Posttraumatic Anosmia Research Articles

Traumatic brain injury-induced inflammatory changes in the olfactory bulb disrupt neuronal networks leading to olfactory dysfunction

Approximately 20–68% of traumatic brain injury (TBI) patients exhibit trauma-associated olfactory deficits (OD) which can compromise not only the quality of life but also cognitive and neuropsychiatric functions. However, few studies to date have examined the impact of experimental TBI on OD. The present study examined inflammation and neuronal dysfunction in the olfactory bulb (OB) and the underlying mechanisms associated with OD in male mice using a controlled cortical impact (CCI) model. TBI caused a rapid inflammatory response in the OB as early as 24 h post-injury, including elevated mRNA levels of proinflammatory cytokines, increased numbers of microglia and infiltrating myeloid cells, and increased IL1β and IL6 production in these cells. These changes were sustained for up to 90 days after TBI. Moreover, we observed significant upregulation of the voltage-gated proton channel Hv1 and NOX2 expression levels, which were predominantly localized in microglia/macrophages and accompanied by increased reactive oxygen species production. In vivo OB neuronal firing activities showed early neuronal hyperexcitation and later hypo-neuronal activity in both glomerular layer and mitral cell layer after TBI, which were improved in the absence of Hv1. In a battery of olfactory behavioral tests, WT/TBI mice displayed significant OD. In contrast, neither Hv1 KO/TBI nor NOX2 KO/TBI mice showed robust OD. Finally, seven days of intranasal delivery of a NOX2 inhibitor (NOX2ds-tat) ameliorated post-traumatic OD. Collectively, these findings highlight the importance of OB neuronal networks and its role in TBI-mediated OD. Thus, targeting Hv1/NOX2 may be a potential intervention for improving post-traumatic anosmia.

Brain structural analysis in patients with post-traumatic anosmia: Voxel-based and surface-based morphometry

Purpose and backgroundVoxel-based morphometry (VBM) and surfaced-based morphometry (SBM) investigate the characteristics of gray matter (GM) in various diseases such as post-traumatic anosmia (PTA). This study uses SBM and VBM to examine neuroanatomical measurements of GM and its functional correlates in patients with PTA. MethodsMRI images and olfactory test results were collected from 39 PTA patients and 39 healthy controls. Sniffin’ Sticks test was used to assess olfactory function. GM structure was analyzed using CAT12 and FreeSurfer, and olfactory bulb (OB) volume and olfactory sulcus (OS) depth were calculated using 3D-Slicer. ResultsAnosmic patients showed lower scores in the Sniffin’ Sticks olfactory test, as well as reduction of OB volume and OS depth compared to control subjects. In these patients, overlapping changes were found between the VBM and SBM findings in the areas with significant effects, in particular, orbitofrontal cortex, superior and middle frontal gyrus, superior and middle temporal gyrus, anterior cingulate cortex, and insular cortex. Using SBM, decreased cortical thickness clusters were located in inferior and superior parietal gyrus. Further analysis in the region of interest demonstrated correlations between the orbitofrontal cortex and odor threshold score as well as the middle frontal gyrus and smell loss duration. ConclusionThese findings show that the morphological alterations in the OB, OS, and the central olfactory pathways might contribute to the pathogenic mechanism of olfactory dysfunction after head injury.

Patterns of Gray and White Matter Volume Alterations in Patients With Post-Traumatic Anosmia: A Voxel-Based Morphometry Study.

