Can you tell me what causes subcortical foci of hypodensity and a prominent virchow robin space?

Usually normal: The virchow robin space is a perivascular space in the brain that surrounds the perforating arteries. It is believed to act as a buffer and reservoir of the extracelluar space for the neurons. These are normal findings that are best seen on the MRI scans of the brain. However, more recent studies suggest that these become prominent in neurodegenerative diseases where there is loss of neurons.