25332              BILOCULAR ANEYRYSM OF UPPER END OF BASILAR ARTERY

This woman aged 41 became rapidly comatose after the sudden onset of severe headache.  The B.P. was 90/60 and lumbar puncture next morning showed bloodstained CSF.  During the next few days the state of consciousness fluctuated.  Carotid angiography revealed an aneurysm at the upper bifurcation of the basilar artery and on brain scan there was delayed perfusion in the left hemisphere.  A month later there was a further sudden severe subarachnoid bleeding over the base of the brain.

The specimen consists of a coronal slice through the hemisphere to reveal a bilocular aneurysm springing from the upper end of the basilar artery and extending forwards into the interpeduncular fossa on the right side, where it lies immediately medial to the optic radiation.  Notching of the inferior surfaces of both hippocampal gyri can be seen, and there is recent blood in the subarachnoid space over the anterior surface of the pons.  The hemispheres are somewhat swollen, especially the left, and the septum pellucidum is deviated slightly to the right.