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.