The case demonstrates the different key structures and anatomical landmarks which are essential in interpretation of MRI of the hippocampus.
The hippocampus classified into head, body, and tail.
The anatomical landmarks of the head include the basilar artery, and foramen of Monro. Key structures at this level include uncinate gyrus , mammillary body and temporal lobe stems.
The red nucleus is the anatomical landmark for the body of the hippocampus. The posterior cerebral artery in the ambient cistern is a key structure . This explains the posterior cerebral artery infarction that takes place in severe uncial herniation.
The hippocampal tail is best identified by the appearance of the mesencephalic quadrigeminal plate (superior and inferior colliculi) and quadrigeminal cistern. Key structures at this level; crura of the fornix, pulvinar nucleus, internal cerebral veins, and splenium of corpus callosum.
The fornix is the main output fibers of the hippocampus. It is classified into three parts; pre-commissural, commissural and postcommissural in relation to the anterior commissure.The pre-commissural fibers of the fornix ends in the septal region. Commissural fibers travel transversely along the anterior commissure to reach the contralateral hippocampus. The posterior commissural fibers end in the mammillary body of the hypothalamus.
The entorhinal cortex is a major source of input (afferent) fibers to the hippocampus.