A Study of E2020 in Patients With Dementia With Lewy Bodies (DLB), Followed by a Long-term Extension Phase

1. Patients diagnosed as probable dementia with Lewy bodies (DLB) according to the consensus diagnostic criteria for DLB

2. Patients having caregivers throughout the study who submited written consent to cooperate with this study, who routinely stayed with patients 3 days or more a week (at least 4 hours a day), provided patients' information necessary for this study, assisted treatment compliance, and escorted the patients on required visits to study institution

3. Clinical Dementia Rating (CDR) score ≥ 0.5

4. Mini-Mental State Examination (MMSE) score of 10 to 26

1. Patients diagnosed with Parkinson's disease with dementia (PDD)

2. Patients who received anti-dementia drug therapy at the same institution

3. Patients who received anti-dementia drug therapy within 12 weeks before start of Screening

4. Patients with a complication of serious neuropsychiatric disease(s) such as stroke, brain tumor, schizophrenia, epilepsy, normal pressure hydrocephalus, mental retardation, brain trauma with unconsciousness, or a history of brain surgery causing unrecovered deficiency

5. Patients with severe extrapyramidal disorders (Hoehn and Hahr staging score ≥ IV)

6. Patients whose systolic blood pressure was less than 90 mmHg or pulse rate was less than 50 bpm at screening