A comparative study of brain perfusion single-photon emission computed tomography and magnetic resonance imaging in patients with post-traumatic anosmia
Loss of smell is a problem that can occur in up to 30% of patients with head trauma. The olfactory function investigation methods so far in use have mostly relied on subjective responses given by patients. Recently, some studies have used magnetic resonance imaging (MRI) and single-photon emission computed tomography (SPECT) to evaluate patients with post-traumatic anosmia. The present study seeks to detect post-traumatic anosmia and the areas in the brain that are related to olfactory impairment by using SPECT and MRI as imaging techniques.
The study was conducted on 21 patients suffering from head injury and consequently anosmia as defined by an olfactory identification test. Two control groups (traumatic normosmic and nontraumatic healthy individuals) were selected. Brain MRI, qualitative and semiquantitative SPECT with 99mtc-ethyl-cysteinate-dimer were taken from all the patients. Then the brain SPECT and MRI were compared with each other.
Semi-quantitative assessment of the brain perfusion SPECT revealed frontal, left parietal, and left temporal hypoperfusion as compared with the two control groups. Eighty-five percent of the anosmic patients had abnormal brain MRI. Regarding the MRI, the main abnormality proved to be in the anterior inferior region of the frontal lobes and olfactory bulbs.
The findings of this study suggest that damage to the frontal lobes and olfactory bulbs as shown in the brain MRI and hypoperfusion in the frontal, left parietal, and left temporal lobes in the semiquantitative SPECT corresponds to post-traumatic anosmia. Further neurophysiological and imaging studies are definitely needed to set the idea completely.
Available from: Léa Gagnon
- "The lower BOLD signal observed in the mOFC of our COI participants is in accordance with structural and metabolic changes within this region following the loss of smell perception. These changes include grey matter volume reductions (Bitter, Bruderle, Gudziol, Burmeister, & Guntinas-Lichius, 2010; Bitter, Gudziol et al., 2010), increased grey matter thickness (Frasnelli, Fark, Lehmann, Gerber, & Hummel, 2013), hypometabolism (Varney, Pinkston, & Wu, 2001) and hypoperfusion (Eftekhari et al., 2006; Atighechi et al., 2009). Two previous studies reported a positive correlation between olfactory performance and grey matter thickness in the mOFC in healthy individuals (Frasnelli et al., 2010; Seubert, Freiherr, Frasnelli, Hummel, & Lundstrom, 2012). "
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ABSTRACT: Olfaction and gustation contribute both to the appreciation of food flavours. Although acquired loss of smell has profound consequences on the pleasure of eating, food habits and body weight, less is known about the impact of congenital olfactory impairment on gustatory processing. Here we examined taste identification accuracy and its neural correlates using functional magnetic resonance imaging (fMRI) in 12 congenitally olfactory impaired individuals and 8 normosmic controls. Results showed that taste identification was worse in congenitally olfactory impaired compared to control subjects. The fMRI results demonstrated that olfactory impaired individuals had reduced activation in medial orbitofrontal cortex (mOFC) relative to normosmic subjects while tasting. In addition, olfactory performance as measured with the Sniffin' Sticks correlated positively with taste-induced BOLD signal increases in bilateral mOFC and anterior insula. Our data provide a neurological underpinning for the reduced taste perception in congenitally olfactory impaired individuals.
Neuropsychologia 09/2014; 62. DOI:10.1016/j.neuropsychologia.2014.07.018 · 3.30 Impact Factor
- "Nine functional neuro-imaging studies[31–39] identified in the literature search provided evidence for reduced metabolic activity in prefrontal regions at rest or relative hypo-perfusion during olfactory activations. The findings were consistent across different imaging modalities, different methods of data analysis, and the use of different procedures for assessing olfactory function. "
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ABSTRACT: To evaluate via a research literature survey the anterior neurological significance of decreased olfactory functioning following traumatic brain injuries.
A computer literature review was performed to locate all functional neuro-imaging studies on patients with post-traumatic anosmia and other olfactory deficits.
A convergence of findings from nine functional neuro-imaging studies indicating evidence for reduced metabolic activity at rest or relative hypo-perfusion during olfactory activations. Hypo-activation of the prefrontal regions was apparent in all nine post-traumatic samples, with three samples yielding evidence of reduced activity in the temporal regions as well.
The practical ramifications include the reasonable hypothesis that a total anosmic head trauma patient likely has frontal lobe involvement.
Indian Journal of Psychological Medicine 07/2010; 32(2):93-8. DOI:10.4103/0253-7176.78504
Available from: Stefan Förster
- "tive complexity, evoked either symmetrical or predominantly right-hemispheric activations in the orbitofrontal cortex, amygdala, piriform cortex, insular cortex, anterior cingulate cortex, and cerebellum of healthy subjects  . These empirical findings suggest a central role for the non-dominant hemisphere in olfactory processing, although others have noted an association between left hemispheric traumatic injury and anosmia . The authors of one PET activation study investigated the pattern of cerebral activation with olfactory tasks of increasing cognitive complexity , and concluded that the olfactory system is organized in a parallel and hierarchical manner. "
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ABSTRACT: We used [18F]fluorodeoxyglucose (FDG) PET analysis to determine performance in different olfactory domains of patients with early AD compared to cognitively healthy subjects, and to map the functional metabolic representation of olfactory impairment in the patient sample. A cohort of patients with early AD (n=24), consisting of 6 subjects with incipient AD and 18 subjects with mild AD, and a control group of 28 age-matched non-demented individuals were assembled. Patients and controls were tested for olfactory performance using the "Sniffin' Sticks" test battery [odor identification (ID), discrimination (DIS) and threshold (THR)], while patients additionally underwent resting state FDG-PET. Voxel-wise PET results in the patients were correlated with olfaction scores using the general linear model in SPM5. Patients with early AD showed significantly reduced function in all three olfactory subdomains compared to controls. After controlling for effects due to patients' age, gender, cognitive status, and treating scores in the two other olfactory subdomains as nuisance variables, ID scores correlated with normalized FDG uptake in clusters with peaks in the right superior parietal lobule, fusiform gyrus, inferior frontal gyrus, and precuneus, while DIS scores correlated with a single cluster in the left postcentral cortex, and THR scores correlated with clusters in the right thalamus and cerebellum. The subtests employed in the "Sniffin' Sticks" test battery are complementary indicators of different aspects of olfactory dysfunction in early AD, and support the theory of a parallel organized olfactory system, revealed by FDG-PET correlation analysis.
Journal of Alzheimer's disease: JAD 01/2010; 22(2):581-91. DOI:10.3233/JAD-2010-091549 · 4.15 Impact Factor
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