Sudden severe headache is the commonest presentation of subarachnoid haemorrhage.> Mortality rate is about 50% in first month. Arteriovenous malformation presents as stroke in young person. 85% of the aneurysms occur in the anterior circulation of Willis. Prodromal symptoms help to localize unruptured aneurysm.> 3rd nerve palsy with loss of light reflex and pain above or behind eye: Aneurysm at junction of posterior communicating & internal carotid artery. 6th nerve palsy: Aneurysm at cavernous sinus.> Occipital or posterior cervical pain: Aneurysm at posterior inferior cerebellar artery or anterior inferior cerebellar artery. Four major causes of delayed neurological deficit are - rerupture, hydrocephalus, vasospasm and hyponatraemia. Vasospasm is the major cause of delayed neurological deficit.; The incidence of rerupture is maximum at 7th day. The signs of vasospasm are maximum at 7th day.> MC cause of CVA - Thrombosis> MC site of Hypertensive bleeds Putamen> MC site of berry aneurysm-Ant, cerebral- ant, communicating art, junction# This one has been repeated so many times. Excluding trauma, the most common cause of subarachnoid hemorrhag e is rupture of aneurysm# Causes of subarachnoid hemorrhage: Trauma (most common); Rupture of Berry's aneurysm; Rupture of A.V. malformation> Causes of subarachnoid haemorrhage: Aneurysms ... 70% Arteriovenous malformations ... 10% Idiopathic... 5% Other: Spinal AVM, Tumour, Coagulopathy">