xRead - Olfactory Disorders (September 2023)

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PATEL et al.

TABLE IX-21 Evidence for medical therapy for management of intracranial disease–, neurochemistry/neurotransmitter imbalance–, and neurodegenerative disease–realated olfactory loss Study Year LOE Study design Study groups Clinical end point Conclusions Haehner et al 1488 2013 2 Single-center, Patients with a diagnosis of PD: rasagiline 1 mg once No significant

SS-TDI Retronasal testing Olfactory ERP

improvement for any component of TDI score, retronasal testing, or olfactory ERP No significant difference for TDI score or any subcomponent Treated patients with disease < 8yearshad better discrimination

prospective, randomized, controlled, double-blind

daily for 120 days (n = 17), placebo (n = 17)

Haehner et al 1489

2015 4

Single-center,

Patients with diagnosis of PD (n = 224): rasagiline 1 mg every day (n = 74), controls (n = 150)

SS-TDI

cross-sectional

Albers

2018 4

Case report

ORS (n = 1)

POEM

Improvement in

et al 1481

symptoms and odor identification after treatment with olanzapine

Rosenfeldt et al 1482

2016 3

Single-site,

Patients diagnosed with PD: aerobic exercise (n = 23), placebo (n = 15)

UPSIT R

Stabilization of UPSIT R over 8 weeks of exercise relative to controls (3-point decline over 8 weeks)

unblinded, placebo controlled

ERP = event-related potential; LOE = level of evidence; ORS = olfactory reference syndrome; PD = Parkinson disease; POEM = Percepts of Odor Episodic Memory; SS-TDI = Sniffin’ Sticks threshold, discrimination, identification combination; TDI = threshold, discrimination, and identification; UPSIT R = University of Pennsylvania Smell Identification Test.

nerves were the portal of entry. 1507 Although the majority of children recovered their sense of smell, there were anec dotal reports of permanent smell loss. 1508 More recently, over-the-counter topical intranasal zinc sprays were mar keted to treat the common cold but later implicated in the development of anosmia based on two case series with some overlapping patients. 376,377 The product was ulti mately pulled from the market. The dose of zinc delivered by this product was extremely low relative to that used in animal studies and human polio trials, access to the OC was very limited with the spray, and the well-established cause of typical postviral anosmia was hard to exclude. 1509 Nevertheless, intranasal medications can damage the olfactory mucosa and this possibility needs to be consid ered with the development of intranasal drugs in general. Vitamin A has significant effects on epithelial differen tiation and it was considered a promising agent to treat peripheral olfactory loss, especially if patients may have an underlying deficiency. In the only known study examining a population of patients known to be deficient in vitamin A, high-dose replacement did appear to have a beneficial effect on OF. 1510 In contrast, when no deficiency is noted, vitamin A, given systemically at a dosage of 10,000 IU/day for 3 months, was reported to be ineffective on revers ing olfactory loss. 456 Five years after this initial study,

and was found specifically in patients with increased IgG4 plasmacytes in the nasal mucosa. 448 It has been demon strated that steroids are very effective in the treatment of IgG4-related disease, helping to reverse associated epithe lial damage as well as CNS dysfunction. 1502 Treatment of OD related to mineral and vitamin deficiency For many years, the questions of whether zinc deficiency can cause OD and whether zinc replacement can be a use ful treatment option have been investigated. 1503 It is now known that zinc deficiency only rarely causes OD, but it is much more commonly associated with taste deficits that typically reverse with zinc replacement. 1504,1505 On the other hand, intranasal zinc, applied in a high concentration topical solution, has long been used as an experimental model of temporary olfactory loss in animals. 1506 This concept was adapted as a means of chemoprophylaxis against polio in the era before vaccina tion. Topical intranasal zinc, in high concentration, was applied to the OC during pandemics to induce temporary anosmia in an attempt to reduce spread of the virus to the CNS, as it was assumed (incorrectly) that the olfactory