Deafness in Children of Very Low Birth Weight.

In the course of a survey of over a thousand children weighing 4 lb. (1,800 g.) or less at birth, there was an opportunity to investigate the occurrence of deafness in these children. This survey was made with the Society of Medical Officers of Health and was undertaken primarily to study the aetiology of cerebral palsy (McDonald, 1963). Deafness sufficient to require special schooling is very uncommon. The Ministry of Education (1946) has estimated a prevalence of 0 7 to 1 per 1,000 in children of school age; Barton, Court and Walker (1962) in a survey in Northumberland and Durham found a rate of 0 7 per 1,000: in this survey deafness was thought to be hereditary in 25 %, to have followed meningitis or some other infection in a further 25 %, but in 50% of children the cause was unknown. Rubella in early pregnancy and severe haemolytic disease of the newborn each accounted for less than 1% of the total. Among the cases of unexplained deafness, 7.60% of the children had a birth weight of less than 4 lb. (1,800 g.), which may be compared with approximately 0*4% in the general population (Gibson and McKeown, 1951). Several surveys have shown that children weighing not more than 51 lb. (2,500 g.) at birth have a higher rate of deafness than those weighing over 5 lb. (Johnsen, 1952; Fisch and Osborn, 1954; McDonald, 1962b). Drillien (1961), in a study of 50 children aged 5 years who had weighed 3 lb. (1,400 g.) or less at birth, found 5 (10%) with hearing defects. The audiograms of premature children with perceptive deafness were found by Fisch and Osborn to be similar to those of children who had kernikterus in infancy, and to those of children with a history of asphyxia at birth. Characteristically the audiograms showed moderate or severe high frequency loss with never more than moderate low frequency loss. Campanelli, Pollock and Henner (1958), in a study of 44 children aged 6 years who had been admitted to a premature baby nursery, found high frequency deafness in 7 (16%); 44 children weighing over 51 lb. (2,500 g.) at birth had normal hearing. The 7 deaf children were lighter than the 37 who were not deaf (mean weight, 981 g., compared with 1,718 g.), and they had a much shorter mean gestation period (26 3 weeks compared with 33 weeks). The deaf children were kept in an incubator for an average of 24 days compared with 8 days for those who were not deaf, but it was thought improbable that excessive oxygen administration was responsible for the deafness because no association between retrolental fibroplasia and deafness has been observed. Fraser (1962) suggested that the association between prematurity and deafness might be due to streptomycin. Premature infants are frequently given streptomycin and may be more sensitive to it than adults. Pathological evidence on the nature of lesions causing perceptive deafness is scanty. Dublin (1951) and Gerrard (1952) reported destruction of nerve cells in the cochlear nuclei at autopsy in kernikterus; but in none of the cases had hearing been tested. Haymaker, Margoles, Pentschew, Jacob, Lindenberg, Arroyo, Stochdorph and Stowens (1961) found only slight gliosis in the cochlear nuclei of two children with post-kernikteric encephalopathy who were known to have been deaf.