Early identification of hearing loss and intervention results in a significantly better outcome for language development.7
With the implementation of the NHSP not only are more children with PHI being identified,8
the age at identification of the hearing loss has also reduced significantly.9
Looking for the cause of PHI in children can be a challenging but rewarding exercise, both for the parents and clinician.10
The yield from investigations is variable; the aetiology can remain unknown in about 40% cases,11
but as our knowledge increases this figure should decrease.10
A multidisciplinary and systematic approach increases the yield from investigations.12
The results from this study show a good awareness towards the importance of taking a detailed paediatric and family history and also carrying out a thorough examination, including developmental examination. There appeared to be major disparity between specialists in requesting family audiograms. One reason for this difference is a lack of resources in some parts of the country as indicated by comments from some of the respondents. One respondent stated that there was an ongoing negotiation and business case with the commissioners for family audiogram. Another respondent indicated that there were funding implications with family audiograms as only the patient would be paid for on payment by result (PBR). The other reason could be a lack of awareness of the importance of certain investigations such as family audiograms. Age-appropriate hearing assessment of first-degree relatives has been recommended even if there are no concerns, as unsuspected abnormalities may be uncovered and the configuration of the audiogram may also show a similar pattern among family members.2
The frequency of routinely testing for congenital cytomegalovirus (cCMV) appears to be less than optimal across all the specialist subgroups. CMV is the most common cause of congenital infections in humans13
and is a leading cause of non-hereditary SNHL.14–15
Children with both symptomatic and asymptomatic congenital CMV can develop SNHL.16
The hearing loss can be progressive or of delayed onset.16
Not diagnosing cCMV infection can have important implications as parents may not be counselled about the chance of concurrent disabilities. Another important reason for diagnosing cCMV is that early antiviral therapy has been shown to prevent onset or deterioration of hearing loss in both symptomatic17
and asymptomatic 18
cCMV infections. Therefore, routine testing for cCMV is important. The diagnosis of cCMV can also be made retrospectively from the child's dried blood spot (DBS or Guthrie card). This has been shown to be a valid and effective method, with the added advantage that diagnosis can be made after many years as the Guthrie card can be stored for long periods.19
The most common cause of genetic deafness is mutations in the Gap Junction Beta 2 gene (GJB2), located on chromosome 13q and encoding the protein Connexin 26.20–21
The 35 delG mutation is the commonest22–23
and has been reported to account for more than 80% of the GJB2 mutations in the Caucasian population.24
Homozygotes for the c.35delG mutation have been reported to have more significant hearing impairment than other genotypes.21
In this study, all audiovestibular physicians and community paediatricians and most of the paediatricians and paediatricians in audiology would offer Connexin testing routinely, but only half of ENT surgeons did so. Not diagnosing a case of genetic deafness such as GJB2 would mean that parents may not be counselled about the high risk of recurrence in future pregnancies.
The level 1 investigation which seemed to demonstrate the maximum variation according to specialty was MRI scan of Internal Auditory Meati (IAM). Whereas all audiovestibular physicians and three-quarters of paediatricians in audiology offered this routinely, only two-thirds of community paediatricians, a third of paediatricians and a fifth of ENT surgeons did so. This finding is quite different from that of Wilson et al
who found that community paediatricians requested imaging less often than ENT surgeons. Local policy and funding seems to be one of the factors influencing the decision of not offering routine imaging, especially from the community as three community paediatricians commented about the difficulty in arranging MRI scans. Decision of the individual clinician was another factor as five ENT surgeons commented that they would arrange for the MRI scan only if cochlear implantation was being considered. However, imaging has been shown to have a high diagnostic yield in the investigation of PHI in children26
and MRI is a level 1 investigation. High-resolution MRI has the added advantage of screening the central nervous system (CNS), enabling other neuro-developmental abnormalities to be detected.27
Characteristic findings on MRI can also lead to a retrospective diagnosis of congenital CMV.28
A dilated vestibular aqueduct (DVA) is the commonest abnormality noted on imaging.2
The hearing loss in DVA can be progressive or there may be sudden drops in hearing triggered by minor head trauma.29
Identification of a DVA thus enables the clinician to give parents information on prognosis and to discuss important management strategies such as avoiding contact sports which have a risk of head trauma. DVA may also be associated with thyroid disease in Pendred syndrome and parents need to be counselled about this. Therefore, the use of MRI must not be limited to cases only where cochlear implantation is being considered, but should be offered to all children with permanent severe-to-profound hearing loss.
