Patients with acquired, idiopathic olfactory dysfunction (OD) commonly undergo magnetic resonance imaging (MRI) evaluation to rule out intracranial pathologies. This practice is highly debated given the expense of MRI relative to the probability of detecting a treatable lesion. This, combined with the increasing use of MRI in research to investigate the mechanisms underlying OD, provided the impetus for this comprehensive review.
Objective
The purpose of this systematic review was to both assess the utility of MRI in diagnosis of idiopathic OD and to describe MRI findings among mixed OD etiologies to better understand its role as a research tool in this patient population.
Methods
A literature search of PubMed, Embase, Cochrane, Web of Science, and Scopus for studies with original MRI data for patients with OD was completed. Studies exclusively investigating patients with neurocognitive deficits or those studying traumatic or congenital etiologies of OD were excluded.
Results
From 1758 candidate articles, 33 studies were included. Four studies reviewed patients with idiopathic OD for structural pathologies on MRI, of which 17 of 372 (4.6%) patients had a potential central cause identified, and 3 (0.8%) had an olfactory meningioma or olfactory neuroblastoma. Fourteen studies (42.4%) reported significant correlation between olfactory bulb volume and olfactory outcomes, and 6 studies (18.8%) reported gray matter volume reduction, specifically in the orbitofrontal cortex, anterior cingulate cortex, insular cortex, parahippocampal, and piriform cortex areas, in patients with mixed OD etiologies. Functional MRI studies reported reduced brain activation and functional connectivity in olfactory network areas.
Conclusion
MRI uncommonly detects intracranial pathology in patients with idiopathic OD. Among patients with mixed OD etiologies, reduced olfactory bulb and gray matter volume are the most common abnormal findings on MRI. Further research is required to better understand the role of MRI and its cost-effectiveness in patients with acquired, idiopathic OD.
Van RegemorterVHummelTRosenzweigF, et al. Mechanisms linking olfactory impairment and risk of mortality. Front Neurosci.2020;14:140.
2.
KohliPSolerZMNguyenSA, et al. The association between olfaction and depression: a systematic review. Chem Senses [Internet]. 2016;41(6):479–486. Available from:http://www.ncbi.nlm.nih.gov/pubmed/27170667
3.
PintoJMWroblewskiKEKernDW, et al. Olfactory dysfunction predicts 5-year mortality in older adults. PLoS One. 2014;9(10):e107541.
4.
HummelTWhitcroftKLAndrewsP, et al. Position paper on olfactory dysfunction. Rhinology. 2017;54:1–30.
NeulandCBitterTMarschnerH, et al. Health-related and specific olfaction-related quality of life in patients with chronic functional anosmia or severe hyposmia. Laryngoscope [Internet]. 2011;121(4):867–872. Available from:http://www.ncbi.nlm.nih.gov/pubmed/21298638
HoekmanPKHoultonJJSeidenAM. The utility of magnetic resonance imaging in the diagnostic evaluation of idiopathic olfactory loss. Laryngoscope [Internet]. 2014;124(2):365–368. Available from:https://doi.wiley.com/10.1002/lary.24248
10.
FonteynSHuartCDeggoujN, et al. Non-sinonasal-related olfactory dysfunction: a cohort of 496 patients. Eur Ann Otorhinolaryngol Head Neck Dis [Internet]. 2014;131(2):87–91. Available from:https://linkinghub.elsevier.com/retrieve/pii/S1879729613000963
11.
DeemsDADotyRLSettleG, et al. Smell and taste disorders, a study of 750 patients from the university of pennsylvania smell and taste center. Arch Otolaryngol Neck Surg. 1991;117(5):519–528.
YousemDMOguzKKLiC. Imaging of the olfactory system. Semin Ultrasound CT MR. 2001;22(6):456–472.
14.
MoherDLiberatiATetzlaffJ, et al. Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement. PLoS Med.2009;6(7):e1000097.
15.
OCEBM Levels of Evidence Working Group. The Oxford Levels of Evidence 2.
16.
WellsGSheaBO’ConnellD, et al. The Newcastle-Ottawa scale (NOS) for assessing the quality of nonrandomised studies in meta-analyses. 2019.
