Chapter 13: Olfactory disorders

Topical platelet-rich plasma as a possible treatment for olfactory dysfunction-A randomized controlled trial

BACKGROUND

Olfactory dysfunction (OD) affects many survivors of COVID-19. Prior studies have investigated the use of platelet-rich plasma (PRP) injections for OD. We describe the first randomized controlled trial investigating topical PRP for OD treatment and contribute to existing literature illustrating PRP as an emerging therapeutic.

METHODS

This is a single-blinded, randomized controlled trial conducted from July 2022 to December 2023. Adult patients with OD ≥6 months secondary to COVID-19 with Brief Smell Identification Test (BSIT) scores of ≤8/12 or SCENTinel odor intensity of ≤40/100 were included. Patients were randomized to three, monthly PRP or placebo-impregnated Surgifoam treatments into bilateral olfactory clefts. The BSIT, SCENTinel, and Questionnaire of Olfactory Disorders-Negative Statements (QOD-NS) were completed monthly through month 12.

RESULTS

Of 104 patients screened, 83 participated. No significant differences in age, OD duration, BSIT, SCENTinel, or QOD-NS scores were found between PRP (n = 42) and placebo (n = 41) patients at baseline. PRP patients experienced a statistically significant increase in BSIT scores from baseline at months 5‒9, 11, and 12, while placebo patients did not (p < 0.05). However, total BSIT scores were similar between the two groups throughout the study. Neither the SCENTinel odor intensity scores nor the change from baseline were significantly different between the treatment groups. At month 12, PRP patients experienced minor improvement in OD-related quality-of-life compared with placebo.

CONCLUSIONS

This study is the first to describe topical PRP as a safe, experimental treatment for OD in humans. PRP may impact odor identification in post-COVID-19 OD patients, although the lack of difference in total BSIT scores highlights the need for further study.

The olfactory deficits of depressed patients are restored after remission with venlafaxine treatment

BACKGROUND

It is unclear whether olfactory deficits improve after remission in depressed patients. Therefore, we aimed to assess in drug-free patients the olfactory performance of patients with major depressive episodes (MDE) and its change after antidepressant treatment.

METHODS

In the DEP-ARREST-CLIN study, 69 drug-free patients with a current MDE in the context of major depressive disorder (MDD) were assessed for their olfactory performances and depression severity, before and after 1 (M1) and 3 (M3) months of venlafaxine antidepressant treatment. They were compared to 32 age- and sex-matched healthy controls (HCs). Olfaction was assessed with a psychophysical test, the Sniffin' Sticks test (Threshold: T score; Discrimination: D score; Identification: I score; total score: T + D + I = TDI score) and Pleasantness (pleasantness score: p score; neutral score: N score; unpleasantness score: U score).

RESULTS

As compared to HCs, depressed patients had lower TDI olfactory scores [mean (s.d.) 30.0(4.5) v. 33.3(4.2), p < 0.001], T scores [5.6(2.6) v. 7.4(2.6), p < 0.01], p scores [7.5(3.0) v. 9.8(2.8), p < 0.001)] and higher N scores [3.5(2.6) v. 2.1(1.8), p < 0.01]. T, p and N scores at baseline were independent from depression and anhedonia severity. After venlafaxine treatment, significant increases of T scores [M1: 7.0(2.6) and M3: 6.8(3.1), p < 0.01] and p scores [M1: 8.1(3.0) and M3: 8.4(3.3), p < 0.05] were evidenced, in remitters only (T: p < 0.01; P: p < 0.01). Olfaction improvement was mediated by depression improvement.

CONCLUSIONS

The olfactory signature of MDE is restored after venlafaxine treatment. This olfaction improvement is mediated by depression improvement.

