Frontotemporal Dementia

1. Clinical Overview

Summary

Frontotemporal dementia (FTD) represents a heterogeneous group of neurodegenerative disorders characterized by progressive atrophy of the frontal and/or temporal lobes, representing the second most common cause of early-onset dementia (age less than 65 years) after Alzheimer's disease. Unlike Alzheimer's disease, FTD typically presents with early and prominent changes in personality, behavior, and/or language, with relative preservation of episodic memory and visuospatial function in early stages. [1,2]

FTD encompasses three main clinical syndromes: behavioral variant FTD (bvFTD), semantic variant primary progressive aphasia (svPPA), and nonfluent variant primary progressive aphasia (nfvPPA). [3] The underlying neuropathology—frontotemporal lobar degeneration (FTLD)—is characterized by abnormal accumulation of either tau protein (FTLD-tau) or TDP-43 protein (FTLD-TDP), with rare cases showing FUS protein inclusions. [4,17]

There is significant clinical and pathological overlap with motor neuron disease (MND/ALS), with approximately 15% of FTD patients developing MND features, and both conditions sharing genetic risk factors, particularly C9orf72 hexanucleotide repeat expansions. [5,6] Currently, there is no disease-modifying treatment; management focuses on symptomatic relief and caregiver support. [7]

Key Facts

• Definition: Progressive dementia due to frontal and/or temporal lobe degeneration
• Epidemiology: Incidence 2-5 per 100,000 per year; peak onset 55-65 years [1]
• Clinical Variants:
  • Behavioral variant FTD (bvFTD) - 60% of cases
  • Semantic variant PPA (svPPA) - 25% of cases
  • Nonfluent variant PPA (nfvPPA) - 15% of cases
• Pathology: FTLD-tau (40-50%), FTLD-TDP (45-50%), FTLD-FUS (less than 5%) [4,17]
• Genetics: 10-25% autosomal dominant; key genes MAPT, GRN, C9orf72 [8,18]
• Key Feature: Personality/behavior change (bvFTD) or language deterioration (PPA) before memory loss
• Memory: Often PRESERVED early (unlike Alzheimer's disease)
• Biomarkers: Elevated plasma neurofilament light chain (NfL), specific atrophy patterns on MRI [11]
• Treatment: No disease-modifying therapy; SSRIs for behavioral symptoms [7]

Clinical Pearls

"Personality Before Memory": In FTD, personality and behavior change or language difficulties appear BEFORE episodic memory loss. This is the cardinal distinction from Alzheimer's disease, where memory impairment is typically the presenting feature.

"Think FTD if Under 65": FTD accounts for 10-20% of early-onset dementia cases (age less than 65) and may be the most common cause in the 45-65 age group. Always consider it in younger patients with behavioral or language decline, especially with a family history. [1]

"Donepezil Doesn't Work (and May Worsen)": Unlike Alzheimer's disease, FTD is not primarily a cholinergic disorder. Acetylcholinesterase inhibitors are generally NOT effective and may worsen behavioral symptoms. [7,19]

"The FTD-MND Spectrum": Approximately 15% of FTD patients develop motor neurone disease features, and conversely, up to 50% of ALS patients show cognitive/behavioral changes. [5,6] Look for bulbar signs, fasciculations, and limb weakness. The C9orf72 gene links both conditions.

"Sweet Tooth and Stereotypies": Hyperorality (sweet food cravings, dietary changes) and compulsive/stereotyped behaviors are highly characteristic of bvFTD and help distinguish it from psychiatric disorders and Alzheimer's disease. [2]

"Asymmetric Atrophy Matters": Imaging often shows asymmetric frontal or temporal atrophy. Left temporal predominance suggests svPPA; left frontal/insular predominance suggests nfvPPA; right frontal predominance may present with prominent behavioral changes and loss of social cognition.

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2. Epidemiology

Incidence and Prevalence

• Incidence: 2-5 per 100,000 person-years [1]
• Prevalence: 15-22 per 100,000 (age 45-64 years)
• Early-Onset Dementia: Second most common cause after Alzheimer's disease (10-20% of cases)
• Age-Specific: May be the MOST common dementia in the 45-65 age group

Demographics

Age at Onset:

• Peak onset: 55-65 years (range 21-80 years) [1]
• Mean age at diagnosis: 58-60 years
• Earlier onset associated with genetic forms (mean age 49 years for MAPT mutations) [18]

Sex Distribution:

• Overall: Roughly equal M:F ratio
• bvFTD: Slight male predominance (M:F ≈ 1.3:1)
• PPA variants: Slight female predominance

Genetics and Family History

Heritability: [8]

• 40% of patients have a positive family history of dementia
• 10-25% have autosomal dominant inheritance
• 9-13% have identifiable pathogenic mutations

Major Genes:

C9orf72 Expansion:

• Hexanucleotide (GGGGCC) repeat expansion on chromosome 9 [6]
• Normal: less than 30 repeats; Pathogenic: > 60 repeats (often hundreds/thousands)
• Most common genetic cause of both FTD and ALS
• Associated with TDP-43 type B pathology and psychotic symptoms [9]

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3. Pathophysiology

Macroscopic Neuropathology

Gross Pathology:

• Selective atrophy of frontal and anterior temporal lobes
• Pattern varies by clinical syndrome:
  • "bvFTD: Frontal > temporal, often asymmetric"
  • "svPPA: Anterior temporal (left > right)"
  • "nfvPPA: Left posterior frontal and insular regions"
• Atrophy extends to:
  • "Subcortical structures: caudate, thalamus, substantia nigra"
  • "White matter: corpus callosum, internal capsule"
  • Posterior regions typically spared until late stages

Weight Loss:

• Brain weight may be reduced to 800-1000g (normal ~1400g)
• "Walnut brain" or "knife-blade" atrophy in severe cases

Microscopic Neuropathology

Cellular Changes:

• Neuronal loss (layers II-III cortex predominantly)
• Gliosis (astrocytic and microglial activation) [20]
• Spongiosis (microvacuolation) in superficial cortical layers
• Abnormal protein inclusions (tau, TDP-43, or FUS)

