Mapping brain activation to odorants in patients with smell loss by functional MRI.
OBJECTIVE
Our goal was to use functional MRI (fMRI) to develop an objective, noninvasive technique by which patients with smell loss can be identified, their abnormalities quantitated, their results compared with findings in normal subjects, and visual representation of their CNS pathology obtained.


METHODS
Functional MR brain scans were obtained in eight patients with hyposmia in response to three olfactory stimuli (pyridine, menthone, amyl acetate) in three coronal brain sections selected from anterior to posterior temporal brain regions using multislice FLASH MRI. Results were compared with similar studies performed in 17 normal subjects. Activation images were derived using correlation analysis, and ratios of area of brain activated to total brain area were obtained.


RESULTS
Brain activation to each stimulus was lower in each section in patients compared with normal subjects and reached statistical significance for mean activation for each odor and in six of the nine individual sections studied. Activation in patients was found in regions previously associated with CNS processing of olfactory stimuli in normal subjects, but activation in patients was much less, particularly in inferior frontal and cingulate gyral regions of frontal cortex and in regions of medial and posterior temporal cortex.


CONCLUSIONS
These results demonstrate quantitative CNS changes in smell function in response to olfactory stimuli in patients with hyposmia, demonstrate a novel, objective method by which these patients can be identified, and provide maps of the CNS changes associated with their smell loss.
Levy
L M
LM
Department of Radiology, Georgetown University Hospital, Washington, D.C., USA.
Henkin
R I
RI
Hutter
A
A
Lin
C S
CS
Schellinger
D
D
D000328:Adult; D000368:Aged; D001927:Brain Diseases / Q000150:complications / Q000175:diagnosis*; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000473:pathology*; D016009:Chi-Square Distribution; D006259:Craniocerebral Trauma / Q000150:complications; D005260:Female; D005625:Frontal Lobe / Q000033:anatomy & histology / Q000473:pathology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D000857:Olfaction Disorders / Q000209:etiology*; D012016:Reference Values; D012221:Rhinitis, Allergic, Perennial / Q000150:complications; D013702:Temporal Lobe / Q000033:anatomy & histology / Q000473:pathology*