SMJ 2003 48(4): 117-119
Christine MacAndie,
Specialist
Registrar in Otolaryngology, Royal Hospital for Sick Children,
Haytham Kubba,
Specialist
Registrar in Otolaryngology,
Margaret
McFarlane, Educational Audiologist,
Address
for correspondence:
Mrs
C MacAndie,
Email: cmacandie@yahoo.co.uk
ABSTRACT
This
retrospective study was undertaken to document the epidemiology of permanent
childhood hearing impairment (PCHI) in Glasgow and to make some assessment of
the current practice to identify these children before universal neonatal
hearing screening (UNHS) is implemented. Subjects were those with bilateral
permanent hearing impairments of at least 40dB in the better hearing ear, born
between 1985 and 1994, in Greater Glasgow.
The subjects were identified and data extracted from the Educational
Audiology database. The case
records at the Royal Hospital for Sick Children were also reviewed to identify
possible aetiology groups. The
prevalence rate of all permanent hearing impairments was 1.23 per thousand live
births. Eleven percent of all
hearing impairments were acquired or progressive.
There was no significant effect of sex on aetiology (X2=6.509,
df=6, p,=1), age at identification of hearing impairment and hearing aid
provision (Kruskal Wallis, p=0.484 and 0.782 respectively).
For those identified as congenitally hearing impaired, the median ages at
diagnosis of hearing impairment and hearing aid provision were 18 months and 31
months respectively. Age at
diagnosis of hearing impairment and hearing aid provision were unaffected by
aetiology of hearing impairment (Kruskal Wallis, p=0.782 and p=0.484
respectively). The prevalence rate
of PCHI and the ages at identification and intervention in Glasgow are typical
of the rest of the UK. Audiological
surveillance measures are falling well below the standard of care expected today
and the introduction of UNHS is likely to improve outcomes as long as the
additional health and educational resources are in place to deal with the
earlier identification of these children.
Keywords: epidemiology, permanent childhood hearing impairment, hearing
screening, neonatal, risk factors, aetiology
INTRODUCTION
Bilateral
permanent hearing loss in childhood is said to affect 1 in every 1,000 live
births. Failure to identify and
rehabilitate these hearing losses has a profound impact on language acquisition,
educational achievement and employment prospects 1,
2
. Early detection of
congenital hearing loss and intervention within six months of age is associated
with improved outcomes 3
. The National Deaf
Children’s Society (NDCS) in 1994 set an ambitious target of identifying 40%
of congenital hearing impairments by six months of age and 80% within 1 year 4
. Parental suspicion is
inadequate for identification of these hearing losses as approximately 50% of
parents are unaware of their child’s hearing impairment at the time of
diagnosis 5, 6
. It is for this reason that
most countries in western Europe have universal infant hearing screening
programmes 7
. In addition, those infants
in identified high risk groups for hearing impairment, such as a family history
of childhood deafness, admission to a neonatal intensive care unit (NICU), a
craniofacial syndrome or meningitis, may be referred for early assessment with a
high yield 8
. The United Kingdom also
screens all children at school entry age for hearing loss.
Despite
these measures, the mean age at confirmation of hearing loss is twenty six
months and for provision of hearing aids; thirty two months 9
. Universal neonatal hearing
screening programmes in the United States and more recently in the United
Kingdom have been shown to reduce the age at diagnosis of congenital hearing
loss 10, 11
.
The
perceived failings of the infant hearing screening has led to calls for
universal neonatal hearing screening (UNHS).
In Scotland, the National Screening Committee has recommended the
introduction of a phased neonatal hearing screening programme 12
. Two pilot sites are to be established with screening beginning in April
2002, in preparation for the programme to commence throughout Scotland in April
2003 and to be fully implemented by April 2005.
The
purpose of this retrospective study was to look at the epidemiology of permanent
childhood hearing impairment (PCHI) in Glasgow and make some assessment of the
current practice for the identification of hearing impaired children before UNHS
is implemented. The current
practice is targeted screening in identified high risk groups and the health
visitor distraction test at 8 months of age.
SUBJECTS
& METHODS
Children
born from 1985-1994 in Greater Glasgow with bilateral hearing impairments of at
least 40dB in the better hearing ear were identified from the Educational
Audiology database. This birth
cohort was selected as all the children will have achieved school age and
therefore be identified on the Educational Audiology database.
In addition, at this age it would be extremely unusual to have a
congenital or early acquired permanent hearing loss remain unidentified.
Data
were extracted from the Educational Audiology database and the case notes at the
Royal Hospital for Sick Children. Demographic
data recorded included sex, date of birth, and postcode.
Information was also extracted regarding maternal health throughout
pregnancy, birth history, perinatal problems, admission to a NICU, family
history of congenital hearing impairment and craniofacial abnormality.
