A patient presented with thunder clap headache followed by unconsciousness with pregressive 111 ranial nerve palsy. Likely diagnosis is
Extradural hemorrhage
Aneurysmal subarachnoid hemorrhage
Basilar migraine
Cluster headache
davidson's principles and practices of medicine 22nd edition. *85% of SAH are caused by saccular or berry aneurysm arise from bifurcation of cerebral aeries *SAH typically presented with a sudden ,severe ,thunderclap headache (often occipital) , which lasts for hours or even days,often accompanied by vomitting , raised blood pressure and neck stiffness or pain. *there may be loos of consciousness at the onset ,so SAHshould be consider if patient is comatose *focal neurological signs like hemiparesis,aphasia may be present at onset if there is an associated intracerebral hematoma *a third nerve palsy present due to local pressure from an aneurysm of posterior communicating aery. Ref Harrison20th edition pg 2456
C.N.S