International consensus statement on allergy and rhinology: Olfaction

BACKGROUND

The literature regarding clinical olfaction, olfactory loss, and olfactory dysfunction has expanded rapidly over the past two decades, with an exponential rise in the past year. There is substantial variability in the quality of this literature and a need to consolidate and critically review the evidence. It is with that aim that we have gathered experts from around the world to produce this International Consensus on Allergy and Rhinology: Olfaction (ICAR:O).

METHODS

Using previously described methodology, specific topics were developed relating to olfaction. Each topic was assigned a literature review, evidence-based review, or evidence-based review with recommendations format as dictated by available evidence and scope within the ICAR:O document. Following iterative reviews of each topic, the ICAR:O document was integrated and reviewed by all authors for final consensus.

RESULTS

The ICAR:O document reviews nearly 100 separate topics within the realm of olfaction, including diagnosis, epidemiology, disease burden, diagnosis, testing, etiology, treatment, and associated pathologies.

CONCLUSION

This critical review of the existing clinical olfaction literature provides much needed insight and clarity into the evaluation, diagnosis, and treatment of patients with olfactory dysfunction, while also clearly delineating gaps in our knowledge and evidence base that we should investigate further.

[Diagnosis and Therapy of Olfactory Dysfunction - State of the ArtThe neglected sense-new evidence highlights the significance of the human sense of smell]

Zunehmende Evidenz belegt, dass der menschliche Geruchssinn eine große Bedeutung für die Gesundheit und Lebensqualität einnimmt sowie eine besondere Leistungsfähigkeit aufweist. Durch die häufig auftretende Riechstörung im Rahmen der Infektion mit SARS-CoV‑2 rückt das klinische Interesse in der Behandlung von Patienten mit Verlust des Geruchs- und Geschmackssinnes in den Vordergrund. Der vorliegende Artikel beleuchtet wichtige Aspekte in der Diagnose und Therapie der chemischen Sinne.

Comparison of Magnetic Resonance Imaging and Computed Tomography in the Evaluation of the Olfactory Cleft and Ethmoidal Cells

ABSTRACT

No study has examined whether magnetic resonance imaging (MRI) alone can be used for evaluating olfactory cleft and ethmoidal sinus in patients with olfactory disorders. Therefore, we analyzed the discrepancies between computed tomography (CT) and MRI in the imaging of the olfactory cleft and ethmoidal sinus. Patients who underwent CT and MRI within 30 days were evaluated. Age, sex, diagnosis, presence of bronchial asthma (BA), peripheral blood eosinophil percentage, and CT and MRI findings were retrospectively reviewed, and the sinuses were assessed on a scale of 0 to 3. Overall, 146 patients with 292 sinuses were enrolled. The ethmoid sinus score and the olfactory cleft score had 77.1% and 72.6% image similarity in CT and MRI. Sex and BA status were not associated with olfactory cleft score discrepancies (sex: P = 0.52, BA: P = 0.41). Magnetic resonance imaging scores tended to be rated higher than the CT scores as age increased, although this difference was not statistically significant (P = 0.09). The higher the peripheral blood eosinophil percentage, the more the magnitude by which the CT score tended to exceed the MRI score; however, this finding was also not statistically significant (P = 0.11). Magnetic resonance imaging scans should be limited to the evaluation of intracranial regions. Scans of olfactory cleft and ethmoid cells are not accurate for the assessment of olfactory dysfunction.

Relationship Between Olfactory Disturbance After Acute Ischemic Stroke and Latent Thalamic Hypoperfusion

Odor detection, recognition, and identification were assessed in 19 acute ischemic stroke patients who had no magnetic resonance imaging-detectable thalamic lesions but in whom technetium-99m ethyl cysteinate dimer single photon emission tomography revealed thalamic hypoperfusion. Although these patients were unaware of reduced olfactory function, they exhibited significantly lower scores in tests for odor identification and recognition threshold as compared with 9 ischemic stroke controls that had normal thalamic hypoperfusion. However, absolute odor detection thresholds were similar in the 2 groups. These results demonstrate the usefulness of cerebral perfusion scintigraphy in assessing sensory loss after ischemic stroke and provide further evidence for the role of the thalamus in olfaction.

Diffusion tensor imaging: a smart move to olfactory pathway imaging; comparative study of chronic sinonasal polyposis patients and normal control

Background

Olfaction is critically important for a good quality of life and incorporated in many physiological domains such as attention, emotion, memory, and airflow motor control. Olfactory researches have been expanded in the last decade due to close relation between the olfactory disorders and different brain diseases. Diagnosis of anosmia and hyposmia are based on history, smell tests, and physical examination which rely on the patient’s response without an objective measure of impairment. This study assessed the value of volumetry and DTI parameters as objective measurements for olfactory dysfunction.

Fourteen patients with chronic sinonasal polyposis for at least 6 months were included in this study; all of them underwent tailored MRI examination including volumetry and DTI for olfactory bulbs and tracts. The results were compared to the same number of age and sex-matched healthy control group.

Results

The study results showed that olfactory bulb and tract (OB/T) volume, FA and ADC could distinguish between patients and healthy controls. Statistically significant differences were noticed between the FA & ADC values of patient and control groups (p < 0.05) and a highly significant one was noticed as regarding the OT volume (p < 0.001).

