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.
Brain cell death or malfunction: The cause of certain brain lesions, like those seen with Parkinson's disease, are due in part to the malfunction and death of brain cells that produce dopamine. However, the underlying cause may be related to genetics, toxic exposures, or various other combinations of potential causes.