Molecular Pathology: FTLD Classification

Frontotemporal lobar degeneration (FTLD) is classified by the predominant abnormal protein: [4]

FTLD-Tau (40-50% of FTLD)

Tau is a microtubule-associated protein that normally stabilizes microtubules in neurons. In FTLD-tau, mutations in the MAPT gene on chromosome 17 disrupt normal tau binding to tubulin, resulting in pathological deposits of hyperphosphorylated tau protein. [17,18] Alternative splicing of the MAPT gene yields six tau protein isoforms, each containing either three or four microtubule-binding repeat domains (3R or 4R tau), which are associated with dynamic and stable microtubules respectively. [18]

Subtypes Based on Tau Isoforms:

• 3R tau: Pick's disease (spherical Pick bodies, ballooned neurons)
• 4R tau: Progressive supranuclear palsy (PSP), corticobasal degeneration (CBD), argyrophilic grain disease (AgD), globular glial tauopathy (GGT)
• 3R + 4R tau: Rare, includes some familial cases with MAPT mutations

Key Pathologies:

FTLD-TDP (45-50% of FTLD)

TDP-43 (TAR DNA-binding protein 43): [4,10,21]

• Nuclear protein involved in RNA processing and gene regulation
• In disease: mislocalized to cytoplasm, hyperphosphorylated, ubiquitinated, cleaved into C-terminal fragments
• Forms neuronal cytoplasmic inclusions (NCIs), dystrophic neurites (DNs), and neuronal intranuclear inclusions (NIIs)
• TDP-43 pathology is now recognized as a continuum spanning over 100 years of neuropathological observation [21]

FTLD-TDP Subtypes (Mackenzie classification):

FTLD-FUS (less than 5% of FTLD)

FUS (Fused in Sarcoma): [10]

• RNA-binding protein
• Rare; associated with:
  • Atypical FTLD with ubiquitin-positive inclusions (aFTLD-U)
  • Neuronal intermediate filament inclusion disease (NIFID)
  • Basophilic inclusion body disease (BIBD)
• Typically young onset (less than 40 years), aggressive course

Why Behavior and Language Are Affected

Frontal Lobe Functions (affected in bvFTD):

• Executive function: planning, organization, working memory
• Social cognition: empathy, theory of mind
• Behavioral regulation: impulse control, initiation, motivation
• Emotional processing: apathy, emotional blunting

Temporal Lobe Functions (affected in svPPA):

• Left anterior temporal: Semantic memory (word and object meaning)
• Right anterior temporal: Face recognition, social perception, emotional processing
• Ventral temporal cortex: Object recognition, conceptual knowledge

Left Frontal/Insular Functions (affected in nfvPPA):

• Motor speech programming (Broca's area, insula)
• Syntax processing (inferior frontal gyrus)
• Phonological processing

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4. Clinical Presentation

Clinical Variants and Diagnostic Criteria

The three main FTD syndromes are defined by consensus diagnostic criteria: [2,3]

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Behavioral Variant FTD (bvFTD)

Definition: Most common FTD variant (60%), characterized by progressive behavioral and personality changes with frontal and/or temporal lobe atrophy.

Revised Diagnostic Criteria (Rascovsky et al., 2011) [2]:

I. Possible bvFTD (3 of 6 features required):

1. Early behavioral disinhibition (≥1):

   • Socially inappropriate behavior (e.g., inappropriate jokes, overfamiliarity with strangers)
   • Loss of social tact or decorum
   • Impulsive, rash, or careless actions

2. Early apathy or inertia (≥1):

   • Loss of motivation, drive, spontaneity
   • Reduced initiation of activities
   • Emotional indifference

3. Early loss of sympathy or empathy (≥1):

   • Reduced emotional responsiveness to others' needs
   • Diminished social interest, interrelatedness, or personal warmth
   • Loss of insight into emotional states of others

4. Early perseverative, stereotyped, or compulsive/ritualistic behavior (≥1):

   • Simple repetitive movements (hand rubbing, clapping, tapping)
   • Complex compulsive or ritualistic behaviors (hoarding, checking, counting)
   • Stereotypy of speech (echolalia, perseveration, stock phrases)

5. Hyperorality and dietary changes (≥1):

   • Sweet food preference or increased consumption
   • Dietary changes (hyperphagia, food fads, increased smoking/alcohol)
   • Oral exploration or consumption of inedible objects

6. Executive deficits with relative sparing of memory and visuospatial functions:

   • Impaired planning, organization, problem-solving
   • Reduced abstract reasoning, mental flexibility
   • Episodic memory relatively preserved (vs. Alzheimer's disease)
   • Visuospatial skills intact (can copy complex figures, navigate)

II. Probable bvFTD requires:

• Meets criteria for possible bvFTD, PLUS
• Functional decline (caregiver report or clinical assessment)
• Imaging showing frontal and/or temporal atrophy, hypometabolism, or hypoperfusion

III. Definite bvFTD requires:

• Meets criteria for possible or probable bvFTD, PLUS
• Histopathological evidence of FTLD, OR
• Known pathogenic mutation

Clinical Progression of bvFTD:

bvFTD Phenocopies ("Phenocopy Syndrome"): [11]

• 10-30% of patients with behavioral changes suggestive of bvFTD show no progression over many years
• Neuroimaging shows no/minimal atrophy
• Plasma neurofilament light chain (NfL) levels are normal [11]
• May represent psychiatric disorder, personality disorder, or static brain injury
• Important to distinguish from true bvFTD to avoid unnecessary investigations and prognostic counseling

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Semantic Variant Primary Progressive Aphasia (svPPA)

Definition: Progressive loss of semantic memory (knowledge of word and object meaning) with fluent but empty speech, associated with left-predominant anterior temporal lobe atrophy. [3]

Core Diagnostic Features (Gorno-Tempini et al., 2011) [3]:

Both of the following must be present:

1. Impaired confrontation naming (cannot name objects shown to them)
2. Impaired single-word comprehension (cannot point to named objects)

