More than 50 conditions are associated with dementia, including degenerative neurological disorders (such as Parkinson's disease and Alzheimer's disease), vascular disorders (such as deep vein thrombosis), inherited disorders (such as Huntington's disease), and infectious diseases (such as human immunodeficiency virus or HIV).
AIDS dementia complex (ADC): AIDS dementia complex (ADC), also known as HIV dementia, HIV encephalopathy, and HIV-associated dementia, is a common brain disorder associated with HIV infection and AIDS. Researchers believe that HIV itself causes ADC, but it is not clear exactly how the virus damages the brain cells. It has been suggested that the HIV proteins may damage nerve cells directly or indirectly.
Many researchers suspect that HIV damages the neurons indirectly. According to some scientists, HIV either infects or activates cells called macrophages and microglia. These cells then produce toxins that can stimulate a series of reactions, which instruct nerve cells (called neurons) to kill themselves. The infected macrophages and microglia also appear to produce proteins called chemokines and cytokines that mediate and regulate immunity, inflammation, and the development of blood cells. These chemokines and cytokines can also affect neurons, as well as astrocytes. The affected astrocytes, which normally protect and nurture neurons, may cause damage to neurons.
Alcoholism: Alcoholism can lead to vitamin B1 (thiamin) deficiency, seizures, and head injuries that produce dementia. Chronic drug abuse, with drugs such as cocaine and heroin, also can cause symptoms of dementia.
Alzheimer's disease: Alzheimer's disease (AD) causes 50-70% of all cases of dementia. AD is the progressive deterioration of areas in the brain essential for learning and memory. Several factors, including age, gender, and lifestyle choices have been associated with AD.
In addition, people with family histories of AD appear to have an increased risk of developing the disease. However, the genetic risk factors associated with the condition remain largely unexplained. Researchers have identified a few genetic mutations that greatly increase the risk in some families. A clear inherited pattern of AD exists in less than 10% of cases.
Early-onset familial Alzheimer's disease has been associated with three predisposition genes: PS1 on chromosome 14, PS2 on chromosome 1, and APP on chromosome 21. These genes affect the production of the amyloid precursor protein and the production of toxic beta-amyloid, creating plaques associated with Alzheimer's disease. Mutations in PS1 account for 30-50% of patients younger than 60 with a strong family history. More than 70 different mutations in the PS1 gene have been reported. All three genes are inherited as autosomal dominant genes. This means that carriers of the genes have a 50% chance of passing their genes to their children.
Up to 20% of pre-senile AD cases are due to the presence of susceptibility genes. Susceptibility genes cause the disease to occur earlier in life than it would without the gene. It is important to note that the mechanism by which this earlier onset occurs is not well understood.
One of the most well-understood genetic risk factors for Alzheimer's disease is the apolipoprotein E (APOE) gene. Mutations in this gene increase the chances of developing late-onset AD. The APOE gene is found in three different forms: APOE 2, APOE 3, and APOE 4. APOE 4 has been associated with an increased risk for developing AD. Unlike the predisposition genes, not all patients with the susceptibility gene APOE 4 will develop AD. Carrying an APOE 4 gene does not predict that a patient will definitely develop AD. Patients with two copies of the APOE 4 gene have a significantly increased risk of developing the condition, and patients with only one copy have a three-fold increased risk compared to the general population. Researchers expect to discover more susceptibility and risk reducing genes.
In addition, nearly all people with Down syndrome who live into their 40s develop AD. Down syndrome is a condition in which extra genetic material causes delays in the way a child develops and often leads to intellectual disabilities.
Amyotrophic lateral sclerosis: Amyotrophic lateral sclerosis (ALS), also called Lou Gehrig's disease, is a progressive neuromuscular disease that weakens and eventually destroys motor neurons. Neurons are components of the nervous system that connect the brain with the skeletal muscles. Most experts believe that ALS does not affect an individual's mental processes. In most people, neither cognitive processes (such as thinking, learning, memory, and speech) nor behavior is affected. Occasionally, however, a person with ALS does experience dementia. Dementia in ALS is thought to be due to destruction of cells in the frontal lobe of the brain. Dementia is rare in ALS. It occurs in all ethnic groups and in both men and women. People aged 55-65 years are most likely to be affected.
