3Congenital & perinatal causes
Congenital hearing loss — present at or near birth — is where most paediatric implantation starts, and it is the most time-pressured of all the causes, because the brain it must reach is still building its language system. About one or two newborns in a thousand are affected, and the causes divide almost evenly into the genetic and the acquired. The genetic half is the business of Chapter 6; this module surveys the rest — congenital infection, and the perinatal injuries of prematurity, oxygen lack, jaundice and sepsis — and frames the whole group by the clock it runs against.
FDeafness present from the start
Permanent hearing loss is found in roughly 1–2 of every 1000 newborns, and more among those who spent time in neonatal intensive care. It is the commonest congenital sensory disorder, and because it is present before language begins, it carries a developmental urgency that adult-onset loss does not. This is the population that universal newborn screening exists to find.
FHalf genetic, half acquired
The classic teaching — that about half of congenital sensorineural loss is genetic and half acquired — is a useful first approximation, even as newborn CMV testing and gene panels keep redrawing the line. The genetic half (syndromic and non-syndromic, the connexins, the spiral-ganglion story) is the subject of the genetics chapter. The acquired half is dominated by one infection — congenital CMV — with the perinatal injuries behind it, and a residue that stays unexplained.
FTThe perinatal risks
Several insults around the time of birth can damage the cochlea or its nerve. Prematurity and its complications, perinatal hypoxia, severe hyperbilirubinaemia (kernicterus, which has a particular affinity for the auditory brainstem and can cause auditory neuropathy), and neonatal sepsis — often with the aminoglycosides used to treat it — make up the recognised high-risk register. These are exactly the babies flagged for automated-ABR screening rather than otoacoustic emissions alone, because some of them have a neural rather than a purely sensory lesion.
CThe developmental clock
What sets the congenital causes apart is not only the lesion but the timing. A child deaf from birth has a central auditory system that has never received sound, and the sensitive period for wiring it is finite (Chapter 3). So in this group the cause is only half the story; the other half is how quickly the diagnosis is made and the implant delivered. Screening, prompt confirmation, and early implantation are the levers — and they all depend on identifying these causes early. The next two modules take the two most consequential of them in turn: meningitis, and congenital CMV.
What does the OAE-present, ABR-absent pattern suggest, and why was AABR the right screen here?
Roughly how does congenital sensorineural hearing loss divide by cause?
Why are high-risk newborns (e.g. NICU graduates) screened with automated ABR rather than OAE alone?