Congenital Hearing Loss
Many people would be surprised to learn that the most common cause of congenital sensorineural hearing loss in the United States is a virus called cytomegalovirus, or CMV (Jenson, H.B., 2009). CMV is a very common infection that doesn’t usually cause problems for the majority of the population. When CMV is contracted after birth, it usually only causes mild flu-like symptoms unless a person is immunocompromised. On the other hand, CMV can cause serious and sometimes life threatening complications in an unborn baby. If a woman contracts CMV for the first time while pregnant, or a pre-existing infection reactivates during pregnancy, her baby can become infected. The most common complication from congenital CMV is hearing loss. Hearing loss from CMV can sometimes be late in onset, fluctuating, improving, and/or progressive (Foulon, I., Naessens, A., Foulon, W., Casteels, A., Gordts, F., 2008) which can make the hearing loss difficult to diagnose and manage.
About one in 150 babies in the United States is born with a congenital CMV infection (March of Dimes, 2009). Of those, about 8,000 babies develop lasting complications from the infection each year (March of Dimes, 2009). Most babies born with CMV do not have symptoms at birth and the majority of babies born without symptoms do not develop any long term complications from the infection. However, babies born with CMV who are asymptomatic at birth still have about a 10-15 percent chance of having complications from the virus (March of Dimes, 2009). The most common complication is hearing loss, which can sometimes be late in onset and therefore may not be diagnosed promptly. It has been estimated that 7-15 percent of newborns born without symptoms of CMV but who are infected, have sensorineural hearing loss caused by CMV (Choi, K.Y., et al., 2009).
On the contrary, infected babies who are born with symptoms of CMV have a much greater chance than those without symptoms of developing serious consequences. Up to 20 percent of babies born with symptomatic CMV die from the infection. Additionally, about 80-90 percent of surviving babies born with symptoms of CMV at birth develop lasting complications such as cognitive delay, cerebral palsy, seizures, vision loss, and hearing loss (March of Dimes, 2009). Sensorineural hearing loss occurs in 35-65 percent of symptomatic newborns infected with CMV (Choi, K.Y., et al., 2009).
CMV is spread through blood and body fluids including urine, saliva, breast milk, blood, tears, semen, and vaginal fluids (Centers for Disease Control and Prevention, 2008). Young children are more likely to have CMV in their urine, saliva, and nasal secretions from a recent primary infection. Many babies and children contract CMV at daycare or from other playmates (Adler, S.P., 2005). Although not harmful to the child, it can be a risk for a pregnant woman who has contact with that child. Therefore it’s especially important for pregnant women to avoid sharing utensils, food, and drinks with young children/babies, avoid kissing babies or children on the lips, and practice good hand hygiene after changing diapers or after touching nasal secretions or saliva to help avoid contracting a primary infection during pregnancy.
It is not yet routine for newborns to be tested for CMV at birth unless obvious symptoms are present. Sometimes symptoms are present but are subtle or falsely attributed to something else. There is evidence to show that routine testing of newborns or at the very least newborns who fail their newborn hearing screen would prove to be useful (Choi, K.Y., et al., 2009). This testing could be performed with the blood spot testing that is already routinely done at birth. Early identification of babies who are infected with CMV would help ensure that these babies are followed closely and tested routinely for hearing loss (Adler, S.P., 2005) and other potential issues. The primary reason why testing for CMV is not standard practice is the cost. It is costly to add additional tests to the newborn screen. At this time treatment with antiviral therapy such as ganciclovir or valganciclovir is only recommended for newborns born with symptomatic CMV. Antiviral therapy can help reduce the severity of long term sequelae; however, the risk of severe side effects precludes it from being used for all babies born with CMV.
Our daughter, Amelia (21 months now), was the first person that we know of in our family to be born hard of hearing. We began to suspect CMV as a cause of her hearing loss when her hearing loss worsened at six months of age and we had already ruled out the most common genetic cause. That is when we found out the statistics regarding CMV and discovered that it was the most common cause of congenital sensorineural hearing loss. As a health care provider working with newborns, I was at a higher risk for contracting CMV. It is a real possibility that I contracted it during pregnancy or that I was already infected and had a reactivation of the infection while pregnant.
We had Amelia tested for CMV at six months of age and she tested positive and was shown to have long term immunity, not recent infection. However, we’ll never know for certain if she contracted it in utero or after birth since she wasn’t tested in the newborn period. Despite this unknown, we chose to have her treated with the antiviral drug valganciclovir and thankfully she was able to complete the course of therapy. Her hearing loss over the past year has either improved or she is testing better. Either way, the audiologist has been able to turn down her hearing aid amplification on two occasions due to how well she is hearing in the sound booth during behavioral testing.
I still remember the anguish we felt after the initial diagnosis and then again at six months of age when we prepared for the possibility that Amelia’s hearing loss would continue to get worse. However, as we realized how little control we had, we learned to accept our lack of control. She has never ceased to impress us with her ability to learn. Just today, I was reminded of that as I listened to her enthusiastically singing her rendition of “Twinkle Twinkle Little Star”, “The Wheels on the Bus”, and the “ABC Song” in the car. My hope is that we’ll be able to help convince states to include CMV testing in the newborn screening panel. Despite the argument that the benefit is not worth the cost, this is hard to believe considering how beneficial early diagnosis would be for many babies born with CMV. More importantly, we hope that more people will learn about CMV and how to prevent primary infections during pregnancy.
Adler, S. P. (2005). Congenital cytomegalovirus screening. Pediatric Infectious Disease Journal, 24(12), 1105-1106.
Centers for Disease Control and Prevention (2008). Frequently asked questions about CMV. Retrieved March 6, 2010, from http://www.cdc.gov/cmv/overview.html
Choi, K. Y., Schimmenti, L. A., Jurek, A. M., Sharon, B., Daly, K., Khan, D., McCann, M., Schleiss, M. R. (2009). Detection of cytomegalovirus DNA in dried blood spots of Minnesota infants who do not pass newborn hearing screening. Pediatric Infectious Disease Journal, 28(12), 1095-1098.
Foulon, I., Naessens, A., Foulon, W., Casteels, A., Gordts, F. (2008). A 10-year prospective study of sensorineural hearing loss in children with congenital cytomegalovirus infection. The Journal of Pediatrics, July 2008, 84-88.
Jenson, H. B. (2009). Hearing loss and congenital cytomegalovirus infection. Internal Medicine Alert.
March of Dimes (2009). Cytomegalovirus infection in pregnancy. Retrieved January 30, 2010, from http://www.marchofdimes.com/professionals/14332_1195.asp