Frontotemporal Dementia (FTD)

Frontotemporal dementia (FTD) encompasses a clinically and pathologically heterogeneous group of neurodegenerative disorders that preferentially affect the frontal and temporal lobes of the brain. Unlike Alzheimer's disease, where memory loss is the hallmark early feature, FTD typically presents with progressive deterioration of behaviour, personality, and/or language, often in individuals younger than 65 years. This distinctive clinical profile leads to frequent misdiagnosis as a primary psychiatric disorder, with Australian studies reporting a median diagnostic delay of 3–5 years from symptom onset.

FTD accounts for an estimated 10–20% of all young-onset dementia cases in Australia and is the second most common cause of dementia in people under 65 years of age. The Australian Institute of Health and Welfare (AIHW) estimates that approximately 26,000 Australians are living with younger-onset dementia (before age 65), with FTD constituting a substantial proportion. The age of onset is typically between 45 and 65 years, though cases in the 30s and into the 70s are recognised. There is no significant sex predilection, although some studies suggest men may present slightly earlier with behavioural variant.

The pathological hallmarks of FTD include neuronal loss, gliosis, and microvacuolation in the frontal and temporal cortices. The majority of cases (~60%) are associated with tau-positive inclusions (including Pick bodies, corticobasal inclusions, and progressive supranuclear palsy pathology), while approximately 40% harbour TDP-43 proteinopathy. A small fraction (~5–10%) show fused-in-sarcoma (FUS) protein inclusions. This pathological heterogeneity underpins the clinical variability observed across FTD subtypes.

A positive family history consistent with autosomal dominant inheritance is present in approximately 30–50% of FTD cases, making it one of the most heritable neurodegenerative conditions. Three genes account for the majority of familial cases: MAPT (microtubule-associated protein tau), GRN (progranulin), and the C9orf72 hexanucleotide repeat expansion — the latter being the most common known genetic cause of both familial FTD and familial motor neuron disease (MND) in Australian and international cohorts.

Behavioural variant FTD is the most common clinical subtype, accounting for approximately 50–60% of all FTD cases. It is characterised by insidious and progressive changes in behaviour and personality that represent a departure from the individual's premorbid character. The International bvFTD Criteria Consortium (Rascovsky et al., 2011) stratates diagnosis into possible, probable, and definite bvFTD based on clinical, imaging, and neuropathological features.

Core Diagnostic Features (Probable bvFTD)

Probable bvFTD requires three or more of the following behavioural/cognitive symptoms, with significant functional decline:

• Early disinhibition: socially inappropriate behaviour, loss of social etiquette, impulsive or rash acts, tactless comments — often the presenting concern raised by family members or employers.
• Apathy/Inertia: marked loss of motivation, reduced initiative, neglect of personal hygiene and household responsibilities; often mistaken for depression.
• Loss of sympathy or empathy: diminished emotional responsiveness to others' distress, reduced interpersonal warmth, apparent coldness.
• Perseverative, stereotyped, or compulsive behaviours: repetitive routines, hoarding, ritualistic behaviour, repetitive use of phrases or gestures.
• Hyperorality and dietary changes: sweet food cravings, binge eating, putting objects in the mouth, marked change in food preferences.
• Neuropsychological profile: executive dysfunction with relative preservation of memory and visuospatial abilities on formal testing.

Supportive Diagnostic Features

• Progressive decline in social cognition and/or cognition
• Relative preservation of episodic memory in early stages
• Relative preservation of visuospatial skills
• Preserved basic motor and sensory functions
• Frontal and/or anterior temporal lobe atrophy on MRI or hypometabolism on FDG-PET

Neuroanatomical Correlates

bvFTD preferentially affects the medial prefrontal cortex, orbitofrontal cortex, anterior cingulate, and anterior temporal poles. On MRI, characteristic patterns include bilateral frontal atrophy with or without anterior temporal involvement. Right-predominant atrophy tends to produce more pronounced behavioural and personality changes, while left-predominant patterns may present with earlier language difficulties.

Primary progressive aphasia (PPA) is defined by progressive language impairment as the most prominent early feature, with relative preservation of other cognitive domains for at least the first two years. The consensus classification (Gorno-Tempini et al., 2011) recognises three variants, each with distinct linguistic profiles and neuroanatomical correlates.

