Paroxysmal bilateral dysosmia treated by resection of the olfactory bulbs

Parosmia in patients with post-infectious olfactory dysfunction in the era of COVID-19-associated olfactory impairment

OBJECTIVES

A large number of patients with olfactory impairment are affected by parosmia or phantosmia. This study aimed to examine the demographic and clinical characteristics of parosmia.

METHODS

We performed a retrospective data analysis of patients consulting at our Smell and Taste Outpatient Clinic. A total of 297 patients were included (203 women, mean age 44.4 ± 13.7 years). Olfactory function was quantified using the "Sniffin' Sticks" composite TDI (odor threshold, determination, and identification) score. The presence of qualitative olfactory impairment was assessed trough medical history and a parosmia questionnaire.

RESULTS

Most of the patients showed olfactory impairment after an infection with SARS-CoV‑2 (84%) and were diagnosed with parosmia (49%). Patients with parosmia (PAR) (n = 201) were significantly younger compared to the group without parosmia (noPAR; n = 92) (PAR 43.2 ± 13 years vs. noPAR 47 ± 15.1 years, p = 0.03) and had a slightly shorter duration of disease, without reaching statistical significance (PAR 10.3 ± 4.9 months, noPAR 13.6 ± 37.6 months, p = 0.23). They also had higher TDI scores (PAR 24.3 ± 7 points, noPAR 21.4 ± 8.2 points, p = 0.003).

CONCLUSIONS

Patients affected by parosmia were younger and had a better olfactory function compared to patients without parosmia.

Olfactory Function and Olfactory Disorders

The sense of smell is important. This became especially clear to patients with infection-related olfactory loss during the SARS-CoV-2 pandemic. We react, for example, to the body odors of other humans. The sense of smell warns us of danger, and it allows us to perceive flavors when eating and drinking. In essence, this means quality of life. Therefore, anosmia must be taken seriously. Although olfactory receptor neurons are characterized by regenerative capacity, anosmia is relatively common with about 5 % of anosmic people in the general population. Olfactory disorders are classified according to their causes (e. g., infections of the upper respiratory tract, traumatic brain injury, chronic rhinosinusitis, age) with the resulting different therapeutic options and prognoses. Thorough history taking is therefore important. A wide variety of tools are available for diagnosis, ranging from short screening tests and detailed multidimensional test procedures to electrophysiological and imaging methods. Thus, quantitative olfactory disorders are easily assessable and traceable. For qualitative olfactory disorders such as parosmia, however, no objectifying diagnostic procedures are currently available. Therapeutic options for olfactory disorders are limited. Nevertheless, there are effective options consisting of olfactory training as well as various additive drug therapies. The consultation and the competent discussion with the patients are of major importance.

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.

Prevalence and correlates of parosmia and phantosmia among smell disorders

Among those many individuals who experience a reduced odor sensitivity (hyposmia/anosmia), some individuals also have disorders that lead to odor distortion, such as parosmia (i.e. distorted odor with a known source), or odor phantoms (i.e. odor sensation without an odor source). We surveyed a large population with at least one olfactory disorder (N = 2031) and found that odor distortions were common (46%), with respondents reporting either parosmia (19%), phantosmia (11%), or both (16%). In comparison to respondents with hyposmia or anosmia, respondents with parosmia were more likely to be female, young, and suffering from post-viral olfactory loss (P < 0.001), while respondents with phantosmia were more likely to be middle-aged (P < 0.01) and experiencing symptoms caused by head trauma (P < 0.01). In addition, parosmia, compared to phantosmia or anosmia/hyposmia, was most prevalent 3 months to a year after olfactory symptom onset (P < 0.001), which coincides with the timeline of physiological recovery. Finally, we observed that the frequency and duration of distortions negatively affects the quality of life, with parosmia showing a higher range of severity than phantosmia (P < 0.001). Previous research often grouped these distortions together, but our results show that they have distinct patterns of demographics, medical history, and loss in quality of life.

A novel surgical treatment for long lasting unilateral peripheral parosmia: Olfactory cleft blocking technique

The treatment of qualitative olfactory disease is challenging. We aimed to treat parosmia using a new minimally invasive surgical technique-the olfactory cleft blocking technique- by preventing odorants from reaching the olfactory epithelium. A novel surgical procedure for blocking the anterior and inferior openings of the olfactory cleft was accomplished in a patient with unilateral persistent peripheral parosmia. The HRCT and endoscopy were performed preoperatively and postoperatively to evaluate the anatomical structure of the olfactory cleft. The T&T olfactometer was used to assess the preoperative and postoperative olfactory function. After surgery, the patient's parosmia disappeared. Endoscopic examination and CT scan showed complete obstruction of the anterior and inferior portions of the olfactory cleft. No recurrence was reported during a 2-year follow-up. No surgical complications were reported except olfactory loss in the operative nostril. For patients with long-term unilateral peripheral olfactory dysfunction, the olfactory cleft blocking technique seems a novel, simple, safe and effective treatment. Further studies are required with a larger number of patients in order to access success rate.

