A reduced sense of smell is common in MS patients, and the problem seems to worsen as the disease progresses. These are the findings of study titled “Longitudinal Testing of Olfactory and Gustatory Function in Patients with Multiple Sclerosis”, published in the journal PLOS ONE.
In the study 20 people with MS were tested over a three year period with the aim of seeing how the disease affects senses of taste (gustatory functioning) and smell (olfactory function). Two tests were used to assess smell. One was the Threshold Discrimination Identification test (TDI), which covers both an ability to detect smells and to tell the difference between smells.
The second smell test was the Olfactory Evoked Potential test, or OEP which measures delays in the brain’s reaction to smells. Patients were also tested for their sense of taste, using the Taste Strip Test (TST). This test measures patients’ ability to differentiate between four different qualities of taste (sweet, sour, salty and bitter).
Researchers used the smell tests to group patients in three categories: those with anosmia, or total loss of smell; hyposmia, or reduced sense of smell; and normosmia, or normal smell.
Nine patients, or 45% of the 20 patients studied, were classed as having a reduced sense of smell on the basis of their TDI results, and 10 or 50% were classed as having a reduced sense of smell on the basis of their OEP results. None of the patients were classified as having a total loss of smell. A total of 20% of the patients displayed a reduced sense of taste both at the start and end of the study.
The authors concluded: “Olfactory dysfunction is a symptom in MS patients and may be a useful parameter to estimate disease progression in MS patients. As the discrimination of odours is processed in higher central regions of the central nervous system (CNS), the results suggest that olfactory dysfunction could be due to CNS damage.” The authors said the same would apply to loss of MS patients’ sense of taste.
Source : PLOS ONE January 20, 2017