Frontotemporal lobar degeneration

Frontotemporal lobar degeneration (FTLD), also known as Pick’s Disease, is a deterioration of the physical structure of the frontal lobe of the brain. There are three clinical syndromes that result from this deterioration, frontotemporal dementia, progressive nonfluent aphasia and semantic dementia. These syndromes involve perception of self and others, social skills and language. Symptoms of this malady may include impaired social and personal conduct, blunted emotions and loss of insight, and language disorder that may include nonfluent spontaneous speech fluent, meaningless spontaneous speech, and impaired word meaning. Unlike Alzheimer’s disease, FTLD patients’ memories remain intact and visuospatial skills are unimpaired. The causes are unknown although there are possible genetic precursors that indicate the disease is inherited. Genetic mutations of chromosome 17 have been identified in some cases but this is not consistent in all cases of the disorder.

Clinical Criteria

Core clinical features supporting diagnostic criteria of the subtypes:

Frontotemporal dementia

The most common clinical subtype of FTLD characterised by personality change and impaired social conduct in its initial stages

• decline in social interpersonal conduct
• impairment in regulation of personal conduct
• emotional blunting
• loss of insight

Other common features

• disinhibition
• neglect of personal hygygiene, mental rigidity,
• perseverative behaviour
• voracious appetite
• hyperorality

Progressive nonfluent aphasia

Nonfluent spontaneous speech with at least one of the following:

• agrammatism: A form of aphasia. The ability to speak is impaired to different degrees. In less extreme cases, the patient speaks in telegraphic speech (simplistic sentence structure similar to a telegraph message) but in more profound extremes by speaking in short groups of words, usually using nouns, without any grammatical structure. However, the patient understands what others are saying and can respond appropriately.
• phonemic paraphasias,
• anomia

Semantic dementia

Language disorder characterized by

• progressive, fluent, empty spontaneous speech
• loss of word meaning, manifest by impaired naming and comprehension
• semantic paraphasias

Perceptual disorder characterized by

• prosopagnosia: impaired recognition of identity of familiar faces
• associative agnosia: impaired recognition of object identity

Cognitive abilities that are preserved, i.e. not impaired

• perceptual matching and drawing reproduction
• single-word repetition
• ability to read aloud and write to dictation orthographically regular words

Neuropathology

A common method of diagnosing FTLD patients is the use of scanning technology including MRI (magnetic resonance imaging), single photon emission computed tomography (SPECT) and PET (Positron Emission Tomography). These scans show that there is atrophy of certain areas of the brain, specifically a decrease in the size of the frontal and anterior temporal lobes.

Histopathology

Type 1

• prominent microvacuolar change in layer II and upper layer III of the cortical lamina
• no specific histologic features meaning the absence of staining with immunohistochemical markers
• in some cases neurons stain with an antibody to a B crystallin

Type 2

• severe astrocytic gliosis with or without ballooned neurons and inclusion bodies (Pick type or Pick's disease).
• when present, ballooned neurons and inclusion bodies of the Pick type stain with antibodies directed against tau protein.
• ballooned neurons also stain for neurofilament protein

Differential Diagnosis

Alzheimer’s disease

• tau pathology in addition to amyloid pathology and generalised atrophy

corticobasal degeneration (CBD)

• tau pathology
• may start as clinical syndromes similar to FTLD

progressive supranuclear palsy (PSP)

• tau pathology
• may start as clinical syndromes similar to FTLD

Genetics

There have been familial studies that strongly indicate the disease may be inherited. Gene mutations of tau protein on chromosome 17 have been found in some cases. However, there are numerous cases which have no evidence of this mutation. Similarly, the apolipoprotein E4 allele which is a risk factor in Alzheimer’s shows no association with FTLD.