By Penny Stern, MD
NEW YORK, Mar 02 (Reuters Health) -- Few things frighten parents of young
children as much as the seizures caused by high fevers. While most children
suffer no permanent damage from these episodes, new research suggests that
febrile seizures in childhood may increase the risk of epilepsy in adulthood.
A study conducted by Drs. Tallie Z. Baram and Ivan Soltesz of the University
of California at Irvine and colleagues, showed that prolonged febrile seizures
produced permanent changes in the brains of young rats. When the rats grew to
adulthood, they were found to be more sensitive to seizure-inducing drugs,
suggesting that these changes in the brain may lead to a higher risk of epilepsy
later in life.
"More than 90% of febrile seizures last less than 10 minutes (and) these
probably do not relate to later epilepsy," Baram told Reuters Health. But when
seizures last for more than 20 minutes, they may cause lasting changes to nerve
cells of the hippocampus, a part of the brain involved in many sensory
activities.
The brain's electrical activity can be recorded on a tracing called an
electroencephalogram (EEG). This technique is often used to localize the part of
the brain involved in a seizure by detecting unusually active or 'excitable'
areas of the brain. Previous studies have shown that the hippocampus is
frequently identified as a center of seizure activity.
Writing in the Annals of Neurology, the study authors note that rats who had
experimentally-induced seizures in infancy were found to be more sensitive to
drugs that can artificially elicit seizures in adulthood.
The research team suggests that this "reduced threshold to chemical
convulsants" signifies that brain tissue in these rats is very responsive to
stimulation, possibly as a result of the hippocampal nerve cell changes, and
that this increased "excitability... may facilitate the development of
epilepsy."
Can these results be applied to people? Baram explained that "the immature
rat is a reasonable model for seizures of the immature human (since) the
fundamental molecules and the interactions between these molecules seem to be
very similar in both rats and humans."
For parents who might be concerned about their child's seizure history,
Baram stressed that "this study involved long febrile seizures. We feel strongly
that the rare long febrile seizures may be different from the majority of these
seizures that are short."
But if a child does have a documented history of seizures lasting at least
20 minutes, Baram believes a discussion with the doctor is warranted to help
determine why such a prolonged event occurred. Imaging studies and an EEG may be
helpful in this regard, the researcher added.
"There is a lot more work that needs to be done to sort out the meaning of
our findings," Baram noted. "We hope that by pinpointing the precise changes
that occur in brain cells, we will be able to find ways to prevent them from
happening after long febrile seizures."