ObjectiveTraumatic brain injury is one of the major causes of human olfactory dysfunction and leads to brain structure alterations, mainly in the cortical olfactory regions. Our study aimed to investigate volume changes in the gray matter (GM) and white matter (WM) in patients with post-traumatic anosmia and then to explore the relationship between GM volume and olfactory function.MethodsEthics committee approved prospective studies which included 22 patients with post-traumatic anosmia and 18 age- and gender-matched healthy volunteers. Olfactory function was assessed using the Sniffin' Sticks. High-resolution 3-dimensional T1 MRIs of the participants were acquired on a 3T scanner and the data were collected for voxel-based morphometry (VBM) analysis. Furthermore, the GM and WM volumes of the whole brain regions were compared and correlated with olfactory function.ResultsThe analysis revealed significant GM volume reduction in the orbitofrontal cortex (OFC), gyrus rectus (GR), olfactory cortex, insula, parahippocampal, temporal pole, and cerebellum (all P < 0.001) in patients. Besides, WM volume loss was also found in the OFC, GR, and insula (all P < 0.001) in patients. All WM atrophy areas were connected to areas of GM volume loss spatially. Correlation analysis showed the olfactory scores were significantly positively correlated with the GM volume of the occipital cortex (P < 0.001, and PFWE < 0.05), while no significant correlation was found between the Sniffin' Sticks test scores and the WM volume in patients.ConclusionThe reduction of GM and WM volume in olfactory-related regions was responsible for olfactory dysfunction in post-traumatic patients. The occipital cortex may play a compensation mechanism to maintain the residual olfactory function. To our knowledge, we report here for the first time on white matter volume alterations specifically in post-traumatic patients with anosmia.

Medicolegal aspect of loss of smell and olfactory event-related potentials

BackgroundIt is not straightforward to objectively evaluate the olfactory dysfunction that occurs following forensic incidents. The olfactory event-related potentials method, based on electrophysiological records, may provide objective data in the evaluation of posttraumatic anosmia cases from the medicolegal perspective. This study, where a quantitative evaluation of the cases with the complaints of olfactory sensation disorder was performed using the olfactory event-related potentials test, aims to identify the factors that should be considered in the evaluation of olfactory dysfunction from the medicolegal perspective.ResultsThis study first evaluated the complaints of 98 patients admitted because of posttraumatic impaired smell and then administered electrophysiological odor tests on the patients. Because of this, the relationship between the EEG responses of the cases and the olfactory disorder was examined. Of the 98 cases that participated in the study, 68 (69.4%) were male and 30 (30.6%) were female. Of all cases, 53 (54.1%) had complaints of not being able to smell at all, 14 (14.3%) had complaints of reduced smell, whereas, in addition to the existing complaints of olfactory dysfunction, 44 (44.9%) of them had complaints of taste perception and 18 (18.3%) reported having vision disorders. 21 of 37 cases who reported being unable to smell during the test turned out to be anosmic. Furthermore, 16 cases stated that, though having had a response in the odor test, they had no sense of smell following the test.ConclusionsAlthough it seems possible to prove that there is a relationship between the olfactory event-related potential test and the diagnosis of anosmia, there is still ongoing research on its use in clinical practice. Performing both subjective and electrophysiological tests together to detect olfactory dysfunctions that occur after a forensic incident enable provide more reliable results in diagnosis.

Altered glucose metabolism of the olfactory-related cortices in anosmia patients with traumatic brain injury.

Impaired brain cortices contribute significantly to the pathophysiological mechanisms of post-traumatic olfactory dysfunction (PTOD). This study aimed to use 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) to measure cerebral cortices' metabolism activity and then to explore their associations with olfaction in patients with PTOD. Ethics committee-approved prospective studies included 15 patients with post-traumatic anosmia and 11 healthy volunteers. Olfactory function was assessed using the Sniffin' Sticks. Participants underwent 18F-FDG PET/CT scan and the image data were collected for the voxel-based whole brain analysis. Furthermore, the standardized uptake value ratio (SUVR) of the whole brain regions was measured and correlated with olfactory function. Patients with post-traumatic anosmia showed significantly reduced glucose metabolism in bilateral rectus, bilateral superior and medial orbitofrontal cortex (OFC), bilateral thalamus, left hippocampus and parahippocampus and left superior temporal pole (all p < 0.001). In contrast, patients with post-traumatic anosmia had significantly increased glucose metabolism in the bilateral insula (all p < 0.001). SUVR values among a total of 17 cerebral cortices including frontal, limbic, and temporal regions were significantly and positively correlated with olfactory function. The cerebral cortices with the top three correlations were the right middle frontal OFC (r = 0.765, p = 0.001), right caudate (r = 0.652, p = 0.010) and right putamen (r = 0.623, p = 0.002). Patients with post-traumatic anosmia presented with distinct patterns of brain metabolism and key cortices that highly associated with the retained olfactory function were identified. The preliminary results further support the potential use of PET imaging for precisely assessing brain metabolism in patients with PTOD.

