Objectives: We conducted this latency study to clarify the neurophysiologic
al mechanism underlying the synchronous appearance of independent occipital
and frontopolar spike discharges in childhood epilepsies.
Methods: The subjects were 13 children with localization-related epilepsies
(LRE) who showed apparently synchronous occipital and frontopolar EEG spik
e discharges. There was idiopathic LRE in 7 children, symptomatic LRE in 4,
and cryptogenic LRE and a history of cryptogenic West syndrome in one pati
ent each. Patient ages at the time of the study ranged from 4 years 3 month
s to 14 years 0 month with a mean of 9 years 4 months. The EEGs were digiti
zed at 1024 samples/s. The latency was measured between the peak of the occ
ipital and frontopolar spike discharges. The conduction velocity was calcul
ated by dividing the distance between the occipital and frontopolar electro
des by the latencies.
Results: We studied 19 EEGs including 6 serial EEGs recorded longitudinally
in 5 patients. The number of occipito-frontal spike discharges available f
or the study ranged from 12 to 70 with an average of 36 +/- 17 in each EEG
record. Occipital spikes always preceded the frontopolar spikes by 11.1-31.
6 ms (average 19.3 +/-5.4 ms). The estimated conduction velocity ranged fro
m 6.7 to 19.2 m/s with a mean of 12.2 +/-3.7 m/s.
Conclusions: The synchronizing spike phenomenon we showed in this study was
in the posterior to anterior direction (intrahemispheric synchrony) in con
trast to that of secondary bilateral interhemispheric synchrony through the
corpus callosum. It is suggested that the long occipito-frontal associatio
n fibers play a role in synchronizing both spike discharges. This secondary
occipito-frontopolar synchrony should be one of the developmental EEG phen
omena related to the maturation of brain, and contribute to the multiplicat
ion or diffusion of the preexisting localized spike discharges often seen i
n pediatric LRE regardless of etiology. (C) 2001 Elsevier Science Ireland L
td. All rights reserved.