Relationship between Landau-Kleffner syndrome and ESES

We describe 11 cases of Landau-Kleffner Syndrome (LKS) with an average follow-up of 9 yrs 8 mths. Polygraphic EEG recordings disclosed a bitemporal electrical status during sleep (BTESS) with persistent continuous abnormalities during N-REM and REM sleep. Four patients presented a shift from BTESS towards an ESES with overall regression of cognitive and behavioural functions in 3/4 cases. Although these two syndromes have been described separately, our patients support the hypothesis that the same brain dysfunction underlies both. The manifestation of one condition rather than the other appears correlated to the localization, generalization and duration of continuous spike-wave discharges during sleep. This hypothesis is further supported by recent findings in neurophysiology, brain imaging and neurosurgery.