Conclusion

MR volumetry and DTI parameters can be used as objective measurements for the olfactory dysfunction for patients with chronic sinonasal polyposis.

Significance of imaging in the diagnosis of olfactory disorder

The aim of this retrospective analysis was to examine olfactory disorders among the patients in the Ear, Nose, and Throat Clinic of Tampere University Hospital, Finland, from 2001 to 2011, and to evaluate the necessity of imaging in the examination of patients with olfactory disorders. Charts of 143 consecutive patients with a primary olfactory disorder were examined, and 69 patients who had undergone the necessary testing were included in the study. The most common causes of olfactory disorder were upper respiratory infection (23%), chronic rhinosinusitis (19%), head trauma (17%), and allergic or nonallergic rhinitis (6%). In 25% of the patients, no obvious cause for the symptoms was found. Computed tomography (CT) scans were normal in 37 of 52 (71%) patients and magnetic resonance imaging was normal in 21 of 25 (84%) patients. No intracranial or intranasal tumors were found in the overall cohort. Of the patients with additional symptoms (facial pain, headache, nasal discharge, or stuffiness), 58% had chronic rhinosinusitis. Of the patients with no additional symptoms or signs associated with chronic rhinosinusitis on clinical evaluation, only 2% had chronic rhinosinusitis on imaging. Only the detection of chronic rhinosinusitis and head trauma had clinical value in the determination of the etiology. A sinonasal CT scan should be considered in patients who have at least one symptom associated with sinusitis in addition to an olfactory disorder to confirm the etiology and to find those patients who may benefit from medical therapy or surgical treatment.

Disrupted Odor Perception

Olfactory loss is frequent. However, in public not many people complain of that, or they are even not (fully) aware of it. This indicates that it is possible to live a life without a sense of smell, albeit it is more dangerous, less pleasant, and food tastes much less interesting. Most common causes for smell loss are sinunasal disease (chronic rhinosinusitis with and without nasal polyps), acute infections of the upper airways, head trauma, and neurodegenerative disorders. In many people smell loss seems to be due to the aging process. Before treatment olfactory disorders are diagnosed according to cause with the medical history being a big portion of the diagnostic process. Olfactory disorders are in principle reversible, with a relatively high degree of spontaneous improvement in olfactory loss following infections of the upper respiratory tract. Medical treatment is according to cause. It also involves surgical approaches as well as conservative treatments including the use of corticosteroids, antibiotics, or smell training. Because today olfactory dysfunction seems to receive more attention than in previous years it can be expected that tomorrow we will have more specific and effective treatment options available.

Twice-daily application of topical corticosteroids with a squirt system for patients with steroid-responsive olfactory impairment

CONCLUSION

Twice-daily topical corticosteroid treatment using a squirt system was beneficial in maintaining improvements in olfactory dysfunction which had been achieved by oral steroid treatment.

OBJECTIVES

Some patients suffering from olfactory dysfunction respond well to corticosteroids. However, maintaining these improvements is challenging. The aim of this study was to evaluate the maintenance effect of twice-daily topical steroid treatment using a squirt system.

METHODS

Twenty-two anosmic patients with an increase in odor threshold, discrimination, and identification (TDI) scores in Sniffin' Sticks tests by more than six points after 1-week of oral steroid treatment were enrolled. All the patients used a squirt system to apply topical corticosteroids and were followed up at 1, 3, and 6 months.

RESULTS

Nineteen, 16, and 10 patients were followed-up at 1, 3, and 6 months after treatment, respectively. All the patients had significant visual analog scale scores improvements compared to pre-treatment. The mean improvements in TDI scores were 9.80 (p < 0.001), 11.58 (p = 0.001), and 13.87 (p = 0.005) after 1, 3, and 6 months of treatment, respectively. The self-rated and objective olfactory function scores were maintained with steroid squirt therapy without significant decline, even in the patients who were followed up for 6 months.

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.

Olfactory dysfunction in nasal polyposis: correlation with computed tomography findings

AIMS

This study evaluates if a computed tomography (CT) scan is useful to assess the olfactory loss in sinonasal disease, and if a preoperative CT scan has a predictive value for the long-term outcome regarding olfaction.

METHODS

Thirty-one patients with nasal polyposis were included. Olfactory function was assessed with the 'Sniffin' Sticks' test and subjective perception recorded with a visual analogue scale. CT scans were assessed with the Lund-Mackay system and the Damm nasal segmentation. Patients were retested after endoscopic sinus surgery in a follow-up appointment at least 1 year later.

RESULTS

Disease in the upper meatus and the posterior portion of the middle meatus strongly affects olfactory function. Lund-Mackay scores were significantly correlated with preoperative olfactory test results. Preoperative subjective ratings had a significant correlation only with present disease in the anterior upper meatus. Postoperative results were significantly decreased. Their relative percentage change was correlated only with the preoperative presence of disease in the anterior upper meatus. No correlation was found between the Lund-Mackay score and the postoperative olfactory results.

CONCLUSIONS

Olfactory dysfunction in nasal polyposis is strongly related to specific obstructed nasal areas. A CT scan has no predictive value for the long-term surgical outcome regarding olfaction.