A common cause of childhood hearing loss
Cytomegalovirus (pronounced sy-toe-MEG-a-low-vy-rus), or CMV, is a common virus that infects people of all ages. In the United States, nearly one in three children are already infected with CMV by age 5 years.
Over half of adults by age 40 have been infected with CMV. Once CMV is in a person’s body, it stays there for life and can reactivate. A person can also be reinfected with a different strain (variety) of the virus.
Most people infected with CMV show no signs or symptoms. That’s because a healthy person’s immune system usually keeps the virus from causing illness. However, CMV infection can cause serious health problems for people with weakened immune systems, as well as babies infected with the virus before they are born.
CMV can be transmitted by the mother during pregnancy (congenital CMV) or via breastmilk and from direct contact via saliva or urine. Since most people are unaware that they have symptoms, most mother’s who pass on the virus have no reason to think that there will be any issues. Simple tests can be used to diagnose CMV infections in people who have symptoms.
Hearing Loss typical of CMV
Identification of CMV as the cause of hearing loss. Ideally, the saliva or urine of all babies would be tested to identify the CMV virus in the first 2 weeks of life. The CMV virus cannot be determined as the cause of hearing loss after 3 weeks by a simple urine test. After this early period the only way to identify CMV as the cause of hearing loss is to detect the DNA of the CMV virus in dried blood samples from the first 3 weeks of life or the dried umbilical cord.
Potential treatment of CMV. Small studies have shown that treatment of infants with congenital CMV infection with antiviral drugs such as valganciclovir can prevent progression or development of hearing loss, and in some cases can even reverse existing hearing loss. Larger studies are currently ongoing to confirm this effect, which is extremely promising as the first known treatment for congenital sensorineural hearing loss in these selected cases (source).
Degree of hearing loss. Congenital CMV (both symptomatic and non-symptomatic) is the most common and accounts for around 1/3 of all hearing loss in children. Hearing loss associated with CMV may be both late onset and progressive within the first years of life. So 90% of children with hearing loss caused by CMV will be asymptomatic and likely to pass hearing screening. If a child is identified as having a late-onset hearing loss it is likely that it is due either to CMV or genetics and either of these causes can result in hearing loss that progresses over time.
It is usually difficult to identify newborns with CMV
Asymptomatic at Birth
At birth, 90% of babies born with congenital CMV will present as asymptomatic, showing no obvious and visible symptoms of the virus. These children are expected to live healthy lives, typically following standard growth and development patterns. Your child may experience minor challenges as he or she develops, so if you are concerned about a mental, behavioral, or physical developmental issue, please consult your child’s pediatrician.
Most commonly, approximately 10-15% of asymptomatic babies may experience hearing loss, which can occur at birth or later in life. These children should be closely monitored, even if they pass the newborn hearing screen in the hospital. Hearing loss for asymptomatic children will usually begin in one ear, and then may progress to severe or profound hearing loss in one or both ears.
Sometimes, hearing loss can progress over months to several years, throughout childhood, adolescence, and even into young adulthood. Because of this, regular and ongoing audiology screening with a pediatric specialist is recommended to closely monitor hearing loss.
The cognitive outcome, or intelligence and ability to learn, of children born with asymptomatic congenital CMV is typically within normal ranges for the majority of children.
Babies with CMV symptoms at birth – more challenges
Symptomatic at Birth
Ten percent (10%) of babies born with congenital CMV will be symptomatic at birth and may exhibit visible symptoms, such as small size for gestational age, jaundice or yellow color of the skin, a “blueberry muffin” skin rash called petechiae/purpira, and/or an enlarged liver or spleen. These babies may also have a small head size (microcephaly) and may have problems with their blood cell counts and low platelets.
Approximately 75% of these babies will have signs of brain involvement and may experience major challenges as they grow, including problems with hearing, vision, nutrition, growth, cognition, learning, and motor/muscle tone.
It is best to not make any assumptions, but rather be prepared. Each child is unique.
Hearing problems occur in up to 75% of babies with symptomatic congenital CMV. In almost all of these children, the hearing loss will progress throughout the course of their lives. Therefore, hearing evaluations should be performed on a regular basis throughout their lives to detect hearing loss and its progression, and regular speech and language therapy should be a part of a child’s ongoing curriculum.
A child born with symptomatic congenital CMV, specifically with microcephaly and moderate-to-severe brain calcifications, is very likely to have cognition issues. However, this child will be able to learn according to his or her own timeline, so utilizing available educational resources and understanding how to alter your approach to teaching will help provide meaningful assistance to both you and your child.
A child with a normal head size at birth and little or only mild brain involvement is very likely to have a normal or near normal ability to learn at the pace of his or her peers.
Posted July 2016. Our thanks to the National CMV Foundation as the source of most of the information.