xRead - Olfactory Disorders (September 2023)

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PATEL et al.

TABLE VII.4 (Continued) Study

Year LOE Study design Study groups

Clinical end point SS-TDI Nasal secretion analysis Inspiratory nasal flow

Conclusions

No significant difference in inspiratory nasal flow between groups Perennial and seasonal AR groups had significantly lower TDI scores Eosinophilic protein levels and tryptase significantly higher in the seasonal AR group, with no correlation with TDI score Mice with AR from local intranasal and systemic sensitization demonstrated significant OD as measured by time to detect food pellets and on histopathologic examination Mice with AR exhibited reduced numbers of olfactory sphere cells (neural stem cells) with increased apoptosis TNF- α and IL-5 synergistically induce stem cell apoptosis Mice with AR exhibit OD with increased size and number of olfactory glands Infiltration of inflammatory cells observed, including eosinophils, mast cells, plasma cells, macrophages, and neutrophils

Becker et al

2012 4

Case-control

Seasonal AR: 23 patients Perennial AR: 16 patients Control group: 33 patients

Jung and Hyo Kim

2020 2

RCT

Control group: 8 mice Local nasal allergy: 8 mice Systemic allergy: 8 mice Positive controls: 8 mice Budesonide treatment group: 8 mice

Odor detection Histopathologic evaluation Measurement of olfactory marker protein

Kimet al

2019 2

RCT

Control group: 25 mice AR: 25mice

Immunohistochemical staining

Ozaki et al

2010 2

RCT

Control group: 10 mice AR group: 10 mice

1 Odor detection Immunohistochemical staining

AR = allergic rhinitis; CCCRC = Connecticut Chemosensory Clinical Research Center; CRS chronic rhinosinusitis; HC = healthy control; IL = interleukin; NVF = nasal volume flow; OD = olfactory dysfunction; OE = olfactory epithelium; QOL = quality of life; SS-TDI = Sniffin’ Sticks threshold, discrimination, identification combination; TDI = threshold, discrimination, identification; TNF- α , tumor necrosis factor α ; UPSIT R = University of Pennsylvania Smell Identification Test; VAS = visual analog scale. *Level of evidence (LOE) downgraded because of heterogeneity of results and lack of randomized controlled trials (RCTs).

the pathophysiology of OD may be the result of several underlying factors. Postinfectious changes can extend further along the olfactory pathways. PVOD decreases the size of the OB on imaging studies. 253 The volume of the OB negatively correlates with the level of OD. 254 It is unclear whether the OB is decreasing in size because of the lack of neu ral input caused by damage in the OE or whether the OB is decreasing as a direct impact from viral damage in the bulb itself. 255 Viral inoculation in the nostrils of mice have shown spongiotic damage to the OB likely related to the infiltration of the bulb by lymphocytes and

neutrophils. The OBs in the inoculated mice were still decreased 5 months after injection. 247 Another study also showed direct cellular damage at the level of the OB in mice when inoculated with the influenza virus. 256 This appears to be consistent with human imaging studies in patients with hyposmia/anosmia. Another possible influence on PVOD is the host immune response to viruses. One study using a viral analog to induce an immune response showed that the neutrophil-mediated innate immune response damages neuroepithelial cells. 257 Another study found IL-6 to be significantly elevated in the plasma, saliva, and nasal