Olfactory bedside test. A simple approach to identify temporo-orbitofrontal dysfunction
I. Savic, S. Y. Bookheimer, I. Fried and J. Engel Jr
Department of Neurology, University of California, Los Angeles, USA.
BACKGROUND: Olfactory memory and discrimination are processed by the
anteromesial temporal cortex and the orbitofrontal cortex. Both functions
may therefore be impaired in limbic epilepsy. METHODS: Twenty-seven
patients with mesial temporal lobe seizures (MTLS), 10 patients with
neocortical seizures (NS), and 10 matched healthy control subjects
underwent evaluation for olfactory quality discrimination (OD) and delayed
recognition memory (OM). All patients were referred for presurgical
evaluation. The olfactory tests were performed in a same-different paradigm
with 10 seconds (OD) and 60 minutes (OM) between presentations of the
odors, using the standardized University of Pennsylvania Smell
Identification Test. The presentations were monorhinal in the OD and
birhinal in the OM tests. The results were related to regional glucose
metabolism measured with fludeoxyglucose F 18 positron emission tomography.
RESULTS: Patients with MTLS had an impaired OD ipsilateral to the
epileptogenic region (P < .001) and a higher total number of errors
(including both tests) (P = .002). They also had lower OM scores, but not
significantly lower than those of patients with NS (P = .05). The combined
OM and OD tests correctly identified patients with MTLS with a sensitivity
of 85% and a specificity of 90%, offering a correct lateralization in 74%
of patients. Patients with MTLS whose OD was more impaired than OM differed
from those with more impaired OM by having a significant hypometabolism not
only over the neocortex of the epileptogenic temporal lobe (P = .02) but
also in the ipsilateral anterior (P = .008) and orbitofrontal cortex (P =
.007) (2-way analysis of variance). CONCLUSIONS: Tests of olfactory
function are useful in distinguishing between NS and MTLS. The impairments
of OM and OD can be dissociated in pathological states and therefore
mediated by different structures.
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Rupp et al.
Schizophr Bull 2005;31:155-165.
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Hudry et al.
Brain 2003;126:1851-1863.
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Hudry et al.
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Finkel et al.
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Psychometrics of Odor Quality Discrimination: Method for Threshold Determination
Olsson and Cain
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Right-nostril Dominance in Discrimination of Unfamiliar, but Not Familiar, Odours
Savic and Berglund
Chem Senses 2000;25:517-523.
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Odor Identification: Influences of Age, Gender, Cognition, and Personality
Larsson et al.
J. Gerontol. B Psychol. Sci. Soc. Sci. 2000;55:304P-310.
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