Dementia is characterized by the development of multiple cognitive deficits, including memory (deficits in learning new information or in recalling previously learned information) and at least one of the following: language (word retrieval difficulties, defects in understanding complex commands, loss of semantic knowledge), perception (problems in the identification of objects or in the recognition of familiar places), praxis (impairment in the ability to carry out complex movements), and executive functions (inability to plan and organize behavior). Calculation ability defects and conceptual difficulties are also commonly found. These deficits are usually progressive but in some cases are static. Dementia also comprises personality and emotional changes. Lack of awareness of the cognitive defects is frequently found. Psychiatric symptoms such as delusional ideation and hallucinations also might develop. As the disease progresses, these deficits impair the social and occupational functioning of the individual.
The acquired component of dementia distinguishes it from congenital mental retardation. The diagnosis of dementia requires a decline from the previous level of functioning. Dementia should be distinguished from delirium, which is an acute impairment of cognitive and behavioral functioning with fluctuating disturbance of attention. Delirium lasts hours or days; in dementia, a relatively stable symptomatology is found. Dementia is more frequently seen in the elderly, and it needs to be differentiated from the age-related cognitive changes that are characteristic of normal aging. Normal elderly individuals frequently suffer from memory decline, but other cognitive areas are usually better preserved. Memory defects in normal aging are observed in the memory recall stage (poor retrieval of nouns and proper names, but improvement is seen with recognition or cueing) rather than in the storage of new information. Severe depression in elders may mimic a dementia (pseudodementia). Depression affects all measures that depend on speed, effort, and attention; memory retrieval difficulties are also frequent. Contrary to dementia patients, depressed patients are usually aware of their memory problems and complain about them. It is important to note that depression might coexist with dementia and that depression can be a major feature of many dementia types, particularly fronto-subcortical dementias.
Dementia increases sharply with age. Most dementias are found in people older than 65. The prevalence for all dementias is over 2% by age 65 and over 30% for those 85 or older. Fifty percent to 70% of the cases of dementia correspond to an Alzheimer-type dementia; approximately 35% have pure Alzheimer’s disease (AD); the remaining have AD associated with vascular disease or Lewy body pathology. The second most common type of dementia is vascular dementia, making up 10% to 30% of the dementia cases. The prevalence of fronto-temporal dementia has been estimated at 5%. The prevalence of other types of dementia is less clear.
Subtypes Of Dementia
Several classifications of dementia have been proposed. They can be divided into cortical versus fronto-subcortical dementias based on clinical characteristics. Cortical dementias, such as AD, affect language, memory, praxis, perception, spatial skills, and executive functions; they involve the cerebral cortex. Most of the other dementias (i.e., Parkinson’s, Huntington’s, vascular, Lewy body, and human immunodeficiency virus [HIV] dementias) engage the fronto-subcortical structures (thalamus, caudate, and subcortical white matter), and the predominant features are lack of motivation, attentional difficulties, movement disorders, and slowing of cognition. Dementias can also be classified based on the etiology or cause of the dementia. There are degenerative dementias such as AD, Parkinson’s disease dementia, and Huntington’s disease dementia. Vascular dementias result from cerebrovascular insufficiency in different parts of the brain. Other types of dementias are infectious dementias produced by viruses, bacteria, fungi, and parasites. Examples are HIV-associated dementias, neurosyphilis, Lyme disease, herpes encephalitis, and cysticercosis. Prion dementias, such as Creutzfeldt-Jakob disease, are produced by small proteinaceous infectious particles that produce spongiform disease of the brain. Toxic-metabolic dementias are seen in cases of prolonged exposure to neurotoxins (alcoholic dementia, Wernicke-Korsakoff syndrome) or lengthened metabolic disruptions (hepatic encephalopathy, dialysis dementia, chronic hypoxia). Other types of dementia are traumatic, secondary to repeated blows to the head, and neoplastic, secondary to large brain tumors. Cognitive deficits are frequently associated with some psychiatric conditions and can produce psychiatric-related dementias. Depression, for example, presents psychomotor retardation and cognitive impairment that in most cases are rather secondary to the mood impairment than to a real dementia. The term pseudodementia (mimic dementia) has been used to describe the cognitive changes observed in depression. When dementia and depression coexist, the cognitive deficits are more severe. There is also dementia associated with bipolar disorders and schizophrenia.
