Parahippocampal pathology in Creutzfeldt-Jakob disease

The hippocampal lesions in Creutzfeldt-Jakob disease (CJD) have been reported to be characteristically mild, but it has not been well known how the lesions change pathologically from the entorhinal cortex to the hippocampus.

This study was designed to clarify the ambiguity attending the parahippocampal lesions in CJD. Fourteen cases with pathologically diagnosed CJD were studied. They were classified into 2 groups: group I, which did not have cortical status spongiosus (SS) and included 5 cases; and group II, which had cortical SS and included 9 cases. Neuronal loss, astrocytosis, and spongiform change were studied in lesions in the entorhinal cortex, parasubiculum, presubiculum (external and internal principal laminae), subiculum, and prosubiculum, respectively.

The results of this study showed that in group I neuronal loss and astrocytosis were more severe in the parasubiculum and the external principal lamina of the presubiculum than in the other regions including the entorhinal cortex, and in group II the lesions in the entorhinal cortex, parasubiculum, and the external principal lamina of the presubiculum were more severe than in the other regions. In both groups in this study the lesions from the internal principal lamina of the presubiculum through the prosubiculum in the direction of the hippocampus were mild, which could be the least vulnerable in the parahippocampal gyrus in CJD.

On the contrary, our findings also raise the possibility that the parasubiculum and the external principal lamina of the presubiculum may be the structures most vulnerable to early lesions in the parahippocampal gyrus in CJD. To know the pathogenesis of these lesions may be the clue to delineate the mechanisms by which the neurons could be spared.