Congenital cytomegalovirus (CMV) infection and hearing deficit

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Abstract

Background

The association between congenital cytomegalovirus (CMV) infection and sensorineural hearing loss (SNHL) was first described in 1964. Studies over the past four decades have further described the relationship between congenital CMV infection and SNHL in children.

Objectives

This manuscript will review the current knowledge of CMV-related SNHL and summarize the studies completed at the University of Alabama at Birmingham (UAB).

Study Design

A review of the series of studies at UAB that has led to a more detailed characterization of hearing loss due to congenital CMV infection.

Results

Approximately, 22%–65% of symptomatic and 6%–23% of asymptomatic children will have hearing loss following congenital CMV infection. CMV-related SNHL may be present at birth or occur later in childhood. Variability in the severity of CMV-related hearing loss ranges from unilateral high frequency losses to profound bilateral losses.

Conclusions

Congenital CMV infection significantly contributes to SNHL in many infant populations. Although, most children with congenital CMV infection do not develop hearing loss, it is difficult to predict which children with congenital CMV infection will develop hearing loss and, among those who do develop loss, whether or not the loss will continue to deteriorate.

Introduction

The association between congenital cytomegalovirus (CMV) infection and sensorineural hearing loss (SNHL) has been known for over four decades, although the mechanism by which the virus causes hearing impairment in some children and not others is still not fully understood today. The association of SNHL in children with symptomatic congenital CMV infection was first described by Medearis in 1964 where over 40% (2/5) of the surviving infants with cytomegaiic inclusion disease (CID) were found to be deaf (Medearis, 1964). Another study by McCracken et al. (1969) described 13 surviving infants with CID of which four (31%) had hearing loss diagnosed after the first year of life (McCracken et al., 1969). In the 1970s other investigators begin to describe SNHL in children following inapparent or asymptomatic congenital CMV infection (Dahle et al., 1974, Hanshaw et al., 1976, Reynolds et al., 1974, Stagno et al., 1977). In the 1970s and 1980s, further investigations continued to describe the characteristics of SNHL in children following congenital CMV infection, as to whether the nature of the loss was progressive, symmetric or delayed until after the newborn period (Dahle et al., 1979, Pass et al., 1980, Williamson et al., 1982). Population based studies began in the 1970s and 1980s also describing the hearing loss in children with congenital CMV infection who had been followed longitudinally over time in different populations as seen in Table 1 (Ahlfors et al., 1984, Dahle et al., 2000, Kumar et al., 1984, Numazaki and Fujikawa, 2004, Preece et al., 1984, Saigal et al., 1982, Williamson et al., 1982, Williamson et al., 1992). Although these studies occurred in differing populations, the rates and variability of SNHL were remarkably similar.

In summary these investigations indicate that children with symptomatic congenital CMV infection are at greater risk for hearing impairment than those with asymptomatic infection; with 22%–65% of children with symptomatic infection having subsequent SNHL compared to only 6%–23% of the children with asymptomatic infection. Also, hearing loss following congenital CMV infection may be present at birth or occur later in the first years of life. Furthermore, SNHL following congenital CMV infection does not have a pathognomonic audiometric configuration and is variable in the severity of loss with both unilateral and bilateral hearing losses occurring in children with congenital CMV infection. Progression (audiometric threshold  10 dB deterioration) and fluctuation of hearing loss may also occur in children with congenital CMV infection.

In the 1990s and 2000s a series of studies at the University of Alabama at Birmingham (UAB) have further characterized hearing loss due to congenital CMV infection and will be described below.

Section snippets

The UAB cohort-characteristics of CMV-related hearing loss

A cohort of 860 children with congenital CMV infection who were born between 1966 and 1999 has been followed in a longitudinal study at UAB to describe the characteristics of CMV-related hearing loss in children (Dahle et al., 2000). Children were identified either by referral (37%) or as part of routine newborn CMV screening at two hospitals in Birmingham (63%). All infections were confirmed by isolation of virus in urine or saliva in our laboratories. Infected children were followed in a

Timing of hearing loss due to CMV

Since risk criteria-based hearing screening missed infants with congenital CMV infection, we evaluated whether universal hearing screening would be more successful in identifying most of the CMV-related SNHL (Fowler et al., 1999). A cohort of 388 children with congenital CMV infection born between 1980 and 1996 was enrolled in a follow-up program and received repeated hearing evaluations to assess whether hearing loss had occurred. The study population was 86.9% black and 51.6% were the

Possible risk factors for hearing loss due to CMV

Although some children with mild unilateral high frequency hearing loss will eventually progress to bilateral severe or profound hearing loss, other children with SNHL due to congenital CMV infection will have stable loss. Since most children with congenital CMV infection do not develop hearing loss, it is difficult to predict which children with congenital CMV infection will develop hearing loss and, among those who do develop loss, whether or not the loss will continue to deteriorate.

In the

Impact of universal newborn hearing screening on detection of hearing loss due to CMV

Previous work (Hicks et al., 1993) has established that risk criteria-based neonatal auditory screening was not successful in identifying SNHL due to congenital CMV infection (Hicks et al., 1993). In fact between 1985 and 1998, at which time risk criteria-based auditory screening was employed at UAB, only 17.6% of the children with SNHL due to congenital CMV infection were identified by this screening method (Table 3). Most children with congenital CMV infection (81%) did not receive a hearing

Relative contribution of CMV to childhood hearing loss

Only one report, a study from Malmö, Sweden, has estimated the relative contribution of congenital CMV infection to bilateral profound SNHL in a newborn population (Harris et al., 1984). Harris et al. (1984) combined data from their retrospective and prospective studies, identifying 10 (0.08%) children out of 12,000 children with profound bilateral SNHL; four due to congenital CMV infection, four due to hereditary or syndromic causes, and two with uncertain or unknown etiology. Other studies

Conclusion

Congenital CMV infection significantly contributes to SNHL in many infant populations. Based on previous studies, 22%–65% of symptomatic children and 6%–23% of asymptomatic children will have hearing loss following congenital CMV infection. Also, symptomatic children are more likely to have bilateral hearing losses and less likely to have high frequency (4000–8000 Hz) or fluctuating losses compared to asymptomatic children. However, in both groups of infected children, over 55% of the children

Acknowledgements

This work was supported in part by grants from the National Institute of Child Health and Human Development (P01 HD10699), the National Institute on Deafness and Communication Disorders (R01 DC02139, K08 DC00079, R01 DC04163), the National Institute of Allergy and Infectious Diseases (P01 AI43681) and the UAB General Clinical Research Center (M01 RR00032).

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