Introduction & Clinical Features
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Dementia is a neurodegenerative clinical syndrome encompassing a wide range of diseases (including Alzheimer Disease Opens in new window and Parkinson’s Opens in new window, vascular constriction, head trauma and infectious disease such as AIDS and Creutzfeldt-Jakob disease) characterized by progressive decline in mental functioning. The syndrome is characterized by compromised functioning in domains such as language Opens in new window, memory Opens in new window, visual or spatial abilities, or judgment severe enough to interfere with daily life.
In dementia, cognitive impairment is typically insidious in onset (except in some cases of vascular dementia Opens in new window), progressive in nature with eventual complete loss of ability to converse. Awareness, alertness and attention are generally intact (unless there is superimposed delirium Opens in new window, though not an uncommon situation). Forgetfulness, decrease in intellectual ability, and personality change (exaggeration of premorbid personality traits such as querulousness, suspiciousness, and impulsivity) are also prominent in dementia.
To date, more than 24 million people worldwide are affected by dementia, and this prevalence is predicted to quadruple over the next three decades. Although onset sometimes occurs before 60 years of age, the prevalence of dementia increases strongly with age, and among the elderly it is a primary contributor to disability and dependence (Sousa et al., 2009, 2010).
As a consequence, due to the current demographic changes associated with significant population aging, dementia is a significant public health concern not only in industrialized countries, in which it has triggered profound government responses, but also in developing countries.
In the United States alone, the monetary cost of dementia amounts to $157-$215 billion annually, making this syndrome more costly than heart disease or cancer (Hurd et al., 2013). The bulk of the economic cost of dementia does not stem from medical services but from the need for long-term institutional and home-based care.
Memory deficits are classic with severe impairment in short-term memory Opens in new window, severe impairment in ability to form new memories with remote memory Opens in new window remaining intact until the late stages.
Some individuals with incipient memory loss are aware of their declining abilities, but most patients with evolving dementia never acknowledge that they have memory dysfunction. It becomes apparent over time to observers that persons with incipient dementia routinely forget recent events and conversations and repeat themselves.
Behind the forgetfulness that appears benign may be more serious mistakes such as forgotten bills, missed appointments, misdirected travels, and improperly taken medications. For example, a patient who took a prescribed pill at 9 P.M. may not remember at 10 P.M. that he had already taken the medicine, so he may take an additional dose at 10.
At 11 P.M. he may have again forgotten taking the pill at 10, and so on. Accidental overdoses of this kind are quite common among elderly patients with mild to moderate dementia. Thus, dementia, or cognitive impairment severe enough to interfere with social and occupational function, is a common but abnormal condition in the elderly, affecting 10–20% of that population.
Dementia is defined in the DSM-IV-TR Opens in new window as a series of disorders characterized by the development of multiple cognitive deficits (including memory impairment) that are due to the direct physiological effects of a general medical condition, the persisting effects of a substance, or multiple etiologies (e.g. the combined effects of a metabolic and a degenerative disorder).
The disorders constituting the dementias share a common symptom presentation and are identified and classified as follows, on the basis of etiology:
- Dementia of the Alzheimer’s Type, With Early Onset,
- Dementia of the Alzheimer’s Type, With Late Onset,
- Dementia Due to Pick’s Disease,
- Dementia Due to Parkinson’s Disease,
- Dementia Due to Huntington’s Disease,
- Vascular Dementia,
- Dementia Due to HIV Disease,
- Dementia Due to Head Trauma,
- Dementia Due to Other General Medical Conditions,
- Substance Induced Persisting Dementia, and
- Dementia Due to Multiple Etiologies.
In diagnosing dementia, the cognitive deficits exhibited in these disorders must be sufficient to interfere with either occupational functioning or the individual’s usual social activities or relationships. In addition, the observed deficits must represent a decline from a higher level of function and not be the consequence of a delirium.