Characteristics Of The Most Frequent Types Of Dementia
Alzheimer’s disease is characterized by the presence of progressive cognitive decline in at least two cognitive domains. The decline in memory with deficits in episodic memory that progresses to amnesia is characteristic of AD. Word-finding difficulties that evolve into an anomia (poor naming) and impaired comprehension are usually observed. Visuospatial difficulties and inability to perform learned movements (apraxia) constitute another important characteristic of AD. In addition, AD is characterized by personality and social changes such as lack of initiative, decreased motivation, indifference, and apathy. AD has important hereditary components.
Vascular dementia includes a group of dementing disorders that results from cerebrovascular insufficiency such as thromboembolism or multiple cortical or subcortical strokes and hemorrhagic events. Risk factors for vascular dementia are advancing age, male gender, a history of hypertension, and previous strokes. The dementia characteristics of vascular dementia depend on the site of the lesions. Cortical lesions produce a cortical dementia type with symptoms of amnesia, agnosia, aphasia, and apraxia. Subcortical lesions, on the other hand, are characterized by psychomotor symptoms and attentional and behavioral difficulties.
Fronto-temporal dementia is characterized by severe personality and behavioral disturbances that usually precede the cognitive decline.
Assessment Of Dementia
Dementia is a behavioral and cognitive syndrome, and its diagnosis is based on observable deficits that can be evaluated and measured through cognitive assessment, clinical observation, and neuropsychological evaluation. The cognitive and behavioral assessments must be interpreted in the context of the neurologic examination. The presence of motor disturbances, for example, points toward a more fronto-subcortical dementia, while normal motor examination results plus cognitive deficits point to a cortical dementia. In addition, laboratory tests such as blood tests, urinalyses, and thyroid tests, as well as neuroimaging procedures (computed tomography or magnetic resonance imaging) help to establish the differential diagnosis among dementia syndromes.
Treatment Of Dementia
The treatment of dementia has two components. One is the pharmacological treatment directed to the patient who suffers from dementia. The other component is the dementia management directed toward the family and caregivers.
The pharmacological treatment of dementia varies depending on the etiology of the dementia. In the majority of cases, the conditions associated with dementia have no cure, but management of the symptoms or prevention can be undertaken. In the case of AD, researchers have identified some factors that can reduce the risks for developing AD; for example, preventing head injuries, exercising regularly, and using agents that reduce oxidative injury such as vitamin E. The fact that the brains of AD patients present a decrease in the levels of acetylcholine has led to the use of medications that increase the action of this neurotransmitter with very modest results. The treatment for vascular dementia includes the management of hypertension and the prevention of new strokes by using anticoagulants, cerebral vasodilators, and selective thrombin inhibitors. Dopaminergic therapy has been useful with motor and cognitive symptoms of Parkinson’s dementia and Lewy body dementia. Infectious dementias are treated with antibiotics.
The patient usually loses insight, and in most cases the impact of dementia is greater for the family than for the patient. The family and caregivers need to learn how to manage the patient through the cognitive and behavioral gradual decline. Caregivers slowly assume the patient’s activities of instrumental living such as shopping, cooking, and driving. They also assist the patient in daily living activities such as dressing, eating, bathing, and toileting. Caregivers should promote functional independence by skills practice, positive reinforcement, and assistance of occupational and physical therapy. However, it is recommended to structure the patient’s activities and to avoid changes in routine. Dementia patients should also be cognitively stimulated. Memory aids, notebooks, pegboards, and word association have been shown to be useful in cases of dementia. The family needs to learn how to maintain good communication and appropriate interaction with the patient. Behavioral disturbances, particularly irritability, aggression, and delusions, frequently require the patient’s hospitalization. The family can learn to identify the precipitating factors of behavioral aggression, and family interventions can help to reduce the frequency of these events. Family education and counseling are essential to improve caregiver satisfaction and to delay nursing home placement. Family members also require legal counsel. After patients lose their decision-making capacity, the presence of a legal representative for health care decisions is important.
- American Psychiatric Association. (2000). Diagnostic and statistical manual of mental disorders (4th , text revision). Washington, DC: Author.
- com, http://www.dementia.com/
- Mendez, M. F., & Cummings, J. L. (2003). Dementia: A clinical approach (3rd ed.). Philadelphia: Butterworth Heinemann.