Clinical features and diagnosis of frontotemporal dementia

Abstract

Frontotemporal degeneration (FTD), formerly known as Pick's disease has become recognized as a distinct and relatively common entity encompassing behavioural (bvFTD language (PPA) and extrapyramidal (CBD/PSP) presentations. Further clinical subdivisions such as semantic dementia(SD), and pathological subtypes such as mesial temporal sclerosis increase the complexity of diagnosis.The relatively younger age of onset, the typical presentations of syndromes and focal asymmetrical frontotemporal atrophy on imaging allows experienced clinicians to make the diagnosis confidently as long as the overlap between the syndromes is recognized. There is also an overlap with ALS pathologically and clinically. The underlying histology in FTD/Pick complex is ubiquitin positive tau and synuclein negative neuronal inclusions (FTLD-U) in more than half of autopsies and tau positive CBD/PSP/ Pick bodies (FTLD-T) in the rest. The clinical syndromes of bvFTD and SD are likely associated with FTLD-U and PPA/CBDS/PSP with FTLD-T, but there is too much overlap to predict the pathology from the clinical syndromes reliably. The ubiquitin-tau pathological dichotomy is best considered under the Pick complex umbrella to allow for the significant overlap. So far trazodone in behavior and galantamine in aphasia had symptomatic benefit in small trials and SSRI-sand antipsychotics in uncontrolled reports were used as symptomatic therapies. Recent discoveries of tau and progranulin (in the ubiquitin-positive cases) mutations on chromosome 17 and other mutations on chromosome 3 and 9 in the high incidence of autosomal dominant families and a common protein abnormality, the TDP-43 in FTLD-U and ALS are likely to be important in finding therapeutic targets.