A patient with suspected subarachnoid haemorrhage presents with blood isolated in the fourth ventricle on a CT scan. Aneurysmal rupture is likely to have resulted from -
Posterior Inferior Cerebellar Artery Aneurysm
Anterior Communicating Artery Aneurysm
Posterior Communicating Artery Aneurysm
Basilar Artery Tip Aneurysm