A 57 year old lady presents to A&E following a fall in the supermarket. She has some mild bruising on her shins but is not in any pain. She denies any head injury and recalls feeling dizzy prior to the fall, when she was looking for some tinned tomatoes on a high shelf. She has been having similar dizzy spells when waking up over the last week but is otherwise well. There is no limb weakness, slurred speech, or facial drooping. Past medical history includes Hypertension for which she is on Amlodipine.
Neurological examination and vital observations are normal.
What is her most likely diagnosis?