de·men·tia 
(dĭ-mĕnshə)
(dĭ-mĕnshə)n.
Loss of cognitive abilities, including memory, concentration, communication, planning, and abstract thinking, resulting from brain injury or from a disease such as Alzheimer's disease or Parkinson's disease. It is sometimes accompanied by emotional disturbance and personality changes.
[Latin dēmentia, madness, from dēmēns, dēment-, senseless; see DEMENT.]
de·mential adj.