The landmarks for delineating the parietal lobe include:
- central sulcus
- parieto-occipital sulcus
- lateral ventricle
- sylvian fissure
- superior temporal sulcus (horizontal and ascending)
- anterior calcarine
- Parahippocampal gyrus
- Fusiform gyrus
- The parietal lobe is traced in the sagittal plane. The parietal lobe is defined as the portion of the cerebrum superior and anterior to the parieto-occipital sulcus, posterior to the central sulcus, and superior to the corpus callosum (Fig. 1).
- To locate the central sulcus, go to the axial plane and identify the superior frontal sulcus which will run directly perpendicular to the pre-central sulcus. The sulcus immediately posterior to the pre-central sulcus is the central sulcus (Fig. 2).
- Delineation begins slightly off center from midline and proceeds laterally in the sagittal plane. As you move laterally, the corpus callosum disappears and the parietal lobe is then traced as all matter above the lateral ventricle down to the tip of the hippocampus (Fig. 3).
- Next, a line is drawn from the hippocampus to the parieto-occipital sulcus to distinguish the inferior boundary (Fig. 4).
- Once the parieto-occipital sulcus disappears, the lateral ventricle replaces the hippocampus as the inferior boundary for the lobe. Furthermore, the cortical model is then used as a guide to trace a line from the termination point of the parieto-occipital sulcus to the horizontal ramus of the superior temporal sulcus (Fig. 5).
- Going back to the sagittal slice view, once the lateral ventricle disappears, the medial most segment of the sylvian fissure is connected to the horizontal ramus of the superior temporal sulcus (Fig. 6 & Fig. 7). Drawing is continued laterally until you can no longer distinguish brain matter.
- As a final check, all parietal lobe anatomy is corroborated with the 3D cortical model (Fig. 8, Fig. 9, Fig. 10, & Fig. 11). In the basal view of the 3D cortical model, a check is made to make sure neither the parahippocampal nor fusiform gyrus is included but making sure the anterior calcarine is the lateral boundary (Fig. 11).