Acoustic Impedance Measurement as Screening Procedure in Children: Discussion Paper

Middle ear effusion (MEE) has probably been a recognized aural condition since Hippocrates (4th century BC) wrote about 'humours of the ear'. More than two millenia later MEE is undoubtedly the major cause of auditory dysfunction in school children. It is a condition that occupies a substantial part of the time of the otologist and which costs society a great deal for its alleviation. Anything, therefore, which gives promise of earlier or better diagnosis should surely be welcomed by those responsible for the health care of children. A tool giving such promise emerged through the development of acoustic impedance measurement. Over a decade ago the concept was advanced that MEE might be detected more swiftly and efficiently by adding acoustic impedance measurement to the routine screening of hearing (Brooks 1971). The reception of this proposal in the UK has been at best unenthusiastic and the purpose of this paper is to discuss critically the major objections to the concept, these being (1) that it is unnecessary because children recover from MEE spontaneously, given time; (2) that impedance screening is unnecessary because present diagnostic methods are adequate; (3) that pure-tone screening is adequate to identify children with auditory deficits; (4) that impedance testing will not detect sensorineural hearing loss; (5) that the procedure is over-sensitive and would cause overloading of the treatment services; (6) that it is too costly; and (7) that the procedure is not safe. The first objection seems, at first sight, to have circumstantial support. Though probably 206/o or more of all first-year school children have episodes of MEE, by the age of 10 or 11 years the prevalence has fallen to only 2 or 3% (Brooks 1974). Recovery is spontaneous for the majority. Why then attempt to detect MEE at an early age? Firstly, although many children eventually grow out of the condition, they may still have persistent or episodic MEE accompanied by some degree of hearing loss for a period of two or three years. There is growing evidence that such minor hearing losses can, in some children, result in educational or linguistic retardation (Bennett et al. 1980, Sak & Ruben 1981, Zinkus 1982) or behavioural problems (McGee et al. 1982). Secondly, in a small number of children the mild problems of MEE may gradually change into more severe middle ear problems such as atalectasis (Sade & Berco 1976), tympanosclerosis (Schiff et al. 1980), or cholesteatoma (Paparella & Lim 1967). Thirdly, MEE may give rise to sensorineural hearing loss (Moore & Best 1980), or vertigo (Stell 1978). Early detection should lead to earlier treatment (which may be educational as well as medical or surgical) and a greater probability of avoiding untoward effects. The second counter-argument has two facets: first, that medical diagnosis is adequate in time, and secondly that it is adequate in accuracy. But is it correct that all children with remediable MEE are seen at an early stage of the disease process? The answer has to be 'no'. The study of Ferrer (1984) found that of 25 children who were eventually operated on for MEE, at least 18 had almost certainly had the condition in chronic form for at least 2 years but had not been identified by parents, teachers, family practitioners or otolaryngologists. Similar long term undiagnosed MEE was reported by Brooks (1976a). Regarding the accuracy of diagnosis, there are a number of studies highlighting the deficiencies of otoscopy even when performed by skilled practitioners. Roeser et al. (1977)