Platelet rich plasma in management of anosmia

Background: Anosmia is a loss of sense of smell that means inability to perceive odors. Functional anosmia is loss of smell due to nasal obstruction while organic anosmia is due to damage of the peripheral olfactory area causing permanent loss of smell as post-traumatic anosmia. Objectives: A diagnostic approach to detect the effect of platelet-rich plasma (PRP) injection in the olfactory area as a treatment for anosmia. Study design and methodology: A prospective study was done in otorhinolaryngology department, Aswan university hospital from June 2018 to August 2019, 80 patients were fulfilling the inclusion criteria presented with anosmia were enrolled from otorhinolaryngology outpatient to share in this study. Approximately an amount of 1mL of PRP was injected in each nasal cavity in the olfactory area (located on superior turbinate and superior portion of lateral and medial walls of nasal cavity) guided by nasal endoscope. The procedure is done with follow-up of patients after 1 month. Results: Results of our study revealed that 46 out of 80 patients (57.5%) said that “their smell came back” while 34 out of 80 patients (42.5%) showed no improvement, thus these results show no statistical significance between proportion in a group showing improvement and proportion in the group showing no improvement. 5 patients with idiopathic anosmia improved with 100% ratio. Conclusion: Although there is no statistical significance difference between the two groups of patients all patients with idiopathic anosmia were improved.

Subjective and Objective Assessments of Post-traumatic Olfactory Dysfunction.

Introduction: Traumatic brain injuries are the most common cause of olfactory dysfunction. Deficits in olfaction may be conductive or neurosensory in nature, with varying degrees of impairment resulting in a diminished quality of life and an increased risk for personal injury among patients. The aim of this research is to evaluate the results of the subjective and objective quantitative examinations of olfactory function in a group of patients with post-traumatic anosmia in order to predict its value in identifying olfactory deficits in clinical practice.Materials and Methods: The present study included 38 patients who reported anosmia or hyposmia caused by a traumatic head injury, and a group of 31 age- and sex-matched controls without olfactory dysfunction or prior history of head injury. The comparison of odor perception and identification of two oils (mint and anise) was assessed with the use of blast olfactometry with cortical olfactory event-related potentials.Results: Subjective olfactory tests revealed anosmia or hyposmia in 94% of patients with head injury-related olfactory dysfunction. Objective tests revealed olfactory event-related potentials from cranial nerve I produced by the stimulation with both mint and anise in 20 patients (52.6%). Olfactory event-related potentials from cranial nerve V produced by the stimulation with mint were registered in 26 patients (68.4%). The lack of any responses, from both cranial nerve I and V, was found in 12 patients (32% of cases).Conclusions: Findings from our study indicate the application of both subjective and objective examinations in the evaluation of patients with olfactory impairment. In the diagnosis of post-traumatic anosmia or hyposmia, objective examinations are particularly useful when the patients' level of cognition may be impaired or when subjects may be exaggerating their olfactory defects for a secondary gain. The diagnosis of damage to the olfactory system, specifically in the receptive part of the olfactory pathway, can be established in patients who showed reduced amplitudes or absent cortical responses in addition to absent odor identification and perception threshold in the subjective examination.

Functional MRI as an Objective Measure of Olfaction Deficit in Patients with Traumatic Anosmia.