At least 3 of the following: 3. Impaired object knowledge (cannot describe what an object is used for) 4. Surface dyslexia or dysgraphia (irregular word reading errors: "yacht" → "yatched") 5. Spared repetition (can repeat sentences verbatim) 6. Spared speech production (grammar, motor speech intact)

Clinical Features:

• Language:

  • Fluent, grammatically correct speech but semantically empty
  • Loss of word meaning → circumlocution ("the thing you use to cut" for "knife")
  • Anomia (word-finding difficulty) for low-frequency words initially
  • Cannot define words or match words to pictures
  • "Surface dyslexia: Cannot read irregular words (rely on phonetics)"
  • Preserved repetition and phonology

• Behavioral (especially right temporal involvement):

  • Loss of empathy and social knowledge
  • Behavioral changes similar to bvFTD (loss of sympathy, rigidity, compulsions)
  • Prosopagnosia (face recognition deficits) if right temporal lobe affected

• Preserved:

  • Episodic memory (day-to-day memory for events)
  • Visuospatial skills
  • Motor speech (fluent speech production)

Progression:

• Gradual extension of semantic loss (high-frequency words eventually affected)
• Behavioral changes emerge (especially with right temporal progression)
• Eventually global dementia with mutism, severe behavioral disturbance

Typical Patient Presentation:

A 62-year-old woman presents with 2-year history of difficulty finding words. She describes objects ("the thing for opening wine") rather than naming them. Reading aloud is impaired for irregular words ("pint" → "pint" rhyming with "hint"). She can repeat sentences perfectly but doesn't understand what "walrus" or "anchor" mean. Memory for recent events is intact. MRI shows left anterior temporal atrophy.

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Nonfluent Variant Primary Progressive Aphasia (nfvPPA)

Definition: Progressive apraxia of speech and/or agrammatism with effortful, halting speech, associated with left posterior frontal/insular atrophy. [3,22]

Core Diagnostic Features (Gorno-Tempini et al., 2011) [3]:

At least one of the following must be present:

1. Agrammatism in language production (simplified grammar, omission of grammatical morphemes)
2. Effortful, halting speech with inconsistent speech sound errors and distortions (apraxia of speech) [22]

At least 2 of 3 of the following: 3. Impaired comprehension of syntactically complex sentences (preserved for simple sentences) 4. Spared single-word comprehension 5. Spared object knowledge

Clinical Features:

• Speech and Language:

  • "Apraxia of speech: Effortful, slow, halting; articulatory errors; distorted sounds [22]"
  • Agrammatism: Telegraphic speech ("man... walk... dog" instead of "The man is walking the dog")
  • Omission of grammatical morphemes (articles, prepositions, verb endings)
  • Difficulty with complex sentence comprehension (reversible passives: "The dog was chased by the cat")
  • "Preserved: Single-word comprehension, object knowledge, word meaning"

• Motor Speech:

  • Reduced speech rate (often less than 100 words/minute)
  • Phonemic paraphasias (sound substitutions)
  • Speech becomes increasingly effortful and limited
  • Eventually may progress to mutism

• Cognition:

  • Executive dysfunction (related to frontal involvement)
  • Episodic memory relatively preserved
  • Visuospatial skills intact

Overlap with Motor Syndromes:

• Progressive supranuclear palsy (PSP): Vertical gaze palsy, axial rigidity, falls
• Corticobasal syndrome (CBS): Asymmetric rigidity, limb apraxia, myoclonus, alien limb
• nfvPPA often evolves to include parkinsonism and motor features

Typical Patient Presentation:

A 58-year-old man presents with 18-month history of "struggling to get words out." Speech is slow and effortful. He omits small words ("went shop yesterday" instead of "I went to the shop yesterday"). He understands conversations and knows what objects are. Repeat speech examination shows inconsistent sound distortions. MRI shows left frontal and insular atrophy.

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Associated Motor Syndromes

FTD frequently overlaps with movement disorders:

FTD-Motor Neuron Disease (FTD-MND)

Epidemiology: [5,6]

• 15% of FTD patients develop MND features
• 30-50% of ALS patients have cognitive/behavioral impairment
• Male predominance (M:F = 3:1)

Clinical Features:

• Combination of behavioral/cognitive changes (bvFTD-like) PLUS:
  • "Upper motor neuron signs: Spasticity, hyperreflexia, extensor plantars"
  • "Lower motor neuron signs: Weakness, wasting, fasciculations"
  • "Bulbar dysfunction: Dysarthria, dysphagia, tongue wasting/fasciculations"
• Rapid progression (median survival 2-3 years)

Genetics:

• C9orf72 hexanucleotide expansion most common (50% of familial FTD-MND) [6]
• Also: TARDBP, VCP, SQSTM1, CHCHD10, TBK1

Pathology:

• FTLD-TDP (usually Type B with C9orf72)
• TDP-43 inclusions in both cortex and spinal cord motor neurons

FTD with Parkinsonism

Progressive Supranuclear Palsy (PSP):

• Vertical supranuclear gaze palsy (downgaze first)
• Axial rigidity > limb rigidity
• Early postural instability and falls (backwards)
• bvFTD or nfvPPA phenotype
• 4R tau pathology

Corticobasal Syndrome (CBS):

• Asymmetric rigidity and bradykinesia
• Limb apraxia, alien limb phenomenon
• Cortical sensory loss, myoclonus
• nfvPPA or cognitive impairment
• 4R tau (CBD) or Alzheimer pathology

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5. Clinical Examination

History Taking

Key Questions:

Behavioral Changes (for bvFTD):

• "Have you noticed changes in your/their personality or behavior?"
• "Any inappropriate comments, actions, or loss of social awareness?"
• "Changes in motivation, interest, or emotional response?"
• "Any repetitive behaviors, routines, or compulsions?"
• "Changes in food preferences, particularly sweet foods?"
• "Any changes in personal hygiene or self-care?"

Language Changes (for PPA):

• "Any difficulty finding words or understanding speech?"
• "Changes in speech fluency or articulation?"
• "Difficulty understanding conversations or written material?"

