Hippocampus Guidelines
2/5/2016
HIPPOCAMPAL FORMATION:
Subiculum
Ammon's horn (hippocampus proper)
Dentate gyrus
SAGITTAL TRACE:
Begin where first slice (medial to lateral) shows cerebral peduncle separated from upper pons
Head of hippocampus appears as a small conical structure within the
uncus/ambient gyrus just in front of the cerebral peduncle
At this level, the head is anteriorly bordered by the alveus
(white matter tract) which was excluded from the measurements
Moving laterally:
anterior - outlined by the alveus and the uncal recess
dorsally - CSF of the temporal horn of the lateral ventricle
outlines the body
tail - pulvinar thalami serves as the border for the tail
Medial slices: body is bordered by the fimbria (which is excluded from the trace)
Posterior border: formed by CSF of the lateral ventricle
Ventral border: Defined by the white matter of the temporal lobe
In all cases, the slice that shows amygdala/hippocampal transition zone is examined.
At that slice, the head of the hippocampus bends anteriorly and forms a small tip
that points toward the frontal lobe
This usually appears on the fourth or fifth slice after the starting slice
CORONAL TRACE:
Start with the most anterior slice displaying more than two telegraphed crosses from the
sagittal guideline traces.
It is difficult to distinguish hippocampal head from the amygdala just above it but the alveus may be identified and serve as a border between the hippocampus and
the amygdala (white matter has higher signal intensity)
Exclude the alveus when identified
The head of the hippocampus appears as a transversely-oriented oval or crescent-shaped
structure
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Hippocampus Guidelines
2/5/2016
Lateral: temporal horn of the lateral ventricle serves as border
The edge between gm and wm is sometimes blurred on the tissue classified image;
need to use T1- and T2- weighted images as reference
Dorsal: Follow the line defined by the telegraphed crosses
Exclude the alveus if visible
Uncal sulcus usually obliterated on the most anterior slices
When the uncal sulcus becomes visible, the uncal recess serves as the dorsal
border
Medial: telegraphed crosses provide an orientation on the most anterior slices.
Tracing includes parts of the ambient gyrus, and on some slices the entorhinal sulcus
serve as a border.
Ventral: Laterally defined by the WM of the temporal lobe
Medially the subiculum has to be cut off from the cortex of the parahippocampal gyrus.
Do this by following the horizontal line that is defined by the subiculum/WM border
BODY [on CORONAL]:
Comes into view at about the level of the red nucleus
Lateral: Marked by the temporal stem and inferior horn of the lateral ventricle
Dorsal: Exclude the alveus and fimbria.
Note the CSF of the lateral ventricle
Medial: CSF of the ambient cistern and the crus cerebri serve as border
Ventral: Defined by the WM of the temporal lobe.
Exlude the parahippocampal gyrus
Tail: Starts at the level where the brainstem becomes separated from the midbrain
(level of the superior colliculus/pineal gland)
Lateral: Demarcated by the ascending crus of the fornix and CSF of the atrium
of the lateral ventricles.
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Hippocampus Guidelines
2/5/2016
It is difficult to differentiate the intraventricular part of the tail from ventricular CSF
(use the telegraphed crosses as guideline)
Dorsal: border defined by the pulvinar of the thalamus
Separation of the hippocampal head may be difficult due to partial voluming
effects - sag plane should be used as reference
On the most caudal slice, dorsal border is marked by lower part of the splenium
of the corpus callosum
(This part of hippocampal tail sometimes referred to as the subsplenial gyrus)
Medial: CSF of the quadrigeminal cistern serves as border
Terminal slices: Include the fasciola cinerea and the gyrus fasciolaris as well as
the gyrus of Andreas Retzius
Ventral border: Defined by the WM of the temporal lobe (parahippocampal gyrus)
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