This was used to categorise the subjects into groups reflecting most
likely aetiology. CT scanning of
the temporal bones and genetic testing were not routinely performed.
Hearing impairments were categorised into congenital, acquired or
progressive. For the congenital hearing losses, age at confirmation of
hearing loss and provision of hearing aids was recorded.
The
live birth rates for Greater Glasgow for each year studied were used to
calculate the incidence of congenital hearing impairment (Information Services
Office, Greater Glasgow Health Board). All
the data were collected from June to November 2000.
RESULTS
The
total live birth rate in Greater Glasgow from 1985-1994 was 105,517 . From this
birth cohort, 130 children with permanent hearing impairment were identified, an
incidence of 1.23 per thousand live births.
Of these children, 116 were congenitally hearing impaired (1.09 per
thousand live births). Fourteen
(11%) of the permanent hearing impairments were postnatally acquired or
progressive.
Seventy
six (58%) boys and fifty four (42%) girls were hearing impaired.
There was no significant effect of sex on aetiology (X2=6.509,
df=6, p,=1), age at identification of hearing impairment or hearing aid
provision (Kruskal Wallis, p=0.484 and 0.782 respectively).
Following
case note review the subjects were divided into the following aetiology groups:
family history of congenital hearing impairment (n=40, 31%), craniofacial
syndrome (n=15, 12%), admission to NICU [prematurity, low birthweight, ototoxic
drugs and jaundice all potential contributors to the PCHI] (n=20, 15%), post
natal infection such as meningitis (n=9, 7%), prenatal infection such as rubella
(n=4, 3%), unknown [i.e. all above factors excluded, presumed genetic] (n=15,
12%) and uncategorised [insufficient data available to identify risk factors]
(n=21, 16%). Of the 14 late onset
hearing losses, 5 children had evidence of a progressive hearing loss, and the
other nine were acquired due to post natal infections.
For
those identified as congenitally hearing impaired, the median age at diagnosis
of hearing impairment and hearing aid provision was 18 months and 31 months
respectively (Figure 1).
Age at diagnosis of hearing impairment and hearing aid provision was
unaffected by aetiology of hearing impairment (Kruskal Wallis, p=0.782 and
p=0.484 respectively). This means that those high risk groups are not being
identified and rehabilitated any quicker than those with no known risk factors.
DISCUSSION
The
incidence of PCHI in Glasgow is in keeping with UK national figures, at just
over one in a thousand at birth 13
. Every hearing impaired
child in Glasgow should have contact with the educational audiology service
before they begin school, and the educational audiology records are
comprehensive, prospective and cross-checked with hospital records.
We, therefore, feel that cases of PCHI which remain unidentified are
likely to be minimal in this study.
The
aetiologies identified in our study are very similar to those found in the UK
Trent Region 14
, and in studied from the USA 15
, the only appreciable difference being a higher proportion of children
with craniofacial abnormalities in our series (Table
1). The reasons for such a
difference are unclear. While the
incidence of congenital rubella is falling due to population vaccination, other
causes of PCHI (with the possible exception of meningitis) are not preventable.
The emphasis in management of the condition is, therefore, in timely
diagnosis and provision of amplification, together with appropriate educational
support.
Age
at confirmation of hearing loss and hearing aid provision are used as surrogate
measures of the efficacy of infant hearing screening programmes and Glasgow’s
figures are typical for Scotland 16,
17
and indeed the rest of the UK 9
. This standard of care is
falling well below expectations in the face of advancing technology enabling
earlier detection of PCHI.
The
average ages at diagnosis and aiding are no lower for the high risk children
that should have been identified and referred for audiological testing at birth,
as compared with the group as a whole. This
is particularly disappointing, and suggests that the early, targeted referral
system is not working well. Since
the study was performed, however, a pilot study of neonatal OAE testing in high
risk neonates has led to a threefold increase in the referral rate in this
subgroup (Ruth Hamilton, personal communication).
Clearly a proactive approach is required by all concerned, including
neonatologists.
In
the USA, guidelines for early hearing detection and intervention programs issued
by the National Institutes of Health (Joint Committee on Infant Hearing Year
2000 Position Statement, available at http://www.infanthearing.org/jcih/) state
that audiological evaluation should be in progress by three months of age and
those with confirmed hearing losses should receive intervention before six
months of age.
Yoshinaga-Itano
and colleagues demonstrated that intervention in PCHI by the age of six months
resulted in significantly better language acquisition than when those hearing
losses were identified and treated later than six months 3
. UNHS programmes in the UK
and USA are achieving these aims after an initial settling in period 9,
18
.
