Which of the following structure is most likely to be compressed by an aneurysm of the posterior communicating aery:

Answer is A (Occulomotor nerve): The occulomotor nerve courses in close relationship to the posterior communicating aery and is frequently compressed by an enlarging aneurysm of the posterior communicating aery The occulomotor nerve(Ill rd C.N) courses through the inter-pedicular cistern in close relationship to the posterior communicating aery Growth of an aneurysm may injure the nerve by direct compression or the aneurysm may rupture into the nerve The commonest cause of third nerve palsy in cases of SAH is direct compression of the nerve by an enlarging or ruptured aneurysm