Regulation of chitosan-mediated differentiation of human olfactory receptor neurons by insulin-like growth factor binding protein-2

Olfaction is normally taken for granted in our lives, not only assisting us to escape from dangers, but also increasing our quality of life. Although olfactory neuroepithelium (ON) can reconstitute its olfactory receptor neurons (ORNs) after injury, no adequate treatment for olfactory loss has yet emerged. The present study investigates the role of glycosaminoglycans (GAGs) in modulating olfactory neuronal homeostasis and elucidates the regulatory mechanism. This work isolates and cultures human olfactory neuroepithelial cells (HONCs) with various GAGs for 7 days, and find that chitosan promotes ORN maturation, expressing olfactory marker protein (OMP) and its functional components. Growth factor protein array, ELISA and western blot analysis reveal that insulin-like growth factor binding protein 2 (IGFBP2) shows a higher level in chitosan-treated HONCs than in controls. Biological activity of insulin-like growth factor-1 (IGF-1), IGF-2 and IGF-1 receptor (IGF1R) is further investigated. Experimental results indicate that IGF-1 and IGF-2 enhance the growth of immature ORNs, expressing βIII tubulin, but decrease mature ORNs. Instead, down-regulation of phosphorylated IGF1R lifts the OMP expression, and lowers the βIII tubulin expression, by incubation with the phosphorylated inhibitor of IGF1R, OSI-906. Finally, the effect of chitosan on ORN maturity is antagonized by concurrently adding IGFBP2 protease, matrix metallopeptidase-1. Overall, our data demonstrate that chitosan promotes ORN differentiation by raising the level of IGFBP2 to sequestrate the IGFs-IGF1R signaling. STATEMENT OF SIGNIFICANCE: Olfactory dysfunction serves as a crucial alarm in neurodegenerative diseases, and one of its causes is lacking of sufficient mature olfactory receptor neurons to detect odorants in the air. However, the clinical treatment for olfactory dysfunction is still controversial. Chitosan is the natural linear polysaccharide and exists in rat olfactory neuroepithelium. Previously, chitosan has been demonstrated to mediate the differentiation of olfactory receptor neurons in an in vitro rat model, but the mechanism is unknown. The study aims to evaluate the role and mechanism of chitosan in an in vitro human olfactory neurons model. Overall, these results reveal that chitosan is a potential agent for treating olfactory disorder by the maintenance of olfactory neural homeostasis. This is the first report to demonstrate that chitosan promotes differentiation of olfactory receptor neurons through increasing IGFBP2 to sequestrate the IGFs-IGF1R.

Pediatric anosmia: A case series

INTRODUCTION

Little is known about the etiology of olfactory dysfunction in the pediatric population. The aim of this study is to characterize the etiology and clinical features of anosmia and to explore evaluation options in a pediatric population.

METHODS

Olfactory dysfunction was identified at a tertiary pediatric hospital between January 2003 and October 2014 using a text-based and ICD-9 search of the electronic health record system. Clinical information gathered included history, physical examination and imaging study. A phone questionnaire was completed to determine persistence and development of other rhinologic, endocrine, or neurologic symptoms.

RESULTS

37 children (male/female = 17/20) with mean/median ages of 13.28/14. 19 years were identified. The distribution of etiology was: rhinologic disease (N = 16), congenital (N = 4), trauma (N = 1), neoplasm (N = 1) and unknown (N = 15). Rhinologic disease included chronic rhinosinusitis (N = 3) and other nasal anatomic lesions. None of the four subjects with congenital anosmia had classic Kallmann syndrome. The utility of imaging in confirming an etiology of anosmia was noted in 1 of 8 CT and 5 of 22 MRI. The most significant finding of the questionnaire was confirmation of normal puberty in the congenital group.

CONCLUSION

Similar to the adult population, rhinologic disease is the most common cause. Absence or hypoplasia of the olfactory bulbs without associated delayed puberty is the presentation of congenital anosmia in our cohort. MRI had a higher utility than CT in evaluating anosmia in general and congenital anosmia in specific. MRI to evaluate children with a history of congenital olfactory dysfunction is recommended.

Development of Taiwan Smell Identification Test: a quick office-based smell screening test for Taiwanese

BACKGROUND

Objective smell tests not only identify levels of smelling ability but also provide information on changes in olfaction after treatment. Odor identification is strongly socially and culturally dependent; therefore, the odorants used in a smell identification test should be familiar to the test population. We developed this smell test for Taiwanese populations with two aims: the test odors should be familiar to Taiwanese and the test should be easily and quickly administered in a busy clinic.

