Журнал «Здоровье ребенка» 2 (45) 2013

Introduction

Among problems of perinatal period in premature newborns, one of the most important is considered to be hearing impairment. According to the WHO data, severe hearing impairments are observed in 0.1-0.2% of newborns, and impairments of mild and moderate degree of manifestation are observed in 1-2% of newborns [3,4]. Hearing impairments in newborns with perinatal pathology that require intensive therapy occur more frequently: in 10-15% of children. In recent years the significance of perinatal pathology has increased essentially as one of the main cause of hearing loss and deafness development in newborns and premature infants to a greater extend [1,2].

It is thought that the fullest coverage of newborn population aimed at determination of hearing impairments is possible with the use of screening programs, as well as risk group formation due to hearing loss and deafness. If hearing loss is diagnosed within first 6 months of life and adequate sound amplification in a newborn is reached until he/she is aged six months, psychoemotional and speech development will not differ from the one of his/her peers with no pathology [3,5,6,7].

Child’s deprivation of hearing-and-speech surrounding may lead to irreversible influences on his/her posterior ability to use potential possibilities of his/her residual hearing [4,5,6,8,9].

Aim of the study

To reveal the incidence and factors, which determine hearing impairments in premature newborns with perinatal pathology due to their gestation term.

Materials and methods

Hearing examination was carried out in 1,537 premature newborns with perinatal pathology with gestation term between 22 and 36 weeks, who received their treatment in Kharkiv Municipal Perinatal Centre between 2009 and 2012. Peculiarities of clinical, biochemical, ultrasound polymorphism of perinatal pathology were analyzed in the newborns examined aged between 2 and 4 months taking into consideration the dynamics of their state, sex and disease severity. The initial hearing screening was carried out in 1,281 premature newborns, and audiological re-screening was carried out in 256 newborns in 2-6 weeks after the first test with further monitoring of their hearing function. Repeated examination was carried out from 1 to 4 times depending on the term of child’s staying in the hospital.

Due to their body weight values, all the newborns examined were divided as follows: 44 (3.4 %) newborns with extremely low body weight at birth (under 1,000 g), 215 (16.8%) newborns with very low body weight at birth (1,000 – 1,499 g), 464 (36.2%) newborns with low body weight at birth (1,500 – 1,999 g), 531 (41.5%) newborns with body weight at birth of 2,000 – 2,500 g, and 27 (2.1%) newborns with body weight over 2,500 g.

Methods of hearing examination are subdivided into 2 large groups: psychoacoustic ones that are based on registration of patient’s subjective sound perception (which is impossible in neonatal practice), and objective ones that are based on a bioelectric response of auditory analyzer structures to sound stimulus. Registration of otoacoustic emission (OAE) belongs to objective methods of hearing examination. Screening apparatuses for hearing examination in newborns have been created on the basis of this method.

Audiologic screening in newborns was carried out with apparatus “OtoRid” /Denmark/. It is a high-performance compact automatic device, which allows to conduct accurate, safe, noninvasive and painless detection of defects in sound information perception. The newborns were examined in the morning after feeding in their rest state or during their physiological sleep. Positive screening result indicates to the normal function of cochlea hair cells in newborn examined. The newborns with the result “test is not passed” form the group of newborns, who require further auditory organ examination: medical examination of otolaryngologist to exclude external and middle ear pathology, and audiologist’s advice with conduction of thorough audiologic examination.

Results and discussion

Risk factors of hearing loss and deafness in newborns have been analyzed. Factor analysis demonstrates that all the newborns examined had 2 or more perinatal risk factors.

Mothers of all the newborns examined belonged to high risk group of perinatal pathology, with gestation course complicated by various pathological states.

During examinations conducted, screening result “test is passed” (i.e., determination of otoacoustic emission) was registered in 893 premature newborns, which makes 67.9% of all newborns examined at initial screening. Result “test is not passed” was registered in 388 newborns (30.3 % of all newborns examined at initial screening). Binaural screening result “test is not passed” was determined in 237 newborns (18.5% of all examined), one-war screening result “test is not passed” was determined in 151 newborns (11.8% of all newborns examined at initial screening).

According to the term of gestation, newborns with negative result of audiologic screening were divided as follows: 34-36 weeks – 94 newborns, 32-33 weeks – 87 newborns, 30-31 weeks – 109 newborns, 28-29 weeks – 49 newborns, and less than 28 weeks of gestation – 49 newborns.

Children with negative audiologic screening results had severe perinatal pathology, and CNS pathology was determined in most of them.

Hearing monitoring in 256 premature children as repeated audiologic screening conduction revealed binaural otoacoustic emission in 71 infants, which is 29.9% of all children who did not pass the initial screening. One-ear otoacoustic emission was found in 29 children (12.2%) and in 60 children (25.3%) negative test result did not change. Out of 151 children total with result “test is not passed” for one ear, during repeated examinations 73 infants (48.3%) passed the test binaurally and no change in results was observed in 39 children. It should be noted that in children with improved test results clinical and laboratory improvements of health state were also revealed, first of all in their neurological status (brain edema arrest, intraventricular hemorrhage lysis, and decrease in the degree of perfusion-weighted MRI imaging).

Thus, when conducting hearing monitoring in children in Kharkiv Municipal Perinatal Centre, out of 388 children with negative result of the initial screening, 144 children demonstrated binaural result “test is passed” at repeated screening, which is 37% of total number of children with negative initial result, and 29 children demonstrated one-ear result “test is passed” (7.5%, respectively). The results obtained support specialists’ opinion that premature newborns, who have severe perinatal pathology, require conduction of several examinations in dynamics with increase of their post-conception age.

With introduction of modern perinatal technologies into Kharkiv Municipal Perinatal Centre survival rate of children with extremely low body weight at birth has increased. During the period of 2009-2012, hearing examinations were conducted in 44 children with body weight under 1,000 g. The test was passed only in 6 children (13.6%); the test was not passed for both ears in 31 children (70.4%) and for one ear – in 7 children (16%). In the result of multiple repeated examinations in 23 children (52.4%) out of 44 the result remained negative. Post-conception age of these children at the time of examination was 31-44 weeks of gestation. Peculiarities of premature children with very low and extremely low body weight at birth include severe neurological and metabolic disorders at the background of immaturity of both CNS and sensory part of auditory analyzer.

Everything stated above proves the need for development and realization of a complex of effective measures on early diagnosis and therapy of hearing impairment in premature newborns.

Conclusions

1. Conduction of audiologic screening is required in all newborns, in premature ones in particular. The optimal term for initial audiologic screening in premature newborns should be 32-33 weeks of gestation.
2. Registration of otoacoustic emission with apparatus “OtoRid” /Denmark/ is an objective, accurate, fast and painless test conducted to reveal the defects in sound information perception in premature newborns.
3. The frequency of hearing impairments at the initial examination in premature newborns with perinatal pathology is significantly higher against the one in general population and is 30.3%.
4. Among children with extremely low body weight at birth, the frequency of hearing impairments is 86.4% at the initial screening, which is associated with the severity of perinatal CNS lesions and immaturity of sensory part of auditory analyzer.
5. Severe hypoxic CNS lesions in premature newborns lead to lesions in sensory part of auditory analyzer under other conditions equal.