Retronasal Olfactory Function After Olfactory Training: A Prospective Single-Arm Study

Area of Science:

• Neuroscience
• Ophthalmology
• Sensory science

Background:

• Retronasal olfaction is crucial for perceiving aromas, impacting diet and quality of life.
• Olfactory dysfunction (OD) impairs retronasal olfaction.
• Olfactory training (OT) is a rehabilitative method for smell disorders, but its effect on retronasal function is unclear.

Purpose of the Study:

• To determine if OT improves retronasal odour identification.
• To investigate the relationship between improved retronasal function and recovery of orthonasal odour identification.

Main Methods:

• A prospective, single-arm study involving 53 patients with OD (mainly post-COVID-19).
• Patients underwent 3 months of bi-daily olfactory training with four distinct odours.
• Retronasal function was assessed using the ThreeT test, and orthonasal function with the Sniffin' Sticks battery, both pre- and post-training.

Main Results:

• Olfactory training significantly improved both retronasal and orthonasal odour identification scores (p < 0.001).
• Improvements in retronasal performance moderately correlated with improvements in orthonasal identification (r=0.38, p=0.006).
• Clinically significant retronasal improvement increased the likelihood of orthonasal recovery (OR=4.00, p=0.024).

Conclusions:

• Olfactory training is effective in enhancing retronasal odour identification.
• The findings suggest that the recovery mechanisms for orthonasal and retronasal olfaction may share common pathways.