A delirium Opens in new window can be superimposed on a dementia, however, and both can be diagnosed if the dementia is observed when the delirium is not in evidence. Dementia typically is chronic and occurs in the presence of a clear sensorium. If clouding of consciousness occurs, the diagnosis of delirium should be considered.
Essential to the diagnosis of dementia is the presence of cognitive deficits that include memory impairment and at least one of the following abnormalities of cognition: aphasia, agnosia, aprasia, or a disturbance in executive function.
Memory function is divided into three compartments that can easily be evaluated during a Mental Status Examination. These are immediate recall (primary memory), recent (secondary) memory, and remote (tertiary memory).
- Primary Memory
Primary memory is characterized by a limited capacity, rapid accessibility, and a duration of seconds to minutes. The anatomic site of destruction of primary memory is the reticular activating system, and the principal activity of the primary memory is the registration of new information.
Primary memory is generally tested by asking the patient to repeat immediately a series of numbers in the order given. Because primary memory-testing measures such parameters as attention, concentration, and the ability to follow instructions, the results are often abnormal for the demented patient. This loss of ability to register new information accounts in part for the confusion and frustration the demented patient feels when confronted with unexpected changes in daily routine.
- Secondary Memory
Secondary memory has a much larger capacity than primary memory, a duration of minutes to years, and relatively slow accessibility. The anatomic site of dysfunction for secondary memory is the limbic system, and individuals with a lesion in this area may have little difficulty repeating digits immediately, but show rapid decay of these new memories.
In minutes, the patient with limbic involvement may be totally unable to recall the digits or even remember that a test has been administered. Thus, secondary memory represents the retention and recall of information that has been previously registered by primary memory.
Clinically, secondary memory is tested by having the individual repeat three objects after having been distracted (usually by the examiner’s continuation of the Mental Status Examination) for 3–5 minutes. Like primary memory, secondary recall is often impaired in dementia.
Patients with an early or mild dementia may be able to retrieve memories if given some sort of clue, such as “One of the objects you missed was a color.” Giving clues to the demented patient with a primary memory loss is pointless, because the memories were never registered. Wermicke-Korsakoff syndrome is an example of a condition in which primary memory may be intact while secondary recall is impaired.
- Tertiary Memory
Tertiary (remote) memory has a capacity that is probably unlimited, and such memories are often permanently retained. Access to tertiary memories is rapid, and the anatomical dysfunction in tertiary memory loss is in the association cortex.
In the early stages of dementia, tertiary memory is generally intact. It is tested by instructing the individual to remember personal information or past material. The personal significance of the information often influences the patient’s ability to remember it. For example, a woman who worked for many years as a seamstress might remember many details related to that occupation, but could not recall the names of past residents or three large cities in the United States.
Thus, a patient’s inability to remember highly significant past material is an ominous finding. Collateral data from informants are essential in the proper assessment of memory function. In summary, primary and secondary memories are most likely to be impaired in dementia, with tertiary memory often spared until late in the course of the disease.
Aphasia is an abnormality of language that often occurs in Vascular Dementias Opens in new window involving the dominant hemisphere. Because this hemisphere controls verbal, written, and sign language, these patients may have significant problems interacting with people in their environment.
Patients with dementia and aphasia may exhibit paucity of speech, poor articulation, and a telegraphic pattern of speech (nonfluent, Broca’s aphasia). This form of aphasia generally involves the middle cerebral artery with resultant paresis of the right arm and lower face.
Despite faulty communication skills, patients with dementia with nonfluent aphasia have normal comprehension and awareness of their language impairment. As a result, such patients often present with significant depression, anxiety, and frustration.
By contrast, patients with dementia with fluent (Wermicke’s) aphasia may be quite verbose and articulate, but much of the language is nonsensical and rife with such paraphasia as neologisms Opens in new window and clang (rhyming) associations.
