In Hydrocephalus ex vacuo, the compensatory enlargement of ventricles and an increase in CSF volume due to brain atrophy is seen in-: (A) Alzheimers diseae, (B) Picks diseases, (C) Both, (D) None of the above
Answer is C. Hydrocephalus ex vacuo

Insignificant cortical atrophy, there is compensatory ventricular enlargement secondary to loss of parenchyma → Hydrocephalus ex vacuo.
This can be seen in Alzheimer disease and Pick disease. - Anderson 10th/ep. 2740.