17.
BusabaNY. Is imaging necessary in the evaluation of the patient with an isolated complaint of anosmia?Ear Nose Throat J [Internet]. 2001;80(12):892–896. Available from:http://www.ncbi.nlm.nih.gov/pubmed/11775525
18.
DeckerJRMeenEKKernRC, et al. Cost effectiveness of magnetic resonance imaging in the workup of the dysosmia patient. Int Forum Allergy Rhinol [Internet]. 2013;3(1):56–61. Available from:https://doi.wiley.com/10.1002/alr.21066
19.
LiuJPintoJMYangL, et al. Evaluation of idiopathic olfactory loss with chemosensory event-related potentials and magnetic resonance imaging. Int Forum Allergy Rhinol [Internet]. 2018;8(11):1315–1322. Available from:https://doi.wiley.com/10.1002/alr.22144
RombauxPPotierHMarkessisE, et al. Olfactory bulb volume and depth of olfactory sulcus in patients with idiopathic olfactory loss. Eur Arch Oto-Rhino-Laryngology [Internet]. 2010;267(10):1551–1556. Available from:http://link.springer.com/10.1007/s00405-010-1230-2
GellrichJHanPManesseC, et al. Brain volume changes in hyposmic patients before and after olfactory training. Laryngoscope [Internet]. 2018;128(7):1531–1536. Available from:https://doi.wiley.com/10.1002/lary.27045
24.
KollndorferKFischmeisterFPSKowalczykK, et al. Olfactory training induces changes in regional functional connectivity in patients with long-term smell loss. NeuroImage Clin [Internet]. 2015;9:401–410. Available from:https://linkinghub.elsevier.com/retrieve/pii/S2213158215001643
RombauxPMartinageSHuartC, et al. Post-infectious olfactory loss: a cohort study and update. B-ENT [Internet]. 2009;5(Suppl 13):89–95. Available from:http://www.ncbi.nlm.nih.gov/pubmed/20084809
27.
RombauxPMourauxABertrandB, et al. Olfactory function and olfactory bulb volume in patients with postinfectious olfactory loss. Laryngoscope. 2006;116(3):436–439.
28.
YaoLYiXPintoJM, et al. Olfactory cortex and olfactory bulb volume alterations in patients with post-infectious olfactory loss. Brain Imaging Behav [Internet]. 2018;12(5):1355–1362. Available from:http://link.springer.com/10.1007/s11682-017-9807-7
29.
AlarabawyRAEltomeyMAShehataEM. Volumetric study of the olfactory bulb in patients with chronic rhinonasal sinusitis using MRI. Egypt J Radiol Nucl Med [Internet]. 2016;47(2):487–491. Available from:https://linkinghub.elsevier.com/retrieve/pii/S0378603X16300018
HerzallahIRAskarSMAmerHS, et al. Olfactory bulb volume changes in patients with sinonasal polyposis: a magnetic resonance imaging study. Otolaryngol Head Neck Surg [Internet]. 2013;148(4):689–693. Available from:http://www.ncbi.nlm.nih.gov/pubmed/23401253
32.
SadeghiMAmaliAEzabadiSR, et al. Evaluation of the olfactory bulb volume and olfactory threshold in patients with nasal polyps and impact of functional endoscopic sinus surgery: a longitudinal study. Int Forum Allergy Rhinol [Internet]. 2015;5(4):356–360. Available from:https://doi.wiley.com/10.1002/alr.21478
ChungMSChoiWRJeongH-Y, et al. MR Imaging–based evaluations of olfactory bulb atrophy in patients with olfactory dysfunction. Am J Neuroradiol [Internet]. 2018;39(3):532–537. Available from:http://www.ajnr.org/lookup/doi/10.3174/ajnr.A5491
35.