UNHS
will be fully implemented by April 2005 in Scotland using otoacoustic emissions
(OAE) technology. Transient evoked
otoacoustic emissions (TEOAE) are sensitive, specific, objective and quick and
OAE screeners need not have specific qualifications in audiology 10,
11
. However, the test only
reflects the integrity of the cochlear outer hair cells and so those rare
congenital hearing losses due to defects of the auditory nerve, brainstem or
cortex would be missed 19
. The use of behavioural
tests are required to know whether a child can actually hear, and so the need
for continued surveillance for childhood hearing loss remains following the
introduction of universal neonatal screening to pick up retrocochlear losses and
late onset or progressive hearing losses.
Parental
anxiety caused by UNHS is an area of concern but studies have shown that on the
whole parental attitudes are positive as long as they are adequately informed
and have access to appropriate support from health professionals following test
failures 20-22
.
Although there is no doubt that UNHS will achieve better outcomes for those PCHIs identified, Davis and colleagues found that, while assessing the current state of audiology services within the UK, there was a difference between existing standards of care and what actually was being done in practice due to a lack of resources 9 . It is therefore important to consider the additional health and educational resources needed due to earlier identification of PCHI when UNHS commences.
REFERENCES
1.
Davis J, Elfenbein J, Schum R, Bentler R.
Effects of mild and moderate hearing impairments on language, educational
and psychosocial behaviour of children. Journal of Speech and Hearing Disorders 1986; 51: 53-62.
2.
Downs M. The case for
detection and intervention at birth. Seminars
in Hearing 1994; 15:
76-83.
3.
Yoshinaga-Itano C, Sedey A, Coulter D, Mehl A.
Language of Early- and Later -identified Children with Hearing Loss.
Pediatrics 1998;
102(5): 1161-1171.
4.
National Deaf Children's Society. Quality standards in paediatric
audiology. London: NDCS; 1994.
5.
Hovind H, Parving A. Detection
of hearing impairment in early childhood. Scandinavian
Audiology 1987; 16:
187-193.
6.
Watkin P, Baldwin M, Laoide S. Parental
suspicion and identification of hearing impairment. Archives of Disease in
Childhood 1990; 65:
846-850.
7.
Francois M, Bonfils P, Narcy P. Screening
for neonatal and infant deafness in Europe in 1992. International Journal
of Pediatric Otorhinolaryngology 1995;
31: 175-182.
8.
Comerford D, Watson C, Khan M, Hussain S.
The Bradford and Airedale baby hearing project. An assessment of the
impact of screening on the early detection of infant hearing loss.
Clinical Otolaryngology 1995;
20: 536-539.
9.
Davis A, Bamford J, Wilson I, Ramkalawan T, Forshaw M, Wright S.
A critical review of the role of neonatal hearing screening in the
detection of childhood hearing impairment.
Health Technology Assessment 1997;
1(10).
10.
Watkin P. Neonatal
otoacoustic emission screening and the identification of deafness.
Archives of Disease in Childhood.
Fetal and Neonatal Edition 1996;
74: F16-F25.
11.
Kennedy C, 352:1957-1964. L. Controlled
trial of universal neonatal hearing screening for early identification of
permanent congenital hearing impairment. Lancet
1998; 352: 1957-1964.
12.
Scottish Executive Health Department. Neonatal Hearing Screening (letter)
HDL(2001)51: NHS; 2001.
13.
Fortnum H, Summerfield A, Marshall D, Davis A, Bamford J. Prevalence of permanent childhood hearing impairment in the
United Kingdom and implications for universal neonatal hearing screening:
questionnaire based ascertainment study. BMJ
2001; 323: 536-540.
14.
Fortnum H, Davis A. Epidemiology
of permanent childhood hearing impairment in Trent Region, 1985-1993.
British Journal of Audiology 1997;
31(6): 409-46.
15.
Billings K, Kenna M. Causes
of pediatric sensorineural hearing loss: yesterday and today. Archives of
Otolaryngology-Head and Neck Surgery 1999; 125: 517-521.
16.
O'Hare A, Green D, Grigor J. Avoidable
late diagnosis of significant sensorineural hearing loss: implications for
practice. British Journal of Audiology 1998; 32(1): 19-25.
17.
Kubba H. The detection of
childhood hearing loss in Ayrshire. Health Bulletin 1999; 57(6):
399-405.
18.
Hayes D. Newborn hearing
screening: selected experience in the United States.
Scandinavian Audiology 2001;
53 (supp): 29-32.
19.
Owen M, Webb M, Evans K. Community
based universal neonatal hearing screening by health visitors using otoacoustic
emissions. Archives of Disease in Childhood. Fetal and Neonatal Edition 2001;
84(3): F157-F162.
20.
Weichbold V, Welzl-Meuller K, Mussbacher E.
The impact of information on maternal attitudes towards universal
neonatal hearing screening. British Journal of Audiology 2001; 35(1): 59-66.
21.
Magnuson M, Hergils L. The
parents' view on hearing screening in newborns.
Feelings, thoughts and opinions on otoacoustic emissions screening.
Scandinavian Audiology 1999;
28(1): 47-56.