In adult patients undergoing multidetector computed tomography (CT) of the brain, we observed linear calcification along the deep venous system on thin (<3 mm) sagittal reconstructions. We found no reports of this finding in the velum interpositum (VI) in the imaging literature. We performed a focused examination of the VI on 2 autopsy cases and retrospectively reviewed sagittal, thin-section reconstructions of CT scans of 273 consecutive adult patients.On 2 routine autopsies of the brain, sampling and histologic evaluation was performed of structures within the VI. A series of 273 unselected, sequentially acquired clinical head CT scans of patients ≥60 years old were retrospectively reviewed on a three-dimensional workstation to determine the incidence of this finding and its correlation with patient age.In 1 of the autopsy cases, calcified choroid plexus was identified in the region of the VI; this was also visible on the patient's premorbid CT. In the series of CT scans, linear calcification of ≥9 mm along the deep venous system was evident in 24.5% of cases. The median age of the cases without calcifications was 72 years, while the median age of the cases with calcification was 82; this difference was statistically significant (χ2, P < 0.0005).Evidence supports that linear midline calcification along the internal cerebral veins represents age-related, physiologic calcification of extraventricular choroid plexus within the VI. Awareness of this previously unreported finding on CT will prevent mistaking these physiologic calcifications on CT for evidence of underlying venous pathology. This finding provides additional support that the midline choroid plexus lies within the VI rather than in the third ventricle and expands our understanding of the detailed anatomy of the VI.