My Mom is 86 yrs old and has 6 children ranging from 46 to 60 yrs old. My 46yr old brother passed away last year.

There are some possibilities for her dementia. She should see a neurologist to have a physical exam, a blood test, and imaging studies such as CT scan MRI.
1. Alzheimer's disease
Alzheimer's disease is the most common cause of dementia in people age 65 and older. Symptoms usually appear after age 60, but early-onset forms of the disease can occur, usually as the result of a defective gene. Although in most cases the exact cause of Alzheimer's disease isn't known, two types of brain cell (neuron) damage are common. These include plaques and tangles. Plaques are clumps of a normally harmless protein called beta-amyloid, and tangles are fibrous tangles made up of an abnormal protein called tau protein. Alzheimer's disease usually progresses slowly, over seven to 10 years, causing a gradual decline in cognitive abilities. Eventually, the affected areas of the brain don't work properly, including those parts involving memory, movement, language, judgment, behavior and abstract thinking.
2. Lewy body dementia. Dementia with Lewy bodies affects approximately 20 percent of people with dementia, making it one of the most common types of dementia. Lewy body dementia becomes more common with age. Lewy bodies are abnormal clumps of protein that have been found in the brains of people with Lewy body dementia, Alzheimer's disease and Parkinson's disease. The symptoms of this dementia are similar to Alzheimer's disease, but its unique features often include fluctuations between confusion and clear thinking (lucidity), visual hallucinations, and Parkinson's signs such as tremor and rigidity. People with Lewy body dementia often have a condition called REM sleep behavior disorder that involves acting out dreams, including thrashing or kicking during sleep.
3. Vascular dementia
The second most common dementia after Alzheimer's disease is a result of damage to your brain caused by problems with the arteries serving your brain or heart. Symptoms begin suddenly, often after a stroke, and may occur in people with high blood pressure, or who have had previous strokes or heart attacks. Vascular dementia may also be caused by infection of a heart valve (endocarditis) or a buildup of amyloid protein in the brain's blood vessels (amyloid angiopathy) that sometimes causes "bleeding" (hemorrhagic) strokes.
4. Frontotemporal dementia. This less common cause of dementia tends to occur at a younger age than does Alzheimer's disease, generally between the ages of 40 and 70. This is a group of diseases characterized by the degeneration of nerve cells in the frontal and temporal lobes of the brain — the areas generally associated with personality, behavior and language. Signs and symptoms of frontotemporal dementia can include socially inappropriate behaviors, loss of mental flexibility, language problems, and difficulty with thinking and concentration. As with others dementias, the cause isn't known, although in some cases this dementia is related to certain genetic mutations. But many people with frontotemporal dementia have no family history of the disease. One form of this condition is called Pick's disease. Pick's disease affects parts of the brain that contain fibrous tangles made up of the abnormal protein called tau protein. Pick's disease causes progressive dementia.
Some causes of dementia or dementia-like symptoms can be reversed.
1. Infections and immune disorders.
meningitis and encephalitis, untreated syphilis, Lyme disease, and conditions that cause a completely compromised immune system, such as leukemia. Conditions such as multiple sclerosis that arise from the body's immune system attacking nerve cells also can cause dementia.
2. Metabolic problems and endocrine abnormalities. These include thyroid problems, too little sugar in the bloodstream (hypoglycemia), too little or too much sodium or calcium, and an impaired ability to absorb vitamin B-12.
3. Nutritional deficiencies. Symptoms can occur as a result of dehydration, not having enough thiamin (vitamin B-1) — a condition common in people with chronic alcoholism — and deficiencies in vitamins B-6 and B-12. Bananas, lentils, spinach, fortified breakfast cereals, salmon, pork, chicken, whole-wheat bread, milk and eggs are all good sources of these B vitamins.
4. Subdural hematomas. These are caused by bleeding between the brain's surface and its outer covering.
5. Brain tumors. It's rare, but dementia can be the result of damage caused by a brain tumor.
6. Heart and lung problems. Your brain can't survive without oxygen. Symptoms may occur in people with chronic lung problems or a heart condition that deprives the brain of the oxygen it needs.
Any questions?