EXPERIMENTAL HYDROCEPHALUS AND HYDROMYELIA - A NEW INSIGHT IN MECHANISM OF THEIR DEVELOPMENT

One group of cats had an acrylic screw implanted into the adqueduct of Sylvius, while the other group of animals received a solution of kaol in into the cisterna magna. Three weeks later the dye phenolsulphonpht halein was instilled into the lateral ventricle to ascertain communica tion between CSF compartments, and thereafter the brain was perfused w ith formalin. As shown by planimetry of brain ventricles both groups o f experimental animals developed hydrocephalus, i.e., coronal surface of brain ventricles was about 10 times larger in kaolin and about 3 ti mes in aqueductal screw experiments than in the controls, respectively . In aqueductal screw experiments communication of CSF between lateral ventricle and subarachnoid spaces was nor blocked but only restricted , i.e., an aqueductal stenosis was produced. In kaolin experiments com munication of CSF between lateral ventricles and spinal subarachnoid s pace was blocked by thick meningeal adhesions in the upper cervical re gion, while the central spinal canal was dilated (hydromyelia) with en hanced CSF communication between it and the lumbar subarachnoid space. We assume that during systolic expansion of brain the CSF is displace d from the cranial cavity toward the spinal subarachnoid space which a ccommodates an additional volume of CSF primarily due to compliance of the spinal dural sac, while during diastole CSF recoils in the opposi te direction. Thus, in case of aqueductal stenosis the undisplaced vol ume of CSF from the ventricles can be accommodated due to diminution o f cerebral blood volume and brain parenchyma so that hydrocephalus dev elops over rime. Since the cervical subarachnoid space is blocked in k aolin experiments the systolic brain expansion forces CSF from basal c isterns via the fourth ventricle into the aqueduct and central canal w ith consequent development of hydrocephalus and hydromyelia.