abnormal mri

I'm a 56 y/o female. I went to the ER c/o unusual headache. They did a ct of my head which was abnormal so a MRI was done.It showed moderately-severe periventricular and deep white matter signal abnormalities which mildly extend into the basal ganglia but involves the brainstem, specifically the upper pons. Also a cystic lesion in the posterior aspect of the splenule of the corpus callosum. I've since had LP done and was negative. I have no neurological deficits. I do have chronic hypertension. What does all this mean? I know MS is a concern but has not been diagnosed..Should I be concerned and what is the prognosis for the future?  Thank you for your help............Sal