Congenital anosmia

Olfactory Dysfunction in Children: A Scoping Review

OBJECTIVE

Olfactory disorders are well-studied in the adult population, however, there is a paucity of literature characterizing olfactory dysfunction in pediatric patients. The purpose of this scoping review was to identify known causes of olfactory loss in pediatric populations, clarify the extent of use and validity of smell tests, and summarize current therapies for olfactory loss.

DATA SOURCES

PubMed, Ovid MEDLINE, and Web of Science.

REVIEW METHODS

Databases were systematically searched in September 2020. Two independent reviewers conducted the title and abstract screen, followed by review of full-texts for inclusion based on preset inclusion and exclusion criteria. Extracted data included study type, age/age-range of participants, gender, radiological evidence of olfactory dysfunction, types and results of smell tests used, etiology of olfactory loss, and therapies employed for olfactory loss.

RESULTS

A total of 103 articles (n = 1654) were eligible for final data extraction. The University of Pennsylvania Smell Identification Test was used most frequently for smell testing (21% of studies). In total, 45 causes of olfactory dysfunction have been elucidated by this study: 22 congenital and 23 acquired. Few therapies were described, and all were specific to the etiology of olfactory loss.

CONCLUSION

Olfactory dysfunction has a wide range of etiologies in the pediatric population, and clinicians should have a diagnostic algorithm for how to identify a cause should they encounter it in practice. If no etiology can be identified, education around safety should be provided to both the patient and their caregivers.

An Extremely Rare Cause of Isolated Congenital Anosmia

A 14-year-old adolescent was referred to a regional paediatric outpatient clinic with anosmia by her family doctor in Western Australia. The patient has no recollection of her previous ability to smell, suggesting the possibility of congenital anosmia. She was assessed in the paediatric outpatient clinic. A “noncontrast high-resolution MRI-brain scan with Anosmia-Protocol” was requested as the first-line investigation of choice by the treating paediatrician. The MRI was reported as “absence of olfactory tracts with preserved olfactory bulb volume.” We report an extremely rare case of “isolated agenesis of the olfactory tract with intact olfactory bulbs” and discuss the clinical approach in bedside assessment of isolated congenital anosmia (ICA). Congenital anosmia can be a presentation of olfactory bulb aplasia; however, little is known about isolated olfactory tract agenesis and its treatment options. The patient was counselled on the diagnosis and safety advice provided.

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.

Hidden consequences of olfactory dysfunction: a patient report series

BACKGROUND

The negative consequences of olfactory dysfunction for the quality of life are not widely appreciated and the condition is therefore often ignored or trivialized.

METHODS

1,000 patients with olfactory dysfunction participated in an online study by submitting accounts of their subjective experiences of how they have been affected by their condition. In addition, they were given the chance to answer 43 specific questions about the consequences of their olfactory dysfunction.

RESULTS

Although there are less practical problems associated with impaired or distorted odor perception than with impairments in visual or auditory perception, many affected individuals report experiencing olfactory dysfunction as a debilitating condition. Smell loss-induced social isolation and smell loss-induced anhedonia can severely affect quality of life.

CONCLUSIONS

Olfactory dysfunction is a serious condition for those affected by it and it deserves more attention from doctors who treat affected patients as well as from scientist who research treatment options.

Learning about the functions of the olfactory system from people without a sense of smell

The olfactory system provides numerous functions to humans, influencing ingestive behavior, awareness of environmental hazards and social communication. Approximately 1/5 of the general population exhibit an impaired sense of smell. However, in contrast to the many affected, only few patients complain of their impairment. So how important is it for humans to have an intact sense of smell? Or is it even dispensable, at least in the Western world? To investigate this, we compared 32 patients, who were born without a sense of smell (isolated congenital anosmia--ICA) with 36 age-matched controls. A broad questionnaire was used, containing domains relevant to olfaction in daily life, along with a questionnaire about social relationships and the BDI-questionnaire. ICA-patients differed only slightly from controls in functions of daily life related to olfaction. These differences included enhanced social insecurity, increased risk for depressive symptoms and increased risk for household accidents. In these domains the sense of olfaction seems to play a key role.

Mutations in Olfactory Signal Transduction Genes Are Not a Major Cause of Human Congenital General Anosmia

Anosmia affects the western world population, mostly the elderly, reaching to 5% in subjects over the age of 45 years and strongly lowering their quality of life. A smaller minority (about 0.01%) is born without a sense of smell, afflicted with congenital general anosmia (CGA). No causative genes for human CGA have been identified yet, except for some syndromic cases such as Kallman syndrome. In mice, however, deletion of any of the 3 main olfactory transduction components (guanidine triphosphate binding protein, adenylyl cyclase, and the cyclic adenosine monophosphate-gated channel) causes profound reduction of physiological responses to odorants. In an attempt to identify human CGA-related mutations, we performed whole-genome linkage analysis in affected families, but no significant linkage signals were observed, probably due to the small size of families analyzed. We further carried out direct mutation screening in the 3 main olfactory transduction genes in 64 unrelated anosmic individuals. No potentially causative mutations were identified, indicating that transduction gene variations underlie human CGA rarely and that mutations in other genes have to be identified. The screened genes were found to be under purifying selection, suggesting that they play a crucial functional role not only in olfaction but also potentially in additional pathways.

Olfactory evaluation in children: application to the CHARGE syndrome

OBJECTIVE

To find an efficient tool for testing olfactory function in children and use it to investigate a group of children with CHARGE (coloboma, congenital heart disease, choanal atresia, mental and growth retardation, genital anomalies, and ear malformations and hearing loss) syndrome.

METHODS

We adapted for children an olfaction test that had just been validated in an adult French population and investigated a control group of 25 healthy children aged 6 to 13 years. We then tested the olfactory capacity of a group of 14 children with CHARGE syndrome, aged 6 to 18 years. A questionnaire was completed with the parents about their children's feeding difficulties and their ability to recognize odors in everyday life. We recorded and scored the histories of feeding behavior anomalies, the visual and auditory status, and current intellectual levels. MRI of the olfactory tracts and bulbs was analyzed for 9 of 14 children.

RESULTS

We showed that healthy children have similar olfactory function to that of the adult control group, which was representative of the general population, without any difference for either gender or age. We also showed that all children with CHARGE syndrome had olfactory deficiency. Half of them were anosmic, and the others had olfactory residual function (hyposmic). We found no association between olfactory deficiency and feeding behavior, visual or auditory impairment, or intellectual level. Parental subjective evaluations were accurate for only half of the group. All of the MRIs showed anomalies of the olfactory tracts and bulbs varying from moderate hypoplasia to complete aplasia, without any relation between the radiologic and the functional results.

CONCLUSIONS

Olfaction can be assessed in children, even the young and disabled. Our results support the proposition that rhinencephalon anomalies should be included as a major criterion for the diagnosis of CHARGE syndrome.