Creutzfeldt-Jakob disease: Creutzfeldt-Jakob disease (CJD) is a transmissible, rapidly progressing, neurodegenerative disorder called a spongiform degeneration and is related to "mad cow disease." The initial symptom of CJD is usually a vague personality change, followed within weeks or months by rapidly progressing dementia. The dementia is often accompanied by other central nervous system problems, such as visual disturbances and involuntary jerks of the limbs termed myoclonus.
Huntington's disease: Huntington's disease (HD) is an inherited condition caused by a single abnormal gene. Each child of an HD parent has a 50% chance of inheriting the HD gene. Because signs and symptoms typically appear in middle age, some parents may not know they carry the gene until they have already had children and possibly passed on the trait. If a child does not inherit the HD gene, he or she will not develop the disease and cannot pass it to subsequent generations. In most cases, a person who inherits the HD gene will eventually develop the disease.
Infection: Disease caused by viral, bacterial, or fungal infection can lead to impaired cognitive function. In some cases, appropriate treatment of the underlying condition can reverse symptoms. Infections that may cause dementia-like symptoms include meningitis (inflammation of the membranes that cover the brain and spinal cord) and encephalitis (inflammation of the brain). Human immunodeficiency virus (HIV) and acquired immunodeficiency syndrome (AIDS) are viral infections that may lead to AIDS dementia complex during late stages of the disease. Antiretroviral therapy has been reported to reduce the incidence of AIDS dementia.
Lewy body dementia: Lewy body dementia is similar to AD, but may progress more rapidly. Abnormal brain cells called cortical Lewy bodies occur throughout the brain and produce symptoms such as a decline in cognitive function and memory loss.
Medications: Prescription and non-prescription drugs that may cause dementia include: anticholinergics, such as hyoscyamine (Levsin®) or tolterodine (Detrol®); barbiturates, such as secobarbital (Seconal®); benzodiazepines, such as alprazolam (Xanax®) and diazepam (Valium®); cough suppressants, such as dextromethorphan; digitalis (Lanoxin®); monoamine oxidase inhibitors, such as phenelzine (Nardil®); and tricyclic antidepressants (TCAs), such as amitriptylline (Elavil®), doxepin (Sinequan®), and imipramine (Tofranil®). These medications are more likely to cause signs of dementia in the elderly than in younger, healthier individuals.
Metabolic disorders: Metabolic disorders, such as hypothyroidism (low level of thyroid hormone or thyroid stimulating hormone), hypoglycemia (low blood sugar level), hypercalcemia (high blood calcium level), and liver disease, can affect cognitive function. Treating the underlying condition can restore function.
Multi-infarct disease: Multi-infarct disease is the second most common cause of irreversible dementia. In this condition, multiple strokes lead to a progressive decline in cognition. Strokes are neurological damage in the brain due to a lack of oxygen. Multiple infarct dementia is more common in men over 50 years old. A person with this condition may also experience motor weakness, urinary incontinence, and ataxia (irregular muscle coordination) and may develop hypertension, diabetes, or vascular disease.
Neurosyphilis dementia: Neurosyphilis dementia may result from late-stage syphilis. This disease also may cause heart problems, tremors, ataxia (loss of muscle coordination), paralysis, and blindness. Damage may be irreversible.
Parkinson's disease: Several factors, including age, gender, exposure to pesticides and herbicides, reduced estrogen levels, and medications, are thought to play a role in Parkinson's disease. In addition, having one or more close relatives with Parkinson's disease increases the chances that the person will also develop the disease. However, the risk of developing Parkinson's disease is still less than five percent if a relative has the condition.
Pick's disease: Pick's disease is also similar to AD. In most patients, the frontal and temporal lobes of the brain atrophy (partial or complete wasting). This illness usually affects people between the ages of 40-60 years.
Progressive supranuclear palsy:
Progressive supranuclear palsy produces clinical features similar to Parkinson's disease and often causes severe cognitive difficulties.
Structural abnormalities: Structural abnormalities that can produce dementia include brain tumors located in areas involved with cognitive function, chronic subdural hematoma (blood clot in the brain) resulting from head injury (common in the elderly and alcoholics), hydrocephalus, and normal pressure hydrocephalus. Surgical treatment may relieve symptoms.
