Question of the Week
For December 6, 2016
A 78-year-old woman with a history of hypertension and hypercholesterolemia is brought to the clinic by her daughter, who reports that during the past 12 months her mother has been slow to accomplish things around the house, lacks initiative, and walks more slowly than usual. The patient denies feeling depressed and does not report any recent illnesses. Her blood pressure has been under good control, and she has adhered to her medications.
She scores 24 out of 30 on the Folstein Mini–Mental Status Examination, indicating mild cognitive impairment. She lost points for calculation and orientation but had intact registration, immediate memory, delayed recall, and visuospatial construction. The rest of her neurologic examination is normal, except for a reduced gait speed.
Laboratory evaluation reveals normal vitamin B12 and thyroid-stimulating hormone levels and a negative rapid plasma reagin test.
MRI of the brain reveals extensive periventricular and subcortical white-matter hyperintensities without any ventriculomegaly.
Which one of the following diagnoses is most likely in this patient?