What are the signs of frontotemporal dementia (FTD)?

Signs of Frontotemporal Dementia

Frontotemporal dementia presents with progressive behavioral changes, language deficits, or both, typically beginning between ages 40-70 with an insidious onset and gradual progression over time. 1

Core Behavioral Features (Behavioral Variant FTD)

The behavioral variant requires at least three of six core features for diagnosis 2:

• Disinhibition: Socially inappropriate behavior, loss of manners, impulsive actions 1, 2
• Apathy/Inertia: Loss of motivation, reduced initiative, though this may be underrecognized by caregivers 1, 3
• Loss of sympathy/empathy: Diminished response to others' needs and feelings, reduced social interest 2
• Perseverative/compulsive behaviors: Repetitive movements, rituals, hoarding 1
• Hyperorality: Dietary changes, binge eating, oral exploration of objects 2
• Dysexecutive profile: Impaired planning, organization, and abstract thinking 2

Language Variants (Primary Progressive Aphasia)

Semantic variant PPA demonstrates 4:

• Progressive naming difficulties and word comprehension deficits
• Loss of object knowledge and semantic memory
• Left anterior temporal lobe atrophy predominates 5, 4

Nonfluent/agrammatic variant PPA shows 6, 5:

• Effortful, halting speech with grammatical errors
• Speech apraxia and phonological errors
• Left frontal cortex and insula degeneration 5

Critical Distinguishing Features from Psychiatric Disorders

Key clinical indicators favoring FTD over primary psychiatric disorders 1:

• Age of onset: Middle to late adulthood (40-70 years) rather than adolescence/early adulthood 1
• Insidious, progressive course: Gradual worsening over months to years, not episodic or fluctuating 1
• Impaired insight: Almost universally present; patients lack awareness of behavioral changes 1, 3
• Specific behavioral markers: Emotional flatness/indifference, inappropriateness, stereotypies, and alien hand phenomenon favor FTD over psychiatric illness 1
• Preserved memory: Episodic memory characteristically spared early, unlike Alzheimer's disease 2

Associated Neurological Signs

Look for features suggesting FTLD-spectrum disorders 1:

• Parkinsonism: Present in 25-80% of FTD cases 3
• Motor neuron disease features: Dysphagia, fasciculations, weakness (ALS overlap) 1
• Alien limb phenomenon: Suggests corticobasal degeneration 1
• Falls and vertical gaze palsy: Indicate progressive supranuclear palsy 1

Genetic and Psychiatric Presentations

C9orf72 mutation carriers present unique challenges 1, 7:

• May have prominent psychiatric prodrome (delusions, hallucinations) preceding classic FTD by up to a decade 1
• Psychotic symptoms occur in 21-56% of C9orf72 carriers, far exceeding sporadic FTD (up to 26%) 1
• Can show very slow progression over 22 years with initially normal imaging 1, 3

GRN mutations may present with 1:

• Visual hallucinations and delusions in up to 25% of cases
• Late-onset bipolar disorder evolving into bvFTD 1

Assessment Tools

Frontal Behavioral Inventory (FBI) 1:

• Score ≥12 on positive subscale indicates bvFTD in late-onset behavioral changes 1
• Specific items favoring FTD: aphasia/verbal apraxia, emotional flatness, alien hand, inappropriateness 1
• Irritability more indicative of psychiatric disorder 1

Stereotypy Rating Inventory (SRI) 1:

• Stereotypies more common in bvFTD than psychiatric disorders 1

Cognitive screening 3:

• MMSE often normal in early bvFTD (poor sensitivity) 3
• Montreal Cognitive Assessment (MoCA) superior with 78% sensitivity and 98% specificity 3

Neuroimaging Patterns

Structural MRI findings 1, 5:

• Frontal and anterior temporal lobe atrophy with characteristic "knife-like gyri" 1
• Behavioral variant: Asymmetric involvement of prefrontal cortices, insula, anterior cingulate, striatum 1, 5
• Semantic variant: Focal anterior temporal lobe atrophy, worse on left 1, 5

FDG-PET demonstrates 1:

• Bilateral frontal and temporal hypometabolism with precuneus sparing 1
• 96% sensitivity and 73% specificity when combined with structural MRI 1

Common Diagnostic Pitfalls

Avoid these errors 1, 3:

• Dismissing diagnosis due to positive psychiatric history—remain vigilant for emerging FTD signs in chronic mental illness 1
• Relying on patient self-report given universal lack of insight 3
• Missing diagnosis due to family psychiatric history, which biases against recognizing bvFTD 1
• Accepting normal MMSE as excluding FTD—use MoCA instead 3
• Misinterpreting restlessness as anxiety rather than FTD-related agitation 3

Essential History Elements

Obtain collateral history from caregivers (patient insight impaired) 1:

• Precise symptom timeline with age of onset
• Predominant early symptoms (behavior vs. language vs. memory)
• Relationship to life stressors
• Detailed family history including FTD, ALS, Parkinson's disease, and late-onset psychiatric disorders 1, 7
• Developmental/educational history to establish premorbid functioning 1