A diagnosis of dementia requires a medical history, physical examination (including neurological examination), and appropriate laboratory tests.
Medical history: Taking a thorough medical history involves gathering information about the onset, duration, and progression of symptoms. Also, any possible risk factors for dementia, such as a family history of the disorder or other neurological diseases, past medical history (conditions or diseases), and drug use (prescription, recreational, and non-prescription), will be evaluated.
The American Psychiatric Association has established two generally accepted criteria for the diagnosis of dementia: (1) a decline in recent and past memory and (2) impairment of one or more of the following functions: language (aphasia or the misuse of words or inability to remember and use words correctly); motor activity (apraxia or unable to perform motor activities even though physical ability remains intact); recognition (agnosia or unable to recognize objects, even though sensory function is intact); and executive function (unable to plan, organize, and think abstractly). Symptoms often develop gradually and show a progressive deterioration in function.
Delirium: The doctor must distinguish between delirium and dementia. Delirium is a transient (occurring over a short period of time), acute mental disturbance that manifests as disorganized thinking and a decreased ability to pay attention to the external world. Delirium is often caused by infectious disease, brain tumor(s), poisoning, drug or alcohol intoxication or withdrawal, seizures, head trauma, and metabolic disorders. It is important to treat underlying conditions promptly, as they may be life-threatening or progressive if left untreated. Symptoms of delirium include disorientation related to person, place, and time, memory impairment, rambling (irrelevant, incoherent speech), and a reduced level of consciousness.
Pseudodementia: Pseudodementia, a type of severe depression that occurs mainly in elderly people, causes many older individuals to fear that their memory and other mental abilities are diminishing as they age, even if this is not the case. A doctor will determine if the individual is suffering from this condition. The cognitive changes that resemble dementia include slow motor movements and thinking and short-term memory loss. Individuals who are depressed may be apathetic and answer questions without attempting to provide the correct response. They may exhibit poor eye contact and little spontaneous movement.
Blood tests: Blood tests to determine basic health will be used. A complete blood count (CBC) will determine thyroid problems, liver health, blood sugar levels, electrolyte (such as sodium and potassium) balances, vitamin deficiencies, and immune health. Blood tests can also determine if sexually transmitted diseases exist, such as human immunodeficiency virus (HIV) or syphilis.
Neuropsychological testing: Sometimes doctors undertake a more extensive assessment of memory, problem-solving abilities, attention spans, counting skills, and language. This is especially helpful in trying to detect dementias at an early stage. Doctors use formal psychological tests to determine if an individual's mental abilities are as expected for his or her age and education. The patterns of any mental deficits observed during neuropsychological testing can help doctors sort out possible causes of dementia.
A Mental status evaluation screens memory, problem-solving abilities, attention spans, counting skills, and language skills. Questions such as "what day is it today?" or "who is the president of the United States?" may be asked. Recall tests are another example. Doctors may list familiar objects and then ask a person to repeat them immediately and again five minutes later. The Clock Drawing Test, the Mini-Mental State Examination (MMSE), and the Functional Assessment Staging (FAST) are commonly used mental status evaluation tools for determining if Alzheimer's disease or dementia are present.
Brain scans: Doctors may want to take a picture of the brain using a brain scan. Several types of brain scans are available, including computerized tomography (CT) scan, magnetic resonance imaging (MRI) scan, and positron emission tomography (PET) scan. Doctors can pinpoint visible abnormalities in the brain using these imaging techniques.
Electroencephalography: Electroencephalography (EEG) traces brain wave activity. Some central nervous system disorders cause distinct changes in brain wave activity. Alzheimer's disease generally reveals "slow" waves. An EEG can help distinguish a severely depressed or delirious individual whose brain waves are normal from an individual with a degenerative neurological disease.
Genetic testing: Huntington's disease is diagnosed by analyzing DNA in the blood sample to determine if the gene exists for that condition. Huntington's disease is due to a single gene on chromosome 4. If someone has Huntington's disease he/she has a 50% chance of passing that gene to his/her children, causing the development of the disease.
