Frontotemporal dementia (FTD) is the second most common type of
presenile dementia. Three clinical prototypes have been defined; behavioral variant FTD,
semantic dementia, and
progressive nonfluent aphasia.
Progressive supranuclear palsy,
corticobasal degeneration, and
motor neuron disease may possess clinical and pathological characteristics that overlap with FTD, and it is possible that they may all belong to the same clinicopathological spectrum.
Frontotemporal lobar degeneration (
FTLD) is a clinicopathological syndrome that encompasses a heterogenous group of
neurodegenerative disorders. Owing to the advancement in the field of molecular genetics, diagnostic imaging, and pathology,
FTLD has been the focus of great interest. Nevertheless,
parkinsonism in
FTLD has received relatively less attention.
Parkinsonism is found in approximately 20-30% of patients in
FTLD. Furthermore,
parkinsonism can be seen in all
FTLD subtypes, and some patients with familial and sporadic
FTLD can present with prominent
parkinsonism. Therefore, there is a need to understand
parkinsonism in
FTLD in order to obtain a better understanding of the disease. With regard to the clinical characteristics, the akinetic rigid type of
parkinsonism has predominantly been described.
Parkinsonism is frequently observed in familial FTD, more specifically, in FTD with
parkinsonism linked to chromosome 17q (FTDP-17). The genes associated with
parkinsonism are
microtubule associated protein tau (MAPT),
progranulin (GRN or PGRN), and chromosome 9 open reading frame 72 (C9ORF72) repeat expansion. The neural substrate of
parkinsonism remains to be unveiled.
Dopamine transporter (DAT) imaging revealed decreased uptake of DAT, and imaging findings indicated atrophic changes of the basal ganglia.
Parkinsonism can be an important feature in
FTLD and, therefore, increased attention is needed on the subject.