<prompt> 28 yr old man presented with headache. CT head shows a low attenuation mass in left temporoparietal region which has similar density to CSF and shows no enhancement following contrast administration. Diffusion weighted MRI shows high signal. Which of the following is most probable diagnosis?MigraineArachnoid cystEpidermoid cystMultiple sclerosis  <response>: When there is Diffusion Restriction, DW-MRI gives a bright signal and has low apparent Diffusion CoefficientADC value. Lesions showing Diffusion Restriction InfarctAcute Infarct- IOC Abscess Medulloblastoma Other Cellularity Tumours Epidermoid Cyst There is free diffusion of water within arachnoid cysts therefore DW-MRI is useful to differentiate bw arachnoid and epidermoid cyst. Clinical history not suppoive of Migraine. Option D: Multiple sclerosis shows Dawsons fingers. 