Olfactory dysfunction in multiple sclerosis

Atalar, Arife Çimen; Erdal, Yuksel; Tekin, Betül; Yıldız, Muhammed Gazi; Akdoğan, Özlem; Emre, Ufuk

doi:10.1016/j.msard.2018.02.032

Cited by 21 publications

(12 citation statements)

References 25 publications

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“…A obvious hint was present for the highestorder olfactory cortex that revealed disturbance, which implied a complicated pattern of the olfactory network maladjustment in MS. From the perspective of fMRI, this study corroborated the previous landmark study, which unequivocally validated the direct proportion of the plaque activity in the olfactory-related central brain region with olfactory deficits. 3,30 However, the study on olfactory structure revealed that the olfactory tract and bulb atrophied in early stages of olfactory impairment, 21 suggesting the change of highest-order olfactory cortex might be secondary to the primary neuron deficit. In addition, the visualized changes were present in the olfactionrelated brain network in MS, and whether differential activation of distinct brain regions exhibited a hyperactivation or compensatory olfactory process, as in Parkinson's Disease, 31 warrants further investigation.…”

Section: Discussionmentioning

confidence: 99%

Change in Functional Brain Activation Patterns Induced by Olfactory Stimulation in Multiple Sclerosis

Ouyang¹,

Wang

Zhang³

et al. 2020

NDT

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Background: Olfactory disorder is one of the commonly appearing symptoms in diseases like Parkinson's disease (PD) and Alzheimer's disease (AD). However, reports of olfactory changes in multiple sclerosis (MS) are scarce and usually ignored or seldom recognized by clinicians. The majority of current research is based on subjective answers obtained by smelling odorants. Objective: To gain better insights into the central brain regions involved in the olfactory process. We measured preliminary contrast assessment characteristics of brain activation in MS patients and healthy controls using functional magnetic resonance imaging (fMRI) under an odor stimulation task. Methods: Olfactory event-related fMRI was used to assess the olfactory network neuronal activity during passively inhaled volatile gases of lavender and rose solutions alternately in 18 MS patients and 20 healthy sex-and age-matched adults. Spearman correlation analysis was conducted between the lesions in central and olfactory-induced activated brain regions. Results: We observed significant reductions in the number of activated brain areas compared with healthy controls in MS patients under a standard activation mode; the right insula, right amygdala, right inferior frontal gyrus, right frontal middle gyrus, and left supramarginal gyrus were activated in MS patients (t = 2.04, P < 0.05). Meanwhile, the intensity of the activated olfactory brain network revealed attenuation. The Spearman correlation analysis indicated the distribution and number of demyelination lesions, exerting a little impact on major activation of brain regions during olfactory stimulation (r =-0.524, P = 0.054). Conclusion: This study establishes that olfaction-related brain regions were altered in patients with MS confirmed by fMRI. The finding refreshes the awareness that olfactory disturbance involved just in structural pathology like olfactory bulbs and tracts or olfactory sulcus, which reportedly is responsible for the deficits.

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Section: Discussionmentioning

confidence: 99%

Change in Functional Brain Activation Patterns Induced by Olfactory Stimulation in Multiple Sclerosis

Ouyang¹,

Wang

Zhang³

et al. 2020

NDT

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“…Although the etiology of MS remains disputed, it is postulated that genetic factors ( Ebers and Sadovnick 1994 ) and viral pathogens, such as HCoV, induce CNS demyelination via chronic infection of oligodendrocytes ( Perlman 1998 ; Arbour et al 2000 ; Fazakerley and Walker 2003 ). Interestingly, recent studies have indicated that olfactory dysfunction is correlated with progressive cognitive impairment and physical disability in MS patients ( Atalar et al 2018 ; Carotenuto et al 2019 ). Certainly, this hypothesis would require longitudinal patient studies to delineate and gather more evidence on the progressive decline of neurological function.…”