While posttraumatic anosmia is not uncommon, the olfactory function evaluation has strongly relied on subjective responses given by patients. We aimed to examine the utility of fMRI as an objective tool for diagnosing traumatic anosmia. Sixteen patients (11 men and 5 women; mean age, 42.2 ± 10.4 years) with clinically diagnosed traumatic anosmia and 19 healthy control subjects (11 men and 8 women; mean age, 29.3 ± 8.5 years) underwent fMRI during olfactory stimulation with citral (a pleasant odor) or β-mercaptoethanol (an unpleasant odor). All patients were subjected to a clinical olfactory functional assessment and nasal endoscopic exploration. Two-sample t tests were conducted with age as a covariate to examine group differences in brain activation responses to olfactory stimulation (false discovery rate-corrected P < .05). Compared with healthy control subjects, patients with traumatic anosmia had reduced activation in the bilateral primary and secondary olfactory cortices and the limbic system in response to β-mercaptoethanol stimulation, whereas reduced activation was observed only in the left frontal subgyral region in response to citral stimulation. Brain activation was decreased in the bilateral primary and secondary olfactory cortices as well as the limbic system in response to olfactory stimulation in patients with traumatic anosmia compared with healthy control subjects. These preliminary results may shed light on the potential of fMRI for the diagnosis of traumatic anosmia.

Neurotization of nasal mucosa by end-to-side nerve graft: preliminary report of smell restoration

Nerve regeneration after an end-to-side neurorrhaphy had been well established in the literature. Both sensory and motor functions could be achieved using this technique. Autonomic and special sensory restoration (e.g., smell sensation) were not studied extensively before. Post-traumatic anosmia has an overall prevalence rate of 7%, with a variable rate of recovery. In this preliminary report, olfactory sensation was restored in a case with a long-standing anosmia using end-to-side nerve graft. The patient reported regaining of smell, which was confirmed by a smell identification test. This technique has the potential to be a promising method for smell restoration; however, it needs further workup and investigations. Level of Evidence: Level V, therapeutic study.

Post-traumatic taste disorders: a case series.

Since 1800s there are reports of post-traumatic anosmia, but few studies investigated post-traumatic gustatory deficit and adopted validated evaluation tests. Peripheral and/or central mechanisms may be involved in the genesis of post-traumatic gustatory dysfunction. Beyond a reduction/loss (hypogeusia/ageusia) of gustatory function following a trauma, qualitative taste changes (dysgeusia) may occur. Especially when persistent, taste deficits might be particularly relevant for patient's quality of life and activities of daily life, but knowledge on this topic is limited. Fifty-three consecutive patients with previous head trauma were recruited. Every patient underwent a careful history taking and thorough olfactory and gustatory chemosensory testing by Sniffin'Sticks Extended test, Whole Mouth Test and Taste Strips Test. All patients had olfactory abnormalities (hyposmia: n=10, functional anosmia: n=43), while 10 of them (19%) showed taste deficits (dysgeusia: n=3, dysgeusia with hypogeusia: n=1, hypogeusia: n=5, ageusia: n=1). Here, we report clinical and neuroimaging data and detailed description of four meaningful cases representing central and peripheral injury patterns. Chemosensory evaluation might be useful to explore taste disorder, a still neglected and underestimated sequela of head trauma.

Evaluation for disability in a case of posttraumatic anosmia

To investigate the process of apoptosis in lungs and liver induced by crushing hindlimbs of rat, and study the mechanism of crush injury. The rat experimental model of hindlimbs crush injury was established. The cell apoptosis in lungs and liver was detected by TUNEL assay, and the expression of Bax, Bcl-2 and caspase-3 apoptin was examined by immunohistochemistry. Compared with the control group, the partial muscle injury of rat's hindlimbs was more serious with more apoptosis observed in lungs and liver (P < 0.05). The expression of Bax was up-regulated and Bcl-2 was down-regulated, whereas caspase-3 expression was activated (P < 0.05). The cell apoptosis has increased significantly in lungs and liver after crush injury of hindlimbs in rat. The correlation factor released during tissue injury may mediate apoptosis process.

