Behavioural Variant Frontotemporal Dementia or Alzheimer’s Disease? How to tell?

Written by Nea Lulik, MSc in Psychology of Individual Differences

Frontotemporal dementia (FTD) is a clinical syndrome of frontotemporal lobar degeneration and it is the second most common neurodegenerative dementia in patients under the age of 65 (Bathgate, Snowden, Varma, Blackshaw, & Neary, 2001) (Barsuglia, et al., 2014). Behavioural variant frontotemporal dementia (bvFTD) is a progressive deterioration in social functioning and personality (Piguet, Hornberger, & Mioshi, 2011) (Barsuglia, et al., 2014) and it is the most common subtype of FTD. Alzheimer's disease (AD) is the most common type of dementia and it is characterized by progressive deterioration in memory and cognitive functions. It typically manifests after the age of 65 (Galton, Patterson, Xuereb, & Hodges, 2000).

Behavioural changes are the prevailing clinical symptom in bvFTD and are present from the early stage of the disease (Bathgate, Snowden, Varma, Blackshaw, & Neary, 2001). Behavioural changes show high sensitivity to bvFTD. These behaviour changes are loss of basic and social emotions, selfishness, disinhibition, irritability, neglect of personal hygiene, loss of interest/apathy, gluttony, preferences for sweet food, wandering, pacing, hyposexuality, motor and verbal stereotypes (Pressman & Miller, 2014). Also personality changes occur at the initial stage, including social disinhibition and impulsivity (Pressman & Miller, 2014). AD patients manifest behavioural and personality changes as well, which are very similar to bvFTD, but these manifestations occur later in the stage of AD disease, while bvTFD patients display them from the beginning. Also, the loss of basic emotions (for example: fear, happiness, sadness, anger, surprise, disgust) is predominant in bvFTD and not very common in AD. The loss of feeling of embarrassment is as well strictly predominant in bvFTD patients (Bathgate, Snowden, Varma, Blackshaw, & Neary, 2001).

Barsuglia et al. (Barsuglia, et al., 2014) have found 3 main behavioural clusters in bvFTD, which are diminished interest and initiation in seeking social interactions, lack of social bonding or sustaining attachment and inter-subjectivity, and poor awareness and adherence to social boundaries and norms. There findings are consistent with the previous studies regarding apathy and disinhibition in bvTFD patients and are also in line with the neuropsychiatric symptoms of the disease. Interpersonal dysfunction is uncommon in AD patients (Pressman & Miller, 2014). Inappropriate social behaviours, also called emotional blunting, is found to be highly sensitive in distinguishing bvTFD and AD. Caregivers report more severe changes in emotional blunting in patients with bvTFD than AD patients, and the results of the study were 90% accurate (Joshi, et al., 2014).

Typical for bvFTD patients is also overeating, especially sweet food. This is also consistent with the study of reward-seeking behaviours in bvFTD (Perry, et al., 2014). They have a tendency to keep eating as long the food is present, they steal food from other people’s plates, and they crave it even when the food is not present. Eating disturbances are significantly more common in patients with bvFTD than patients with AD (Bathgate, Snowden, Varma, Blackshaw, & Neary, 2001) (Jenner, Reali, Puopolo, & Silveri, 2006).

Loss of awareness of pain is reported in 41% of the patients with bvFTD, while is not usual for AD patients (Bathgate, Snowden, Varma, Blackshaw, & Neary, 2001).

Behaviours in relation to memory and spatial dysfunction are more prevalent in patients with AD than bvFTD. AD patients are characterized by reduced spatial orientation (Henderson, Mack, & Williams, 1989), while in bvFTD patients this happen to a lesser extent. AD patients have more difficulties in locating or mislaying objects (Pena-Casanova, Sanchez-Benavides, de Sola, Manero-Borras, & Casals-Coll, 2012), feel more disoriented. Regarding the language, the use of wrong words is more common in AD patients, while echolalia and mutism is more frequent in bvFTD (Bathgate, Snowden, Varma, Blackshaw, & Neary, 2001). In regard to the feeling of knowing, metacognition studies has shown that bvFTD patients have severe levels of anosognosia. AD patients show impaired feeling of knowing, however, the feeling of knowing is less severe and less diffuse in comparison with bvFTD patients (Jenner, Reali, Puopolo, & Silveri, 2006).

Studies (Bathgate, Snowden, Varma, Blackshaw, & Neary, 2001) have shown that repetitive and compulsive behaviours are common in bvFTD. The tendency to pace or wander in a fixed path and no attention to details, might be due to the lack of insightfulness which is very common in bvFTD patients (Bathgate, Snowden, Varma, Blackshaw, & Neary, 2001) (Rosen, et al., 2014). AD patients do not show repetitive or compulsive behaviours. They do tend to pace and wander on random paths, rather than fixed ones, like bvFTD patients do.

A study (Lopez, et al., 1996) showed that depression is more common in bvFTD patients than AD patients, while psychotic symptoms, especially delusions, are more common in AD than bvFTD. BvFTD patients also tend to have more mood disorders than AD patients. However, considering that apathy and loss of volition are major features in patients with bvFTD (Bathgate, Snowden, Varma, Blackshaw, & Neary, 2001), the results of the Lopez et al. study (1996) are not very sensitive in regard of bvFTD.

Anterograde episodic memory is the earliest neuropsychological impairment of AD (Galton, Patterson, Xuereb, & Hodges, 2000). Only recently they discovered that impairment of retrograde and anterograde memories manifests in bvFTD as well (Wong, Flanagan, Savage, Hodges, & Hornberg, 2014). Previous studies always discarded bvFTD when amnesia was present, because it was a diagnostic exclusion criteria. But confirmed bvFTD cases report episodic memory deficit in the initial stages of the disease, and recent findings report these deficits are firmly related to executive deficits, specifically impairment in strategic retrieval processes. Galton et al. (2000) have proven that bvFTD patients can have memory impairment of the same magnitude as AD patients.

There are symptoms which are more common in AD and some that are more common in bvFTD, but it is not possible to say it with an absolute certainty. AD and bvFTD are difficult to differentiate because many times the symptoms overlap, therefore it is very difficult to find tests that are sufficiently sensitive to distinguishing between the two.

Cognitive tests have proven some difficulties with assessing bvFTD patients. The issue that can arise is due to the fact that bvFTD patients have difficulties staying focused, have poor insight and have apathy. Which raises the question: Are their test results due to cognitive deficit or behavioural deficit?

The diagnosis of the early stage of the disease is really important, because it can establish a proper treatment and management of the disease. In order to support a diagnosis, imaging techniques should be performed, such as MRI scans, although, these might not detect any changes in the initial stage of the disease (Gregory, Serra-Mestres, & Hodges, 1999). The fluorodeoxyglucose-PET is preferred to the MRI as it has increased sensitivity in detecting structural changes and it can also be effective in distinguishing bvFTD from AD (Pressman & Miller, 2014).

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