Retronasal Function Research Articles

Orthonasal and retronasal odor identification in patients with parosmia

ObjectiveTo compare retronasal and orthonasal perception in parosmic COVID-19 patients, in order to determine whether COVID-19 has a differential effect on these functions.MethodsUsing the Sniffin Sticks test battery orthonasal function was examined for odor threshold, discrimination and identification. Retronasal function was assessed using 20 tasteless aromatized powders. Gustatory function was measured using the Taste Strips test.ResultsThis study included 177 patients (127 women, 50 men; mean age 45 years), of whom 127 (72%) were hyposmic and 50 (28%) normosmic. Compared to patients without parosmia, parosmic patients performed worse in odor identification for both orthonasal (F = 4.94, p = 0.03) and retronasal tests (F = 11.95, p < 0.01). However, an interaction effect between route of odor identification (orthonasal or retronasal) and parosmia status was found (F = 4.67, p = 0.03): patients with parosmia had relatively lower retronasal scores than patients without parosmia.ConclusionOur results suggest that COVID-19 may affect the olfactory mucosa differently along the anterior–posterior axis, thereby possibly contributing to the pathophysiology of parosmia. Patients with parosmia also exhibit a higher degree of impairment when odors are presented through the retronasal route during eating and drinking.

Investigation of chemosensitivity during and after an acute cold.

Viral rhinitis (the "common" cold) is a frequent worldwide disease. Olfactory dysfunction is one complication that arises during infection, which in most cases heals up spontaneously upon recovery, whereas in some cases it may persist as a partial or total loss of olfaction. The aim of this prospective study was to investigate the change of other chemosensory systems during a cold. Fifty-eight patients (age 18 to 69 years) with an acute cold were compared to a healthy control group (n = 59; age 19 to 63 years). All patients were examined on 2 occasions separated by approximately 4 weeks. Orthonasal, retronasal, gustatory, and trigeminal nasal function were investigated. Furthermore, ratings of real foods, in terms of intensity and pleasantness, were obtained. Compared to the control group, patients showed a decreased orthonasal (threshold and discrimination) and retronasal function. Furthermore, patients exhibited a decreased sensitivity to salt and a reduced ability to localize menthol, indicating a decreased taste and trigeminal function, respectively. Upon recovery from the infection, orthonasal olfactory and trigeminal sensitivity increased, whereas retronasal sensitivity showed no improvement and salt sensitivity decreased. This comprehensive study provides empirical evidence that chemosensory impairment is prevalent during a cold, and additionally shows for the first time that chemosensory features associated with food consumption persist postinfection.