Diseases of the nasal cavity

Despite garnering minimal attention from the medical community overall, olfaction is indisputably critical in the manner in which we as humans interact with our surrounding environment. As the initial anatomical structure in the olfactory pathway, the nasal airway plays a crucial role in the transmission and perception of olfactory stimuli. The goal of this chapter is to provide a comprehensive overview of olfactory disturbances as it pertains to the sinonasal airway. This comprises an in-depth discussion of clinically relevant nasal olfactory anatomy and physiology, classification systems of olfactory disturbance, as well as the various etiologies and pathophysiologic mechanisms giving rise to this important disease entity. A systematic clinical approach to the diagnosis and clinical workup of olfactory disturbances is also provided in addition to an extensive review of the medical and surgical therapeutic modalities currently available.

Treatments for smell and taste disorders: A critical review

A key concern of both the patient and physician is whether treatment is available that will eliminate or quell a given chemosensory disturbance. In cases where obvious oral, nasal, or intracranial pathology is involved, rational straightforward approaches to treatment are often available. In cases where damage to the sensory pathways is secondary to chronic inflammatory disease, trauma, viral invasion, toxic exposure, or unknown causes, the direction for therapy is more challenging. Indeed, many chemosensory disorders, if present for any period of time, cannot be reversed, while others spontaneously remit without any therapeutic intervention. This review assesses the strengths and weaknesses of more than two dozen approaches to treatment that have been suggested for a wide range of taste and smell disorders.

Management of long-lasting phantosmia: a systematic review

BACKGROUND

Interest in the pathophysiology and management of phantom smells has increased rapidly over the last decade. A PubMed search for the term "phantosmia" demonstrated a near-doubling of articles published on phantosmia within the past 7 years. We aimed to systematically review the literature on the management of phantosmia.

METHODS

The PubMed, EMBASE, and Cochrane databases were searched for articles published since January 1990, using terms combined with pertinent Boolean search operators. We included articles evaluating management of phantosmia written in the English language, with original data and a minimum of 6 months of follow-up, on at least 2 patients and with well-defined and measurable outcomes.

RESULTS

A total of 2151 unique titles were returned upon the initial search. Of these, 146 abstracts were examined, yielding 7 articles meeting the inclusion criteria. All articles were predominantly level 4 evidence. One prospective level 3 study was included. The studies included a total of 96 patients, with follow-up ranging from 6 months to 11 years. Endpoints were primarily based on subjective patient responses. Management options included observation and medical and surgical therapy. Olfactory mucosa excision was the only surgical intervention studied, with short-term symptomatic improvement in 10 of 11 patients. Forty-one patients were treated medically, which included antipsychotic, antimigraine, and antiseizure medications, transcranial stimulation, and topical cocaine application.

CONCLUSION

Despite increasing interest in the treatment of phantosmia and reports of successful therapies, there remains a paucity of data and lack of consensus regarding optimal management of this difficult condition.

The olfactory system as the gateway to the neural correlates of consciousness

How consciousness is generated by the nervous system remains one of the greatest mysteries in science. Investigators from diverse fields have begun to unravel this puzzle by contrasting conscious and unconscious processes. In this way, it has been revealed that the two kinds of processes differ in terms of the underlying neural events and associated cognitive mechanisms. We propose that, for several reasons, the olfactory system provides a unique portal through which to examine this contrast. For this purpose, the olfactory system is beneficial in terms of its (a) neuroanatomical aspects, (b) phenomenological and cognitive/mechanistic properties, and (c) neurodynamic (e.g., brain oscillations) properties. In this review, we discuss how each of these properties and aspects of the olfactory system can illuminate the contrast between conscious and unconscious processing in the brain. We conclude by delineating the most fruitful avenues of research and by entertaining hypotheses that, in order for an olfactory content to be conscious, that content must participate in a network that is large-scale, both in terms of the neural systems involved and the scope of information integration.