Section: Possible Mechanisms Of Anosmia In Sars-cov-2 Patientsmentioning

confidence: 99%

Anosmia in COVID-19: Mechanisms and Significance

et al. 2020

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Abstract The global pandemic of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remains a challenge for prevention due to asymptomatic or paucisymptomatic patients. Anecdotal and preliminary evidence from multiple institutions shows that these patients present with a sudden onset of anosmia without rhinitis. We aim to review the pathophysiology of anosmia related to viral upper respiratory infections and the prognostic implications. Current evidence suggests that SARS-CoV-2-related anosmia may be a new viral syndrome specific to COVID-19 and can be mediated by intranasal inoculation of SARS-CoV-2 into the olfactory neural circuitry. The clinical course of neuroinvasion of SARS-CoV-2 is yet unclear; however, an extended follow-up of these patients to assess for neurological sequelae, including encephalitis, cerebrovascular accidents, and long-term neurodegenerative risk may be indicated.

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“…It is well known that the olfactory system represents a key entry port for pathogens including viruses and environmental toxins to the CNS [4]. OD is known as occasional presymptomatic sign of various neuroimmunological and neurodegenerative disorders [8], and it is predictive of cognitive decline in mild cognitive impairment, Alzheimer’ disease, Parkinson’s disease [7], multiple sclerosis [23], and in dementia-free older adults [4]. The possible contribution of inflammation and viral infections (e.g., human herpesviruses and cytomegalovirus) in the pathogenesis of mild cognitive impairment and Alzheimer’s disease is worth mentioning [24, 25], but given the high prevalence of those viruses, the meaning of these epidemiological data is difficult to interpret.…”

Section: Discussion/conclusionmentioning

confidence: 99%

Hyposmia Is Associated with Reduced Cognitive Function in COVID-19: First Preliminary Results

Pirker-Kees

Platho-Elwischger

Häfner

et al. 2021

Dement Geriatr Cogn Disord

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Background: Hyposmia is frequently reported as an initial symptom in coronavirus disease 2019 (COVID-19). Objective: As hyposmia accompanies cognitive impairment in several neurological disorders, we aimed to study whether hyposmia represents a clinical biomarker for both neurological involvement and cognitive impairment in mild COVID-19. We aimed to study whether olfactory dysfunction (OD) represents a clinical biomarker for both neurological involvement and cognitive impairment in mild COVID-19. Methods: Formal olfactory testing using the Sniffin’Sticks® Screening test, neuropsychological assessment using the Montreal Cognitive Assessment (MoCA), and detailed neurological examination were performed in 7 COVID-19 patients with mild disease course and no history of olfactory or cognitive impairment, and 7 controls matched for age, sex, and education. Controls were initially admitted to a dedicated COVID-19 screening ward but tested negative by real-time PCR. Results: The number of correctly identified odors was significantly lower in COVID-19 than in controls (6 ± 3, vs. 10 ± 1 p = 0.028, r = 0.58). Total MoCA score was significantly lower in COVID-19 patients than in controls (20 ± 5 vs. 26 ± 3, p = 0.042, r = 0.54). Cognitive performance indicated by MoCA was associated with number of correctly identified odors in COVID-19 patients and controls (COVID-19: p = 0.018, 95% CI = 9–19; controls: p = 0.18, r = 0.63, 95% CI = 13–18.5 r = 0.64). Discussion/Conclusion: OD is associated with cognitive impairment in controls and mild COVID-19. OD may represent a potentially useful clinical biomarker for subtle and even subclinical neurological involvement in severe acute respiratory distress syndrome coronavirus-2 infection.

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Olfactory dysfunction in multiple sclerosis

Cited by 21 publications

References 25 publications

<p>Change in Functional Brain Activation Patterns Induced by Olfactory Stimulation in Multiple Sclerosis</p>

<p>Change in Functional Brain Activation Patterns Induced by Olfactory Stimulation in Multiple Sclerosis</p>

Anosmia in COVID-19: Mechanisms and Significance

Hyposmia Is Associated with Reduced Cognitive Function in COVID-19: First Preliminary Results

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