Semantic Variant PPA (svPPA)

Also known as semantic dementia, svPPA is characterised by:

• Confrontation naming impairment: progressive loss of the ability to name objects and understand single-word meanings (semantic knowledge).
• Impaired single-word comprehension: patients cannot recognise the meaning of words, even common ones (e.g., "What is a kangaroo?").
• Relatively preserved speech fluency: connected speech is fluent, grammatically correct, and well-articulated but becomes increasingly empty and devoid of specific content words.
• Surface dyslexia and dysgraphia: difficulty reading and spelling irregular words with preserved ability for regular words (e.g., reading "yacht" as "yatcht").
• Associative agnosia: may fail to recognise familiar faces (prosopagnosia) or objects (object agnosia).
• Neuroimaging: asymmetric (usually left > right) anterior temporal lobe atrophy, particularly affecting the inferior and middle temporal gyri.

Nonfluent/Agrammatic Variant PPA (nfvPPA)

nfvPPA is characterised by:

• Agrammatism: errors in sentence production with simplified, "telegraphic" speech, incorrect word order, and omission of grammatical morphemes.
class="guideline-li">Effortful, halting speech: apraxia of speech (motor planning difficulty for speech) with groping articulatory movements and distorted sound production.
• Spare single-word comprehension and object knowledge: in contrast to svPPA, word meaning is preserved in early stages.
• Spare motor speech: oral reading and repetition may be affected; sentence comprehension is impaired for syntactically complex sentences.
• Neuroimaging: left posterior frontoinsular atrophy, often involving the inferior frontal gyrus (Broca's area) and insula; FDG-PET shows corresponding hypometabolism.

Logopenic Variant PPA (lvPPA)

lvPPA is clinically distinct from the other PPA variants and is most commonly associated with Alzheimer's disease pathology (amyloid and tau) rather than FTD pathology:

• Impaired single-word retrieval in spontaneous speech: frequent word-finding pauses and anomia.
• Impaired repetition of sentences and phrases: difficulty repeating sentences of increasing length, while single-word repetition is relatively preserved.
• Phonological errors: speech sound paraphasias and phonological paraphasias in naming.
• Spare motor speech and grammar.
• Neuroimaging: left posterior peritemporal and parietal atrophy/hypometabolism; amyloid PET is often positive (distinguishing it from other PPA variants pathologically).

The co-occurrence of frontotemporal dementia and motor neuron disease (MND, also known as amyotrophic lateral sclerosis or ALS) represents one of the most clinically significant overlaps in neurodegeneration. Approximately 10–15% of FTD patients develop MND during the disease course, while up to 50% of MND patients show evidence of cognitive or behavioural impairment meeting criteria for FTD or FTD-spectrum disorder.

Clinical Features

• FTD-MND typically presents with behavioural or cognitive changes (most often bvFTD phenotype) preceding, coinciding with, or following motor neuron features.
• Motor features include upper motor neuron signs (spasticity, hyperreflexia, extensor plantar responses) and lower motor neuron signs (fasciculation, muscle wasting, weakness), commonly affecting bulbar and limb musculature.
• Bulbar involvement (dysarthria, dysphagia) is common and has major implications for communication, nutrition, and aspiration risk.
• Patients with FTD-MND may also exhibit a semantic dementia or nonfluent aphasia phenotype, though bvFTD is most common.

Genetic Associations

The C9orf72 hexanucleotide repeat expansion (GGGGCC repeat) is the most common genetic cause of both familial FTD and familial MND, and is found in a large proportion of FTD-MND cases. In Australian populations, C9orf72 expansions are identified in approximately 25–40% of familial FTD-MND cases. Genetic testing for C9orf72, MAPT, and GRN should be offered to all patients with FTD-MND and their families through a clinical genetics service with genetic counselling support.

Management Considerations

Management of FTD-MND requires a multidisciplinary team approach including neurology, speech pathology, dietetics, respiratory medicine, palliative care, and allied health. Key considerations include:

• Swallowing assessment: early and regular speech pathology input for dysphagia management and aspiration prevention.
• Nutritional support: dietitian involvement; PEG placement discussion early in the disease course while the patient can participate in decision-making.
• Respiratory monitoring: serial spirometry (FVC), sniff nasal inspiratory pressure (SNIP), overnight oximetry, and consideration of NIV referral when respiratory insufficiency develops.
• Communication aids: early referral to augmentative and alternative communication (AAC) services for both language impairment and dysarthria.
• Palliative care integration: early referral to specialist palliative care for symptom management and advance care planning.

There are currently no TGA-approved disease-modifying therapies for FTD. Management is therefore centred on non-pharmacological behavioural strategies, environmental modification, caregiver support, and judicious use of symptomatic pharmacotherapy. Early behavioural intervention and comprehensive family education are the cornerstones of optimal FTD care.