Cognitive Changes:

• "Any problems with memory, planning, or organization?"
• "Difficulties with navigation or recognizing familiar places/faces?"

Motor Symptoms (for FTD-MND):

• "Any weakness, clumsiness, or changes in walking?"
• "Difficulty with speech or swallowing?"
• "Muscle twitching?"

Family History:

• "Any family history of dementia, especially early-onset?"
• "Any family history of motor neuron disease or ALS?"

Functional Impact:

• "Has this affected work, finances, driving, or daily activities?"
• "Who manages household tasks and medications?"

Mental State Examination

Appearance and Behavior:

• Disinhibited behavior: overfamiliarity, inappropriate comments
• Apathy: reduced spontaneity, flat affect, lack of engagement
• Stereotyped behaviors: repetitive movements, rituals
• Hyperorality: eating during interview, chewing objects
• Poor hygiene or social presentation (in contrast to preserved dressing)

Speech:

• bvFTD: Reduced spontaneous speech; may be echolalic or perseverative
• svPPA: Fluent but empty; circumlocutions; anomia
• nfvPPA: Non-fluent, effortful, halting; agrammatic; apraxic errors

Mood and Affect:

• Emotional blunting, reduced empathy
• Lack of insight (anosognosia)
• May exhibit euphoria or inappropriate jocularity
• Depression or anxiety (especially early stages or PPA variants)

Thought:

• Concrete thinking, reduced abstraction
• Perseveration, rigidity of thought
• Delusions (more common in FTLD-TDP, especially C9orf72) [9]

Cognitive Assessment

Bedside Cognitive Tests:

General Screens (often INSENSITIVE in FTD):

• MMSE: May be NORMAL or mildly impaired (especially in PPA; fails to assess executive/language adequately)
• MoCA: Better than MMSE; includes executive tasks
• ACE-III: Preferred; subscales for language, fluency, memory, visuospatial

Executive Function Tests:

• Verbal fluency:
  • "Phonemic (FAS): Impaired in all FTD subtypes (especially bvFTD, nfvPPA)"
  • "Semantic (animals, fruits): Most impaired in svPPA"
  • less than 10 words in 1 minute is abnormal
• Proverb interpretation: Concrete, literal responses
• Frontal Assessment Battery (FAB): Assesses executive functions

Language Assessment (for PPA):

• Naming: Boston Naming Test, Graded Naming Test (impaired in svPPA > nfvPPA)
• Comprehension: Word-picture matching (impaired in svPPA)
• Repetition: Preserved in svPPA; impaired in nfvPPA (apraxia of speech)
• Reading aloud: Surface dyslexia in svPPA (irregular word errors)
• Sentence comprehension: Impaired for syntactically complex sentences in nfvPPA

Memory:

• Episodic memory: Relatively PRESERVED in early FTD (vs. Alzheimer's)
• Recognition better than free recall
• Semantic memory: Impaired in svPPA

Visuospatial:

• PRESERVED in FTD (can copy complex figures, clock drawing)
• Helps distinguish from Alzheimer's disease

Neurological Examination

Key Findings:

Primitive Reflexes (frontal release signs):

• Grasp reflex: Hand closure when palm stroked
• Palmomental reflex: Chin contraction when palm scratched
• Snout/pout reflex: Lip protrusion when tapped
• Glabellar tap: Failure to habituate to repeated tapping
• Present in moderate-advanced bvFTD

Parkinsonism (if overlap with PSP, CBD):

• Rigidity (axial > limbs in PSP; asymmetric in CBS)
• Bradykinesia
• Vertical gaze palsy (PSP)
• Apraxia, alien limb (CBS)
• Myoclonus (CBS)

Motor Neuron Disease Signs (if FTD-MND):

• Upper motor neuron: Spasticity, hyperreflexia, upgoing plantars, brisk jaw jerk
• Lower motor neuron: Weakness, wasting, fasciculations (especially tongue)
• Bulbar signs: Tongue wasting, fasciculations; dysarthria; dysphagia

Speech and Language Examination:

• Spontaneous speech
• Naming (objects, body parts)
• Repetition (words, sentences)
• Comprehension (commands, complex sentences)
• Reading aloud
• Writing

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6. Investigations

Cognitive and Neuropsychological Testing

Detailed Neuropsychology:

• Essential for differential diagnosis and variant classification
• Domains assessed:
  • Executive function (planning, cognitive flexibility, inhibition)
  • Language (naming, comprehension, fluency, syntax)
  • Episodic memory (verbal and visual)
  • Semantic memory (word/object knowledge)
  • Visuospatial function
  • Social cognition (emotion recognition, theory of mind)

FTD Pattern:

• Executive dysfunction: Impaired verbal fluency, trails, Wisconsin card sort
• Memory: Episodic memory relatively preserved (recognition > recall)
• Language: Impaired in PPA variants
• Visuospatial: Preserved (distinguishes from Alzheimer's disease)

Neuroimaging

Structural MRI Brain

Purpose: Identify atrophy patterns, exclude other pathology

FTD-Specific Findings: [12]

Additional Features:

• "Knife-blade" atrophy: Severe gyral atrophy with widened sulci
• Ventricular enlargement (frontal horns)
• Corpus callosum thinning
• Hippocampal atrophy (less prominent than Alzheimer's disease)

MRI May Be Normal: In ~20-30% of early cases, especially bvFTD

Volumetric MRI: Quantitative measures improve sensitivity

Functional Imaging

FDG-PET (Fluorodeoxyglucose Positron Emission Tomography): [12]

• Shows hypometabolism corresponding to clinical syndrome
• More sensitive than MRI, especially in early disease
• Findings mirror structural atrophy patterns:
  • "bvFTD: Frontal and/or anterior temporal hypometabolism"
  • "svPPA: Left anterior temporal hypometabolism"
  • "nfvPPA: Left inferior frontal/insular hypometabolism"
• Useful when MRI is normal but clinical suspicion high

Amyloid PET (if available):

