Discussion

The survey helps to delineate the paucity of treatment provision for this particular group of patients with olfactory dysfunction. Although PIOD represents a smaller percentage of the causes of olfactory disorders overall compared to chronic rhinosinusitis[2], the latter condition benefits from greater attention and PIOD patients typically make up a higher percentage of attendees in a specialist clinic (typically about 25%)[12]. Managing smell loss has previously been identified as a source of frustration for clinicians in Otorhinolaryngology, in part due to the lack of therapeutic options to deploy[5] but can often lead to dismissal of patients[13, 9]. A number of medical and complimentary medicine options have been studied in case series but precious few have been subjected to the scientific rigour of a randomised controlled trial[10]. The recent position paper on olfactory dysfunction has outlined the utility of smell training[6] but despite increasing uptake of this option through information provided on the Fifth Sense website, significant numbers of patients remain markedly affected. It is perhaps the apparent dearth of therapeutic agents that are deemed effective by clinicians that leads to the picture we see here of half the patients reporting a lack of treatment; certainly 93% of participants expressed a strong willingness to participate in any future trials.
This survey has its limitations. Firstly, it may be biased in its respondents being those who have a persistent olfactory disturbance; however, these are the patients who present to doctors seeking further help and for whom any first line treatment has failed. Secondly the participants have self-reported their PIOD and any sinonasal disorders, however our previous work has shown that self-reporting from Fifth Sense members tends to reflect the proportions of doctor-diagnosed cases seen in a specialist smell and taste clinic[14], so we do believe the respondents here are likely to reasonably accurately reflect a genuine group of PIOD patients.
Post-viral olfactory loss typically occurs following viral injury to the olfactory epithelium that leaves the olfactory sensory neurones lacking in cilia and effectively non-functional[15], although the current coronavirus, Covid-19 may wreak its havoc on the olfactory system by different mechanisms[4]. Treatment of this condition does require some insight into the pathophysiology in order to target potential pathways where therapeutic agents can act. It may be possible that stem cell therapy yields some hope in this area in the future. Presently, topical treatments including theophylline[16], Vitamin A[11] and sodium citrate[17-19] have shown some promise and should be considered among potential candidates for more rigorous scientific evaluation.