Behavioural variant frontotemporal lobar degeneration
Behavioural variant frontotemporal lobar degeneration (bvFTLD), also known as behavioural variant frontotemporal dementia, is one of the clinical neurodegenerative diseases associated with frontotemporal lobar degeneration (FTLD).
In the older literature, it is also referred to as Pick disease, although the term should probably be avoided as it denotes a particular histology.
It should also be noted that the term frontotemporal dementia (FTD) is used inconsistently in the literature, sometimes synonymously with bvFTLD or bvFTD, and other times to denote FTLD more generally2-3. As such it is also best avoided.
Diagnostic criteria have been proposed as follows 4:
I. Neurodegenerative disease
The following symptom must be present to meet criteria for bvFTD:
- A. Shows progressive deterioration of behaviour and/or cognition by observation or history (as provided by a knowledgeable informant).
II. Possible bvFTD
Three of the following behavioural/cognitive symptoms (A–F) must be present to meet criteria. Ascertainment requires that symptoms be persistent or recurrent, rather than single or rare events:
- A. Early* behavioural disinhibition [one of the following symptoms (A.1–A.3) must be present]:
- A.1. Socially inappropriate behaviour
- A.2. Loss of manners or decorum
- A.3. Impulsive, rash or careless actions
- B. Early apathy or inertia [one of the following symptoms (B.1–B.2) must be present]:
- B.1. Apathy
- B.2. Inertia
- C. Early loss of sympathy or empathy [one of the following symptoms (C.1–C.2) must be present]:
- C.1. Diminished response to other people’s needs and feelings
- C.2. Diminished social interest, interrelatedness or personal warmth
- D. Early perseverative, stereotyped or compulsive/ritualistic behaviour [one of the following symptoms (D.1–D.3) must be present]:
- D.1. Simple repetitive movements
- D.2. Complex, compulsive or ritualistic behaviours D.3. Stereotypy of speech
- E. Hyperorality and dietary changes [one of the following symptoms (E.1–E.3) must be present]:
- E.1. Altered food preferences
- E.2. Binge eating, increased consumption of alcohol or cigarettes
- E.3. Oral exploration or consumption of inedible objects
- F. Neuropsychological profile: executive/generation deficits with relative sparing of memory and visuospatial functions [all of the following symptoms (F.1–F.3) must be present]:
- F.1. Deficits in executive tasks
- F.2. Relative sparing of episodic memory F.3. Relative sparing of visuospatial skills
III. Probable bvFTD
All of the following symptoms (A–C) must be present to meet criteria.
- A. Meets criteria for possible bvFTD
- B. Exhibits significant functional decline (by caregiver report or as evidenced by Clinical Dementia Rating Scale or Functional Activities Questionnaire scores)
- C. Imaging results consistent with bvFTD [one of the following (C.1–C.2) must be present]:
- C.1. Frontal and/or anterior temporal atrophy on MRI or CT
- C.2. Frontal and/or anterior temporal hypoperfusion or hypometabolism on PET or SPECT IV. Behavioural variant FTD with definite FTLD Pathology
IV. Behavioural variant FTD with definite FTLD Pathology
Criterion A and either criterion B or C must be present to meet criteria.
- A. Meets criteria for possible or probable bvFTD
- B. Histopathological evidence of FTLD on biopsy or at post-mortem
- C. Presence of a known pathogenic mutation
V. Exclusionary criteria for bvFTD
Criteria A and B must be answered negatively for any bvFTD diagnosis. Criterion C can be positive for possible bvFTD but must be negative for probable bvFTD.
- A. Pattern of deficits is better accounted for by other non-degenerative nervous system or medical disorders
- B. Behavioural disturbance is better accounted for by a psychiatric diagnosis
- C. Biomarkers strongly indicative of Alzheimer disease or other neurodegenerative process
Patients with behavioural variant FTD typically present with a dysexecutive cognitive syndrome associated with changes in personality and social behaviour.
As the disease progresses, impairments in language and memory may develop and the cognitive phenotype may come to resemble one of the language variants of FTD.
Both CT and MRI are able to demonstrate the typical changes, although as is usually the case, MRI does so with a greater degree of detail.
The typical radiographic finding is atrophy of the frontal lobes and, to a lesser extent, the temporal lobes. The degree of atrophy can be very asymmetric and is usually associated with a commensurate decrease in volume of the caudate heads. This indicates loss of both efferent and afferent fibres 5.
- 1. Looi JC, Lindberg O, Zandbelt BB et-al. Caudate nucleus volumes in frontotemporal lobar degeneration: differential atrophy in subtypes. AJNR Am J Neuroradiol. 2008;29 (8): 1537-43. doi:10.3174/ajnr.A1168 - Pubmed citation
- 2. Neary D, Snowden JS, Gustafson L et-al. Frontotemporal lobar degeneration: a consensus on clinical diagnostic criteria. Neurology. 1998;51 (6): 1546-54. Neurology (full text) - doi:10.1212/WNL.51.6.1546 - Pubmed citation
- 3. Landqvist Waldö M, Frizell Santillo A, Passant U et-al. Cerebrospinal fluid neurofilament light chain protein levels in subtypes of frontotemporal dementia. BMC Neurol. 2013;13 (1): 54. doi:10.1186/1471-2377-13-54 - Free text at pubmed - Pubmed citation
- 4. Rascovsky K, Hodges JR, Knopman D et-al. Sensitivity of revised diagnostic criteria for the behavioural variant of frontotemporal dementia. Brain. 2011;134 (9): 2456-77. Brain (full text) - doi:10.1093/brain/awr179 - Free text at pubmed - Pubmed citation
Neurodegenerative diseases are legion and their classification just as protean. A useful approach is to divide them according to underlying pathological process, although even using this schema, there is much overlap and thus resulting confusion.
neurodegenerative MRI brain (an approach)
- measurements and ratios
- midbrain to pons area ratio (for PSP)
- Magnetic Resonance Parkinsonism Index (MRPI) (for PSP)
- frontal horn width to intercaudate distance ratio (FH/CC) (for Huntington disease)
- intercaudate distance to inner table width ratio (CC/IT) (for Huntington disease)
- scoring systems
- measurements and ratios
- typical/classical Alzheimer disease
- variant (e.g. posterior cortical atrophy)
- chronic traumatic encephalopathy (CTE)
- corticobasal degeneration
- frontotemporal lobar degeneration (FTLD) (not all are tau)
- Pick disease
- progressive supranuclear palsy (PSP)
- Alzheimer disease
- cerebral amyloid angiopathy (CAA)
- transthyretine-associated cerebral amyloidosis
- neuronal intranuclear hyaline inclusion disease (NIHID)
- spinocerebellar ataxias
- Huntington disease
- hereditary spastic paraplegia
- amyotrophic lateral sclerosis (ALS)
- clinically unclassifiable parkinsonism (CUP)
- Unverricht-Lundborg disease
- prion diseases (not always included as neurodegenerative)