Similarly, an analysis of DNA in the blood sample may reveal the ApoE4 gene, which is found in about one-third of Alzheimer's disease patients. However, until preventative treatment is available, testing an asymptomatic patient for APOE is not recommended. Clinical testing is also available for the PS1 gene, which accounts for many cases of the disease.
signs and symptoms
Symptoms develop when the underlying condition, such as Alzheimer's disease or alcoholism, affects areas of the brain involved with learning, memory, decision-making, and language.
Memory impairment is often the first symptom to be noticed. An individual with dementia may be unable to remember ordinary information, such as their birth date, phone number, and address, and may be unable to recognize friends and family members.
There is a progressive decline in cognitive function, including decision making, judgment, orientation in time and space, problem solving, and verbal communication.
Behavioral changes may be found in eating, dressing, and toileting. Dementia patients may be unable to dress without help and become incontinent or lose the ability to control urine flow. Normal interests, such as hobbies and social groups, are abandoned. Routine activities, such as driving, grocery shopping, and housecleaning, are unable to be performed. Individuals with dementia also have changes in personality, such as inappropriate responses and lack of emotional control.
Trauma may cause prolonged or permanent changes in cognition, memory, emotions, or behavior.
Complications depend on the underlying cause of the dementia. Complications include loss of ability to function or care for self, verbal and physical abusiveness to loved ones, loss of ability to interact, increased infections anywhere in the body, reduced life span, abuse by an overstressed caregiver, side effects of medications used to treat the disorder, and depression (common in patients with Alzheimer's disease).
Infections: In severe and advanced dementia, individuals may lose all ability to care for themselves. This can make them more prone to additional health problems such as pneumonia, which is a bacterial infection of the lungs and respiratory system. The individual may have difficulty swallowing food and liquids, which may cause them to aspirate (inhale) some of what they eat and drink into their airways and lungs, which may lead to pneumonia.
Urinary incontinence may require the placement of a urinary catheter, which increases the risk of urinary tract infections. Untreated urinary tract infections can lead to more serious, life-threatening infections.
Falls and their complications: Individuals with dementia may become disoriented, increasing their risk of falls. Falls can lead to bone fractures that require hospitalization, medications, and surgery, increasing symptoms of dementia such as confusion and agitation. In addition, falls are a common cause of serious head injuries, such as brain hemorrhage (bleeding in the brain). Prolonged immobilization after surgery and hospitalization may also increase the risk of a pulmonary embolism (blood clot in the lungs), which can be life-threatening.
Age: The greatest risk factor for dementia is advanced age. Dementia is considered a late-life disease because it tends to develop mostly in elderly people. About five to eight percent of all people over the age of 65 have some form of dementia; this number doubles every five years above that age. It is estimated that as many as half of people in their 80s suffer from dementia. Research has determined that a decline in cerebral glucosemetabolism commonly found in advanced aging may be a risk factor in the development of dementia.
Heredity: The risk of developing dementia, such as dementia associated with Alzheimer's disease or Huntington's disease, appears to be slightly higher if a first-degree relative (a parent, sister, or brother) has the disease.
Trauma: Trauma to the brain can result in damage to brain cells, leading to dementia. Brain trauma can result from accidents (such as motor vehicle wrecks and falls), assaults (such as gunshot wounds or beatings), or from sports activities (such as boxing) without protective gear. Dementia caused as a result of trauma can be permanent or temporary, depending on the extent of damage and the ability of the individual's body to recover.
Infections: Infections of brain structures, such as meningitis (inflammation of the protective membranes in the brain) and encephalitis (inflammation of the brain), are primary causes of dementia. Other infections, such as human immunodeficiency virus (HIV) or acquired immunodeficiency syndrome (AIDS) and syphilis (a bacterial sexually transmitted disease), can affect the brain in later stages. In all cases, inflammation in the brain damages cells. Damage to memory due to infection can be permanent or temporary, depending upon the extent of the damage and the ability of the individual's body to recover.
Normal pressure hydrocephalus: The brain floats in a clear fluid called cerebrospinal fluid. This fluid also fills internal spaces in the brain called ventricles. If too much fluid collects outside of the brain, it causes a condition known as hydrocephalus. This condition raises the fluid pressure inside the skull and compresses brain tissue from outside. It may cause severe damage and death. If fluid builds up in the ventricles (four communicating cavities filled with cerebrospinal fluid in the brain), the fluid pressure remains normal. This condition is known as normal pressure hydrocephalus, but it causes brain tissue to be compressed from within. The compression on the brain from the fluid build up causes a decrease in the delivery of oxygen to brain tissues, thus causing damage that can lead to permanent or temporary dementia.
