Multiple chemical sensitivity (MCS) patients
usually react to odour compounds and the majority of
neuroimaging studies assessed, especially at the cortical
level, many olfactory-related correlates. The purpose of the
present study was to depict sub-cortical metabolic changes
during a neutral (NC) and pure (OC) olfactory stimulation
by using a recently validated 18F-2-fluoro-2-deoxy-D-glucose
(FDG)-positron emission tomography/computer
tomography procedure in 26 MCS and 11 healthy (HC)
resting subjects undergoing a battery of clinical tests.
Twelve subcortical volumes of interest were identified by
the automated anatomical labeling library and normalized
to thalamus FDG uptake. In both groups, when comparing
OC to NC, the within-subjects ANOVA demonstrated a
relative decreased metabolism in bilateral putamen and
hippocampus and a relative increased metabolism in
bilateral amygdala, olfactory cortex (OLF), caudate and
pallidum. The between-groups ANOVA demonstrated in
MCS a significant higher metabolism in bilateral OLF
during NC. As in HC subjects negative correlations were
found in OC between FDG uptake in bilateral amygdala
and hippocampus and odor pleasantness scale, the latter
positively correlated with MCS subjects' bilateral putamen
FDG uptake in OC. Besides FDG uptake resemblances in
both groups were found, for the first time a relative higher
metabolism increase in OLF in MCS subjects at rest with
respect to HC was found. When merging this aspect to the
different subcortical FDG uptake correlations patterns in
the two groups, the present study demonstrated to describe
a peculiar metabolic index of behavioral and neurological
aspects of MCS complaints.