METHODS

Additives that are familiar to Taiwanese people were selected for this smell identification test. Subsequently, the test was validated with the traditional Chinese version of the University of Pennsylvania Smell Identification Test (TC-UPSIT). Finally, this Taiwan Smell Identification Test (TWSIT) was implemented in daily clinical use, and cut-off points of "normosmia," "hyposmia," and "anosmia" were established.

RESULTS

A total of 1000 subjects were included in the market survey to identify commonly recognized odors. Eight odorants with identification rate greater than 95% were selected. The TWSIT is an array of multiple-choice questions to select the odor. In addition, patient also reported the strength of the odor. The full score was 48. Thirty-seven patients simultaneously received both TWSIT and TC-UPSIT, and the correlation was high (r = 0.874). Based on the testing results of an additional 187 subjects, we concluded that scores of 47-48, 15-44, and 2-12 corresponded to normosmia, hyposmia, and anosmia, respectively. Patients with scores falling in the gaps require retesting at a later time.

CONCLUSION

The TWSIT is a quick, office-based, and useful odor identification tool for Taiwanese. The experience of developing a culturally specific olfaction test like the TWSIT can be applied in different countries and cultures.

Do sinus computed tomography findings predict olfactory dysfunction and its postoperative recovery in chronic rhinosinusitis patients?

BACKGROUND

Olfactory dysfunction secondary to chronic rhinosinusitis (CRS) is a mixed disorder of conductive and sensorineural olfactory impairment. Although endoscopic sinus surgery has some beneficial effects on olfaction, the outcomes are challenging to predict. The aim of this study was to assess the olfactory outcomes after surgery, to investigate the correlation between the severity of regional computed tomography (CT) findings and olfactory performance, and to identify the predictors of postoperative outcomes based on unilateral olfactory threshold analysis.

METHODS

This study included 167 CRS nostrils of 97 patients with/without polyps (68/99 nostrils) undergoing sinus surgery between January 2007 and December 2011. Olfactory function was evaluated using the butanol threshold test (BTT) before and 6 months after surgery. Clinical and nasal factors from sinus CT scan (sinuses, ostiomeatal complex, olfactory cleft [OC], nasal polyps, and unilateral Lund-Mackay CT score) were analyzed to correlate them with pre- and postoperative olfactory performances.

RESULTS

Eighty-two percent of the CRS nostrils had anosmia or hyposmia. After surgery, 42% of them showed an improvement in BTT score. Despite improvement, most of the subjects remained with residual hyposmia. The BTT scores deteriorated after surgery in 23% of the total subjects. The disease severity of the OC, posterior ethmoid, and frontal sinus were the significant risk factors for CRS-related anosmia. The strongest risk factor for anosmia was totally obstructed OC (odds ratio [OR], 16.56; 95% CI, 4.31-63.71; p = 0.000). The nostrils with anosmia or partly opacified anterior ethmoid benefited from surgery with respect to olfaction.

CONCLUSION

Our results can give support to the combined use of the butanol threshold and sinonasal CT findings in the evaluation of olfaction in CRS patients and help us counsel the patients about the likelihood of postoperative olfactory recovery.

Role of the bitter taste receptor T2R38 in upper respiratory infection and chronic rhinosinusitis

PURPOSE OF REVIEW

Taste receptor family 2 (T2R) bitter taste receptors were originally identified and named on the basis of their role in type 2 taste cells of the tongue, in which they serve to detect the presence of potentially harmful ingested chemicals. In 2009, researchers demonstrated that airway epithelial cells also express T2R receptors, but their role in airway physiology and human disease has only recently begun to be identified.

RECENT FINDINGS

Recent research has demonstrated that at least one airway T2R receptor, taste receptor family 2 isoform 38 protein (T2R38) is activated by secreted bacterial products. Activation of T2R38 in sinonasal epithelial cells stimulates nitric oxide production, increasing ciliary beating and directly killing bacteria. Clinical studies have also found correlations of TAS2R38 genotype with susceptibility to gram-negative upper respiratory infection and established T2R38 as an independent risk factor for chronic rhinosinusitis requiring sinus surgery.