Simple hydrocephalus: Simple hydrocephalus may cause typical dementia symptoms or lead to coma. The difference in simple hydrocephalus and normal pressure hydrocephalus is that individuals have trouble walking and become incontinent (unable to control urination) at the same time they start to lose mental functions, such as memory, in simple hydrocephalus. If normal pressure hydrocephalus is diagnosed early, the internal fluid pressure may be lowered by the placement of a shunt. A shunt is a medical device that helps drain excess cerebrospinal fluid from the ventricles, decreasing pressure. This can stop the dementia, gait (pattern of walking) problems, and the incontinence from becoming severe.
Brain tumors: Tumors can contribute to signs and symptoms of dementia in a number of ways. A tumor can press on structures that control hormone secretion in the brain, such as the hypothalamus or pituitary gland. Tumors can also press directly on brain cells, damaging them and causing cell death. Treating the tumor, with chemotherapy, radiation, or surgery, may reverse the symptoms in some cases.
Toxic exposure: Individuals exposed to toxic chemicals, such as those who pave roads or paint cars, especially without adequate protective equipment and ventilation, may develop dementia from the damage these substances can cause to brain cells. Some toxic exposures may be treatable and avoiding further exposure can prevent further damage.
Metabolic disorders: Diseases of the liver, pancreas, or kidneys can lead to dementia by disrupting the balances of substances in the blood, including minerals, vitamins, and sugars. Often, these changes occur rapidly and affect the individual's level of alertness and consciousness. This is called delirium. Although the individual with delirium, like the one with dementia, cannot think well or remember, treatment of the underlying disease may fully reverse the condition. If the underlying disease persists, however, brain cells may die and the individual may develop dementia.
Hormone disorders: Disorders of hormone-secreting and hormone-regulating organs, such as the thyroid gland, the parathyroid glands, the pituitary gland, or the adrenal glands, can lead to hormone imbalances. These imbalances may lead to dementia if not corrected with hormonal supplementation in the form of drugs and supplements.
Hypoxia: Hypoxia is a lack of oxygen in the body. Individuals who do not have enough oxygen in their blood may develop dementia because the blood brings oxygen to the brain cells. Brains cells need oxygen to survive. The most common causes of hypoxia are lung diseases, such as emphysema or pneumonia. These limit oxygen intake or transfer of oxygen from the airways of the lungs to the blood. Cigarette smoking is a frequent cause of emphysema. Smoking can increase hypoxic brain damage by damaging the lungs and also by increasing the levels of carbon monoxide in the blood. Heart disease leading to congestive heart failure may also lower the amount of oxygen in the blood. Sudden, severe hypoxia may also cause brain damage and symptoms of dementia. Sudden hypoxia may occur if an individual is comatose or has to be resuscitated. Vascular dementia, or dementia as a result of a lack of blood flow to the brain, can be caused by anemia. Anemia is the decreased capacity of red blood cells to carry oxygen to the body's tissues. This results in cell death, such as in the brain, causing temporary or permanent dementia.
Drugs: Some prescription and non-prescription drugs can cause temporary problems with memory and concentration as side effects, mainly in the elderly. Misuse or abuse of medications chronically (long-term), whether intentional or accidental, may lead to dementia. Illegal drugs, such as cocaine and heroin, may also lead to signs and symptoms of dementia.
Nutritional deficiencies: Deficiencies of certain nutrients, especially the B vitamins, may lead to dementia if not corrected. Homocysteine levels in the body are increased with vitamin deficiencies including folic acid, vitamin B1 (thiamin), and vitamin B12 (cyanocobalamin). Homocysteine is an amino acid, which helps build proteins in the body. An elevated homocysteine level is thought to be a risk factor for developing dementia along with increasing the risk of developing heart disease. Iron deficiency may lead to anemia, which can lead to brain cell death and eventually dementia.
Chronic alcoholism: Dementia in individuals with chronic (long-term) alcoholism is believed to be a result of other complications such as liver disease and nutritional deficiencies.