The occurrence of weight gain, sweet and carbohydrate craving, hyposex
uality, and compulsions in frontal lobe dementia (FLD) compared to Alz
heimer's disease (AD) was evaluated. FLD is a progressive dementia wit
h a high rate of misdiagnosis and therefore better diagnostic criteria
for FLD are needed. Fourteen patients meeting research criteria for A
D were compared to 14 with suspected FLD. All had cerebral perfusion m
easured with xenon-133 and imaged with HMPAO using brain-dedicated SPE
CT. The FLD group showed frontotemporal and AD posterior temporopariet
al hypoperfusion. The primary caregivers were queried regarding weight
gain, sweet/carbohydrate preference, sexual drive, and compulsions. D
ifferences were compared with Fisher's exact test. The following was f
ound in FLD versus AD: Weight gain in FLD patients amounted to 64% (AD
7%), carbohydrate craving was 79% (vs. 0%) and compulsive behavior 64
% (vs. 14%). The differences for these symptoms were statistically sig
nificant, whereas for the symptoms increased sexual drive (8 vs. 8%) a
nd reduced sexual drive (54 vs. 23%) no significant difference could b
e found. In FLD the first symptoms were often dietary changes or hypos
exuality. Compulsions were more bizarre and severely disabling in FLD
than in AD. Dietary changes, hyposexuality, and disabling compulsions
are prominent early symptoms in FLD but not AD. The cause of these sym
ptoms may be due to both frontal and subcortical serotonin loss and dy
sfunction of the anterior temporal lobes.