Viruses double cerebral palsy risk|
Jan 11, 2006
Children exposed to certain viral infections from their mothers
before, during or just after birth (during the perinatal period) have an
increased risk of developing cerebral palsy, according to research published in
the British Medical Journal.
The South Australian Cerebral Palsy Research Group examined blood samples from
1,326 newborns (443 with cerebral palsy and 883 control subjects) for the
evidence of herpes and related viruses. Testing for the nucleic acids from the
viruses, the researchers found that exposure to varicella-zoster virus (VZV),
human herpes virus 6 or human herpes virus 7 nearly doubles a child's risk of
developing cerebral palsy.
The study draws attention to the roles of herpes 6 and 7 (which are present but
dormant in the vast majority of adults), as well as the possibility that VZV
vaccination of future mothers may reduce cerebral palsy rates in their children.
The study authors hypothesize that viruses may infect the brain and cause direct
damage to neuronal tissues. In the case of herpes viruses, this could happen
after the viruses' incubation period.
Alternatively, chemicals resulting from viral infection may cause indirect
damage by kicking off inflammatory processes that damage developing white matter
and cause eventual periventricular leukomalacia (softening, dysfunction and
death of the white matter) and disruption of the endothelium and ependyma
(membrane that lines the ventricles of the brain).
Samples for the study were collected between 1986 and 1999 in South Australia,
where childhood vaccination against VZV has been available for only the last 10
years. The study suggests that there may be lower rates of cerebral palsy in
children of a vaccinated generation of mothers, similar to the remarkable drop
that occurred in the number of cases of rubella and congenital rubella syndrome
after rubella vaccine became available in 1969.
Many infants in the control group (almost 40 percent) were exposed to viral
infection but did not develop cerebral palsy, which suggests that other
co-factors or triggers are involved in order for brain damage to occur.
The study also showed significantly higher prevalence of cytomegalovirus
exposure in babies born preterm (at less than 37 weeks' gestation), suggesting
that viral infection in the womb may also be associated with preterm delivery.
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