[A case of isolated fourth ventricle due to ruptured cerebral aneurysm].

We present a case of isolated fourth ventricle which developed after massive ventricular hemorrhage, due to a ruptured cerebral aneurysm. In an adult an isolated fourth ventricle seems to be very rare, also the symptom of unconsciousness and respiratory arrest and the rapid development in this case seemed very unusual. The aqueductal occlusion was considered to be related to the intraventricular hematoma which remained as clots over a 2-month-period of time. This case was a 57-year-old woman admitted to our hospital in a state of coma. CT showed a massive ventricular hematoma and right carotid angiogram showed an aneurysm of the anterior communicating artery. Bilateral ventricular drainage was performed because of progressive decerebrate rigidity. Since consciousness gradually arose to the Japan Coma Scale 3, clipping of the neck of the aneurysm was performed 25 days after onset. Premature rupture occurred during the operation. After surgery, CT Showed ring-like high densities due to the premature rupture of aneurysm in both lateral ventricles, and also in the fourth ventricle as well. Although the lateral ventricles drainage functioned effectively, the fourth ventricle showed remarkable gradual dilatation. The patient was stuporous, but respiratory arrest occurred suddenly 43 days after onset. Since it was considered that the intraventricular hematoma blocked the aqueduct, the same as in the outlet of the fourth ventricle and that the dilated fourth ventricle compressed the brain stem, the ventriculostomy was performed through suboccipital craniectomy. The cerebellar hemispheres showed remarkable swelling bilaterally, and no cerebrospinal fluid was found in the cisterna magna.(ABSTRACT TRUNCATED AT 250 WORDS)