Babies Who Can't Hear
The last few years have brought an increasing awareness of the burden caused by unrecognized congenital cytomegalovirus (CMV) infection. CMV is the leading cause of congenital infection in industrialized countries and has been estimated to cause as much as 15%-20% of moderate to profound sensorineural hearing loss (SNHL) in infants. In fact, a study from Australia published earlier this year confirmed that, even in this era of newborn hearing screening, congenital CMV continues to be underdiagnosed and infrequently treated with more than half of infected children missed by screening. This national surveillance study concluded that the overwhelming majority of infected infants, only a fraction of whom are symptomatic, are not recognized. Only a minority, 8%, of infected infants received antiviral therapy despite the fact that 13.5% of the asymptomatic group will develop permanent sequelae. These authors recommend more vigilant screening -- but how? A study from France examined the utility of routine newborn screening for congenital CMV by applying real-time polymerase chain reaction (PCR) assays to dried blood spots (DBS) that are collected from all newborns to screen for genetic and metabolic diseases. In a population of high-risk infants, PCR assays were found to have sensitivity of 95.0%-100% and specificity of 98.1%-99.0%. The authors note, however, that the positive predictive value of 94.1%-96.9% cannot be transposed to a general population of infants in whom the prevalence of congenital CMV is much lower. Robert Pass, MD, a Professor of Pediatrics and Microbiology at the University of Alabama in Birmingham who has studied congenital CMV infection for over 25 years emphasized that fact in an accompanying editorial. Dr. Pass noted that the results of the French study indicate that 3 or 4 uninfected newborns would screen positive for every true positive. Additionally it would not distinguish between infants with viremia who will have no sequelae and the 10%-15% who will develop hearing loss. Another caveat is it is uncertain if treatment with antiviral agents will prevent hearing loss in this undetected group. For now, pediatric clinicians must recognize that congenital viremia continues to pose a risk to infants and routine newborn hearing screening may often miss these infants in whom hearing loss may be delayed in onset or progressive.
Other key points:
Any newborn who tests positive for congenital CMV infection on a DBS or other screening test must have a urine tested for CMV before 3 weeks of age to confirm the diagnosis. Infants with known congenital CMV need repeated hearing testing in the first 2 years of life, the period when hearing loss is most likely to occur and also the age when language development is critical.
Most features of congenital CMV are evident within the first 60 days of life though in the Australian study, one quarter of cases of congenital CMV were diagnosed after this window and neurodevelopmental problems and SNHL were common in this group.
Ganciclovir has been demonstrated to decrease SNHL in symptomatic infants when initiated prior to 30 days of age but intravenous therapy is difficult. A clinical trial comparing this therapy with a longer course of oral valganciclovir is underway that may help determine if this easier-to-administer therapy is as effective.
Whether antiviral treatment of asymptomatic infants will decrease the likelihood of hearing loss or other sequelae is not yet known and routine treatment of asymptomatic infants is not recommended at this time.
Why Is This a Game Changer?
Newborn hearing screening will not reliably detect babies with congenital CMV infection who will have hearing loss. All infants who fail their newborn hearing screen should be tested for congenital CMV infection because infants with congenital CMV infection need to be followed closely for progressive hearing loss. Universal screening for congenital CMV infection may be coming, but it will be years in the future; until then primary care providers need to heighten their vigilance.
Medscape Pediatrics © 2011 WebMD, LLC
Cite this: Laurie E. Scudder. Game Changers in Pediatrics 2011 - Medscape - Nov 23, 2011.