Stage B: the ZMS is visualized as a thicker scalloped high density line with some interdigitation at Stage B. In a late Stage B, a thicker scalloped high-density line can be seen in some areas, and in other areas, two thin, parallel, scalloped, high-density lines close to each other and separated by small low-density spaces (arrow) can already be seen at superior (A) and inferior (B) portions. The parasutural bone density still is decreased [Colour figure can be viewed at wileyonlinelibrary.com]