<prompt> Commonest cause of subarachnoid haemorrhage is:Rupture of circle of Willis aneurysmRupture or veebral aery aneurysmRupture of venecomitants of corpus striatumRupture of dural sinusis  <response>: Answer is A Rupture of circle of Willis aneurysm: Most common cause of subarachnoid haemorrhage is ruptured saccular aneurysms. Most common site of saccular aneurysms is the anterior circulation on the circle of Willis 