Behavioral variant frontotemporal lobar degeneration

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Behavioral variant frontotemporal lobar degeneration (bvFTLD), also known as behavioral variant frontotemporal dementia, is one of the clinical neurodegenerative diseases associated with frontotemporal lobar degeneration (FTLD).

Terminology

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 generally.  As such it is also best avoided.

Diagnostic criteria

Diagnostic criteria have been proposed as follows :

I. Neurodegenerative disease 

The following symptom must be present to meet criteria for bvFTD:

  • A. Shows progressive deterioration of behavior and/or cognition by observation or history (as provided by a knowledgeable informant). 
II. Possible bvFTD 

Three of the following behavioral/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* behavioral disinhibition [one of the following symptoms (A.1–A.3) must be present]: 
    • A.1. Socially inappropriate behavior
    • 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 behavior [one of the following symptoms (D.1–D.3) must be present]:
    • D.1. Simple repetitive movements
    • D.2. Complex, compulsive or ritualistic behaviors 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. Behavioral variant FTD with definite FTLD Pathology
IV. Behavioral 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. Behavioral disturbance is better accounted for by a psychiatric diagnosis
  • C. Biomarkers strongly indicative of Alzheimer disease or other neurodegenerative process 

Clinical presentation

Patients with behavioral variant FTD typically present with a dysexecutive cognitive syndrome associated with changes in personality and social behavior.

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.

Radiographic features

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 fibers .