Smell the mute sense


Your sense of smell is often called the mute sense because you experience memories and emotions without words. Normally the main neurological causes for a loss of smell are neurodegenerative disorders such as Alzheimer’s disease and Parkinson’s disease, however, it would now appear MS patients can also be affected.

In a review of thousands of published articles the authors of this pre-print report a 27.2% chance of smell dysfunction in MS. The figures vary from country to country (see plot below) with 0% observed in Austria and 69.6% in Italy. And not surprisingly in their sub-group analysis they found that the prevalence of smell dysfunction is more likely in EDSS >3.0 as opposed to <3.0. However, there was no association with disease duration or the year in which the study was performed.

A smell screen can be performed using a simple scratch card, and may interest some of you. It is likely the olfactory bulb, which is an extension of the brain, maybe involved in the demyelination process leading to the problem. Areas in the brain dealing with smell that are affected by MS plaques may also result in the same.

Figure: The pooled prevalence of olfactory among patients with MS.


Olfactory Dysfunction in Patients with Multiple Sclerosis; A Systematic Review and Meta-Analysis

Omid Mirmosayyeb, Narges Ebrahimi, Mahdi Barzegar, Alireza Afshari-Safavi, Sara Bagherieh, Vahid Shaygannejad

Objectives Olfactory dysfunction is a major comorbidity observed in patients with multiple sclerosis, yet different prevalence rates are reported for it. Therefore, we have designed this systematic review to estimate the pooled prevalence of olfactory dysfunction in patients with MS. To our knowledge, this is the first systematic review and meta-analysis on the prevalence of olfactory dysfunction in MS patients.

Method We searched PubMed, Scopus, EMBASE, Web of Science, ProQuest, and gray literature including references from the identified studies, review studies, and conference abstracts which were published up to January 2021. Articles that were relevant to our topic and could provide information regarding the prevalence of olfactory dysfunction, or the scores of smell threshold, discrimination, or identification (TDI scores) among MS patients and healthy individuals were included; however, articles published before 1990 and after the end of 2020 were excluded.

Results The literature search found 1630 articles. After eliminating duplicates, 897 articles remained. two abstract conference papers were included for final analysis. A total of 1099 MS cases and 299 MS patients with olfactory dysfunction were included in the analysis. The pooled prevalence of olfactory dysfunction in the included studies was 27.2%. (95% CI: [19.7%, 35.4%]) Also, the overall TDI score in MS patients was lower than that in the control group (SMD=-1.00; 95% CI: [−1.44, −0.56]), and the level of Threshold (SMD= −0.47; 95% CI: [−0.75, −0.19]), Discrimination (SMD=-0.53; 95% CI: [−0.96, −0.10]), and Identification (SMD=-1.02; 95% CI: [−1.36, −0.68]) per se were lower in MS compared with control respectively.

Conclusion The results of this systematic review shows that the prevalence of olfactory dysfunction in MS patients is high and more attention needs to be drawn to this aspect of MS.

About the author

Neuro Doc Gnanapavan


  • Sigh. I had a very mild case COVID-19 in beginning of November last year, had I not lost my smell, I would have just thought it a cold. I never had a fever, and just a sore throat/runny-nose/kinda-achy sort of cold. Now, 8ish months late still no smell (I can BARELY smell nail polish remover and other harsh chemical smells). After reading this, is there a connection between my MS, which after 3 doses of Lemtrada over the course of 4 (or 5 years), has been NEIDA(ish). Thanks in advance.

    • I think in your instance it’s the COVID19. The long-term loss of smell with COVID19 is well described.

  • SO is it good I can remember the smell of first year infant (1975/76 ish) Mrs Chapman’s perfume smell?

  • There was a period of a few months where I kept thinking I smelled sewage in a room, but when I asked other people they always told me they didn’t notice anything. This was before my diagnosis, but in retrospect it was probably MS.

  • My friend (40+ yrs ppms) can’t smell or taste.

    He spends a fortune on good food and always says: “even though I can’t taste or smell it, I know I’m eating good”

    I can’t even try to imagine how frustrated I must be when I can’t smell or taste anymore.

  • Interesting. My sense of smell has, on the contrary, intensified since becoming a pwMS. So much so that I can become overwhelmed, and sometimes results in a headache, nausea, and even can become irritated/agitated.

    My taste however, has definitely suffered. At times muted, and am no longer able to tolerate the taste of spicy foods.



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