The early background EEG pattern among neonates whose
hypoxic-ischemic encephalopathy (HIE) is treated with therapeutic hypothermia
(TH) can help guide how long children need to be monitored with continuous EEG,
according to findings presented here at the annual meeting of the Child
Neurology Society.
Researchers said the findings point to the potential to
greatly shorten the period in which children are monitored at some centers and
could help save resources.
Many centers—including the University of Michigan, where the
study was conducted—provide continuous EEG monitoring throughout the cooling
period of 72 hours and through the re-warming period, for a total of about 84
hours. But many children, according to the retrospective cohort study of 114 neonates,
had no seizures and, if they did, most had seizure onset within the first 24
hours of monitoring, said Giulia Benedetti, MD, assistant professor of
neurology at Seattle Children's Hospital, who worked on the study while at the
University of Michigan.
The study included 114 consecutive neonates who were at
least 36 weeks of gestational age and were treated with TH for suspected
moderate or severe neonatal HIE. Investigators who were blinded to the
children's clinical course reviewed archived clips from the first 24 hours of
continuous EEG, and this background was classified as normal or mildly
abnormal, moderately abnormal, or markedly abnormal based on an assessment of
continuity, amplitude, symmetry, synchrony, epileptiform abnormalities, among
other measures.
Seizures were more common among those children with markedly
abnormal background EEG: 78 percent had seizures compared with 41 percent among
those with moderately abnormal backgrounds and 33 percent with normal or mildly
abnormal background EEG (p< .001).
Sixty-seven percent of children with normal or mildly
abnormal EEG backgrounds did not have seizures at all, and for the 33 percent
who did, seizure onset occurred within the first 24 hours of EEG monitoring.
Only 3.5 percent had seizure onset within 24 to 48 hours,
and they all had markedly abnormal early continuous EEG backgrounds.
In three cases, seizure onset came after more than 72 hours.
Dr. Benedetti noted that two of these cases were not typical HIE: one child had
a markedly abnormal background and was ultimately diagnosed with Ohtahara
syndrome—early infantile epileptic encephalopathy—and died from uncontrolled
seizures; another had a likely genetic metabolic disorder and died from
multisystem organ failure, she said. The third was a more typical case, but
after re-warming the child had a cluster of seizures, and at six-month
follow-up was developing normally.
The message from those cases, Dr. Benedetti said, is that
"if the background is moderately or more severely abnormal, then the [children]
are still at risk for the late-onset seizures."
Those in whom seizures began after 72 hours gave telltale
signs, she noted. "They all had some kind of clinical correlate at some
point with their seizures—like an arm jerk that went along with their
seizures," she said.
Dr. Benedetti proposed a tailored approach to the duration
of EEG monitoring based on the initial EEG background. If an infant has a
normal or mildly abnormal early background and no seizures at 24 hours, that
baby can be disconnected from monitoring. Alternatively, if a baby has a moderately
or markedly abnormal early background, they should be monitored through cooling
and re-warming.
"Continuous EEG monitoring through cooling and
re-warming takes a lot of time and uses a significant amount of
resources," Dr. Benedetti said. "These data suggest that if, at the
24-hour mark, a baby has a mildly abnormal background and no seizures, it is
quite safe to disconnect and there is a very low risk of missing late-onset
seizures."
Commenting on the study, Patricia K. Crumrine, MD, FAAN, a
pediatric neurologist and professor of pediatrics at the Children's Hospital of
Pittsburgh, said that the findings make a persuasive case for using continuous
EEG monitoring more sparingly, even if a larger sample size would be better for
more completely assessing the safety of discontinuing monitoring after 24 hours
for some patients.
She said the findings are strong because of the many
parameters that were considered.
"They're talking not only of background, but the
synchrony between the two hemispheres, the symmetry between the two
hemispheres, and the fact that there aren't EEG seizure discharges that you're
seeing (during interictal periods)."
She said infants are monitored through re-warming at her
center, but that it might be reasonable to re-think that approach in some
cases.
https://journals.lww.com/neurotodayonline/blog/NeurologyTodayConferenceReportersCNSAnnualMeeting/pages/post.aspx?PostID=31
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