xRead - Olfactory Disorders (September 2023)

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INTERNATIONAL CONSENSUS ON OLFACTION

TABLE IX-39 Evidence for platelet-rich plasma injection for the treatment of OD Study Year LOE Study design Study groups

Clinical end point

Conclusions

SS-TDI* at 1 month and 3 months

No adverse events TDI scores improved from mean baseline 19.5 to 23.6 at 3 months Hyposmic patients (16 < TDI < 30) improved by 5.85 at 3 months, most significantly in the threshold subcomponent 2 patients with anosmia (TDI < 16)withno significant improvement Did not control for spontaneous recovery 4 of 5 patients reported “their smell came back” Mean pretreatment score: 0.19,mean posttreatment score: 4.92 Did not control for spontaneous recovery

7 patients with olfactory loss > 6 months but < 12 months, no evidence of sinonasal inflammatory disease, had failed to improve with OT and topical steroid rinses

Yan

2020

4 Prospective

et al 1602

single-arm pilot case series

Single 1-mL PRP

injection in bilateral OCs

Mavrogeni et al 1603

2016

4 Prospective

5 patients with “severe anosmia” without known duration, unresponsive to prior treatment, with no CT abnormalities (1 posttraumatic, 4 postviral smell loss) injections 4 weeks apart, with a 4th injection 3 months later 3 olfactory groove

Self-reported symptom score and authors’ version of a smell identification + discrimination test 10 point total score

single-arm case series

CT = computed tomography; LOE = level of evidence; OC = olfactory cleft; OD = olfactory dysfunction; OT = olfactory training; PRP = platelet-rich plasma; SS-TDI = Sniffin’ Sticks threshold, discrimination, identification combination; TDI = threshold, discrimination, and identification.

administration of intranasal insulin has been shown to tra verse the cribriform plate via olfactory nerves. 1594 How ever, the effect of insulin on olfaction is not clearly established. Ketterer et al 1595 revealed that creating a hyperinsulinemic state with sustained euglycemia leads to a worsened olfactory threshold (reduced sensitivity) on SS testing (threshold reduced by –1.6) in healthy patients versus fasting controls. 1595 Brunner et al 1596 also demonstrated in a controlled study that a single dose of 40 IU of intranasal insulin in normosmic patients worsened threshold (threshold reduced by –1.3 versus saline) on n butanol testing but had no effect on discrimination. Con versely, Thanarajah et al 1597 found an improved threshold with intranasal insulin that was related to both insulin sen sitivity and the intranasal dose applied. Intranasal insulin has also been shown to increase satiety and reduce caloric intake in healthy women, presumably by reducing periph eralOF. 1598 Two studies evaluating intranasal insulin for OD were included in analysis (Table IX-38). Rezaeian et al 1599

evaluated the therapeutic effects of intranasal insulin on patients with undifferentiated hyposmia using a double blinded RCT. An absorbable dressing impregnated with 40 IU insulin or saline was placed endoscopically twice weekly for 4 weeks into the OC. A total of 36 patients with undifferentiated olfactory loss for > 6 months com pleted the trial. A significant improvement was seen on butanol threshold testing in the treatment group ( + 1.11) without a significant effect on serum insulin or glucose. Schöpf et al 1600 found a similar outcome with a single dose of 40 IU of intranasal insulin in a pilot study of 10 patients with PIOD for > 1 year. A total of 60% of the patients had a minimally increased performance in olfactory threshold on SS testing ( + 1) 30 minutes after application, but TDI and all subdomain scores were not significantly changed. They did, however, find a correlation between score improve ment (TDI and identification) after intranasal insulin in patients with increased BMI. The mechanism of action for improvement in OD versus impairment in healthy controls has not been