Observational Study
Copyright ©The Author(s) 2023. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Clin Pediatr. Jun 9, 2023; 12(3): 133-150
Published online Jun 9, 2023. doi: 10.5409/wjcp.v12.i3.133
Evaluation of children and adults with post-COVID-19 persistent smell, taste and trigeminal chemosensory disorders: A hospital based study
Sherifa Ahmed Hamed, Eman Bahaa Kamal-Eldeen, Mohamed Azzam Abdel-Razek Ahmed
Sherifa Ahmed Hamed, Department of Neurology and Psychiatry, Assiut University, Faculty of Medicine, Assiut 71516, Egypt
Eman Bahaa Kamal-Eldeen, Department of Pediatrics, Assiut University, Faculty of Medicine, Assiut 71516, Egypt
Mohamed Azzam Abdel-Razek Ahmed, Department of ENT, Assiut University, Faculty of Medicine, Assiut 71516, Egypt
Author contributions: Hamed SA, Kamal-Eldeen EB and Ahmed MAA designed the conception, did data collection and physical examinations. Ahmed MAA did ear, nose and throat evaluation; Kamal-Eldeen EB and Ahmed MAA referred the patients to the neurologist (Hamed SA) and critically reviewed the manuscript; Hamed SA applied the objective measurements for smell and taste and the final statistical analyses, wrote the manuscript and had the final responsibility to submit the manuscript for publication; All authors had full access to raw data and verified the underlying data and interpretation of the results and final approval of the manuscript.
Institutional review board statement: The protocol of the study was in accordance to the revised Helsinki Declaration (2013) and approved by the medical research ethics committees of the Faculty of Medicine, Assiut University, Assiut, Egypt, No. AUH_SARS-CoV2_SAH/2019.
Informed consent statement: All study participants, or their guardian, provided informed written consent prior to study enrollment.
Conflict-of-interest statement: All the authors report no relevant conflicts of interest for this article.
Data sharing statement: No additional data are available.
STROBE statement: The authors have read the STROBE Statement—checklist of items, and the manuscript was prepared and revised according to the STROBE Statement—checklist of items.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: https://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Sherifa Ahmed Hamed, MD, Professor, Department of Neurology and Psychiatry, Assiut University, Faculty of Medicine, Assiut University Street, Assiut 71516, Egypt. hamedsherifa@aun.edu.eg
Received: February 27, 2023
Peer-review started: February 27, 2023
First decision: March 15, 2023
Revised: March 16, 2023
Accepted: April 20, 2023
Article in press: April 20, 2023
Published online: June 9, 2023
ARTICLE HIGHLIGHTS
Research background

Smell loss with or without taste loss is the most frequent acute manifestation of coronavirus disease 2019 (COVID-19) infection with an estimated prevalence of 16%-20% in children and 40%-86% in adults. Smell disorders are also the most frequent complications of COVID-19 infection with an estimated prevalence of approximately 20%-40% of adults. This indicates that COVID-19 has high affinity to olfactory sensory epithelium (and to less extent gustatory sensory epithelium) compared to other parts of the body. Data from patients and their contacts showed that it is impossible to predict the prognosis of smell loss (i.e. none of the demographics, acute manifestations and severity at onset were predictors for the development of persistent disorders). It has been indicated that the mechanisms of transient smell and taste deficits due to COVID-19 infection are different from that of long-lasting/persistent disorders. It has been suggested that injury of the non-neuronal olfactory epithelial cells by viral infection and their rapid regeneration (within days to weeks) are the causes of transient smell deficits because these cells are important for the health of the neuronal cells. However, lasting smell disorders are due to injury of the neuronal olfactory epithelial cells and disorganization of the receptors within the epithelium, because these cells require months to regenerate after injury and restore olfactory epithelium function. The mechanisms of taste disorders after COVID-19 infection are less understood compared to smell disorders but suggested to be due to injury of the gustatory sensory epithelium by viral infection and disturbed salivary milieu which is necessary for the function of the gustatory neurons.

Research motivation

The research hotspots include determination of (1) The patterns of smell and taste disorders at onset; (2) The course of these disorders till presentation; and (3) Whether or not there is/are distinguished features for children with these disorders which differentiate them from adult patients with the same disorders.

Research objectives

This study aimed to systematically evaluate patients with post-COVID-19 infection persistent smell and taste disorders because related studies from many areas of the world including our country are lacking. The descriptive characteristics of patients at onset and presentation and predictors for the development of these disorders were determined in children and adult populations.

Research methods

Data collection which included a clinical questionnaire (for smell and taste); objective testing which included the sniffin' odor, taste and flavor identification tests and the Questionnaire of Olfactory Disorders-Negative Statements for determination of quality of life in response to these disorders.

Research results

This study included 185 patients (adults = 150, age: 31.41 ± 8.63 years; children = 35; age: 15.66 ± 1.63 years) from both gender and had post-COVID-19 infection smell and taste disorders. The duration of the disorders till the time of presentation ranged from 6 to 24 mo (mean: 11.53 ± 3.97 mo) with nearly half of the patients had duration of at least a year. Parosmia was a frequent manifestation (64.32%) in patients with persistent anosmia and was developed after months from onset (3.05 ± 1.87 ms). Total or partial true ageusi, retronasal olfactory loss (or flavor) and trigeminal chemosensory loss were present in 18%-20% of patients. There were no significant differences in patterns at onset and clinical variables at onset and at presentation between children and adults with persistent disorders. These disorders significantly lower quality of life of patients.

Research conclusions

Persistent smell, taste and trigeminal chemosensory disorders are frequent post-COVID-19 complications in children similar to adults. There were no demographics, clinical variables at onset or specific profile of these disorders which distinguish children from adults’ patients.

Research perspectives

Future studies are needed to: (1) Determine the prevalence of these disorders in children and in adults from understudied populations (e.g. Africans); (2) Determine the relationship between smell and taste disorders due to different COVID-19 variants (alpha, delta or omicron). In the literature, there were no relevant studies which stratified recovery according to COVID-19 variants. Here, the period of patients’ recruitment in this study indicated a high possibility of being infected with the wild types of the virus; and (3) Understand the detailed cellular and molecular pathogenic aspects underlying long-lasting/persistent chemosensory disorders after COVID-19 infection.