Aj. Oliveira et al., Duration of rhythmic EEG patterns in neonates: new evidence for clinical and prognostic significance of brief rhythmic discharges, CLIN NEU, 111(9), 2000, pp. 1646-1653
Objective: This study aimed at identifying the characteristics - especially
the duration - of rhythmic discharges in neonatal EEG, and their associati
on with clinical neonatal problems. Specifically, we aimed at testing the d
iagnostic and prognostic validity of using 10 s as minimal duration for def
ining electroencephalographic seizures.
Design and methods: The polysomnographies of 340 neonates were reviewed, an
d episodes of rhythmic discharges were identified, analyzed, and quantified
. The study sample was divided into 3 groups: one in which the maximal dura
tion of rhythmic discharges was shorter than 10 s (brief rhythmic discharge
s, BRD), a second one in which there were rhythmic discharges longer than 1
0 s (long rhythmic discharges, LRD), and finally a group in which no rhythm
ic discharge was found (No-RD). These 3 groups of subjects were compared fo
r the baseline and outcome clinical data.
Results: From the 340 neonates studied, 210 did not present any form of rhy
thmic discharge, 67 (19.7%) had only BRD episodes, and 63 (18.5%) had at le
ast one LRD episode. Prevalence of rhythmic discharges was low among health
y full term newborns, and was significantly higher among preterm and high-r
isk newborns, Electrophysiological characteristics of rhythmic discharges d
id not differ between healthy neonates and high-risk ones. Accompanying cli
nical manifestations were present in 26.3% of the LRD group, but also in 15
.9% of the BRD group. The presence of BRD was significantly associated with
leukomalacia and with hypoglycemia in the cross-sectional analysis of base
line data, and with an increased risk for abnormal neurodevelopmental outco
me after a mean follow-up period of 47 months (adjusted relative risk = 4.9
0, P < 0.01).
Conclusions: The present data demonstrate an association between BRD and cl
inical history of hypoxic-ischemic encephalopathy, especially when complica
ted by leukomalacia, and also with a prognosis of increased risk for abnorm
al neurodevelopmental outcome. The clinical and prognostic significance of
isolated BRD justifies the need to include these brief episodes in future s
tudies of neonatal seizures. (C) 2000 Elsevier Science Ireland Ltd. All rig
hts reserved.