Does Maternal Smoking Make a Difference in Newborn Hearing Screening with Otoacoustic Emissions?

Abstract

Universal newborn hearing screening is both, crucial and routinely performed because only 50% of babies born with hearing loss carry a hearing loss risk factor. Early detection leads to an efficient treatment of the affected neonates, resulting in a better final prognosis [1][2][3]. Several techniques are used in newborn hearing screening. Otoacoustic emissions (OAEs) are low-level acoustic signals generated by the cochlea and passed through the middle ear into the external ear canal. OAEs are an objective indication of normal cochlear function. OAEs occur in nearly all ears with normal hearing and middle ear function. Transient evoked otoacoustic emission (TEOAE) testing is one of the most frequently used techniques because of its accuracy, simplicity, speed and low cost as described in diverse studies [2,4-6]. TEOAEs are evoked across a broad frequency range when stimulated by temporally short clicks, which have broad spectral bandwidths, and multiple cochlear locations may contribute to TEOAEs measured at any specific frequency. Researchers have compared the sensitivity of evoked OAE testing with pure-tone audiometry and concluded that OAE testing is more sensitive in detecting the early onset of cochlear pathologies before a change in hearing thresholds occur [7].A major drawback of TEOAE testing as a screening technique for newborns relates to the middle ear status, which can severely affect its pass rate. We must keep in mind that, the presence of debris and vermix in the external ear meatus of the newborn can result in false positive screenings. This factors lead to a greater than the actual hearing loss failure rate, thus a two-step newborn hearing screening protocol has been introduced in order to allow a better clearance of the middle and external ear, this means that when newborns fail TEOAE at discharge, an appointment is given to repeat the test in less than one month. This improves specificity of test without delaying adequate diagnosis.Another crucial factor is the newborn's age when the test is done.Data strongly suggests that the prime testing window is beyond 24-48 hrs. of life, as fluid in the middle ear and in the external meatus is normally significantly reduced on the second day of life. For this