Lesions at the foramen of Monro: evaluation by computed tomography, angiography, and pneumoencephalography.

The majority of abnormalities at the foramen of Monro identified by computed tomography (CT) are colloid cysts, but a number of other diseases in this location may produce a similar CT appearance. In a series of 21 patients the radiologic findings included six colloid cysts, two neoplasms, five vascular lesions, three congenital neuroectodermal diseases, four infectious or granulomatous lesions, and one idiopathic calcified mass at the foramen of Monro. The neuroradiologic evaluation included contrast-enhanced and contrast-nonenhanced cranial CT scans and cerebral angiography in the majority of cases. Pneumoencephalography provided useful ancillary diagnostic information in four patients.