SUMMARY

These recent studies identify a role for T2R38 in sinonasal innate immunity and chronic rhinosinusitis. Clinical implications include the potential development of T2R38-directed topical therapies, as well as using taste testing and/or genotyping to predict susceptibility to infection. Further studies are needed to more clearly determine how TAS2R38 genotype affects patient outcomes in chronic rhinosinusitis and other upper airway diseases.

Evaluation of olfaction in patients with pemphigus vulgaris

BACKGROUND

Pemphigus vulgaris (PV) is an autoimmune disease characterized by acantholysis. PV decreases quality of life and leads to morbidity and mortality. Although the association between PV and otolaryngeal disease has been studied, its effect on olfaction has not been investigated objectively and quantitatively.

METHODS

Twenty-eight patients with PV and 28 healthy volunteers were included in the study. Lesions were identified via nasal endoscopic examination. Nasal symptoms (itching, obstruction, pain, bleeding, and crusting) were recorded. Volunteers were asked to evaluate their olfactory function via a visual analog scale. The Connecticut Chemosensory Clinical Research Center (CCCRC) olfactory test was performed (butanol threshold test and identification test), and the score was calculated as the mean ± SD.

RESULTS

The mean age of the PV group (group 1: 10 male 18 female subjects) was 48.7 ± 8.9 years. The mean age of the control group (group 2: 17 male and 11 female subjects) was 48.0 ± 1.1 years. All nasal symptoms, except itching, were more severe in the PV group (p < 0.05). Nasal lesions were more common in the PV group (p = 0.0001). Evaluation of olfactory function revealed significantly lower scores in the PV group for both the butanol threshold test and the identification testing as well as the CCCRC total score (p = 0.001). PV patients with nasal lesions had significantly more nasal symptoms (p < 0.05). A negative correlation was found between the number of lesions and the olfactory scores in group 1 for the butanol threshold test, identification testing, and the CCCRC total scores, respectively (p = 0.002, p = 0.010, and p = 0.001, respectively).

CONCLUSION

PV causes olfactory dysfunction leading to eventual hyposmia that decreases quality of life. We suggest that olfactory testing be included in PV evaluation for the diagnosis and treatment of hyposmia, when necessary.

Functional outcomes of face transplantation

In this study we provide a compilation of functional impairments before and improvements after face transplantation (FT) of five FT recipients of our institution and all FTs reported in current literature. Functional outcome included the ability to smell, breath, eat, speak, grimace and facial sensation. Before FT, all our patients revealed compromised ability to breath, eat, speak, grimace and experience facial sensation. The ability to smell was compromised in two of our five patients. Two patients were dependent on tracheostomy and one on gastrostomy tubes. After FT, all abilities were significantly improved and all patients were independent from artificial air airways and feeding tubes. Including data given in current literature about the other 24 FT recipients in the world, the abilities to smell, eat and feel were enhanced in 100% of cases, while the abilities of breathing, speaking and facial expressions were ameliorated in 93%, 71% and 76% of cases, respectively. All patients that required gastrostomy and 91% of patients depending on tracheostomy were decannulated after FT. Unfortunately, outcomes remain unreported in all other cases and therefore we are unable to comment on improvements.

Validation of the applicability of the traditional Chinese version of the University of Pennsylvania Smell Identification Test in patients with chronic rhinosinusitis

The 40-item University of Pennsylvania Smell Identification Test (UPSIT) is the most widely used smell test in the world. Presently, culturally modified versions of this test are available in multiple languages. A traditional Chinese version of the UPSIT (UPSIT-TC) has been developed for administration in Taiwan. The purpose of this study was to investigate the validity and reliability of the UPSIT-TC in Taiwanese patients with chronic rhinosinusitis (CRS). The phenylethyl alcohol (PEA) odor detection threshold test, the North American version of UPSIT (UPSIT-NA), and the UPSIT-TC were administered to 40 healthy subjects and to 100 CRS patients before and after functional endoscopic sinus surgery (FESS). The UPSIT-TC showed good internal consistency (Cronbach's alpha = 0.887, 0.886, and 0.870 at three test occasions) and test–retest reliability (p < 0.001). The scores of UPSIT-TC were significantly correlated to the PEA thresholds (p < 0.001). The UPSIT-TC scores were significantly higher than those of the UPSIT-NA (p = 0.028) when analysis was performed with logistic regression with independent variables including test occasions (before or after FESS), test methods (UPSIT-NA or UPSIT-TC), status of polyp (with or without), and PEA thresholds (improved or did not improve). In addition, there were significant between-group differences in UPSIT-TC scores including healthy versus CRS, CRS with polyps versus CRS without polyps, and PEA thresholds improved versus PEA thresholds which did not improve. The UPSIT-TC is reliable and valid for measuring olfactory function in Taiwanese patients with rhinosinusitis. In addition, the UPSIT-TC clearly resulted in better performance than that of UPSIT-NA.

