PARENTS who assault their children usually claim the injuries happened by
accident. Sometimes doctors can鈥檛 say for sure what really happened. But
researchers in Pittsburgh may now be on the way to identifying a biochemical
signature that can help distinguish between brain injuries caused by accidents
and those resulting from violent abuse.
The team, led by Patrick Kochanek of the University of Pittsburgh School of
Medicine, is analysing cerebrospinal fluid from children and adults. The
researchers are comparing fluid drained from patients with severe head trauma to
relieve a build-up of pressure with fluid from patients given spinal taps for
other reasons.
Some of the children studied had been injured by adults who admitted abusing
them. Preliminary evidence suggests that victims of abuse usually have a 鈥渨hole
host of biochemical derangements in the brain鈥�, says Kochanek. His team has
studied a range of biochemicals, including amino acids, immune system signalling
molecules called cytokines, and quinolinic acid, produced by immune cells that
slowly infiltrate the brain after an injury.
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鈥淲ith any metabolite that we look at, seven times out of 10 we see really
high levels in victims of child abuse,鈥� says Kochanek. 鈥淚 think it really is a
reflection of how severely these infants are injured.鈥�
High levels of quinolinic acid may be the closest thing so far to a 鈥渕arker鈥�
of child abuse, says Kochanek. Adults who assault children usually don鈥檛 take
them straight to hospital鈥攊nstead, they show up later with a story about
how the child was injured in a fall, or some other 鈥渁ccident鈥�. Because
quinolinic acid accumulates slowly in the brain, its presence may reveal whether
a parent is lying about the timing of the injury. High levels might also
indicate prior injuries, signalling a history of abuse.
Kochanek and his colleagues could find no trace of quinolinic acid in
cerebrospinal fluid taken from 39 adults with head injuries who went to hospital
within 24 hours of being injured. But in a study to be published early next year
in the Journal of Critical Care Medicine, conducted with Melvyn Heyes
of the National Institute of Mental Health near Washington DC, they say that two
out of 17 children with head injuries had high levels of quinolinic acid. Both
children had been abused. A third abused child in the sample did not have
elevated levels of quinolinic acid. Kochanek is now expanding the study. 鈥淲e
need to study more patients to determine if this preliminary finding holds up or
not,鈥� he says.
The team has also found that the cerebrospinal fluid of babies who have been
shaken violently contains particularly high levels of the amino acid
glutamate鈥攚hich causes further damage to neurons in injured brains.
Randall Alexander, former vice-chair of the US Advisory Board on Child Abuse and
Neglect and a paediatrician at the Morehouse School of Medicine in Atlanta, says
that this is further evidence that victims of shaken baby syndrome can suffer
more widespread damage than those who receive blows to the head.
Kochanek warns that levels of a single biochemical are unlikely ever to give
a definitive diagnosis of whether or not a child has been abused. But analysed
together with other evidence, such as X-rays, he believes biochemistry could
become an important tool for doctors investigating suspicions of abuse.