Pathophysiology of aqueductal obstruction in isolated IV ventricle after shunting.

The authors report their cases of isolated IV ventricle and discuss their concepts of secondary obstruction of the aqueduct, analyzing CSF dynamics, pressure measurements, serial CT scan changes, and the outcome of various treatment modalities. Two distinctly different categories were identified: functional obstruction in which the obstructed aqueduct reopened either as the result of decreasing the elevated infratentorial pressure (Raimondi's phenomenon) or from correction of overdrainage of the supratentorial system; permanent obstruction with pathological occlusion of the aqueduct, necessitating a IV ventriculoperitoneal shunt. It is the pathophysiology and pathoanatomy of secondary obstruction of the aqueduct that determine the specific treatment to be used in managing the isolated IV ventricle syndrome.