Hippocampal calcification prevalence at CT: a retrospective review

To determine the prevalence of intrahippocampal calcification at brain computed tomography (CT), evaluate any association with calcification involving the intracranial arteries or lentiform nuclei, and assess the clinical importance of intrahippocampal calcification.

Study approval was obtained by the Southern Health Human Research Ethics Committee, which waived the requirement for informed consent because of the retrospective nature of the study. The presence of intrahippocampal calcification was assessed by four readers through retrospective review of 300 randomly selected nonenhanced brain CT scans. In addition, the presence of calcification involving the intracranial arteries and lentiform nuclei was assessed, and the clinical histories were reviewed in those patients with intrahippocampal calcifications and a matched control cohort without intrahippocampal calcification. Differences in proportion of patients with intrahippocampal calcifications across different age groups were assessed by using χ2 analysis. Interrater agreement and intrarater agreement were assessed by using κ analysis.

Intrahippocampal calcification was demonstrated in 47 (15.7%) of 300 patients, and 47 (21.7%) of 217 patients older than 50 years of age. Its prevalence increased with age (P=.008). All patients with intrahippocampal calcification and the control cohort demonstrated calcification involving the intracranial arteries. Eleven (23.4%) of 47 patients with intrahippocampal calcification had calcification within the lentiform nuclei compared with 14 (29.8%) of 47 in the control cohort (P=.67). The anatomic distribution of intrahippocampal calcification was similar to that described in vascular fibrosis and calcification.

The prevalence of intrahippocampal calcification appears to increase with age and is a relatively common finding in patients older than 50 years. It has a similar anatomic distribution to microscopic vascular fibrosis and calcification and likely reflects its latter stages.