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The circuit of Papez in mesial temporal sclerosis: MRI
H Oikawa1, M Sasaki, Y Tamakawa
1Department of Radiology, Iwate Medical University, Morioka, Japan. oihiro@iwate-med.ac.jp
Abstract:
We looked at abnormalities in the circuit of Papez in patients with the mesial temporal sclerosis (MTS). We reviewed the MRI studies of 15 patients with probable MTS, seeking changes in the fornix, mamillary body, mamillothalamic tract, thalamus and cingulate and parahippocampal gyri. We correlated any abnormalities with each other and with clinical severity. Atrophy and/or signal change in one or more structures in the circuit of Papez were found in five patients. They involved the parahippocampal gyri in all five, the fornices in four, mamillary bodies in three, the thalamus in two and the cingulate gyrus in one. Changes in the fornix, mamillary body, thalamus or cingulate gyrus were always accompanied by hippocampal and parahippocampal atrophy. The patients with abnormalities of the circuit of Papez did not have more severe epilepsy than those without. Changes in the parahippocampal gyrus, including the entorhinal cortex and subiculum, in which forniceal fibres originate, may be crucial in causing abnormalities more distally in the circuit.
Insights
Mesial temporal sclerosis (MTS) can affect the Papez circuit, a brain network crucial for memory. MRI studies reveal structural changes in this circuit in some MTS patients, though not linked to epilepsy severity.
Area of Science:
- Neuroscience
- Neuroradiology
- Epileptology
Background:
- Mesial temporal sclerosis (MTS) is a common cause of epilepsy.
- The Papez circuit, comprising the hippocampus, fornix, mamillary bodies, and thalamus, is vital for memory function.
- Abnormalities in the Papez circuit are implicated in various neurological disorders.
Purpose of the Study:
- To investigate structural abnormalities within the Papez circuit in patients with probable MTS.
- To correlate observed abnormalities with clinical severity of epilepsy.
Main Methods:
- Retrospective review of MRI scans from 15 patients with probable MTS.
- Assessment for atrophy and/or signal changes in key Papez circuit structures: fornix, mamillary body, mamillothalamic tract, thalamus, cingulate gyrus, and parahippocampal gyrus.
- Correlation of imaging findings with clinical epilepsy severity.
Main Results:
- Five out of 15 patients exhibited abnormalities in one or more Papez circuit structures.
- Parahippocampal gyrus involvement was present in all five affected patients.
- Structural changes in the fornix, mamillary body, thalamus, or cingulate gyrus were consistently associated with hippocampal and parahippocampal atrophy.
- No significant correlation was found between Papez circuit abnormalities and epilepsy severity.
Conclusions:
- Structural alterations within the Papez circuit occur in a subset of patients with MTS.
- Parahippocampal gyrus changes, particularly involving the entorhinal cortex and subiculum, may initiate downstream abnormalities in the Papez circuit.
- These findings highlight the interconnectedness of the Papez circuit in MTS, though not directly linked to seizure severity.