• Negative in most FTD cases (helps exclude Alzheimer's disease)
• May be positive in logopenic variant PPA (usually Alzheimer pathology, not FTD)
• Occasionally positive in elderly FTD patients (incidental amyloid)

Tau PET:

• Emerging tool; may distinguish FTLD-tau from FTLD-TDP
• Second-generation tracers show promise for 4R tauopathies (PSP, CBD)

SPECT (Single Photon Emission Computed Tomography)

• Shows hypoperfusion in affected regions
• Less sensitive than FDG-PET; used when PET unavailable

Blood Tests

Purpose: Exclude reversible causes of cognitive impairment

Routine Screen:

• Full blood count (FBC)
• Urea and electrolytes (U&E)
• Liver function tests (LFT)
• Thyroid function (TSH, free T4)
• Vitamin B12 and folate
• Calcium, phosphate
• Glucose / HbA1c
• Syphilis serology (VDRL/TPPA)
• HIV serology (if risk factors or younger patients)

Specialized Tests (if indicated):

• Autoimmune screen: ANA, ANCA, anti-thyroid antibodies
• Inflammatory markers: ESR, CRP
• Vasculitis screen
• Paraneoplastic antibodies (if rapid onset, atypical features)

Biomarkers

Plasma Neurofilament Light Chain (NfL)

Utility: [11]

• Marker of neuronal damage; elevated in neurodegenerative diseases
• Elevated in FTD syndromes (median ~40-45 pg/mL)
• Normal or low in phenocopy bvFTD (median ~14 pg/mL)
• Highest in FTD-MND (median ~80 pg/mL)
• Helps distinguish true FTD from psychiatric mimics and slow progressors
• Levels correlate with disease severity and progression

Interpretation:

• Age-dependent: Increases with age (age-corrected reference ranges needed)
• Non-specific: Elevated in many neurodegenerative diseases (Alzheimer's, MND, MS)

Cerebrospinal Fluid (CSF)

Indications:

• Atypical features
• Exclude inflammatory/infectious causes
• Differentiate from Alzheimer's disease

CSF in FTD:

• Usually normal or non-specific changes
• Mildly elevated total protein (occasional)
• Normal amyloid-β42 and tau (helps exclude Alzheimer's disease)
  • "In Alzheimer's: Low Aβ42, high total tau, high phospho-tau"
  • "In FTD: Normal or mildly abnormal tau; Aβ42 normal"
• Elevated NfL: Correlates with neurodegeneration

Genetic Testing

Indications:

• Age at onset less than 60 years
• Strong family history (≥1 first-degree relative with dementia or MND)
• Autosomal dominant pattern (3 generations affected)
• Specific clinical features (e.g., psychosis suggests C9orf72; parkinsonism suggests MAPT)
• FTD-MND overlap

Genes to Test (in order of frequency):

1. C9orf72 hexanucleotide repeat expansion (most common)
2. GRN (progranulin) gene sequencing
3. MAPT (tau) gene sequencing
4. Additional genes if indicated: TARDBP, VCP, FUS, CHMP2B, SQSTM1, TBK1

Genetic Counseling: Essential before and after testing

Electroencephalography (EEG)

Utility: Limited in FTD

Findings:

• Often normal or non-specific slowing
• May show focal slowing over affected regions
• Helps exclude:
  • Seizure disorders (especially if episodic behavioral changes)
  • Creutzfeldt-Jakob disease (periodic sharp wave complexes absent in FTD)

Lumbar Puncture

Indications:

• Atypical features: rapid progression, inflammatory markers, younger age
• Exclude inflammatory/autoimmune causes: encephalitis, vasculitis, paraneoplastic syndromes
• Exclude infectious causes: HIV, syphilis, Whipple's disease
• Exclude prion disease (if rapid progression, myoclonus)

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7. Differential Diagnosis

Primary Differential Diagnoses

Distinguishing FTD from Alzheimer's Disease

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8. Management

General Principles

No Disease-Modifying Treatment: Currently, no therapies slow or stop FTLD pathology. [7]

Management Goals:

1. Symptomatic management of behavioral and psychiatric symptoms
2. Supportive care for patients and caregivers
3. Safety planning (driving, financial capacity, wandering)
4. Advance care planning early in disease course
5. Multidisciplinary team involvement

Pharmacological Management

Behavioral Symptoms

SSRIs (Selective Serotonin Reuptake Inhibitors): [7,13]

• First-line for behavioral symptoms in bvFTD
• Useful for: disinhibition, compulsive behaviors, irritability, emotional lability, hyperphagia
• Evidence: Limited RCT data, but widely used based on open-label studies and clinical experience
• Agents:
  • Sertraline 50-200 mg daily
  • "Citalopram 20-40 mg daily (caution: QTc prolongation > 20 mg in elderly)"
  • Escitalopram 10-20 mg daily
  • Fluoxetine 20-60 mg daily (longer half-life)
• Start low, titrate slowly, allow 4-8 weeks for effect

Trazodone: [13]

• Low-dose (50-150 mg) for agitation, irritability, sleep disturbance
• Sedating; useful for nighttime behavioral disturbance
• Fewer anticholinergic side effects than tricyclics

Antipsychotics:

• Use with CAUTION: Limited evidence; risk of worsening parkinsonism, sedation, falls, stroke
• Reserve for severe agitation unresponsive to other measures
• If needed:
  • Quetiapine 25-100 mg (sedating, less extrapyramidal side effects)
  • Risperidone 0.5-2 mg (more extrapyramidal effects)
  • Olanzapine 2.5-10 mg (weight gain, metabolic effects)
• Avoid typical antipsychotics (haloperidol) due to extrapyramidal side effects
• Use lowest effective dose for shortest duration

Mood Stabilizers (limited evidence):

• Valproate: For aggression, agitation (hepatotoxicity, tremor, weight gain)
• Carbamazepine: For agitation (drug interactions, hyponatremia)

Cognitive Symptoms

Acetylcholinesterase Inhibitors (Donepezil, Rivastigmine, Galantamine):

