Fronto-temporal dementia (FTD)
by André Delacourte
Fronto-temporal dementia (FTD) refers to the parts of the brain that are preferentially affected: the frontal and temporal lobes (at the front and side of the brain respectively).
FTD are generated by different pathological processes that provoke damage in the frontal or/and temporal parts of the brain. These areas are responsible for different clinical manifestations such as behaviour, emotional responses and language skills.
According to the main location of damage, the different clinical manifestations evolve, giving rise to particular forms of frontal dementia and specific language disorders such as semantic dementia (SD) and primary progressive aphasia (PPA).
The pathological processes responsible for the “FTD” clinical profile are heterogeneous, but mainly related to different dysfunctions of tau gene or tau protein (mutations, aggregation, abnormal production). All these features give rise to a classification which is either based upon specific clinical symptoms (PPA, SD) or to specific lesions (Pick’s disease) or a mixed classification (FTDP-17), 17 being the chromosome that bears tau gene with the pathological mutations responsible for this disease.
Lobar atrophy, fronto-temporal atrophy
Symptoms and course
Damage to the frontal and temporal lobe areas of the brain will cause a variety of different symptoms. Each person will experience the condition in his or her own individual way.
Typically, during the initial stages of fronto-temporal dementia, memory will still be intact, but the personality and behaviour of the person will change. The person may lose their inhibitions and become extrovert, or alternatively may become apathetic and withdrawn.
They may talk to strangers, make inappropriate remarks in public and be rude or impatient. They may become aggressive which may be quite out of character, and may develop fixed routines. Some people begin to hoard things and become obsessive. Behaviour may be sexually suggestive, though a loss of interest in sexual acts themselves is also common. Often the person with dementia will be unaware of the problems.
People may also develop a sweet tooth and overeat leading to gain in weight. Excessive alcohol intake may occur. Spending money and losing cash often causes problems. In the later stages people with the illness may compulsively put objects in their mouths.
In the early stages memory is not usually affected. However sometimes difficulties in organisation and concentration may lead to an apparent memory problem. People may be very distractible.
Later in the disease a more generalised dementia can develop, and symptoms will usually appear to be similar to those with Alzheimer's disease. Those affected may no longer recognise friends and family and may need nursing care, become incontinent and bed-ridden. FTD is gradual progressive and leading to overt dementia. The progression rate is similar to Alzheimer’s disease, of several years. The average age of onset is usually 55 (+/- 10 years).
Duration of the disease from diagnosis is 6 to 8 years. It is longer than Alzheimer’s disease, which is of 4 years (Paquid study).
Causes and risk factors
A number of different types of brain lesions can underlay FTD. Many FTD are characterised by tau lesions, such as the specific Pick bodies observed in Pick’s disease or neurofibrillary tangles or tau accumulation in FTDP-17.
There is also a FTD without tau lesions named Fronto-temporal dementia lacking distinct histo-pathology (DLDH), characterised by a severe neuronal loss and a gliosis (gial cell reaction), but without tau lesions.
DLDH is also a tauopathy, in that the major abnormality is a dramatic decrease in the production of tau proteins. Together, most FTD are affected by tau abnormalities: mutations, aggregation or very low levels of normal tau.
There is a family history in about half of all cases of fronto-temporal degeneration. In these families 50 % can be caused by mutation in tau-gene. Some of these inherited forms have been linked to abnormalities on chromosomes 3. The causes of non-inherited fronto-temporal dementia are so far unknown.
Prevalence of FTD in Minnesota: 24 / 100.000; in Switzerland: 30 - 60 / 100.000 (Ratnavalli et al, 2002).
In order to differentiate FTD from AD, in addition to the clinical assessment, CT and MRI scans may be helpful demonstrating frontal atrophy.
Functional imaging (PET, SPECT) in typical cases show frontal / temporal hypometabolism, reflected by the decrease of blood flow in the affected areas (SPECT), as well as the decrease of glucose consumption (PET). CSF analysis of tau and Abeta levels help to differentiate AD (increase of phospho-tau and decrease of Abeta) from FTD (no modification).
Care and treatment
As yet there is no cure for FTD and the progression of the condition cannot be slowed. Drugs that are designed for the treatment of Alzheimer's disease, such as Aricept® and Exelon®, may increase symptoms. Symptomatic for disinhibition and behavioural problems. Antidepressants for apathy. Trazodone for agitation(Lebert et al, 2003). No prevention.
Ongoing research / clinical trials
In selected cases, cholinesterase inhibitors have been tried and found ineffective. Research on the involvement of tau proteins in FTD.
The Association for Frontotemporal Dementias
- McKhann, G. M., M. S. Albert, et al. (2001). "Clinical and pathological diagnosis of frontotemporal dementia: report of the Work Group on Frontotemporal Dementia and Pick's Disease." Arch Neurol 58(11): 1803-9.
- Lebert F, Stekke W, Hasenbroekx Ch, Pasquier F.Fronto-temporal dementia. A randomized, controlled trial with trazodone. Dem Cogn Disord. (in press)
- Ratnavalli et al, 2002, The prevalence of frontotemporal dementia. Neurology 58, 1615-1621
Last Updated: Friday 09 October 2009