GHENT, BELGIUM–Congenital cytomegalovirus (CMV) is the most common non-hereditary cause of hearing loss in children, according to a study by a group of medical researchers at University Hospital in Ghent. Writing in the November 1 issue of the journal Pediatrics, Julie Goderis, MD, and five colleagues said they reached that conclusion after analyzing the findings of 37 articles on CMV published since 1964, the year the condition was identified.
The virus, which is passed by a pregnant mother to the fetus through the placenta, occurs in only about 0.6% of newborns in developed countries. However, the authors found that 12.6%, about one in eight, of the babies with the condition will experience hearing loss. That represents about 10% to 20% of all cases of hearing impairment in children, the article stated.
The connection between CMV and hearing has not been fully recognized because the condition is usually asymptomatic and newborns are not regularly tested for it. As a result, these seemingly healthy children born with asymptomatic CMV are unlikely to be diagnosed; therefore if they suffer hearing loss later, the underlying cause may go unidentified.
The researchers found that among the 90% of children with CMV whose condition was asymptomatic, about one in ten developed hearing loss. Among the 10% whose CMV was accompanied by symptoms, one third became hearing impaired. CMV symptoms may include inflammation of the retina, low birth weight, rash, enlarged spleen and liver, and small head size.
MOST CASES ARE SEVERE TO PROFOUND
In both groups of babies with CMV, if hearing loss develops it is usually severe to profound, the Pediatrics study reported. However, among those whose CMV was symptomatic, most who develop hearing loss get it in both ears. On the other hand, most of the asymptomatic children develop unilateral losses. In the symptomatic group, 65% developed hearing impairment that warranted the use of amplification, while among the infants who had been asymptomatic, about 43% did.
In both groups, the hearing loss sometimes has a delayed onset, and the condition may have fluctuations and progression.
HOW TO ADDRESS CMV-RELATED HEARING LOSS
In their study, the authors concluded, “This systematic review confirms the important role of congenital CMV in childhood sensorineural hearing loss. However, because of the lack of systematic screening for congenital CMV in newborns and the characteristics of the disease, underestimation of its role in hearing loss is likely.”
They added, “Until a CMV vaccine becomes available, behavioral and educational interventions are the most effective strategy to prevent maternal CMV infection.”
In an interview with the online publication HealthDay News, Julie Goderis, the lead author, said, “Following up a child’s hearing until the age of 6 years is essential to detect delayed onset or progressive hearing loss from CMV.”