PROBLEM TO BE SOLVED: To provide a medicament for preventing or treating lissencephaly patients.SOLUTION: The present invention provides a lissencephaly therapeutic agent comprising an α-diketone compound represented by the formula (I) [Ris a lower alkyl group substituted with a lower alkoxy or a heterocycle, a heterocyclic group, or a group represented by the formula (IIa), Ris a lower alkyl group optionally substituted with a phenyl group, and Ris H, a lower alkyl group optionally substituted with halogen or the like, or a condensed polycyclic hydrocarbon group. (Rand Rindependently represent a lower alkyl group, and m is an integer of 1-6)].SELECTED DRAWING: None【課題】滑脳症患者を予防又は治療する薬剤の提供。【解決手段】下記式（Ｉ）で表されるα－ジケトン化合物を有効成分として含有する滑脳症治療剤。〔Ｒ１は低級アルコキシ或いは複素環置換低級アルキル基、複素環基、又は式（ＩＩａ）で表される基；Ｒ２はフェニル基で置換／非置換の低級アルキル基；Ｒ３はＨ、ハロゲン等で置換／非置換の低級アルキル基又は縮合多環式炭化水素基（Ｒ４及びＲ５は各々独立に低級アルキレン基；ｍは１～６の整数）〕【選択図】なし
