5Congenital CMV & in-utero infections

FInfections before birth

The classic TORCH infections — toxoplasmosis, rubella, cytomegalovirus, herpes, and others such as syphilis and Zika — can cross the placenta and injure the developing cochlea. Rubella was once a major cause of congenital deafness, blindness and cardiac disease, and remains a lesson in the power of vaccination, which has made congenital rubella rare where coverage is good. In much of the world the baton has passed to CMV.

FCMV — the leading cause

Congenital cytomegalovirus is now recognised as the leading non-genetic cause of childhood sensorineural hearing loss. Most infected newborns are asymptomatic at birth, which is precisely why CMV deafness is so easily missed: there is nothing else to see. The virus damages the cochlea — the stria vascularis and the organ of Corti — and can affect the loss in one or both ears, mild to profound.[2014]

CA moving target

The systematic evidence makes one point inescapable: CMV hearing loss is often progressive and delayed in onset. A child may have normal hearing at the newborn screen and deteriorate over months or years; the loss may also fluctuate. No other common cause is so much a process rather than an event. The clinical corollary is surveillance audiology — repeated testing through early childhood for any child known to have congenital CMV — rather than a single reassuring result.

CDetection and treatment

Because the virus must be proven to be congenital rather than acquired, diagnosis depends on detecting CMV in the first two to three weeks of life (saliva or urine PCR, or retrospectively from the newborn dried blood spot). Symptomatic infants may be offered antiviral therapy (valganciclovir), which can modestly stabilise or improve hearing in some — one reason early detection matters. This sits behind the growing interest in targeted or universal newborn CMV screening discussed in the epidemiology chapter.

TWhat it means for the implant

Children with CMV-related deafness do implant well on average, but with more variability than a clean cochlear genetic loss — partly because CMV can affect neural and central structures as well, and partly because associated developmental or vestibular problems can shape rehabilitation. The practical messages are to confirm that the loss has stabilised enough to fit, to keep watching the better ear, and to counsel families that the trajectory, not just the snapshot, is what matters.