Vascular Dementia

A 75-year-old man with hypertension, diabetes, and atrial fibrillation presents with cognitive decline that has worsened ABRUPTLY twice over 3 years, each time following a clinical stroke. He complains of difficulty planning and organizing tasks, and his family notes a shuffling gait. Examination reveals pyramidal signs and frontal release signs. MMSE is 21/30, with preserved recall after cueing but impaired attention and executive function. MRI shows bilateral cortical infarcts, multiple subcortical lacunes, and confluent periventricular white-matter hyperintensities (Fazekas 3) on FLAIR. The hippocampi are relatively preserved (MTA 1). The imaging pattern marked **B** in the diagram is most consistent with which of the following subtypes of vascular dementia?