7 Old age psychiatry7.5 Mental disorders in older people
7.5.4 Frontotemporal dementias
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Written by Resident Doctor Committee · Published
Terminology and syndromes
Frontotemporal lobar degeneration (FTLD) names the pathology and frontotemporal dementia (FTD) the clinical picture, and the two do not map exactly.
The FTLD syndromes are behavioural variant FTD and the semantic and non-fluent variants of primary progressive aphasia (PPA).
Logopenic PPA, with word-finding pauses and poor sentence repetition, is usually driven by Alzheimer's pathology and is not an FTLD syndrome.
Behavioural variant frontotemporal dementia
Behavioural variant FTD (bvFTD) is the commonest FTLD syndrome and starts insidiously, usually before 65.
The frontal lobes underpin personality and social conduct, so frontal disease shows first as a change of character and drive.
Early apathy, disinhibition, loss of empathy and personality change mark bvFTD, whereas early language failure marks the PPAs.
Insight is lost early, and a normal Mini-Mental State Examination does not exclude bvFTD.
Possible bvFTD needs progressive decline plus at least three of these six features.
Feature | Example |
|---|---|
Disinhibition | Inappropriate remarks, impulsivity |
Apathy or inertia | Reduced initiation |
Loss of sympathy or empathy | Indifference to others' needs |
Perseverative or compulsive behaviour | Repeated routines, movements or speech |
Hyperorality and dietary change | Sweet preference, overeating, mouthing objects |
Dysexecutive profile | Executive failure with memory and visuospatial skills relatively spared |
Telling bvFTD from its mimics
Condition | What leads instead of conduct change |
|---|---|
Alzheimer's disease | Early impaired learning of new information |
Lewy body dementia | Fluctuation and hallucinations |
Depression | Mood symptoms such as sadness and guilt |
Huntington's disease | Motor signs, with dominant inheritance |
Personality disorder | Lifelong traits, not a new decline |
Apathy is loss of motivation and can occur without sadness, unlike depression.
Primary progressive aphasias
Feature | Semantic variant (semantic dementia) | Non-fluent variant |
|---|---|---|
Speech | Fluent and grammatical but empty of content | Effortful and agrammatic, often with apraxia of speech |
Comprehension | Single-word meaning lost | Single-word meaning preserved |
Other signs | Anomia, vague substitutions, surface dyslexia | Distorted speech sounds |
Atrophy | Anterior temporal, often left | Left posterior frontoinsular and premotor |
Usual pathology | TDP-43 | Tau |
Non-fluent PPA can evolve into progressive supranuclear palsy or corticobasal syndrome.
Corticobasal degeneration
Corticobasal degeneration is a 4-repeat tauopathy that presents as corticobasal syndrome.
Its signs are asymmetric limb apraxia, rigidity that does not respond to levodopa, dystonia, myoclonus, cortical sensory loss such as astereognosis, and alien limb.
Pathology and imaging
Pathology | Share | Associations |
|---|---|---|
FTLD-tau | About 40% | Pick bodies in Pick's disease; MAPT mutations |
FTLD-TDP | About half | TDP-43; GRN and C9orf72; most motor neurone disease |
FTLD-FUS | Small | Younger behavioural presentations |
Knife-edge atrophy is the circumscribed frontal and anterior temporal atrophy of bvFTD, with gyri thinned to a sharp ridge.
Functional imaging shows matching anterior hypoperfusion or hypometabolism, with parietal and occipital cortex preserved.
Genetics
Familial FTD is autosomal dominant: it appears in every generation, affects both sexes, passes father to son and reaches about half of offspring.
Most cases are sporadic, although around 40% report a family history.
Most heritability comes from C9orf72, GRN and MAPT mutations.
GRN mutation causes familial FTD with ubiquitin-positive TDP-43 inclusions through progranulin deficiency.
C9orf72 links FTD with motor neurone disease, which shortens survival.
Management
The National Institute for Health and Care Excellence advises against cholinesterase inhibitors and memantine in FTD, and cholinesterase inhibitors may worsen behaviour.
Selective serotonin reuptake inhibitors may help disinhibition, repetitive behaviour or eating change, but they do not slow cognitive decline.
Antipsychotics raise mortality, stroke and movement risks, so use them only for severe distress or danger, at the lowest dose, with a withdrawal plan.