Localize
Medial anterior parahippocampal cortex, medial to the collateral sulcus. Exact boundaries are difficult to delineate and definitions vary.
Entorhinal cortex + (ERICA) score)
The entorhinal cortex is a medial temporal lobe cortical region that serves as the major interface between the neocortex and hippocampus, supporting episodic memory and spatial navigation. It is classically associated with Brodmann area 28. pubmed.ncbi.nlm.nih
Reference Images
Assess
Thin coronal imaging perpendicular to the hippocampal long axis, at the level of the mammillary bodies.
Grade
ERICA 0–3. CSF between the entorhinal cortex and tentorium at grades 2 or 3 is the tentorial cleft sign.
Location and imaging anatomy
It occupies the anterior parahippocampal region, including portions of the parahippocampal gyrus and gyrus ambiens. Useful anatomical relationships are: radiopaedia
- Lateral: collateral sulcus.
- Anterior: rhinal sulcus, separating it from olfactory cortex.
- Dorsomedial: hippocampal structures, beneath the hippocampal head and amygdala.
- Posterior: transition toward the presubiculum, parasubiculum, and more posterior parahippocampal cortex. radiopaedia
For imaging localization, think of the cortex along the medial anterior parahippocampal region, medial to the collateral sulcus—not the hippocampus itself. Its exact boundaries are difficult to delineate anatomically, and definitions vary. radiopaedia
What it does
The entorhinal cortex is more than a relay: it integrates information about objects, places, and time into the hippocampal memory system. pubmed.ncbi.nlm.nih
| Component | Principal role |
|---|---|
| Medial entorhinal cortex | Spatial context and navigation; contains grid, head-direction, and border cells. |
| Lateral entorhinal cortex | Information about items and the content of an experience, including relationships to local landmarks. |
These are functional tendencies rather than completely separate systems. sciencedirect
Its superficial layers provide major hippocampal inputs: layer II projects principally to the dentate gyrus and CA2/CA3, while layer III projects to CA1 and the subiculum. The perforant pathway is the major entorhinal afferent system to the hippocampal formation. frontiersin
Why it matters clinically
The transentorhinal and entorhinal regions are among the earliest cortical sites affected by tau pathology in Alzheimer disease. The transentorhinal region is a neighboring transition zone, largely overlapping Brodmann area 35—not simply another name for the entorhinal cortex.
The entorhinal cortical atrophy (ERICA) score has been developed as an alternative to the medial temporal lobe atrophy (MTA) score to help visually identify patients with Alzheimer disease by evaluating the entorhinal cortex for volume loss 1.
Usage An ERICA score of 2 or 3 (see below) has been shown to have higher diagnostic accuracy for distinguishing healthy controls with subjective cognitive decline from individuals with Alzheimer disease than the older medial temporal lobe atrophy (MTA) score 1.
diagnostic accuracy = 91%
sensitivity = 83%
specificity = 98%
Imaging The ERICA score should be calculated on thin coronal imaging at right angles to the long axis of the hippocampus (standard hippocampal views) and assessed at the level of the mammillary bodies 1.
ERICA scoring system
The ERICA score ranges from 0 to 3. Higher values indicate a higher degree of atrophy and a higher likelihood of Alzheimer disease. In the supplied age-matched case-control study, a score ≥2 had 83% sensitivity and 98% specificity for probable Alzheimer disease rather than subjective cognitive decline.
| Score | Volume | Imaging criterion |
|---|---|---|
| 0 | Normal volume of the entorhinal cortex and parahippocampal gyrus | Normal volume |
| 1 | Mild atrophy of the entorhinal cortex and parahippocampal gyrus | Widening of the collateral sulcus |
| 2 | Moderate atrophy of the entorhinal cortex and parahippocampal gyrus | Elevation of the entorhinal cortex away from the adjacent cerebellar tentorium |
| 3 | Marked atrophy of the entorhinal cortex and parahippocampal gyrus | Wide cleft between the entorhinal cortex and adjacent cerebellar tentorium |
The presence of CSF between the entorhinal cortex and the tentorium (ERICA 2 or 3) has been termed the “tentorial cleft sign”
Entorhinal thinning and atrophy can precede symptomatic cognitive impairment and may occur earlier than conspicuous hippocampal atrophy. However, entorhinal atrophy is not specific for Alzheimer disease; it also occurs in other disorders, including frontotemporal dementia. frontiersin
Interpretation and source limitations
The numbered study reference “1” supporting the supplied ERICA performance figures was not identified in the source text. The reported 91% accuracy, 83% sensitivity, and 98% specificity describe the supplied study comparison; the original citation needs confirmation. Entorhinal atrophy is not specific for Alzheimer disease. Figure 6 supplies an MTA teaching comparison; the prose does not provide a complete MTA scoring framework. Figure 1 uses the phrase “between the temporal pole and parahippocampal gyrus,” while the supplied prose places the entorhinal cortex within the anterior parahippocampal region; precise boundaries vary.