Hippocampus and hippocampal connections

Case contributed by Dr Azza Elgendy

Patient Data

Gender: Male

The basilar artery, mammillary bodies, and foramen of monro are the landmarks to identify the head of the Hippocampus.The red nucleus is the landmark for the body of the hippocampus. The superior and inferior colliculi in quadrigeminal cistern are the landmarks for the tail of the hippocampus.

The fornix is the main output fibers of the hippocampus. At the level of  the anterior commissure the fornix divides into pre-commissural, and post-commissural. The post-commissural fibers ends in the mammillary bodies of the hypothalamus. The pre-commissural fibers end into the septal region. The commissural fibers cross the anterior commissure to the contralateral hippocampus. Direct efferent fibers to the entorhinal cortex is also demonstrated

Case Discussion

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.

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Case information

rID: 33687
Published: 31st Jan 2015
Last edited: 8th Sep 2015
Inclusion in quiz mode: Excluded

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