Most of the respondents routinely referred children with PHI for an ophthalmological assessment. This finding is in contrast to the finding of Wilson et al4
that a greater need for routine ophthalmological referral was needed. This may reflect a better understanding of the role and importance of various investigations, possibly contributed to by the NHSP ‘aetiological investigations’ courses over the years. The NHSP Quality Assurance (QA) team visits to local NHSP sites would also have helped to improve the understanding of the role of the various aetiological investigations. Documents such as Quality standards in vision care for deaf children and young people (2009) published jointly by the the National Deaf Children's Society (NDCS) and Sense, add weight to the importance of checking the visual status of children with PHI.30
All audiovestibular physicians and most community paediatricians routinely requested urinalysis or urine dipsticks, but less than two-thirds of ENT surgeons did likewise. This finding was similar to that of Wilson et al
However, the importance of routine urine analysis in the investigation of PHI in the neonatal period can be debated. The average age of presentation with deafness in Alport syndrome is reported to be 11 years,31
a routine urinalysis in the neonate would not necessarily identify this condition and it would need to be repeated in mid-childhood, especially if no cause for the hearing loss has been found or if the hearing loss is progressive.
A bogus question; positron emission tomography (PET) was added to the list of investigations in the questionnaire to increase the validity of the responses. A PET scan is not listed in the investigations recommended in the national guidelines and currently does not form a part of the investigation for PHI in children. Therefore, if any of the respondents had indicated they would offer this routinely, the validity of the rest of their responses could be questioned. However, none of the 52 respondents indicated they would offer a PET scan routinely.
For the question ‘Would your answers have been the same for a child with Unilateral severe-to-profound deafness’; 59% answered ‘no’ and 41% ‘yes’. For the question ‘Would your answers have been the same for a child with mild-to-moderate degree of hearing loss’; 62% answered ‘no’ and 38% ‘yes’. There are now guidelines for investigation of unilateral and mild-to-moderate sensorineural hearing loss32
, but these guidelines are not evidence based.
One of the limitations of the study was the response rate of 52%. However, this response rate could be considered quite acceptable as often the response rate to questionnaires without personal (face to face or telephone) contact with the respondent can be as low as 20%.33
One reason for non-response could be due to the method by which the questionnaires had to be distributed. The questionnaires were sent electronically to all the clinical NHSP leads. However, the clinical lead may not be the person carrying out the investigation in all areas. Even though the covering letter accompanying the questionnaire requested the clinical lead to forward the questionnaire to the appropriate individual, this may not have happened in all cases, thereby reducing the response. Another factor could be that those who responded to the survey are the ones more likely to be carrying out the investigations as per the national guidelines and those who do not comply with the guidelines not responding. Therefore, the real proportion of families offered the full battery of level 1 investigations may be even lower than shown in this survey.
The main limitation of this study was that the MRC Hearing & Communication group, which sent out the questionnaires on behalf of the authors, could not divulge details about the number of recipients in each SHA or provide us with a breakdown of the specialty of all the recipients as they felt this would be a breach of confidentiality. It was not possible for the authors to find out this information as only the MRC Hearing & Communication group had the relevant database. The specialty of the responders was known as this was a mandatory question. Since the specialty of all the recipients was not known, it was difficult to know if any one specialty had a higher percentage of return rates than others, which might create a bias. However, since there was a fairly symmetrical mix of specialty among the responders, the chance of any bias towards any one particular specialty is unlikely. Similarly, the number of responses received from each SHA was known, but the exact number of recipients in each SHA was unknown. Therefore, it is not known if a higher percentage of recipients responded from any particular SHA. Again, as for the specialty of the recipients, since there was a good distribution of responses from the various SHAs, bias towards any particular SHA would not be likely.
This survey highlights the variations from the national guidelines for aetiological investigations of children with PHI. While in some cases this variation has been due to lack of resources, in others this seems to be due to individual choice of the clinician. It seems unlikely that unavailability of MRI scanning or genetic testing would be the only reason these are not offered in all cases. Similarly, not routinely requesting cCMV testing could be due to a lack of appreciation of the importance and implications of this, as it would be unlikely that access to cCMV testing is not available to all clinicians. Clinicians not offering the investigations according to guidelines by choice should be encouraged to change their practice so that the investigations offered for childhood PHI is standardised across the country. We also hope the findings of inequality, due to resources, between geographical regions highlighted in this study would give the clinicians a tool to argue for more funding and resources. Although, over the years the understanding of the role and importance of various investigations for deafness has increased, there is a need for further improvement.