Frontotemporal dementia (FTD), or frontotemporal degeneration disease, or frontotemporal neurocognitive disorder, encompasses several types of dementia involving the progressive degeneration of frontal and temporal lobes. FTDs broadly present as behavioral or language disorders with gradual onsets. The three main subtypes or variant syndromes are a behavioral variant (bvFTD) previously known as Picks disease, and two variants of primary progressive aphasia –
semantic variant (svPPA), and nonfluent variant (nfvPPA). Two rare distinct subtypes of FTD are neuronal intermediate filament inclusion disease (NIFID), and basophilic inclusion body disease. Other related disorders include corticobasal syndrome and FTD  with amyotrophic lateral sclerosis (ALS) FTD-ALS also called FTD-MND.Frontotemporal dementias are mostly early-onset syndromes that are linked to frontotemporal lobar degeneration (FTLD), which is characterized by progressive neuronal loss predominantly involving the frontal or temporal lobes, and a typical loss of more than 70% of spindle neurons, while other neuron types remain intact.FTD was first described by Arnold Pick in 1892 and was originally called Picks disease, a term now reserved only for behavioral variant FTD which shows the presence of Pick bodies and Pick cells. Second only to Alzheimers disease (AD) in prevalence,  FTD accounts for less than, or actually, 20% (number is perhaps rounded) of degenerative dementia cases found at autopsy.Signs and symptoms typically manifest in late adulthood, more commonly between the ages of 45 and 65, approximately equally affecting men and women.Common signs and symptoms include significant changes in social and personal behavior, apathy, blunting of emotions, and deficits in both expressive and receptive language.
However, over time, these ambiguities fade away as this dementia progresses and defining symptoms of apathy, unique to FTD, start to appear.Recent studies over several years have developed new criteria for the diagnosis of behavioral variant frontotemporal dementia (bvFTD).The confirmatory diagnosis is made by brain biopsy, but other tests can be used to help, such as MRI, EEG, CT, and physical examination and history. Six distinct clinical features have been identified as symptoms of bvFTD. Disinhibition
Apathy/Inertia
Loss of Sympathy/Empathy
Perseverative/compulsive behaviors
Hyperorality
Dysexecutive neuropsychological profileOf the six features, three must be present in a patient to diagnose one with possible bvFTD. Similar to standard FTD, the primary diagnosis stems from clinical trials that identify the associated symptoms, instead of imaging studies. The above criteria are used to distinguish bvFTD from disorders such as Alzheimers and other causes of dementia. In addition, the new criteria allow for a diagnostic hierarchy distinguished possible, probable, and definite bvFTD based on the number of symptoms present.A 2021 study, led by researchers at the University of Pennsylvania, determined that using cerebrospinal fluid (CSF) biomarkers of pathologic amyloid plaques, tangles, and neurodegeneration, collectively called ATN, can be useful in diagnosing FTD. Neuropsychological tests
The progression of the degeneration caused by bvFTD may follow a predictable course. The degeneration begins in the orbitofrontal cortex and medial aspects such as ventromedial cortex. In later stages, it gradually expands its area to the dorsolateral cortex and the temporal lobe. Thus, the detection of dysfunction of the orbitofrontal cortex and ventromedial cortex is important in the detection of early stage bvFTD.