• NOT RECOMMENDED in FTD [7,19]
• No evidence of benefit; trials show lack of efficacy [19]
• May worsen behavioral symptoms (disinhibition, agitation)
• Mechanism: FTD not primarily cholinergic deficit (unlike Alzheimer's)

Memantine (NMDA receptor antagonist):

• Limited evidence; some studies suggest worsening
• Not routinely recommended

FTD-MND Specific

Riluzole:

• If motor neuron disease features present
• Modest survival benefit (2-3 months)
• 50 mg twice daily

Symptom Management:

• Sialorrhea: Anticholinergics (glycopyrrolate), botulinum toxin
• Spasticity: Baclofen, tizanidine
• Dysphagia: Speech and language therapy, dietitian, PEG consideration

Non-Pharmacological Management

Behavioral Interventions

Environmental Modifications:

• Structured daily routine
• Reduce environmental complexity and stimuli
• Remove triggers for inappropriate behavior
• Safe environment (lock cupboards, remove sharp objects, install alarms)

Behavioral Strategies:

• Positive reinforcement
• Distraction and redirection
• Avoid confrontation or reasoning (ineffective due to lack of insight)
• Identify triggers (hunger, fatigue, overstimulation)

Multidisciplinary Team

Speech and Language Therapy:

• PPA variants: Communication strategies, augmentative/alternative communication (AAC)
• Dysphagia: Swallowing assessment, diet modification

Occupational Therapy:

• Home safety assessment
• Activity planning, meaningful engagement
• Cognitive and functional strategies

Physiotherapy:

• Mobility assessment
• Falls prevention
• Exercise programs (if parkinsonism or FTD-MND)

Dietitian:

• Nutritional support (hyperphagia vs. dysphagia)
• Manage dietary changes, sweet food cravings
• Texture-modified diet if dysphagia

Clinical Psychology/Psychiatry:

• Carer psychological support
• Management of behavioral symptoms
• Distinguish FTD from primary psychiatric disorder

Social Work:

• Benefits and financial support
• Respite care, day services
• Residential care planning

Caregiver Support

Education:

• Disease course, prognosis, management strategies
• Behavioral management techniques
• Safety planning

Psychological Support:

• Caregiver burden high (behavioral symptoms particularly distressing) [14]
• Psychological therapy, support groups
• Respite care essential

Organizations:

• UK: Rare Dementia Support, Alzheimer's Society, FTD Support Group
• US: Association for Frontotemporal Degeneration (AFTD)
• Australia: FTD Support Group Australia, Dementia Australia

Safety and Legal Considerations

Driving:

• Assess fitness to drive (executive dysfunction impairs driving)
• Inform DVLA (UK) or equivalent authority
• Usually requires cessation of driving

Financial Capacity:

• Assess decision-making capacity early
• Lasting Power of Attorney (LPA) / Enduring Power of Attorney (EPA)
• Protect from financial exploitation (disinhibition, impulsivity)

Capacity Assessment:

• Mental Capacity Act (UK) / equivalent legislation
• Assess capacity for specific decisions (treatment, residence, finances)

Advance Care Planning: [14]

• Advance Directive / Living Will: Preferences for future care
• Do Not Attempt Resuscitation (DNAR) discussions
• PEG feeding: Discuss early (dysphagia common in late FTD)
• Preferred place of care/death
• Complete while patient has capacity (early in disease)

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9. Prognosis and Natural History

Survival

Median Survival: [14]

• Overall: 6-8 years from symptom onset (range 2-20 years)
• bvFTD: 7-8 years
• svPPA: 10-12 years (longest survival)
• nfvPPA: 7-10 years
• FTD-MND: 2-3 years (shortest survival) [5]

Prognostic Factors:

Disease Progression

Typical Course:

Early Stage (Years 1-3):

• Behavioral changes (bvFTD) or language decline (PPA)
• Preserved independence for basic activities
• Loss of employment common
• Social difficulties, relationship strain
• Driving cessation usually required

Middle Stage (Years 3-5):

• Progressive cognitive decline
• Loss of independence for instrumental ADLs
• Require supervision for safety
• Behavioral symptoms intensify
• Communication increasingly impaired (especially PPA → mutism)
• Parkinsonism may emerge

Late Stage (> 5 years):

• Profound cognitive impairment
• Mutism common
• Total dependence for all care
• Immobility, bedbound
• Dysphagia, aspiration risk
• Primitive reflexes
• Incontinence

Causes of Death

Common Causes: [14]

• Pneumonia (aspiration most common)
• Sepsis (urinary, respiratory)
• Complications of immobility: Pressure ulcers, deep vein thrombosis, pulmonary embolism
• Respiratory failure (if FTD-MND)
• Sudden cardiac death (rare)

End-of-Life Care:

• Palliative care involvement
• Symptom management: pain, dyspnea, agitation
• PEG feeding decisions (may prolong dying rather than life; discuss early)
• Preferred place of death (home, hospice, hospital)

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10. Emerging Therapies and Research

Therapeutic Targets

Disease-Modifying Approaches (in clinical trials):

Anti-Tau Therapies: [17,18]

• Tau aggregation inhibitors
• Anti-tau antibodies (passive immunotherapy)
• Tau vaccines (active immunotherapy)
• Microtubule stabilizers
• MAPT gene therapy approaches

Anti-TDP-43 Therapies: [15,21]

• Gene therapy targeting TDP-43 pathology (preclinical success in mouse models)
• Antisense oligonucleotides (ASOs)
• Small molecules to prevent TDP-43 aggregation
• 14-3-3θ targeting to reduce cytoplasmic TDP-43 [15]

Progranulin Replacement (for GRN mutations):

• Recombinant progranulin infusions
• Gene therapy to increase progranulin expression
• Small molecules to enhance progranulin production

Anti-Inflammatory Approaches:

• Microglial modulators
• Anti-inflammatory agents

Neuroprotective Agents:

• Neurotrophic factors
• Autophagy enhancers

Biomarker Development

Fluid Biomarkers:

• Neurofilament light chain (NfL): Progression marker [11]
• Progranulin levels: Low in GRN mutation carriers
• TDP-43: Blood/CSF assays under development
• microRNAs, exosomes: Emerging markers

