Arachnoid cyst of the velum interpositum.

Spiegel et al. (1) recently have reported an interesting case of an arachnoid cyst of the velum interpositum. In their paper they state that this is the first report of such an entity. We wish to report a second case. The patient is a 42-year-old woman with a history of intermittent left-sided headaches for many years. Contrast-enhanced CT showed a CSF-density lesion between the lateral and third ventricles , without significant contrast enhancement of the lesion (Fig. 1 ). MR imaging was performed, and the coronal and sagittal sequences showed a well-defined cystic defect in the velum interpositum, extending posteriorly into the quadrigeminal plate cistern . Its signal intensity on the T1and T2-weighted sequences was equivalent to CSF intensity.