Have dizziness and leg buckling sometimes with it. what causes this? do have signicifcant white matter on brain. 56 yrs old.

This can't be : diagnosed with available info. Medical assessment with history, physical evaluation and possible other studies will be required.

Unsure what you mean: Everyone has white matter in the brain; it's the usual coverings of the nerves as they leave the grey matter and facilitate conduction of electrical impulses. You might want to have a discussion with your ordering physician of the MRI to determine a diagnostic and therapeutic plan.