<prompt> Primary investigation of choice in a patient with suspected subarachnoid haemorrhage should be:Non-contrast computed tomographyMagnetic resonance imaging MRIContrast-enhanced computed tomographyLumbar punture  <response>: Here the investigation of choice is Non-contrast CT; if it is not successful lumbar puncture can be tried. The most sensitive investigation is Digital subtractions angiography of both carotid and veebral aeries. Ref: Mauricio Castillo 2006, Chapter 8, Trauma, In the Book, Neuroradiology Companion: Methods, Guidelines, and Imaging Fundamentals 3rd Edition, Lippincotts Publications, USA, Page 52 ; Current Medical Diagnosis and Treatment, 2003, Page 965 