12 May 2011 Andy Coghlan
WATER-FILLED cysts in the brain of a dead baby should not be taken as proof that the infant has been shaken to death. New findings show that cysts are also found in babies known to have died of innocent causes.
If the brain is starved of oxygen - because of a breathing problem or a blood clot caused by trauma, for example - it will swell up. A study of swollen brains in 20 babies who died aged 5 months or less showed that the longer they had survived before dying, the more likely they were to develop water-filled cysts between the cerebral cortex and the inner regions of the brain.
"While these cysts may be seen as a consequence of trauma, they do not appear to be due to mechanical tissue disruption, and may occur after brain swelling from any cause," says Waney Squier at the John Radcliffe Hospital in Oxford, UK Squier's team suggests that the cysts arise because the brains of young babies have yet to fully develop the plumbing needed to drain excess fluid.
The paper is the latest to cast doubt on post-mortem evidence that has till now been taken to show that abuse has taken place. Last year, evidence emerged to challenge the use of the "triad" - the combination of brain swelling, and bleeding on the surface of the brain and at the back of the eyes - as evidence in such cases.
In January the Crown Prosecution Service in England and Wales issued new guidelines stating that the triad would no longer be sufficient to show that a dead infant had suffered "shaken baby syndrome". As well as requiring additional evidence of possible abuse before a prosecution is started, the guidelines also rename "shaken baby syndrome" as "non-accidental head injury".
"Squier has shown that sub-cortical fluid collections are not [always] the result of primary trauma to the cortex," says Julie Mack, a pathologist studying infant brain injury at Pennsylvania State Hershey Medical Center.
One prominent radiologist in the UK who preferred not to be named says he agrees that the cysts can have innocent causes. But he questions the validity of the new study, adding that he seldom sees evidence of cysts in MRI scans of living infants with swollen brains.