What Causes Severe Dizziness And Headache?

Hi. Mum has been in hospital overnight after been taken to emergency with severe headache and dizziness. She had ct scan blood urine tests all clear. She is home still experiencing once again severe dizziness. They unsure of the problem. Whats your opinion please? Also if this is Vertigo, we read is a build up of calcium in mid. ear, should she cease taking her calcium tablets? She is 72 yrs old. Thanks Dee