Dementia
Overview
Dementia refers to a loss of cognitive function (cognition) due to changes in the brain caused by disease or trauma. The changes may occur gradually or quickly; and how they occur may determine whether dementia is reversible or irreversible.
Cognition is the act or process of thinking, perceiving, and learning. Cognitive functions that may be affected by dementia include the following:
- Decision making, judgment
- Memory
- Spatial orientation
- Thinking, reasoning
- Verbal communication
Dementia also may result in behavioral and personality changes, depending on the area(s) of the brain affected.
Types
Some dementia is reversible and can be cured partially or completely with treatment. The degree of reversibility often depends on how quickly the underlying cause is treated.
Irreversible dementia is caused by an incurable condition (e.g., Alzheimer's disease). Patients with irreversible dementia are eventually unable to care for themselves and may require round-the-clock care.
Incidence and Prevalence
An estimated 2 million people in the United States suffer from severe dementia and another 1 to 5 million people experience mild to moderate dementia. Five to eight percent of people over the age of 65 have some form of dementia and the number doubles every 5 years over age 65.
The prevalence of dementia has increased over the past few decades, either because of greater awareness and more accurate diagnosis, or because increased longevity is creating a larger population of elderly, which is the age group most commonly affected.
Risk Factors
The greatest risk factor for dementia is advanced age. Inheriting the genes associated with Alzheimer's or Huntington's disease is a risk factor. Untreated infectious and metabolic disease and substance abuse also can lead to dementia.
Other risk factors include the following:
- Brain tumor
- Cardiovascular disease (e.g., hypertension, atherosclerosis)
- Head injury
- Kidney failure, liver disease, thyroid disease
- Vitamin deficiencies: B12, folic acid, B1 (thiamine)
Causes
More than 50 conditions are associated with dementia, including degenerative neurological disorders (e.g., Alzheimer's disease), vascular disorders (e.g., multi-infarct disease), inherited disorders (e.g., Huntington's disease), and infectious diseases (e.g., HIV/AIDS).
Alzheimer's disease causes 50-70% of all cases of dementia. Alzheimer's is the progressive deterioration of areas in the brain essential for learning and memory.
Lewy body dementia is similar to Alzheimer's but may progress more rapidly. Abnormal brain cells called cortical Lewy bodies occur throughout the brain and produce symptoms.
Pick's disease is also similar to Alzheimer's. In most patients, the frontal and temporal lobes of the brain atrophy. This illness usually affects people between the ages of 40 and 60.
Amyotrophic lateral sclerosis (Lou Gehrig's disease), Huntington's disease, and Parkinson's disease are also associated with dementia. Progressive supranuclear palsy produces clinical features similar to Parkinson's disease and often causes severe cognitive difficulties.
HIV/AIDS is a viral infection that may lead to AIDS dementia complex during late stages of the disease. Antiretroviral therapy has reduced the incidence of AIDS dementia.
Creutzfeldt-Jakob disease (CJD) is a fatal infectious disease characterized by brain tissue that is filled with holes and looks like a sponge under microscopic examination. 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 (myoclonus).
Multi-infarct disease is the second most common cause of irreversible dementia. In this condition, multiple strokes (infarcts) lead to a progressive decline in cognition. Multiple infarct dementia is more common in men over 50 years old.
A person with this condition also may experiences motor weakness, urinary incontinence, and irregular muscle coordination (ataxia), and may develop hypertension, diabetes, or vascular disease.
Alcoholism can lead to vitamin B1 (thiamine) deficiency, seizures, and head injuries that produce dementia.
Chronic drug abuse also can cause symptoms of dementia. Drugs that may cause dementia include the following:
- Anticholinergics
- Barbiturates
- Benzodiazepines
- Cough suppressants
- Digitalis
- Monoamine oxidase inhibitors
- Tricyclic antidepressants
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; bacterial, viral, or fungal) and encephalitis (inflammation of the brain caused by viral or bacterial infection).
Neurosyphilis dementia may result from late-stage syphilis. This disease also may cause heart problems, tremors, loss of muscle coordination (ataxia), paralysis, and blindness and damage is irreversible.
Structural abnormalities that can produce dementia include brain tumors located in areas involved with cognitive function, chronic subdural hematoma resulting from head injury (common in the elderly and alcoholics), hydrocephalus, and normal pressure hydrocephalus. Surgical treatment can relieve symptoms.
Metabolic disorders such as low level of thyroid hormone or thyroid stimulating hormone (hypothyroidism), low blood sugar level (hypoglycemia), high blood calcium level (hypercalcemia), and liver disease can affect cognitive function. Treating the underlying condition can restore function.
Signs and Symptoms
Symptoms develop when the underlying condition affects areas of the brain involved with learning, memory, decision-making, and language.
Memory impairment is often the first symptom to be noticed. Someone with dementia may be unable to remember ordinary information, such as their birth date and address, and may be unable to recognize friends and family members.
