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February 4, 1999


Toxic levels of neurochemical found in shaken baby syndrome

In a study with implications for the diagnosis and treatment of child abuse, researchers from UPMC Health System's Safar Resuscitation Research Center report that children and infants who have suffered head injury have toxic levels of the neurochemical glutamate.

The findings also show that victims of shaken baby syndrome have extremely high levels of glutamate. Glutamate is both an essential part of normal brain chemistry and, in high levels, an important part of the chemical cascade by which brain cells die.

"This study is the first to document high levels of glutamate in children who have suffered head injury," said Patrick M. Kochanek, associate professor of anesthesiology and critical care medicine and director, Safar Center for Resuscitation Research. "Ou r findings suggest directions for future research, including learning about the effects of glutamate on the developing brain in children and finding ways to block the injurious effect of toxic levels of glutamate and other neuro-chemicals and thus limit d amage from traumatic brain injury, particularly among child abuse victims. In addition, this research suggests the possibility that specific biochemical markers in brain fluid may aid in the diagnosis of child abuse or shaken baby syndrome." Head injury is the most common cause of childhood death and disability in the United States. Brain injury occurs in two stages. Initial or primary damage results from the direct impact of the trauma. Secondary damage occurs as brain tissue around the impa ct site swells, pressure inside the skull rises and a variety of chemical imbalances occur.

Child abuse is an important public health problem in the United States, with more than three million cases of child abuse or neglect reported in 1997. More than one million of these cases, or 15 out of every 1,000 children, were confirmed.

The study examined 37 patients treated at Children's Hospital. The study group consisted of 18 children who had sustained severe traumatic brain injury. The normal comparison group consisted of 19 children who had undergone a spinal tap to rule out the di agnosis of meningitis.

All of the children in the study group had drainage tubes placed as part of their care to allow physicians to monitor the pressure inside the skull and to remove fluid in and around the brain.

High pressure within the skull, which can cause secondary injury to the brain by restricting blood flow, can be relieved in part by draining fluid. The drained fluid was then analyzed for neurochemicals, such as glutamate, aspartate and glycine, which can cause nerve cell injury. While all children with traumatic brain injury had toxic levels of neurochemicals, very young children and shaken-baby patients had extremely high levels of glutamate.

Researchers hypothesize that in shaken baby syndrome both direct impact injury and the violent force of shaking injure the brain. The shaking causes brain tissues and blood vessels of infants to tear. Often, the entire brain is affected by the shaking. In addition, there is often delay in seeking medical attention.

The higher glutamate levels seen in younger patients than in older children or adults may also reflect, in part, an immature response to injury of an infant's developing brain. Previous research has shown that the effects of glutamate on immature brain ce lls change as those cells age. Understanding these differences is critical for the development of effective treatments to limit or prevent secondary brain damage caused by glutamate.

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