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Hearing Loss
Cytomegalovirus-related hearing loss is one of the leading causes of hearing and speech deficits, accounting for about one-third of hearing loss in newborns and immunocompromised adults. This rare virus is part of the Herpesviridae family and can be linked to a number of other severe symptoms, as well. Most commonly, the hearing deficiency is sensorineural hearing loss. Studies done examining CMV- related hearing loss in various populations has shown that newborns infected with symptomatic CMV are more at risk than those with asymptomatic CMV. While asymptomatic CMV is dangerous because it often goes undiagnosed, symptomatic CMV seems to pose a greater threat to patients. Hearing loss due to congenital CMV will likely be seen between birth and the end of the child’s first year. Many studies are available to researchers providing evidence for the link between CMV and hearing loss. The mechanism for exactly how CMV causes hearing loss is still unknown, especially since only some groups of children infected with the virus still develop hearing loss.

Clinical Evidence for CMV-Related Hearing Loss
The DECIBEL study, which observed a randomized group of children with permanent childhood hearing loss, was performed last year in the Netherlands. The study was composed of 179 children with varying degrees of CMV-related hearing loss. Children were screened using a three-step testing procedure to determine the etiology of hearing loss. Researchers also used dried DNA blood spots in CMV analysis and determined a strong correlation between congenital CMV and childhood hearing loss ; twenty three percent of participants’ hearing loss was directly caused by CMV A Swedish study in Malmo also used DNA from dried blood spots of infected newborns to determine that the rate of CMV-related hearing loss is twice the rate of hearing loss attributed to other factors, such as meningitis or pre–H influenzae The Meyer Center for Pediatrics found that CMV directly causes the deterioration of important cells in the inner ear of CMV patients. Because it’s a herpes virus, it’s also prone to long periods of dormancy, linked to some patients’ notable variation in hearing ability. Central nervous system damage is also a possible effect of CMV, however more evidence is needed.

Pathophysiology of the Virus
The Guinea Pig Study has provided the most accurate conclusions as to the pathophysiology of CMV. While most of the research done with CMV and guinea pigs has concentrated on potential treatment and vaccines, the pathophysiology of this phenomenon has also been explored. As in humans, the CMV virus, after being injected into a pregnant guinea pig, has the ability to infiltrate the placenta and infect a fetus. In this particular study, four groups of guinea pigs were given varying doses of the CMV virus. Progressive hearing loss and localized inflammation in the inner ear was seen in pigs that were infected with the highest dosages of the disease. However, no inflammation was seen in the brain. Based on DNA analysis and further research, this study demonstrates the possibility that, as human CMV manifests, it passes rapidly into the inner ear and infects the auditory nerve. In the pigs infected with the highest dosage of the virus, temporal bone involvement was witnessed with hearing loss. Other animal models have shown that both inflammatory and cytopathic responses to CMV within the inner ear play a role in the acquisition of permanent childhood hearing loss. The American Academy of Pediatrics observed brain calcifications in infants with asymptomatic congenital hearing loss, and normal cat scans in infants that do not. However, a definitive cause of hearing loss is still unknown.

Treatment Mechanisms
Newborn Hearing Screening helps many pediatricians identify the virus early on and consider possible treatment mechanisms for varying degrees of hearing loss. Thirty states require that all newborns receive a hearing test prior to discharge, while seventeen states require that all health insurance providers pay for requested screens. In Flanders, Belgium, studies have shown that infants born with hearing impairment due to congenital CMV are less likely to exhibit significant improvement than those detected prior to birth. While the cause isn’t entirely understood, some treatment plans have been set up. Based on a study done at John’s Hopkins University, the majority of children observed with CMV-related deafness had improved speech and auditory perception scores following cochlear implantation. As of yet, some antiviral medications like ganciclovir and cidofovir have been successful treatments for children with permanent CMV-related hearing loss by inhibiting replication of the virus. Due to temperature sensitivity upon release into the ear, the antiviral gels could be potentially modified to break down more quickly or remain dormant in the ear. An experimental treatment setup is also in effect for 2012, which may provide some more real insight as to the pathophysiology of this illness. The goal of this trial is to attempt to protect infected children’s hearing with more advanced antiviral medications.