Setting aside the notion of determining the number of individual animals on the planet for a moment, merely determining the number of species on the Earth is challenging. Science has only been able to offer estimates thus far, and totals vary greatly.
People who have early onset Alzheimer's may be in any stage of dementia â early stage, middle stage or late stage. The disease affects each person differently and symptoms will vary. If you are experiencing memory problems: 1  Have a comprehensive medical evaluation with a doctor who specializes in Alzheimer's disease.
Multiple Sclerosis. Multiple Sclerosis (MS) is a diseases of the central nervous system which leads to recurring attacks of neurological symptoms. Learn more about its causes, symptoms, diagnosis and treatment here. Cerebrovascular Disease. Cerebrovascular disease refers to disorders of the blood vessels that supply blood flow to the brain. Here is information about various cerebrovascular diseases including brain aneurysms and stroke.