Dementia is the loss of cognitive functioning—the ability to think, remember, problem solve or reason—to such an extent that it interferes with a person’s daily life and activities. Dementia ranges in severity from the mildest stage, when it is just beginning to affect a person’s functioning, to the most severe stage, when the person must depend completely on others for basic activities of daily living.

Functions affected include memory, language skills, visual perception, problem solving, self-management, and the ability to focus and pay attention. Some people with dementia cannot control their emotions, and their personalities may change. Signs and symptoms of dementia result when once-healthy neurons (nerve cells) in the brain stop working, lose connections with other brain cells, and die. While everyone loses some neurons as they age, people with dementia experience far greater loss. Unlike dementia, age-related memory loss isn’t disabling.

While dementia is more common with advanced age (as many as half of all people age 85 or older may have some form of dementia), it is not normal part of aging. Many people live into their 90s and beyond without any signs of dementia. The causes of dementia can vary.

Alzheimer's Disease (AD) is an age-related, non-reversible brain disorder that develops over a period of years. Initially, people experience memory loss and confusion, which may be mistaken for the kinds of memory changes that are sometimes associated with normal aging. However, the symptoms of AD gradually lead to behavior and personality changes, a decline in cognitive abilities such as decision-making and language skills, and problems recognizing family and friends. AD ultimately leads to a severe loss of mental function. These losses are related to the worsening breakdown of the connections between certain neurons in the brain and their eventual death. AD is one of a group of disorders called dementias that are characterized by cognitive and behavioral problems. It is the most common cause of dementia among people age 65 and older.

There are three major hallmarks in the brain that are associated with the disease processes of AD.

• Amyloid plaques, which are made up of fragments of a protein called beta-amyloid peptide mixed with a collection of additional proteins, remnants of neurons, and bits and pieces of other nerve cells.
• Neurofibrillary tangles (NFTs), found inside neurons, are abnormal collections of a protein called tau. Normal tau is required for healthy neurons. However, in AD, tau clumps together. As a result, neurons fail to function normally and eventually die.
• Loss of connections between neurons responsible for memory and learning. Neurons can't survive when they lose their connections to other neurons. As neurons die throughout the brain, the affected regions begin to atrophy, or shrink. By the final stage of AD, damage is widespread and brain tissue has shrunk significantly.

Frontotemporal Dementia (FTD) describes a clinical syndrome associated with shrinking of the frontal and temporal anterior lobes of the brain.  Originally known as Pick’s disease, the name and classification of FTD has been a topic of discussion for over a century.  The current designation of the syndrome groups together Pick’s disease, primary progressive aphasia, and semantic dementia as FTD.  Some doctors propose adding corticobasal degeneration and progressive supranuclear palsy to FTD and calling the group Pick Complex.  These designations will continue to be debated.  As it is defined today, the symptoms of FTD fall into two clinical patterns that involve either (1) changes in behavior, or (2) problems with language.  The first type features behavior that can be either impulsive (disinhibited) or bored and listless (apathetic) and includes inappropriate social behavior; lack of social tact; lack of empathy; distractability; loss of insight into the behaviors of oneself and others; an increased interest in sex; changes in food preferences; agitation or, conversely, blunted emotions; neglect of personal hygiene; repetitive or compulsive behavior, and decreased energy and motivation.  The second type primarily features symptoms of language disturbance, including difficulty making or understanding speech, often in conjunction with the behavioral type’s symptoms.  Spatial skills and memory remain intact.  There is a strong genetic component to the disease; FTD often runs in families.

Multi-Infact Dementia (Vascular Dementia) is a common cause of memory loss in the elderly. MID is caused by multiple strokes (disruption of blood flow to the brain).  Disruption of blood flow leads to damaged brain tissue.  Some of these strokes may occur without noticeable clinical symptoms. Doctors refer to these as “silent strokes.”  An individual having a silent stroke may not even know it is happening, but over time, as more areas of the brain are damaged and more small blood vessels are blocked, the symptoms of MID begin to appear.  MID can be diagnosed by an MRI or CT of the brain, along with a neurological examination. Symptoms include confusion or problems with short-term memory; wandering, or getting lost in familiar places; walking with rapid, shuffling steps; losing bladder or bowel control; laughing or crying inappropriately; having difficulty following instructions; and having problems counting money and making monetary transactions.  MID, which typically begins between the ages of 60 and 75, affects men more often than women. Because the symptoms of MID are so similar to Alzheimer’s disease, it can be difficult for a doctor to make a firm diagnosis.  Since the diseases often occur together, making a single diagnosis of one or the other is even more problematic.

Parkinsons Disease (PD) belongs to a group of conditions called motor system disorders, which cause unintended or uncontrollable movements of the body. The precise cause of PD is unknown, but some cases are hereditary while others are thought to occur from a combination of genetics and environmental factors that trigger the disease.  In PD, brain cells become damaged or die in the part of the brain that produces dopamine--a chemical needed to produce smooth, purposeful movement.

The four primary symptoms of PD are:

• tremor--shaking that has a characteristic rhythmic back and forth motion
• rigidity--muscle stiffness or a resistance to movement, where muscles remain constantly tense and contracted
• bradykinesia--slowing of spontaneous and automatic movement that can make it difficult to perform simple tasks or rapidly perform routine movements
• postural instability--impaired balance and changes in posture that can increase the risk of falls.

Other symptoms may include difficulty swallowing, chewing, or speaking; emotional changes; urinary problems or constipation; dementia or other cognitive problems; fatigue; and problems sleeping.

PD usually affects people around the age of 70 years but can occur earlier.  PD affects men more than women.  Currently there are no specific tests that diagnose sporadic PD.