Identification of arachnoid cysts in the quadrigeminal cistern using ultrasonography

The ultrasonographic findings in three small breed dogs with intracranial a rachnoid cysts are described. Ultrasound images were obtained via the foram en magnum, temporal window and persistent bregmatic fontanelle (when possib le). In transverse, dorsal and sagittal transcranial ultrasound images ther e was marked dilation of the lateral ventricles and a well-defined, oval to triangular-shaped anechoic area between the caudal aspect of the occipital lobes, dorsal to the midbrain, and rostral. to the cerebellum. These findi ngs were consistent with a diagnosis of concurrent hydrocephalus and an ara chnoid cyst within the quadrigeminal cistern.