpful to identify the subtype to determine the genetic component and risk to family members, treatment options, access to clinical trials and patient communities, and properly inform physicians. Below are the five subtypes of FTD.

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1. Behavioral Variant Frontotemporal Dementia (bvFTD)

bvFTD is the most common subtype of FTD. It primarily affects the frontal lobes of the brain, which are responsible for personality, behavior, emotion regulation, and executive functions.

Symptoms: 

• Personality Changes: Individuals may exhibit apathy, loss of empathy, or inappropriate social behavior.
• Behavioral Changes: Increased impulsivity, repetitive behaviors, and changes in food preferences (such as craving sweets).‍
• Cognitive Symptoms: Difficulty with planning, decision-making, and problem-solving, but often with relatively preserved memory early in the disease.

Progression: The disease typically progresses over several years, leading to increasing disability and dependency.

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2. Primary Progressive Aphasia (PPA)

PPA is a form of FTD that affects the left frontal and temporal lobes, which are primarily responsible for language skills. It is divided into three main variants:

• Nonfluent/Agrammatic Variant (nfvPPA): Characterized by effortful, halting speech, and difficulty with grammar and sentence construction.
• Semantic Variant (svPPA): Involves a loss of understanding of word meanings, leading to fluent but empty speech.
• Logopenic Variant (lvPPA): Marked by difficulty finding words (a symptom known as anomia) and impaired repetition of phrases or sentences but relatively preserved grammar.

Symptoms:

• Language Impairments: Gradual decline in the ability to speak, understand speech, read, or write, depending on the variant.
• Behavioral Symptoms: Some individuals may develop behavioral changes similar to those seen in bvFTD as the disease progresses.

‍Progression: PPA progresses over time, with language difficulties worsening and other cognitive or behavioral symptoms potentially emerging.

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3. Amyotrophic Lateral Sclerosis (ALS) and Frontotemporal Degeneration

ALS is a motor neuron disease that can co-occur with FTD, leading to a condition known as ALS-FTD. ALS affects motor neurons as well as the frontal temporal lobes, which means it impacts both motor symptoms and cognitive/behavioral symptoms.

Symptoms:

• Motor Symptoms: Muscle weakness, atrophy, and difficulty speaking, swallowing, or breathing due to motor neuron degeneration.
• Cognitive/Behavioral Symptoms: Similar to those seen in bvFTD, including personality changes, executive dysfunction, and apathy.

‍Progression: ALS-FTD typically has a rapid progression, with individuals experiencing a combination of severe physical and cognitive decline.

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4. Corticobasal Syndrome (CBS)

CBS is a rare neurodegenerative disorder that can co-occur with FTD. CBS is associated with atrophy in the cerebral cortex, particularly the parietal lobe, and the basal ganglia, which affects movement and cognition.

Symptoms:

• Motor Symptoms: Asymmetrical movement difficulties, such as stiffness, rigidity, tremors, and dystonia on only one side of the body. Individuals may also experience "alien limb" phenomenon, where a limb seems to move on its own.
• Cognitive/Behavioral Symptoms: Similar to bvFTD, including apathy, executive dysfunction, and changes in personality.
• Aphasia: Some individuals may develop language difficulties, similar to those seen in PPA.

‍Progression: CBS progresses over time, leading to increasing motor disability and cognitive decline.

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5. Progressive Supranuclear Palsy (PSP)

PSP is a rare neurological disorder that can overlap with FTD. It  involves the degeneration in the brainstem, basal ganglia, and frontal lobes, which can lead to problems with balance, movement, vision, speech, and cognition.

Symptoms:

• Motor Symptoms: Difficulty with balance and walking (often leading to falls), stiffness, and problems with eye movements (particularly looking up and down).
• Cognitive/Behavioral Symptoms: Similar to bvFTD, including personality changes, executive dysfunction, and difficulty with planning and problem-solving.
• Speech and Swallowing Difficulties: Individuals may have slow or slurred speech and difficulty swallowing.

‍Progression: PSP progresses gradually, leading to severe physical disability and cognitive decline.

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How to Identify Different Subtypes

If you’re trying to determine if you or a loved one might be experiencing frontotemporal dementia, these are the main differentiating symptoms of each type:

• bvFTD: Primarily affects behavior and personality.
• PPA: Primarily affects language abilities, with different variants depending on specific language deficits.
• ALS with FTD: Involves a combination of motor neuron degeneration and FTD symptoms.
• CBS: Involves asymmetric motor symptoms and cognitive impairments.
• PSP: Primarily affects balance, eye movements, and cognition.

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Using MRI and PET Scans

Brain scans can be crucial in identifying different subtypes of FTD, ruling out other diagnoses, and tracking the disease progression. Brain imaging helps differentiate FTD from other neurodegenerative diseases such as Alzheimer's disease, vascular dementia, or Parkinson’s disease, which may present similar symptoms but affect different areas of the brain. Proper diagnosis is essential for targeting the right treatment and care plan.

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Both MRI and PET scans can track how FTD progresses over time. PET scans, particularly FDG-PET (which measures glucose metabolism in the brain), can reveal metabolic changes in the brain that suggest the patient has FTD before any physical atrophy is visible on MRI. This can help identify FTD at earlier stages and show patterns of brain dysfunction that correspond to specific subtypes.

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In short, MRI and PET scans are important for accurately diagnosing the subtype of FTD, understanding the extent of brain involvement, and planning appropriate treatment and care strategies based on how the disease is affecting the brain.

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No-Cost Genetic Testing 

In addition to identifying the FTD subtype, it is important patients understand their FTD genetic diagnosis. Approximately 15-20% of patients with FTD have an identifiable genetic cause. Clinical trials are increasingly requiring a genetic diagnosis to participate making this an essential step in the diagnostic process for patients with FTD.

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Probably Genetic offers a no-cost genetic testing program for individuals with FTD. The process to apply is straightforward:

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1. Begin the online assessment: Describe the symptoms you or a loved one is experiencing.

2. Complete your profile: Provide additional necessary information, including your address for the sample collection kit.

3. See if you qualify: You’ll be notified via email regarding your eligibility.

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