We report a case of subcortical dementia in a 68-year-old woman. MR examination of the patient’s brain revealed two types of alterations as a possible cause of the dementia, both anomalous in respect of their entity and incidence: the first was a striking enlargement of the Virchow-Robin spaces, and the second an anterograde transneural degeneration of the left mammillo-thalamic tract and mammillary body secondary to a lacunar infarction of the ipsilateral anterior thalamus.