The core study assessed the efficacy of a higher dose of rivastigmine 13.3 mg/24 h transdermally (15 cm^2 patch) compared to a lower dose of the rivastigmine 4.6 mg/24 h transdermally (5 cm^2 patch) in patients with Severe Dementia of the Alzheimer's Type in a 24-week study. The extension study obtained additional safety and efficacy data, as well as provided the higher dose rivastigmine patch to all patients who completed the core study for an additional 24 weeks.