Non-Pharmacological Strategies

Pharmacological Management

Family Counselling and Carer Support

The behavioural changes in FTD are profoundly distressing for families and often lead to relationship breakdown, carer burnout, and grief responses. The personality changes mean that families are effectively "losing" the person while they remain physically present — a process sometimes described as "ambiguous loss." Key elements of family support include:

• Education: Provide clear, written information explaining that the behavioural changes are caused by brain disease, not intentional actions. Reassure families that the changes are not their fault.
• Dementia Australia: Refer to Dementia Australia (1800 100 500; dementia.org.au) for counselling, support groups, and the Dementia Helpline. They offer FTD-specific resources and young-onset dementia programs.
• Younger Onset Dementia Key Worker Program: Available in many Australian regions, this program provides a dedicated case coordinator for people with younger-onset dementia and their families.
• Carer Gateway: Australian Government Carer Gateway (carergateway.gov.au; 1800 422 737) for respite care, counselling, skills training, and financial support for carers.
• NDIS eligibility: People diagnosed with FTD before age 65 may be eligible for the National Disability Insurance Scheme (NDIS). Assist with applications and coordinate with the NDIS Local Area Coordinator.
• Legal and financial planning: Facilitate early powers of attorney (financial and medical), advance care directives, and review of insurance and superannuation (including disability superannuation access and total and permanent disability claims).
• Children and adolescents: Provide age-appropriate support and counselling for children of affected parents; Dementia Australia offers resources for young people in families affected by dementia.

FTD is characterised by selective degeneration of the frontal and temporal lobes, with three major molecular pathology subtypes classified by the predominant protein aggregation pattern:

Key Genetic Mutations

• C9orf72 (chromosome 9p21): Hexanucleotide (GGGGCC) repeat expansion — most common genetic cause of familial FTD and ALS. Normal alleles have <30 repeats; pathogenic alleles have hundreds to thousands. Found in ~40% of familial FTD, ~25% of familial ALS, and ~80% of FTD-MND families. Also causes dipeptide repeat protein (DPR) inclusions via repeat-associated non-ATG (RAN) translation.
• MAPT (chromosome 17q21): >50 known pathogenic mutations causing tau aggregation. Associated with tau-positive FTD pathology. Common haplotypes (H1, H2) also modulate disease risk.
• GRN (chromosome 17q21): Loss-of-function mutations causing haploinsufficiency of progranulin, a secreted glycoprotein involved in lysosomal function, inflammation, and cell survival. Results in TDP-43 type A pathology.

Red Flags for FTD

The following clinical features should prompt consideration of FTD, particularly in patients under 65 years:

• New-onset behavioural or personality change out of character for the individual
• Socially inappropriate behaviour (disinhibition) in a previously well-mannered person
• Loss of empathy, emotional blunting, or apparent callousness
• Progressive aphasia — difficulty finding words, constructing sentences, or understanding language
• New-onset compulsive or ritualistic behaviours
• Marked change in eating habits, particularly sweet food cravings
• Executive dysfunction — poor planning, organisation, and judgment disproportionate to memory impairment
• Psychiatric presentation that does not respond to standard psychiatric treatment
• Progressive speech difficulty (dysarthria) or swallowing difficulty (dysphagia) — consider FTD-MND
• Family history of FTD, MND/ALS, or dementia with autosomal dominant pattern

Exclusion Criteria

Probable bvFTD diagnostic criteria require that the condition is not better accounted for by another neurological disorder (e.g., cerebrovascular disease, multiple sclerosis), medical illness (e.g., hypothyroidism, vitamin B12 deficiency, syphilis), or psychiatric disorder (e.g., major depressive disorder, schizophrenia, bipolar disorder). All patients should have basic blood investigations to exclude reversible causes of cognitive decline.

Initial Screening (Exclude Reversible Causes)

Structural Neuroimaging

Functional Neuroimaging

CSF Biomarkers

Genetic Testing

Neuropsychological Assessment

Prognosis by Subtype

FTD is a progressive condition requiring regular clinical review and proactive management. There is no single biomarker that reliably tracks disease progression in clinical practice, so monitoring relies on structured clinical assessment.

Driving Assessment

FTD causes significant impairment in executive function, judgment, and social cognition, all of which compromise driving safety. Most patients should cease driving at or soon after diagnosis. In most Australian states and territories, the treating medical practitioner has mandatory reporting obligations to the relevant transport authority (e.g., VicRoads/Transport for NSW/TMR Queensland) when a patient has a condition likely to impair safe driving. Refer for formal occupational therapy driving assessment if there is diagnostic uncertainty. Austroads National Assessing Fitness to Drive guidelines (2022 edition) classify dementia as requiring individualised assessment.

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