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Published on: July 19, 2019
Longitudinal Olfactory Patterns in Multiple Sclerosis: A Scoping Review and Implication for Use in Management of
Lauren L Todd1, Ram Sivakumar1, Sharon G Lynch2
1From the School of Medicine (LLT, RS), University of Kansas Medical Center, Kansas City, KS, USA.
Background:
Although studies regarding multiple sclerosis (MS) and olfactory dysfunction (OD) have been previously described and summarized, there is not a sole review of longitudinal studies regarding the matter. This review examines the existing literature investigating MS and its effect on olfaction. In addition, the role of OD in the diagnosis and prognosis of MS is explored.
Methods:
A scoping review of the literature was performed covering longitudinal studies investigating MS and OD. Systematic searches of PubMed, Google Scholar, Web of Science, Embase, PsycInfo, Cumulative Index to Nursing and Allied Health Literature, AgeLine, and MEDLINE were performed using terms that encompassed MS and olfaction. The aim of this review was to build on the existing literature by summarizing only findings that were demonstrated longitudinally.
Results:
Of 6938 articles identified from the search, 9 met the inclusion criteria: longitudinal observation of relapsing-remitting or progressive MS. Olfaction was measured and scored using various testing arrays, and these scores were then correlated with a multitude of clinical markers. Across all studies, patients with MS demonstrated increased OD. Longitudinally, 2 contrasting patterns were identified: (1) clinical markers of acute inflammation correlated with an increased odor threshold and (2) clinical markers of neurodegeneration, or progression of disease, correlated with a decreased ability to discriminate and identify odors.
Conclusions:
These studies suggest that olfaction is a dynamic, dependent variable of neurodegeneration, correlating with inflammation and clinical markers. This opens the door for future exploration of olfaction's relationship with MS diagnosis, characterization, and therapeutic response.
Insights
Olfactory dysfunction (OD) is common in multiple sclerosis (MS). Longitudinal studies show OD changes correlate with MS inflammation and neurodegeneration, suggesting its potential role in disease monitoring.
Area of Science:
- Neuroscience
- Neurology
- Ophthalmology
Background:
- Multiple sclerosis (MS) is a chronic neurological disease.
- Olfactory dysfunction (OD) is a recognized symptom in MS patients.
- Existing reviews lack a focus on longitudinal studies of MS and OD.
Purpose of the Study:
- To review longitudinal studies examining the relationship between multiple sclerosis and olfactory dysfunction.
- To explore the role of olfactory dysfunction in the diagnosis and prognosis of MS.
Main Methods:
- A scoping review of longitudinal studies was conducted.
- Systematic searches were performed across multiple scientific databases.
- Studies investigating MS and olfaction longitudinally were included.
Main Results:
- Nine studies met the inclusion criteria, focusing on relapsing-remitting or progressive MS.
- Patients with MS consistently showed increased olfactory dysfunction.
- Longitudinal analysis revealed two patterns: acute inflammation linked to higher odor thresholds, and neurodegeneration linked to impaired odor discrimination/identification.
Conclusions:
- Olfaction is a dynamic variable in MS, influenced by neurodegeneration and inflammation.
- Olfactory function changes correlate with clinical markers of MS progression.
- Olfaction may serve as a future biomarker for MS diagnosis, characterization, and treatment response.
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