The relationship between chronic otitis media with effusion (COME) and obesity has been obvious for some time. It was firstly suggested, that obesity could have an effect on development of COME. Abnormal anatomy of Eustachian tube, altered function of immune system and obesity related comorbidities were highlighted as potential risk factors. However latest study (1), conducted by South Korean otorhinolaryngologists, proves that the correlation mentioned above presents itself the other way round. COME changes the taste function through a deterioration of chorda tympani nerve, which results in higher risk of pediatric obesity.
Secretory otitis media is a very prevalent condition among children. It was estimated that up to 80% of pediatric patients will have been affected by this disorder by the age of 4 years (2). Only 10% of them will suffer from recurrent or persistent OME. The youngest patients are especially prone to serous otitis media, because of their immature structure of Eustachian tube. Edema of auditory tubeˈs mucosal membrane is usually caused by respiratory infections, allergies and indirect exposure to smoke. Swelling results in the compromise of pressure equalization in the middle ear. As a consequence fluids build up in the cavity and this is how a “glue ear” is developed. Surprisingly it turns out that obesity alone may lead to OME.
Altered cytokine expression, high prevalence of gastro esophageal reflux and fat accumulation in the region of Eustachian tube can be the key factors (3).
The latest study on this subject was performed by clinicians in Seoul and printed in March this year. Scientists aimed at establishing whether the incidence of obesity is higher in the group of patients suffering from COME. Before undergoing the procedure of tympanostomy tube insertion, scientists tested patientsˈ taste function. Researchers collected the evidence of 42 children with COME and 42person control group with confirmed absence of middle ear pathology. Children presenting with deformities, systemic diseases and immune deficiency were excluded from the trial.
The methods used for evaluation of the gustatory system were: quantitative electrogustometry (EGM) and qualitative chemical taste tests.iv EGM involved placing electrodes on various areas of the tongue and recording minimum voltage at which the patient could feel a metallic taste. This is how the information about the taste threshold was obtained. Whereas chemical taste test relied on applying sweet, salty, sour and bitter substances into the entire oral cavity in a row. Minimum dilution at which the taste could be detected was measured and defined as a threshold. It is clear that both methods are rather subjective, especially when taken into consideration the fact that patients were aged 37 years.
The results were surprising. Median BMI of children with COME was significantly higher than in the control group. Taste thresholds measured by EGM were significantly higher in the COME group on the anterior right and left sides of the tongue. It means that more voltage had to be used to generate gustatory stimulus received by the fibres of facial nerve branch chorda tympani. What is more, posterior sides were not changed, which proves that the function of glossopharyngeal nerve, supplying the area, was not altered. What is even more interesting, thresholds measured for sweet and salty were significantly higher in the COME group than in the control. Sour and bitter did not differ from the physiology.
What could be the mechanism of such major changes? Scientists put forward an explanation that chorda tympani deteriorates in the inflammatory environment of middle ear. It is not protected by the surrounding bones but instead exposed to the middle ear cavity. Passing between the malleus and incus, the nerve may be influenced by inflammatory tissue and molecules. Histopathologic examination of chorda tympani in patients with COME shows fibrosis of perineum, destruction of Schwann cells and disorganization of axons (5).This may give rise to the dysfunction of nerve VII.
South Korean clinicians believe, that elevated taste thresholds of sweet and salty tastes increase the amount of consumed food. Children have to eat more to achieve satiety. The researchers emphasize the fact, that the age at which obesity develops is similar to the age, at which otitis media with effusion becomes prevalent. Although the tests are still preliminary and the case control group was rather limited, this discovery may give another look at pathogenesis of pediatric obesity, which seems to be the greatest epidemic of 21st century. It has been estimated that 6 years old obese child has a 25% risk of becoming an obese adult and 12yearold is threatened by a 75% probability. Changes in the management of COME patients might contribute to harnessing obesity of the adults and reducing the risk of cardiovascular and metabolic diseases.
Written by: Natalia Neumann
1.Arch Otolaryngol Head Neck Surg. 2011 Mar;137(3):242-6. Changes in taste function related to obesity and chronic otitis media with effusion. Shin IH, Park DC, Kwon C, Yeo SG.
2.Clin Evid (Online). 2011 Jan 12;2011. pii: 0502. Otitis media with effusion in children. Williamson I.
3.Curr Allergy Asthma Rep. 2009 Nov;9(6):465-72.Relationship between pediatric obesity and otitis media with effusion. Lee SK, Yeo SG.
4.Otolaryngologia 2008, 7(4) ):173-177. Modern methods of olfactory and gustatory examination, , Karolina Dżaman
5.Laryngoscope. 2001 Apr;111(4 Pt 1):724-7. Histopathological changes of chorda tympani in chronic otitis media. Gedikli O, Doğru H, Aydin G, Tüz M, Uygur K, Sari A.