Olfactory Hallucinations without Clinical Motor Activity: A Comparison of Unirhinal with Birhinal Phantosmia

Olfactory hallucinations without subsequent myoclonic activity have not been well characterized or understood. Herein we describe, in a retrospective study, two major forms of olfactory hallucinations labeled phantosmias: one, unirhinal, the other, birhinal. To describe these disorders we performed several procedures to elucidate similarities and differences between these processes. From 1272, patients evaluated for taste and smell dysfunction at The Taste and Smell Clinic, Washington, DC with clinical history, neurological and otolaryngological examinations, evaluations of taste and smell function, EEG and neuroradiological studies 40 exhibited cyclic unirhinal phantosmia (CUP) usually without hyposmia whereas 88 exhibited non-cyclic birhinal phantosmia with associated symptomology (BPAS) with hyposmia. Patients with CUP developed phantosmia spontaneously or after laughing, coughing or shouting initially with spontaneous inhibition and subsequently with Valsalva maneuvers, sleep or nasal water inhalation; they had frequent EEG changes usually ipsilateral sharp waves. Patients with BPAS developed phantosmia secondary to several clinical events usually after hyposmia onset with few EEG changes; their phantosmia could not be initiated or inhibited by any physiological maneuver. CUP is uncommonly encountered and represents a newly defined clinical syndrome. BPAS is commonly encountered, has been observed previously but has not been clearly defined. Mechanisms responsible for phantosmia in each group were related to decreased gamma-aminobutyric acid (GABA) activity in specific brain regions. Treatment which activated brain GABA inhibited phantosmia in both groups.

Distorted olfactory perception: a systematic review

The sense of smell provides people with valuable input from the chemical environment around them. The human sense of smell generally fails in three ways; one is an intensity reduction and the other two are the quality of changes. Smell disorders can be classified into central or peripheral depending on their origin. Central causes can be related to an area of hyper-functioning brain cells generating this odor perception, thus olfactory distortions have also been observed with epilepsy and migraine. In this paper, we present a review of the current clinical understanding of olfactory distortions and discuss how they can be evaluated and therapies to treat this debilitating condition.

Long lasting phantosmia treated with venlafaxine

Qualitative olfactory disorders such as parosmia and phantosmia are not well investigated. In particular, the causes and treatment options for phantosmia are largely unknown. We report a case of long lasting phantosmia that disappeared under anti-depressive treatment, raising the question to what extent certain forms of qualitative olfactory disorders are an early symptom of depression.

Basic and clinical aspects of olfaction

Disturbances of olfaction are a common occurrence in many neurological and neurosurgical patients and their correct diagnosis might be helpful in management and enhancement of quality of life. However, olfaction is seldom checked in most neurosurgical units and the "smell bottles" are often either absent or out of date. This chapter reviews systematically recent advances in our understanding of the anatomy, physiology (olfactory coding) and measurement of olfactory function in the human. The causes and symptoms of smell disorders, risk of damage to the olfactory system by various surgical procedures and, finally, the natural history of recovery and treatment of smell disorders, for example after trauma, are discussed.

Smell and taste disorders

Disorders of taste and smell can present a challenge to the facial plastic surgeon. Obtaining a detailed history and examination is the key to the diagnosis and work-up of olfactory and gustatory dysfunction. Easy-to-administer tests are available for olfactory evaluation(University of Pennsylvania Smell Identification Test) and gustatory (taste sticks, tasting tablets) evaluation. The prognosis and management of olfactory and gustatory disease depend on its etiology. Despite ongoing research, the treatment of the disorders of smell and taste is limited.

Traitement chirurgical d’une parosmie post-rhinitique

Many people experience some degree of olfactory dysfunction during the acute stages of an upper respiratory infection (URI). The olfactory function usually returns to the preinfection level in few days. In some cases, the dysosmia remains even after the reopening of the air passageways. The olfactory loss after URI associates an hyposmia and odor distortions. We report a rare case of odor distortions after URI treated by surgery.

Prevalence and assessment of qualitative olfactory dysfunction in different age groups

The prevalence of parosmia and phantosmia among 363 chemosensory and nasal/sinus patients was studied, as was the accuracy with which our clinical questionnaire could assess these dysfunctions. We then investigated whether patients with parosmia or phantosmia, matched for odor intensity, perform poorer on odor identification than do patients with no dysosmia. More than 40% of the study group evidenced either parosmia (18.7%) and/or phantosmia (25.6%), a finding that suggests that more attention should be paid by the medical practitioner in addressing qualitative olfactory dysfunction. Furthermore, it appears that assessment of these dysfunctions may aid in differential diagnosis, and that questionnaires can be used with reasonable validity irrespective of the patient's age. Finally, the results imply that parosmia may be reflected in a discrepancy between odor identification and detection.