Imaging Biomarkers:

• Tau PET: Second-generation tracers for 4R tau (PSP, CBD)
• Volumetric MRI: Sensitive progression marker
• FDG-PET: Track hypometabolism over time

Genetic Risk Scores:

• Polygenic risk prediction for sporadic FTD

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11. Special Considerations

Young-Onset Dementia Services

Specific Needs: [16]

• Different from older dementia patients:
  • Employment loss, financial impact
  • Young children at home
  • Marital/relationship strain
  • Lack of age-appropriate services
• Require:
  • Specialized young-onset dementia services
  • Peer support groups
  • Financial counseling, disability benefits
  • Genetic counseling for family members
  • Educational support for children

Genetic Counseling

Indications:

• Strong family history (especially autosomal dominant)
• Young onset (less than 60 years)
• Patient/family request

Pre-Test Counseling:

• Inheritance patterns
• Implications for family members
• Insurance, employment discrimination concerns
• Predictive testing in asymptomatic relatives (ethical considerations)

Post-Test Counseling:

• Results interpretation
• Implications for family planning
• Cascade testing for relatives
• Psychological support

Driving and FTD

Risks:

• Executive dysfunction → poor judgment, impulsivity
• Disinhibition → risky driving behaviors
• Reduced insight → lack of awareness of impairment

Assessment:

• Clinical assessment of cognitive/executive function
• On-road driving assessment if borderline
• Most patients require driving cessation at diagnosis or shortly after

Legal Requirements:

• Inform licensing authority (DVLA in UK, DMV in US)
• Physician has duty to warn if patient continues driving against advice

Capacity and Consent

Capacity Assessment:

• FTD patients often lack insight (anosognosia)
• Assess capacity for specific decisions:
  • Medical treatment
  • Research participation
  • Financial decisions
  • Where to live
• Use structured capacity assessments (e.g., Mental Capacity Act framework)

Research Participation:

• Many FTD patients lack capacity for informed consent
• Consultee/proxy consent may be used (depending on jurisdiction)
• Advance consent directives (when patient still has capacity)

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12. Patient and Layperson Explanation

What is Frontotemporal Dementia?

Frontotemporal dementia (FTD) is a type of dementia that affects the front and sides of the brain (the frontal and temporal lobes). These parts of the brain control:

• Personality and behavior
• Language and communication
• Planning and decision-making

FTD usually affects people younger than typical dementia—often in their 50s or early 60s—which is why it's sometimes called "young-onset dementia."

How is FTD Different from Alzheimer's Disease?

The main difference is what changes first:

• Alzheimer's disease: Memory problems come first
• FTD: Personality, behavior, or language problems come first

In FTD, memory often stays quite good in the early stages, which can be confusing because people expect dementia to affect memory first.

What Are the Symptoms?

FTD affects people in different ways depending on which part of the brain is affected:

Behavioral Variant FTD (most common):

• Acting inappropriately or saying embarrassing things
• Loss of empathy or caring about others
• Loss of motivation or interest in activities
• Repetitive behaviors or rituals
• Changes in eating (especially craving sweet foods)
• Personality changes (becoming a "different person")

Language Variants (Primary Progressive Aphasia):

• Semantic variant: Losing the meaning of words, difficulty naming objects, can still speak fluently
• Nonfluent variant: Struggling to get words out, effortful speech, simplified grammar

Why Does FTD Happen?

FTD is caused by abnormal proteins building up in brain cells, causing them to die. The two main proteins are:

• Tau: A protein that normally helps brain cells function [17,18]
• TDP-43: A protein involved in how cells read genetic information [21]

In some families, FTD is inherited (passed down through genes). About 1 in 3 people with FTD have a family history. [8]

Connection to Motor Neuron Disease

About 15 in 100 people with FTD also develop motor neuron disease (also called ALS), which causes muscle weakness. [5,6] The two conditions can overlap because they sometimes involve the same abnormal proteins.

Is There a Treatment?

Unfortunately, there is no cure or treatment that can slow FTD down. However, there are things that can help:

Medications:

• Antidepressants (SSRIs) can help with some behavioral symptoms [7,13]
• Other medications for agitation or sleep problems
• Note: Alzheimer's medications (like donepezil) do NOT work for FTD and may make things worse [7,19]

Support:

• Speech and language therapy (for language variants)
• Occupational therapy (for daily living)
• Structured routines and a safe home environment
• Support for family and carers

What Can Families Expect?

FTD is a progressive disease, meaning it gets worse over time. The course varies:

• Some people progress slowly over 10-15 years
• Others progress more quickly over 3-5 years
• On average, people live 6-8 years after symptoms start [14]

Early stages: Changes in behavior or language, but can still do many daily activities
Middle stages: Need more help with daily tasks, communication becomes harder
Late stages: Need full-time care, difficulty swallowing and moving

Support and Resources

UK:

• Rare Dementia Support: www.raredementiasupport.org
• Alzheimer's Society: www.alzheimers.org.uk
• FTD Support Group UK

United States:

• Association for Frontotemporal Degeneration (AFTD): www.theaftd.org

Australia:

• Dementia Australia: www.dementia.org.au
• FTD Support Group Australia

International:

• FTD Disorders Registry: www.ftdregistry.org

Key Messages for Families

1. You're not alone: FTD affects thousands of families
2. Behavioral changes are the disease, not the person: The person cannot control their behavior
3. Get support early: Connect with support groups and specialized services
4. Plan ahead: Make legal and financial plans while the person can still be involved
5. Look after yourself: Caring for someone with FTD is challenging—respite and support are essential

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13. Evidence and Guidelines

Key Guidelines

1. NICE NG97: Dementia: Assessment, Management and Support for People Living with Dementia and Their Carers (2018, updated 2024)

   • Comprehensive dementia guideline covering diagnosis, management, and support
   • Recommends specialist assessment for suspected FTD
   • Advises against acetylcholinesterase inhibitors in FTD
   • https://www.nice.org.uk/guidance/ng97