Post-traumatic taste disorders: presentation of three meaningful cases

Since the late 1800s there are reports of post-traumatic anosmia [1], but few studies investigated post-traumatic gustatory deficit and adopted validated evaluation tests [2,3,4,5,6,7]. Post-traumatic ageusia is rare, occurring in ~ 0.5% of head traumas, while a gustatory deficit is more frequently referred (5-7%) when olfaction is impaired [2,4]. Unlike olfaction, gustatory sensation is mediated by several cranial nerves (VII, IX, X) and taste receptors are widely spread in the oral cavity, so that taste is considered a “robust” sense. Peripheral and/or central mechanisms may be involved in the genesis of post-traumatic gustatory dysfunction. Beyond a reduction/loss of gustatory function following a trauma, taste changes (dysgeusia) may occur, even if they are reported to be rare [7,8,9]. Gustatory disorders might not be immediately reported because patient often pays attention to other post-traumatic sequelae. Especially when persistent, taste deficits might be particularly relevant for patients’ quality of life. Physicians are often not well-informed on the possible implications or treatment strategies. Fifty-three consecutive patients with previous head trauma and chemosensory disorders were recruited by the olfactory and taste research group of the University of Verona. Every patient underwent a careful clinical examination, olfactory and gustatory testing by Sniffin’Sticks Extended test, Whole Mouth taste test and Taste Strips Test respectively (Burghart, Germany). Among them, we found 10 cases with hyposmia, 43 with functional anosmia, while 10 cases showed taste deficits (dysgeusia: n = 3, dysgeusia with hypogeusia: n = 1, hypogeusia: n = 5, ageusia: n = 1). Here we report anatomical, clinical correlations and detailed description of three cases representing central and peripheral injury patterns.

Evaluation of post-traumatic anosmia with MRI and chemosensory ERPs.

Magnetic resonance imaging (MRI) and chemosensory event-related potentials (ERPs) are important methods to evaluate olfactory function, but there is lack of study to explore the application of MRI and chemosensory ERPs in the patients with traumatic anosmia. The data of 26 post-traumatic anosmic patients and 21 healthy controls were retrospectively surveyed; olfaction and olfactory pathway of all participants were measured clinically using the T&T olfactometer, the Sniffin' Sticks, chemosensory ERPs and MRI. All patients were anosmic based on complaints and clinical examinations. In five patients, the olfactory bulb volume was significantly lower than control group. In 18 patients, the olfactory sulcus (OS) depth was similar to control group, but all the participants had a deeper right OS (right = 7.79 ± 1.31, left = 7.06 ± 1.44, p < 0.01). Olfactory ERPs (oERPs) could be evoked in 17 patients, but these signals showed longer latencies and lower amplitude than controls in the N1 (latency p < 0.05, amplitude p < 0.01) and P2 (latency p < 0.01, amplitude p < 0.05) waves. Nine traumatic anosmic patients had no identifiable oERPs; most of them had olfactory center injury. Trigeminal ERPs were detected in all anosmic patients and controls; patients had longer latencies for N1 (p < 0.05) and P2 (p < 0.05) waves, while there was no similar change in amplitude. Older subjects had smaller OB volume and OS depth. Closed head injury could induce anosmia; the severity extent, injury site and subsequent consciousness are related to the olfaction. oERP is the gold standard for olfactory subjective examination; MRI could indicate the lesions on the olfactory pathway and reflect the possibility of detectable oERPs.

Posttraumatic Anosmia Secondary to Cranial Base Contusion

Peertechz International Open Access, Peer-reviewed Platform to promote qualitative research publications for Science, Engineering, Technology and Medicine journals, with an un-restricted access and at low cost publication fee.

Chemoresponsiveness and breath physiology in anosmia.

Anosmia is a model to study the interaction among chemoreception systems. In the head injury, the traumatic irreversible anosmia caused by damage to olfactory nerve fibers and brain regions is of enviable research interest. In this study, psychophysiological tests for a comprehensive assessment of olfactory function were utilized to investigate anosmia, together with a new technique based on the breath real-time monitoring of volatile organic compounds (VOCs). We applied the breath and VOCs analysis to investigate chemoresponsiveness in the long-term irreversible post-traumatic anosmia.

Does the presence of posttraumatic anosmia mean that you will be disinhibited?