There is progressive decline in these cognitive functions as well:
- Decision making
- Judgment
- Orientation in time and space
- Problem solving
- Verbal communication
Behavioral changes may include the following:
- Eating, dressing, toileting (e.g., unable to dress without help; becomes incontinent)
- Interests (e.g., abandons hobbies)
- Routine activities (e.g., unable to perform household tasks)
- Personality (e.g., inappropriate responses, lack of emotional control)
Diagnosis
A diagnosis of dementia requires a medical history; physical examination, including neurological examination); and appropriate laboratory tests.
Taking a thorough medical history involves gathering information about the onset, duration, and progression of symptoms; any possible risk factors for dementia, such as a family history of the disorder or other neurological disease; history of stroke; and alcohol or other drug (prescription or over-the-counter) use.
The American Psychiatric Association has established two generally accepted criteria for the diagnosis of dementia: (1) erosion of recent and remote memory and (2) impairment of one or more of the following functions:
- Language - misuse of words or inability to remember and use words correctly (i.e., aphasia)
- Motor activity - unable to perform motor activities even though physical ability remains intact (i.e., apraxia)
- Recognition - unable to recognize objects, even though sensory function is intact (i.e., agnosia)
- Executive function - unable to plan, organize, think abstractly
Symptoms often develop gradually and show a progressive deterioration in function.
Differential Diagnosis
Delirium-The physician must distinguish between delirium and dementia. Delirium is a transient, 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, 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 the following:
- Disorientation as to person, place, and time
- Memory impairment
- Rambling, irrelevant, incoherent speech
- Reduced level of consciousness
Pseudodementia-Many elderly people fear that their memory and other mental abilities are diminishing as they grow older, even if this is not the case. Some may be anxious, depressed, or suffering from pseudodementia, a type of severe depression that occurs mostly in elderly people. The cognitive changes that resemble dementia include slow motor movements and thinking and short-term memory loss. Patients 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.
Laboratory Tests
Depending on the patient's medical history and neurological examination, one or more diagnostic tests may be performed to identify the underlying cause of dementia.
Neuropsychological tests are administered to assess difficulties in attention span, perception, memory, problem solving, and social and language skills. Responses to these tests may provide diagnostic clues.
For example, a patient with Alzheimer's disease is usually cooperative, attentive, and gives appropriate responses, but will display memory loss. A patient with hydrocephalus is usually distracted and less cooperative.
Blood tests may be ordered if the history and physical examination indicates an infectious, metabolic, or toxic condition. The results help the physician rule out Alzheimer's and help determine an effective treatment plan.
- B12, folate, thiamine levels (vitamin deficiency)
- Blood glucose (hypoglycemia)
- Complete blood count (anemia)
- Drug screen (drug toxicity)
- Electrolytes (hypercalcemia, hypermagnamesia, hypernatremia)
- Liver function (liver disease)
- Lumbar puncture (normal-pressure hydrocephalus, encephalitis, meningitis)
- Thyroid function (hypothyroidism)
- VDRLT (syphilis and HIV infection)
Huntington's disease is diagnosed by analyzing DNA in the blood sample and counting the number of times the genetic code for the mutated HD gene is repeated. Individuals diagnosed with HD usually have 40 or more such "repeats"; those without it, 28 or fewer.
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.
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 patient whose brain waves are normal from a patient with a degenerative neurological disease. Imaging tests (CT scan or MRI scan) can detect structural, or physical, changes in the brain caused by stroke, blood clots, tumors, head injury, or hydrocephalus. A CT scan can show the characteristic structural changes that occur with Huntington's disease.
Treatment
In some cases, appropriate treatment for the underlying condition can resolve dementia completely or partially. The type of treatment depends on the condition. For example, antibiotics are used to treat infection, and surgery is performed to remove a blood clot or tumor.
The goal of treatment for irreversible conditions is to control symptoms. Three FDA-approved drugs may provide symptomatic relief for Alzheimer's: donepezil (Aricept®), galantamine (Reminyl®), and rivastigmine (Exelon®).
Tranquilizers and sedatives can ease agitation, anxiety, and aggression. Medications or devices may be used to help manage sleeplessness and incontinence. Safety precautions are necessary to protect a person who is disoriented and may wander from home. Many patients with dementia eventually require 24-hour care in a health or residential facility.
Prevention
Some studies indicate that a largely vegetarian diet high in betacarotene and vitamins E and C may lower the risk for dementia and Alzheimer's disease, but this is unproven. Nevertheless, eating a healthy diet that is low in saturated animal fat and not smoking tobacco can reduce the risk for stroke and other cardiovascular disorders that may lead to dementia.
Lifestyle habits that can reduce the risk for head injury include:
- Using seat belts
- Wearing a helmet when riding bicycles and motorcycles
- Wearing protective headgear when playing contact sports
Avoiding substance abuse and addiction can reduce the risk for dementia resulting from disease, vitamin deficiency, seizure, and head injury.
Safer sex practices can help prevent HIV and syphilis infection, reducing the risk for AIDS dementia complex and neurosyphilis dementia. The risk for dementia as a result of other metabolic or toxic conditions can be reduced by receiving prompt medical attention at the first sign of illness (e.g., fever, pain, swelling, heat, confusion, other impairment of cognitive function).