ABSTRACT
The cavum veli interpositi is not a rare ventricular anomaly, however it is usually asymptomatic. A case of primary haemorrhage in the cavum veli interpositi as the bleeding source of intraventricular haemorrhage, without vascular lesion or tumour, was diagnosed and treated by neuroendoscopic surgery. A 17-year-old woman with history of transient visual field loss 2 years ago had sudden onset of headache followed by vomiting. A head CT scan showed intraventricular haemorrhage with predominant haematoma in the cavum veli interpositi. A diagnostic angiography demonstrated no apparent vascular lesion, however remarkably delayed appearance of deep venous system and the straight sinus, with prominent collateral drainage toward the vein of Labbe was noted. An external ventricular drainage was placed immediately, followed by endoscopic removal of intraventricular haemorrhage excluding the haematoma in the cavum veli interpositi on day 3. The left internal cerebral vein was engorged and seemed to be congestive during surgery. The postoperative course showed good recovery without neurological deficit. An angiography was repeated 23 days after the onset and it demonstrated improved venous circulation. This is the first report on a primary haemorrhage in the cavum veli interpositi. The cause of bleeding was unknown however, possible abnormal vascular anatomy in this anomalous space might be associated. The vein of Galen is shifted downward by the cavum veli interpositi and this might cause venous hypertension in the deep venous system. Improvement of the venous circulation on the angiography suggested compression of the veins by haematoma can cause impairment of blood circulation and this fact supports theoretical benefit of haematoma removal. Effectiveness of endoscopic treatment for intraventricular haemorrhage is discussed