Dispute has surrounded the issue of whether the relationship between anosmia and executive dysfunction in traumatic brain injury (TBI) may be artefactual due to poor ascertainment. Three groups matched for age, gender, education, Full Scale IQ, and the Wechsler Working Memory Index and showing adequate symptom validity were compared: 30 anosmic TBIs (TBI-A) matched for posttraumatic amnesia (PTA) and working memory functioning with 36 nonanosmic TBIs (TBI-NA) and 51 controls. The groups performed the FAS test, the Animal Fluency test, the Stroop Neurological Screening Test (SNST), the Wisconsin Card Sorting Test–64 (WCST–64) and the Trail Making Test (TMT-B) as well as tests of emotional functioning and return to work outcome. After adjusting for the covariates (i.e., gender; Wechsler Test of Adult Reading, WTAR; and years of education), a significant effect was found for items successfully completed on the SNST, the FAS task, the Animal Fluency task, and the WCST–64 categories completed. After adjusting for the covariates, a significant difference was found for number of errors on the SNST and for the number and type of errors on TMT-B. The two groups did not differ in terms of their affective functioning (i.e., Beck Depression Inventory or Beck Anxiety Inventory), or in terms of their outcome with regard to return to work. The findings support the notion that the TBI-A group demonstrated considerably weaker performance on executive tasks than did the nonanosmic TBIs. These patients were not, however, more prone to an error-prone pattern of performance, and, if anything, their executive deficit was more likely attributable to a reduced productivity of response.

Functional Neuro-Imaging and Post-Traumatic Olfactory Impairment

Objective:To evaluate via a research literature survey the anterior neurological significance of decreased olfactory functioning following traumatic brain injuries.Materials and Methods:A computer literature review was performed to locate all functional neuro-imaging studies on patients with post-traumatic anosmia and other olfactory deficits.Results: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.Conclusions:The practical ramifications include the reasonable hypothesis that a total anosmic head trauma patient likely has frontal lobe involvement.

Steroid treatment of posttraumatic anosmia

The objective of this study was to treat posttraumatic anosmia with oral steroid and evaluate its effect. One-hundred sixteen posttraumatic patients whose olfactory thresholds were -1.0 by the phenyl ethyl alcohol threshold test assembled in our department. They were treated with a course of high-dose steroid, and followed up for at least 3 months. During the latter period of this study, magnetic resonance imaging was performed to measure the volumes of olfactory bulbs and to detect subfrontal lobe damage. Among them, 19 (16.4%) patients' olfactory thresholds improved after steroid treatment, but the other 97 patients' thresholds did not change. The incidences of loss of consciousness and intracranial hemorrhage after head injury, the ratios of admission and craniotomy, the intervals between head injury and steroid treatment, the volumes of olfactory bulbs, and the incidences of subfrontal lobe damage were not significantly different between patients whose thresholds improved and those whose thresholds did not improve. However, patients with olfactory improvement were significantly younger than those who remained unchanged. Our study showed that oral steroid treatment might improve olfactory acuity in some patients with posttraumatic anosmia, but the possibility of spontaneous recovery cannot be ruled out.

Olfactory Bulb Volume in Taiwanese Patients with Posttraumatic Anosmia

Olfactory bulb (OB) volume has been shown to be an indicator of olfactory function. However, few studies have been done in Asia to investigate the influence of different disorders on OB volume. Data from patients with posttraumatic anosmia were collected in our department. Their olfactory thresholds were assessed by the phenyl ethyl alcohol threshold test. They were treated with a course of high-dose steroid, and followed up for at least 3 months without any olfactory improvement. Magnetic resonance imaging was subsequently used to measure patients' OB volumes. Subjects who self-reported their olfactory function was normal were also included in the control group for comparison. Fifty-four patients with posttraumatic anosmia and 30 subjects who self-reported their olfactory function was normal were enrolled in this study. The mean right OB volume was 45.2 mm3, and the mean left OB volume was 46.3 mm3 in patients with posttraumatic anosmia. The mean right OB volume was 59.7 mm3, and the mean left OB volume was 66.0 mm3 in control subjects. The OB volumes were significantly lower in patients with posttraumatic anosmia. OB volumes were significantly lower in Taiwanese patients with posttraumatic anosmia.

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.