Congenital Cytomegalovirus Infection as a Cause of Sensorineural Hearing Loss in a Highly Immune Population

Aparecida Y. Yamamoto, MD; Marisa Marcia Mussi-Pinhata, MD; Myriam de Lima Isaac, MD; Fabiana R. Amaral, MD; Cristina G. Carvalheiro, MD; Davi C. Aragon, MSc; Alessandra K. da Silva Manfredi, MSc; Suresh B. Boppana, MD; William J. Britt, MD.

Disclosures

Pediatr Infect Dis J. 2011;30(12):1043-1046. 

In This Article

Discussion

This prospective follow-up study of children with congenital CMV infection identified by newborn screening of Brazilian infants demonstrated that congenital CMV infection is an important cause of SNHL even in this population with near universal maternal CMV seroimmunity. The frequency of hearing loss detected in our study (9.8%) is similar to that reported for populations with lower CMV seroprevalence in which the majority of congenital CMV infections was presumed to be a consequence of primary maternal CMV infections[2,6] and for populations with higher CMV seroprevalence in the developed world.[3,13,14] Thus, the findings of our study confirm that although the prevalence of congenital CMV infection may vary with underlying CMV seroprevalence rates and demographic factors, it constitutes an important cause of SNHL worldwide.

Although the type of maternal CMV infection could only be determined in 7/10 infants with CMV-related hearing loss, 6 of these children were born to mothers with nonprimary maternal infection and only one was born to a mother with primary infection. The findings of our study confirm previous evidence from populations in the United States and Northern Europe that the frequency of hearing loss is similar in congenitally infected infants irrespective of the maternal CMV serologic status prior to pregnancy.[5,6] Further, our findings demonstrate the occurrence of bilateral and severe to profound SNHL in congenitally infected children born to women with nonprimary maternal CMV infection.

Although the exact prevalence of SNHL at birth in the study population has not been delineated, available data suggest that the prevalence of hearing loss at birth in Brazilian infants (0.96 per 1000 living newborns)[15] is similar to that observed in the United States. (1.6 per 1000)[16] and Europe (0.78 per 1000).[17] Considering the 1% birth prevalence rate of congenital CMV infection in our population, the hearing impairment because of congenital CMV infection would affect at least 6 per 10,000 live births or 1800 of the 3 million Brazilian infants born annually. Even though most (4/5, 80%) of the infants with bilateral severe hearing loss had been identified due to the presence of multisystem CMV-related signs at birth, approximately half of the children (4/10) with SNHL had no detectable clinical abnormalities at birth and therefore, would not have been identified during the neonatal period if they were not screened for CMV.

A limitation of our study is that the hearing evaluation of CMV-infected children were not performed at similar ages and at least 2 ABR assessments were only performed in 85 of 121 study children with congenital CMV infection. Of the 7 study children with confirmed CMV-associated SNHL who also underwent OAE screening during the neonatal period, only one child with normal hearing during initial testing developed SNHL at a follow-up evaluation at 12 months. However, since newborn hearing screening was not in place during the first 3 years of the study, it is not possible to determine the exact time of onset of hearing impairment or document late-onset and/or progressive SNHL in some of the CMV-infected children with SNHL. In addition, 76% of the study children were followed up for at least 36 months. Therefore, we believe that our data provide reliable estimates of CMVassociated SNHL in a highly seropositive population and suggest that current strategies to prevent morbidity associated with congenital CMV infection including the development of prophylactic vaccines to prevent primary maternal infections during pregnancy may have limited efficacy in these populations.

Similar to the findings from studies conducted in populations with different CMV seroprevalence rates in the United States and Europe, the results of our study indicated that symptomatic infants were significantly more likely to develop SNHL than those with asymptomatic infection.1–3 Thus, the presence of CMVrelated symptoms at birth is a strong predictor of hearing loss, even in populations with high maternal CMV seroprevalence rate. Our findings demonstrate that congenital CMV infection is an important cause of hearing loss, including bilateral and severe to profound deficit, even in countries with transitional economies in which maternal seroimmunity is nearly universal.

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