<prompt> Investigation of choice for acute SAH is?DSAX rayCT scanMRI  <response>: ANSWER: C CT scan REF: Sutton 7th ed p. 1779See APPENDIX-66 for INVESTIGATION OF CHOICESUBARACHNOID HEMORRHAGEInvestigation of choice : non contrast CT scanIf scan fails : lumbar puncture to establish blood in CSFMost sensitive investigation for evaluating etiology : DSA of four vessels carotids and vertebralsMost common intracranial lesion after head injury: sub dural hematomaMost common cause of sub arachnoid hemorrhage: head traumaMost common cause of spontaneous SAH: ruptured aneurysmHEMATOMA ON CT SCAN:Epidural hematoma: biconvex or lens shaped, hyperdense acute 23, hypodense chronic 13Subdural hematoma: crescent, hyperdense 2 weeks, isodense 2-4 weeks , hypodense 4 weeks 