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.
Secondary malignant brain tumours. A secondary malignant brain tumour means that a cancer which started in another part of the body has spread to the brain. Many types of cancer can spread to the brain. The most common types that do this are cancers of the breast, lung, bowel, kidney and skin (melanoma).