Posterior cerebral artery P1 segment at the stoma during endoscopic third ventriculostomy in adults.

<bold>Objectives: </bold>A serious catastrophic complication of endoscopic third ventriculostomy (ETV) is basilar artery (BA) damage. Although the BA has been discussed as the cause of haemorrhage and even pseudoaneurysm, variations of the posterior cerebral artery proximal segment (P1) and its protrusion into the third ventricle floor have not been emphasised. A series of cases are reported in which the P1 segment was located at the stoma during an ETV and was at risk of perforation. Precautionary techniques for complication avoidance are described.<bold>Methods: </bold>A retrospective review was performed of all ETVs performed in adults at our institution between 2004 and 2008. Cases were identified in which the P1 segment was noted to herniate into the stoma at the time of third ventricular floor fenestration.<bold>Results: </bold>Among 65 cases reviewed, six were identified in which the P1 segment significantly herniated into an area of the stoma at the time of third ventricular floor fenestration. In no case was the P1 segment injured by the ETV procedure. Each of the six patients had opaque third ventricle floors. A 'cookie cut' technique was used in which the opaque third ventricle floor was abraded to reveal the underlying translucent membrane, offering an improved view of arteries in the basilar cisterns. In four of six patients, ETV resulted in clinical improvement.<bold>Conclusions: </bold>The posterior cerebral artery P1 segment is potentially at risk during ETV in adults as well as in children. Awareness and proper precautions may help reduce injuries to either the P1 or the basilar apex during an ETV. [ABSTRACT FROM AUTHOR]