<unk>  is traditionally difficult to diagnose owing to the diverse nature of the associated symptoms. Signs and symptoms are classified into three groups based on the affected functions of the frontal and temporal lobes: These are behavioural variant<unk> , semantic dementia, and progressive nonfluent aphasia. An overlap between symptoms can occur as the disease progresses and spreads through the brain regions. Structural MRI scans often reveal frontal lobe and/or anterior temporal lobe atrophy but in early cases the scan may seem normal. Atrophy can be either bilateral or asymmetric. Registration of images at different points of time (e.g., one year apart) can show evidence of atrophy that otherwise (at individual time points) may be reported as normal. Many research groups have begun using techniques such as magnetic resonance spectroscopy, functional imaging and cortical thickness measurements in an attempt to offer an earlier diagnosis to the<unk>  patient. Fluorine-18-fluorodeoxyglucose positron emission tomography (FDG-PET) scans classically show frontal and/or anterior temporal hypometabolism, which helps differentiate the disease from Alzheimer's disease. The PET scan in Alzheimer's disease classically shows biparietal hypometabolism. Meta-analyses based on imaging methods have shown that<unk>  mainly affects a frontomedial network discussed in the context of social cognition or 'theory of mind'. This is entirely in keeping with the notion that on the basis of cognitive neuropsychological evidence, the ventromedial prefrontal cortex is a major locus of dysfunction early on in the course of the behavioural variant of<unk>  degeneration. The language subtypes of<unk>  lobar degeneration (semantic dementia and progressive nonfluent aphasia) can be regionally dissociated by imaging approaches in vivo. The confusion between Alzheimer's and<unk>  is justifiable due to the similarities between their initial symptoms. Patients do not have difficulty with movement and other motor tasks. As<unk>  symptoms appear, it is difficult to differentiate between a diagnosis of Alzheimer's disease and<unk> . There are distinct differences in the behavioral and emotional symptoms of the two dementias, notably, the blunting of emotions seen in<unk>  patients. In the early stages of<unk> , anxiety and depression are common, which may result in an ambiguous diagnosis. However, over time, these ambiguities fade away as this dementia progresses and defining symptoms of apathy, unique to<unk> , start to appear. Recent studies over several years have developed new criteria for the diagnosis of behavioral variant<unk>  (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 profile Of the six features, three must be present in a patient to diagnose one with possible bvFTD. Similar to standard<unk> , 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 Alzheimer's 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<unk> . 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. As stated above, a behavioural change may occur before the appearance of any atrophy in the brain in the course of the disease. Because of that, image scanning such as MRI can be insensitive to the early degeneration and it is difficult to detect early-stage bvFTD. In neuropsychology, there is an increasing interest in using neuropsychological tests such as the Iowa gambling task or Faux Pas Recognition test as an alternative to imaging for the diagnosis of bvFTD. Both the Iowa gambling task and the Faux Pas test are known to be sensitive to dysfunction of the orbitofrontal cortex. Faux Pas Recognition test is intended to measure one’s ability to detect faux pas types of social blunders (accidentally make a statement or an action that offends others). It is suggested that people with orbitofrontal cortex dysfunction show a tendency to make social blunders due to a deficit in self-monitoring. Self-monitoring is the ability of individuals to evaluate their behaviour to make sure that their behaviour is appropriate in particular situations. The impairment in self-monitoring leads to a lack of social emotion signals. The social emotions such as embarrassment are important in the way that they signal the individual to adapt social behaviour in an appropriate manner to maintain relationships with others. Though patients with damage to the OFC retain intact knowledge of social norms, they fail to apply it to actual behaviour because they fail to generate social emotions that promote adaptive social behaviour. The other test, the Iowa gambling task, is a psychological test intended to simulate real-life decision making. The underlying concept of this test is the somatic marker hypothesis. This hypothesis argues that when people have to make complex uncertain decisions, they employ both cognitive and emotional processes to assess the values of the choices available to them. Each time a person makes a decision, both physiological signals and evoked emotion (somatic marker) are associated with their outcomes and it accumulates as experience. People tend to choose the choice which might produce the outcome reinforced with positive stimuli, thus it biases decision-making towards certain behaviours while avoiding others. It is thought that somatic marker is processed in orbitofrontal cortex. The symptoms observed in bvFTD are caused by dysfunction of the orbitofrontal cortex, thus these two neuropsychological tests might be useful in detecting the early stage bvFTD. However, as self-monitoring and somatic marker processes are so complex, it likely involves other brain regions. Therefore, neuropsychological tests are sensitive to the dysfunction of orbitofrontal cortex, yet not specific to it. The weakness of these tests is that they do not necessarily show dysfunction of the orbitofrontal cortex. In order to solve this problem, some researchers combined neuropsychological tests which detect the dysfunction of orbitofrontal cortex into one so that it increases its specificity to the degeneration of the frontal lobe in order to detect the early-stage bvFTD. They invented the Executive and Social Cognition Battery which comprises five neuropsychological tests. * Iowa gambling task * Faux Pas test * Hotel task * Mind in the Eyes * Multiple Errands Task The result has shown that this combined test is more sensitive in detecting the deficits in early bvFTD.
Frontotemporal dementia
Fatal insomnia
Dementia with Lewy bodies
Lewy body dementias
Vascular dementia
Subcortical dementia
Semantic dementia
Early-onset Alzheimer's disease