Computed tomography of colloid cysts of the third ventricle.

Ten cases of colloid cysts of the third ventricle were evaluated by computed tomography (CT). The smallest lesion demonstrated was 6 mm in diameter and the largest 6.5 cm. Six lesions were hyperdense and four isodense. None of the lesions exhibited significant enhancement after the administration of contrast medium. A non-contrast CT scan is essential for the demonstration of a small hyperdense colloid cyst as the latter may simulate normal vascular structures on the post-contrast scan.