1st September 2018, Dr Chee L Khoo
After acute otitis media, the middle ear effusion usually resolves within days although it may take up to 3 months in some children. However, in up to 8% of kids, the effusion persist beyond the 3 months and it becomes chronic otitis media with effusion (COME). Why these 8% is the key research question.
COME is characterised by mucosal hyperplasia, including the proliferation of mucus-secreting goblet cells in the epithelial lining of the antero-inferior middle ear cleft. These changes lead to serous or mucoid middle ear effusion which impairs the transmission of airborne sound. COME is the most common cause of hearing loss in childhood.
COME often follows acute otitis media (AOM) but the role of bacteria in its aetiology is unclear. The usual bacteria that causes AOM, S. pneumoniae (pneumococcus), Haemophilus influenzae (NTHi) and Moraxella catarrhalis are often found in the effusion of children with COME but there are a multitude of other bacteria also present in the effusion. There is some evidence that children who have recurrent episodes of AOM are more likely to have middle ear effusion but it is uncertain whether this represents repeated episodes of acute resolving effusion or continuous non-resolving effusion. There is evidence that the effusion in COME is more likely to resolve in children who are given antibiotics although that effect is relatively small.
The relative importance of host factors in the initiation and perpetuation of chronic OM can be gauged from estimates of the heritability of disease. Twin studies in young children with COME have suggested that heritability of the duration of middle ear effusion is high at 0.73. Which factors are affected in the host has not been elucidated though.
Older literature suggests perhaps, poor aeration of the middle ear due to eustachian tube dysfunction may be a key factor but measure of eustachian tube function is difficult. We know that insertion of grommets is effective in resolving COME but there is no evidence that grommet insertion improves the aeration. Well, it’s a bit hard to measure pressure differences or eustachian function in little kids.
Disturbance of various inflammatory pathways have been suggested as one of the mechanisms that drives COME. We have a long way to go with this theory though with conflicting results in animal studies.
Cochrane review of oral or topical steroids for otitis media with effusion, updated in 2011, found a significant benefit with oral steroids plus antibiotics versus control with antibiotics alone, and a significant point estimate suggesting benefit for oral steroids versus control. Studies were generally small, of poor quality, and short term.
In a randomised parallel, double-blinded placebo controlled trial, 1018 children with COME >3 months were randomised to receive either oral steroid or placebo. At 5 weeks, acceptable hearing was assessed between the groups. A short course of oral prednisolone is not an effective treatment for most children aged 2–8 years with persistent otitis media with effusion, but is well tolerated. One in 14 children might achieve improved hearing but not quality of life.
In terms of elucidating the patho-biology of chronic OM, we still need to understand the relative roles of mucosal versus leukocyte biology in the initiation and perpetuation of middle ear disease, and the role of pathogens and their interaction with host tissues. We do not know whether ventilatory dysfunction in the Eustachian tube is as important a mechanism in pathogenesis as was historically proposed
Access the abstract here.
Reference:
Nick A Francis, Rebecca Cannings-John, Cherry-Ann Waldron, et al. Oral steroids for resolution of otitis media with effusion in children (OSTRICH): a double-blinded, placebo-controlled randomised trial. Lancet 2018; 392: 557–68
Mahmood F. Bhutta, Ruth B. Thornton, Lea-Ann S. Kirkham, Joseph E. Kerschner, andMichael T. Cheeseman. Understanding the aetiology and resolution of chronic otitis media from animal and human studies. Dis Model Mech. 2017 Nov 1; 10(11): 1289–1300.