GoektasOFleinerFSedlmaierB, et al. Correlation of olfactory dysfunction of different etiologies in MRI and comparison with subjective and objective olfactometry. Eur J Radiol [Internet]. 2009;71(3):469–473. Available from:https://linkinghub.elsevier.com/retrieve/pii/S0720048X08005858
HanPCroyIRaueC, et al. Neural processing of odor-associated words: an fMRI study in patients with acquired olfactory loss. Brain Imaging Behav [Internet]. 2020;14(4):1164–1174. Available from:http://link.springer.com/10.1007/s11682-019-00062-2
HummelTUrbigAHuartC, et al. Volume of olfactory bulb and depth of olfactory sulcus in 378 consecutive patients with olfactory loss. J Neurol [Internet]. 2015;262(4):1046–1051. Available from:http://link.springer.com/10.1007/s00415-015-7691-x
41.
PellegrinoRHahnerABojanowskiV, et al. Olfactory function in patients with hyposmia compared to healthy subjects – an fMRI study. Rhinol J [Internet]. 2016;54(4):374–381. Available from:http://www.rhinologyjournal.com/Abstract.php?id=1468
ReichertJLPostmaEMSmeetsPAM, et al. Severity of olfactory deficits is reflected in functional brain networks-an fMRI study. Hum Brain Mapp [Internet]. 2018;39(8):3166–3177. Available from:https://doi.wiley.com/10.1002/hbm.24067
44.
RombauxPHuartCDeggoujN, et al. Prognostic value of olfactory bulb volume measurement for recovery in postinfectious and posttraumatic olfactory loss. Otolaryngol Neck Surg [Internet]. 2012;147(6):1136–1141. Available from:http://journals.sagepub.com/doi/10.1177/0194599812459704
45.
RombauxPWeitzHMourauxA, et al. Olfactory function assessed with orthonasal and retronasal testing, olfactory bulb volume, and chemosensory event–related potentials. Arch Otolaryngol Neck Surg [Internet]. 2006;132(12):1346. Available from:http://archotol.jamanetwork.com/article.aspx?doi=10.1001/archotol.132.12.1346
46.
AltundagASalihogluMTekeliH, et al. Lateralized differences in olfactory function and olfactory bulb volume relate to nasal septum deviation. J Craniofac Surg [Internet]. 2014;25(2):359–362. Available from:http://journals.lww.com/00001665-201403000-00008
47.
CampabadalASeguraBJunqueC, et al. Comparing the accuracy and neuroanatomical correlates of the UPSIT-40 and the Sniffin’ Sticks test in REM sleep behavior disorder. Parkinsonism Relat Disord [Internet]. 2019;65:197–202. Available from:https://linkinghub.elsevier.com/retrieve/pii/S1353802019302767
HigginsTSLaneAP. What is the best imaging modality to investigate olfactory dysfunction in the setting of normal endoscopy?Laryngoscope [Internet]. 2014;124(1):4–5. Available from:https://onlinelibrary.wiley.com/doi/abs/10.1002/lary.23892
51.
BirkenbeuelJLCheungDCSahyouniR, et al. The use of imaging to detect intracranial tumors in idiopathic olfactory dysfunction: a systematic review. Am J Rhinol Allergy [Internet]. 2020;34(2):297–305. Available from:http://journals.sagepub.com/doi/10.1177/1945892419889325
LondonBNabetBFisherAR, et al. Predictors of prognosis in patients with olfactory disturbance. Ann Neurol [Internet]. 2008;63(2):159–166. Available from:https://doi.wiley.com/10.1002/ana.21293
KimDHKimSWHwangSH, et al. Prognosis of olfactory dysfunction according to etiology and timing of treatment. Otolaryngol – Head Neck Surg (United States). 2017;156(2):371–377.
AltunisikEBaykanAHSahinS, et al. Quantitative analysis of the olfactory system in COVID-19: an MR imaging study. Am J Neuroradiol [Internet]. 2021;42(12):2207–2214. Available from:https://www.ajnr.org/lookup/doi/10.3174/ajnr.A7278
58.
KeshavarzPHaseliSYazdanpanahF, et al. A systematic review of imaging studies in olfactory dysfunction secondary to COVID-19. Acad Radiol [Internet]. 2021;28(11):1530–1540. Available from:https://linkinghub.elsevier.com/retrieve/pii/S1076633221003640
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