Mild Cognitive Impairment
Prior to dementia stage, there is a stage called mild cognitive impairment (MCI), which lies between normal aging and dementia. During MCI, the cognitive impairment is much milder and has not yet affected the ability to perform your usual social and daily routines of life. However, during MCI, skills that place greater demands on your cognitive abilities may begin to decline. Some examples include learning new skills for one's work or hobby, managing complex tasks, reading several books at a time and keeping track of the stories, etc

Although Alzheimer's disease is the most common cause of dementia (50-60%), many other causes can be identified by standardized diagnostic assessment, and then properly treated.

• Cerebrovascular Disease
• Lewy Body Disease
• Frontal Lobe Disease
• Depression
• Head Injury
• Brain Tumor
• Metabolic and Infectious Disease
• Normal Pressure Hydrocephalus
• Other Medical Conditions

This white matter is named so because it contains a white substance called myelin that insulates the nerve fibers interconnecting different brain regions. Hence, cerebrovascular disease produces disconnections between different brain regions, resulting in a progressive decline of the affected brain functions.

The cognitive impairment or dementia of cerebrovascular disease preferentially affects the frontal lobe, producing "frontal lobe symptoms" of depression, poor judgment, and reduction in speech, attention problems, difficulty shifting between tasks, and difficulty performing complex tasks.
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Lewy Body Dementia
Lewy body disease is the second most common degenerative cause. It presents with the early appearance of visual hallucinations, difficulty with balance, reduced body movement, and fluctuating levels of clarity or consciousness over days to weeks.

Lewy body disease responds well to medications used for AD. However, antipsychotics can cause a dramatic decline in function, sometimes with poor recovery after stopping these medications. It is therefore important to diagnose this condition to avoid using such agents, particularly since visual hallucinations appear early in Lewy Body disease, and antipsychotic medications are routinely used to treat such symptoms.
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Frontal Lobe Dementia
Frontal lobe disease is a set of degenerative diseases producing many of the same symptoms as vascular cognitive impairment or dementia. Sometimes the only way to distinguish them is by a brain image. Change in personality is often seen with frontal lobe disease. For example, a conservative person may start behaving in an uninhibited fashion. Loss of language and ability to perform complex tasks are other characteristic features of frontal lobe disease.

It is important to distinguish between frontal lobe and cerebrovascular disease because the treatments differ.
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Depression
Depression can produce cognitive impairment or dementia resembling that due to cerebrovascular or frontal lobe disease (short-term memory loss and difficulty planning or executing complex tasks). However, depressed patients usually meet criteria for major depressive disorder, their brain images are normal, and when treated with antidepressants, their cognitive deficits usually resolve or substantially improve.
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Head Injury
Head injury is not usually the sole cause of dementia but can be a contributory factor. Repeated head injuries produce additive damage to the brain, particularly in brain areas resting on bone (the skull). These areas include the base of the frontal and temporal lobes. Repeated head injuries within two weeks of each other produce even more serious damage, which is why professional athletes should not be allowed to play for at least two weeks after they suffer a concussion.

A typical boxer will receive approximately 25,000 blows to the head during their career. Interestingly, head injury produces neurofibrillary tangles, which is one of the pathological hallmarks of Alzheimer's disease. Head injury is known to be a risk factor for Alzheimer's disease, particularly in persons with genetic susceptibility to Alzheimer's disease.
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Brain Tumor
Brain tumor is a relatively uncommon cause of dementia, but is easily diagnosed by a brain image. This is why it is important that a person with dementia have a brain image as part of their evaluation.
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Metabolic and Infectious disease
There are a number of treatable causes of dementia affecting various aspects of the metabolism of brain cells (neurons and glia). These include B12 deficiency, folate deficiency, and thyroid disease. In addition, there are several infectious causes of dementia, including neurosyphyllis and HIV infection. Finally, there are disorders of the connective tissue of the blood vessels in the brain called vasculitis. Each of these causes can be detected by a simple blood test and, with the exception of HIV, are considered to be part of the routine evaluation of a person with dementia. HIV is usually done in persons considered to have a risk factor for a sexually transmitted disease.
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