Cytological changes in nasal secretions accompanying delayed nasal response to allergen challenge

BACKGROUND

Patients with allergic rhinitis when challenged with allergen develop various types of nasal response, such as an immediate nasal response (INR), late nasal response (LNR), dual late nasal response (DLNR), or delayed nasal response (DYNR), probably because of different hypersensitivity mechanisms. This study was designed to investigate the cytological changes in the nasal secretions (NSs) during the DYNR, beginning 24-32 hours, reaching maximum at 32-36 hours, and resolving within 56 hours after the nasal provocation tests (NPTs) with allergens.

METHODS

In 45 allergic rhinitis patients developing 45 positive DYNRs (p < 0.01), the NPTs and the phosphate-buffered saline (PBS) controls were repeated and supplemented with cytological examination of the NSs and determination of interferon (IFN) γ and IL-4 in nasal lavage fluid (NLF).

RESULTS

The repeated DYNR (p < 0.001) was accompanied by significant changes (p < 0.05) in the counts of neutrophils, monocytes, lymphocytes, epithelial and goblet cells, and, to a limited extent, of plasma cells and platelets in the NSs and increased concentrations of IFN-γ but not of IL-4, in NLF between 24 and 48 hours after the NPT. No significant cytological changes were found in NSs during the PBS controls (p > 0.1).

CONCLUSION

The DYNR is associated with cytological profiles in the NS different from those observed during the INR or LNR. The significant count changes of neutrophils, monocytes, lymphocytes, epithelial and goblet cells in NSs, and increased IFN-γ but not of IL-4 concentrations in the NLF, suggest a possible involvement of the cell-mediated hypersensitivity in the DYNR. These results also emphasize the diagnostic value of NPTs combined with cytological examination of the NSs in patients with nasal allergy.

Chapter 6: Nasal polyps

Nasal polyps occur in 1-4% of the population, usually occurring in the setting of an underlying local or systemic disease. The most common associated condition is chronic rhinosinusitis (CRS). A high prevalence of nasal polyps is also seen in allergic fungal rhinosinusitis, aspirin-exacerbated respiratory disease, Churg-Strauss syndrome, and cystic fibrosis. In the setting of CRS, nasal polyps are not likely to be cured by either medical or surgical therapy; however, control is generally attainable. The best medical evidence supports the use of intranasal corticosteroids for maintenance therapy and short courses of oral corticosteroids for exacerbations. The evidence for short- and long-term antibiotics is much less robust. For patients with symptomatic nasal polyposis nonresponsive to medical therapies, functional endoscopic sinus surgery provides an adjunctive therapeutic option.

Chapter 4: Chronic rhinosinusitis

Chronic rhinosinusitis (CRS) is the second most common chronic medical condition in the United States. It represents a group of disorders characterized by inflammation of the nasal mucosa and paranasal sinuses of at least 12 weeks duration. CRS with or without nasal polyps is defined as inflammation of the nose characterized by two or more symptoms, one of which should be either nasal blockage, obstruction, congestion, or nasal discharge (anterior/posterior nasal drip); with or without facial pain/pressure; and/or with or without reduction or loss of smell. Symptomatology should be supported by obvious disease evident in either nasal endoscopy or computed tomography imaging. Although CRS is not likely to be cured by either medical or surgical therapy, it can generally be controlled. Best medical evidence supports maintenance therapy with intranasal corticosteroids and saline irrigation. For exacerbations, short to intermediate courses of antibiotics (up to 4-weeks) with or without oral corticosteroids are recommended. For patients with difficult-to-treat CRS, functional endoscopic sinus surgery provides an adjunctive therapeutic option.