2. International Consensus Criteria for Behavioral Variant FTD (Rascovsky et al., 2011) [2]

   • Defines possible, probable, and definite bvFTD
   • Six core clinical features
   • Widely adopted in research and clinical practice

3. Classification of Primary Progressive Aphasia and Its Variants (Gorno-Tempini et al., 2011) [3]

   • Defines three PPA variants: semantic, nonfluent, logopenic
   • Core diagnostic features and exclusion criteria
   • Neuroimaging and neuropathological correlates

4. EFNS Guidelines on the Diagnosis and Management of Disorders Associated with Dementia (2010)

   • European Federation of Neurological Societies recommendations
   • Diagnostic workup and treatment approaches

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14. Key Clinical Scenarios

Scenario 1: Behavioral Variant FTD

Presentation: A 58-year-old man is brought by his wife with 18-month history of personality change. Previously a conservative accountant, he has become disinhibited, making inappropriate sexual comments to strangers. He has lost interest in his hobbies and family, shows no empathy when his daughter was upset, and has developed rigid routines (must eat at exactly 6 PM). He craves sweets and has gained 8 kg. Memory testing shows good recall of recent events. He has no insight into his behavior.

Examination:

• Overfamiliar with examiner, making inappropriate jokes
• Reduced spontaneous speech
• MMSE 26/30 (loses points on abstraction)
• Verbal fluency: 8 animals in 1 minute (severely impaired)
• Memory: 3/3 recall at 5 minutes (preserved)
• Clock drawing: Normal (visuospatial preserved)
• No focal neurological signs

Investigations:

• MRI brain: Asymmetric frontal atrophy (right > left), involving orbitofrontal and medial frontal cortex
• FDG-PET: Frontal hypometabolism
• Plasma NfL: Elevated (52 pg/mL)
• CSF: Normal Aβ42, normal tau
• Genetic testing: Negative for C9orf72, GRN, MAPT

Diagnosis: Probable behavioral variant FTD (meets Rascovsky criteria: disinhibition, apathy, loss of empathy, stereotyped behavior, hyperorality, executive deficits with preserved memory/visuospatial)

Management:

• Sertraline 50 mg daily, increased to 100 mg (modest improvement in compulsive behaviors)
• Occupational therapy: Home safety assessment, structured routine
• Genetic counseling (negative family history but explained risk to children)
• Capacity assessment: Lacks capacity for financial decisions; wife granted Lasting Power of Attorney
• Driving cessation (informed DVLA)
• Caregiver support: Connected to Rare Dementia Support group
• Advance care planning discussions

Outcome: Progressive behavioral decline over 3 years, developed mutism and parkinsonism, required residential care.

---

Scenario 2: Semantic Variant PPA

Presentation: A 64-year-old retired teacher presents with 2-year history of word-finding difficulty. She can speak fluently but struggles to name objects ("the thing you write with" for "pen"). She recently asked her husband "what is a penguin?" She can repeat sentences perfectly but has stopped reading because she can't understand the words. Memory for day-to-day events is intact.

Examination:

• Fluent, grammatically correct speech but semantically empty
• Confrontation naming: 4/20 on Boston Naming Test (severely impaired)
• Single-word comprehension: Cannot match "anchor" to picture
• Repetition: Intact ("The cat sat on the mat")
• Reading aloud: Surface dyslexia ("yacht" read as "yatched")
• Episodic memory: Intact (recalls recent holiday in detail)
• Visuospatial: Intact

Investigations:

• MRI brain: Left anterior temporal lobe atrophy, extending to temporal pole and fusiform gyrus
• FDG-PET: Left anterior temporal hypometabolism
• Plasma NfL: Elevated (38 pg/mL)
• Neuropsychology: Severe semantic memory impairment, preserved episodic memory and visuospatial function

Diagnosis: Semantic variant primary progressive aphasia (meets Gorno-Tempini criteria)

Management:

• Speech and language therapy: Communication book with pictures, iPad communication app
• Explanation to family about progressive language loss but preserved memory (different from Alzheimer's)
• No pharmacological treatment (SSRIs not indicated in absence of behavioral symptoms)
• Driving assessment: Ceased driving due to inability to read road signs
• Genetic counseling: Explained low genetic risk (no family history, usually sporadic pathology)

Outcome: Gradual progression to global aphasia over 5 years, then developed behavioral changes (right temporal extension), survived 11 years from onset.

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Scenario 3: FTD-MND Overlap

Presentation: A 52-year-old man presents with 1-year history of behavioral change (apathy, disinhibition, hyperphagia) and 6-month history of dysarthria and difficulty swallowing. His wife reports personality change before speech problems. Examination shows tongue wasting and fasciculations, brisk limb reflexes, and upgoing plantars. He has lost 6 kg despite increased food intake.

Examination:

• Disinhibited, apathetic, reduced empathy
• Bulbar dysarthria, tongue fasciculations and wasting
• Limb fasciculations (deltoids, quadriceps)
• Brisk reflexes throughout, extensor plantars
• No sensory loss
• ACE-III: 72/100 (low on fluency, language, memory relatively preserved)

Investigations:

• MRI brain: Frontal atrophy
• EMG/NCS: Widespread denervation, fibrillations
• Plasma NfL: Markedly elevated (95 pg/mL)
• Genetic testing: C9orf72 hexanucleotide repeat expansion (pathogenic)
• Respiratory function: FVC 68% predicted

Diagnosis: FTD-MND with C9orf72 expansion

Management:

• Riluzole 50 mg BD
• Multidisciplinary MND clinic: Neurology, respiratory, dietitian, speech therapy, physiotherapy
• PEG discussion (declined initially)
• Non-invasive ventilation (NIV) assessment
• Genetic counseling: 50% risk to children, offered predictive testing to adult children
• Palliative care referral
• Advance care planning: Completed Advance Directive (declined invasive ventilation)

Outcome: Rapid progression, PEG inserted at 14 months, respiratory failure at 22 months, died 26 months from onset (consistent with FTD-MND prognosis).

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