The posterior (back) portion of the corpus callosum is called the splenium; the anterior (front) is called the genu (or “knee”); between the two is the truncus, or “body”, of the corpus callosum. The part between the body and the splenium is often markedly narrowed and thus referred to as the “isthmus”. The rostrum is the part of the corpus callosum that projects posteriorly and inferiorly from the anteriormost genu, as can be seen on the sagittal image of the brain displayed on the right. The rostrum is so named for its resemblance to a bird's beak.

The corpus callosum substructure region has extensive damage in chronic pain, and the selective microstructural integrity damage was particularly manifested by changes in axons and myelin sheath in the genu and body of corpus callosum ¹⁾.