WALTER DANDY'S classical paper, "Experimental Hydrocephalus," described two critical experiments in cerebrospinal fluid physiology.1 First, he occluded one foramen of Monro, and the ventricle on the same side enlarged. Second, he occluded the foramen of Monro after choroid plexectomy, and the ventricle collapsed. Dandy reached two conclusions: first, the choroid plexus produces cerebrospinal fluid (CSF); and second, if obstruction is interposed in the path of CSF circulation, hydrocephalus develops proximal to the block as a result of back pressure. Without experimental proof he assumed that with both formaina of Monro open, symmetrical hydrocephalus would follow unilateral choroid plexectomy and occlusion of the aqueduct of Sylvius.
Nearly 50 years later Bering2 tested the assumption that back pressure of blocked CSF circulation produces the ventricular enlargement of hydrocephalus. He produced asymmetrical hydrocephalus by removing the choroid plexus from one lateral ventricle leaving the foramen of Monro open. Bering
Wilson CB, Bertan V. Interruption of the Anterior Choroidal Artery in Experimental Hydrocephalus. Arch Neurol. 1967;17(6):614–619. doi:10.1001/archneur.1967.00470300056010
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