Dizziness, legs buckling sometimes. Have significant white matter on brain. 56 years old. Dr said Last brain MRI showed no change from prior MRI?

Not sure. exactly what the question is, but sometimes if there is severe and widespread white matter disease on MRI, it is difficult to tell if there is subtle interval change from scan to scan.
White matter... Everyone has white matter in the brain, so not clear what implications are being suggested. Evaluation of your physical state and historical details will be necessary for further evaluation of your issue.