Two distinct subtypes of right temporal variant frontotemporal dementia.
BACKGROUND
Right temporal frontotemporal dementia (FTD) is an anatomic variant of FTD associated with relatively distinct behavioral and cognitive symptoms. We aimed to determine whether right temporal FTD is a homogeneous clinical, imaging, and pathologic/genetic entity.


METHODS
In this case-control study, 101 subjects with FTD were identified. Atlas-based parcellation generated temporal, frontal, and parietal grey matter volumes which were used to identify subjects with a right temporal dominant atrophy pattern. Clinical, neuropsychological, genetic, and neuropathologic features were reviewed. The subjects with right temporal FTD were grouped by initial clinical diagnosis and voxel-based morphometry was used to assess grey matter loss in the different groups, compared to controls, and each other.


RESULTS
We identified 20 subjects with right temporal FTD. Twelve had been initially diagnosed with behavioral variant FTD (bvFTD), and the other 8 with semantic dementia (SMD). Personality change and inappropriate behaviors were more frequent in the bvFTD group, while prosopagnosia, word-finding difficulties, comprehension problems, and topographagnosia were more frequent in the SMD group. The bvFTD group showed greater loss in frontal lobes than the SMD group. The SMD group showed greater fusiform loss than the bvFTD group. All 8 bvFTD subjects with pathologic/genetic diagnosis showed abnormalities in tau protein (7 with tau mutations), while all three SMD subjects with pathology showed abnormalities in TDP-43 (p = 0.006).


CONCLUSIONS
We have identified 2 subtypes of right temporal variant frontotemporal dementia (FTD) allowing further differentiation of FTD subjects with underlying tau pathology from those with TDP-43 pathology.
Josephs
K A
KA
Department of Neurology, Mayo Clinic, Rochester, MN 55905, USA. josephs.keith@mayo.edu
Whitwell
J L
JL
Knopman
D S
DS
Boeve
B F
BF
Vemuri
P
P
Senjem
M L
ML
Parisi
J E
JE
Ivnik
R J
RJ
Dickson
D W
DW
Petersen
R C
RC
Jack
C R
CR
D000368:Aged; D000369:Aged, 80 and over; D000377:Agnosia / Q000473:pathology; D001284:Atrophy; D016022:Case-Control Studies; D003071:Cognition; D003704:Dementia / Q000235:genetics / Q000378:metabolism / Q000473:pathology* / Q000523:psychology*; D005260:Female; D005625:Frontal Lobe / Q000473:pathology*; D020022:Genetic Predisposition to Disease; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008568:Memory; D009483:Neuropsychological Tests; D010551:Personality; D012919:Social Behavior; D013702:Temporal Lobe / Q000473:pathology*; D016875:tau Proteins / Q000235:genetics*
C054369:MAPT protein, human; D016875:tau Proteins