Agenesis of the Perisylvian Region (Temporal Lobe Agenesis): Neurologic Symptoms and Therapy

The first signs of sylvian depression in embryogenesis may be detected at the end of the 2nd intrauterine month and become more apparent as a sylvian groove at the end of the 3rd month. The temporal operculum grows more effectively in the anterior two-thirds and reaches the sylvian fissure in the 4th month. At the same time, the frontoparietal operculum becomes evident and gradually extends backward to meet the anterior part of the temporal operculum. These changes occur in the later half of the 5th month (2). As the growth energy of the temporal operculum is more intense than that of the frontoparietal, it follows that, when the opercula meet in the 6th intrauterine month, there is more of the sylvian area covered by the temporal than by the frontoparietal operculum.