Lennox-Gastaut syndrome: a new vista.

Lennox-Gastaut syndrome (LGS) is regarded as a model of the epileptic syndrome because of its specific clinicoelectrical manifestation. However, a close investigation reveals that its outline is somewhat vague, having the borderland around it. Precise diagnosis in an individual case is not always easy. In this paper, the diagnostic criteria of LGS are described. According to these criteria, cases with LGS were subclassified into the typical and the atypical cases, and also cases in the borderland of LGS were reviewed. On the other hand, our prospective long-term follow-up study revealed that cortical mechanisms played an important role in the pathophysiology, clinical features and refractoriness of LGS. Secondary bilateral synchrony (SBS) is supposed to be a mode of expression of cortical mechanisms of LGS. A newly developed method with coherence and phase analysis demonstrated that the pathophysiology was based on SBS in 33% of the typical LGS cases. This finding is not only crucial for the choice of rational treatment including epilepsy surgery, such as callosotomy, but also contributes to a more refined subclassification of LGS.