Whereas nonfluent aphasias are usually associated with discrete lesions, fluent aphasia can result from such diffuse conditions as dementia of the Alzheimer’s Type. More commonly, fluent aphasias occur in conjunction with Vascular Dementia secondary to temporal or parietal lobe CVA.
Because the demented patients with fluent aphasia have impaired comprehension, they may seem apathetic and unconcerned with their language deficits, if they are in fact aware of them at all. They do not generally display the emotional distress of patients with dementia and nonfluent aphasia.
Patients with dementia may also lose their ability to recognize. Agnosia is a feature of a dominant hemisphere lesion and involves altered perception in which, despite normal sensations, intellect, and language, the patient cannot recognize objects.
This is in contrast to aphasia, in which the patient with dementia may not be able to name objects, but can recognize them. The type of agnosia depends on the area of the sensory cortex that is involved.
Some demented patients with severe visual agnosia cannot name objects presented, match them to samples, or point to objects named by the examiner. Other patients may present with auditory agnosia and be unable to localize or distinguish such sounds as the ringing of a telephone. A minority of demented patients may exhibit astereognosis, inability to identify an object by palpation.
Demented patients may also lose their ability to carry out selected motor activities despite intact motor abilities, sensory function, and comprehension of the assigned task (apraxia). Affected patients cannot perform such activities as brushing their teeth, chewing food, or waving goodbye when asked to do so.
The two most common forms of apraxia in demented patients are ideational and gait apraxia.
- Ideational apraxia is the inability to perform motor activities that require sequential steps and results from a lesion involving frontal lobes or the complete cerebrum.
- Gait apraxia, often seen in such conditions as normal-pressure hydrocephalus, is the inability to perform various motions of ambulation. It also results from conditions that diffusely affect the cerebrum.
- Executive Functioning
Impairment of executive function Opens in new window affects the ability to think abstractly, plan, initiate, and end complex behavior. On Mental Status Examination, patients with dementia display problems coping with new tasks. Such activities as subtracting serial sevens may be impaired.
Obviously, aphasia, agnosia, apraxia, and impairment of executive function can seriously impede the demented patient’s ability to interact with his or her environment. An appropriate Mental Status Examination of the patient with suspected dementia should include screening for the presence of these abnormalities.
In delirium, the onset of altered memory is acute and the pattern typically fluctuates (waxing and waning) with increased proclivity for confusion during the night. Delirium is more likely to feature autonomic hyperactivity and alterations in the level of consciousness. In some cases a dementia can have a superimposed delirium.
Patients with major depression often complain of lapses in memory and judgment, poor concentration, and seemingly diminished intellectual capacity. Often these symptoms are mistakenly diagnosed as dementia, especially in elderly population.
A thorough medical history and Mental Status Examination Opens in new window focusing on such symptoms as hopelessness, crying episodes, and unrealistic guilt in conjunction with a family history can be diagnostically beneficial. The term pseudodementia has been used to denote cognitive impairment secondary to a functional mental disorder, most commonly depression.
In comparison with demented patients, those with depressive pseudodementia Opens in new window exhibit better insight regarding their cognitive dysfunction, are more likely to give “I don’t know” answers and may exhibit neurovegetative signs of depression.
Pharmacological treatment of the depression should improve the cognitive dysfunction as well. Because of the rapid onset of their antidepressant action, the use of psychostimulants (methylphenidate, dextroamphetamine) to differentiate between dementia and pseudodementia has been advocated by some authors. Some authors have proposed abandonment of the term pseudodementia, suggesting dementia and a superimposed affective disorder.
An amnestic disorder Opens in new window also presents with a signitifant memory deficit, but without the other associated features such as aphasia, agnosia, and apraxia. If cognitive impairment occurs only in the context of drug use, substance intoxication or substance withdrawal is the appropriate diagnosis.
Although mental retardation implies below-average intellect and subsequent impairment in other areas of function, the onset is before 18 years of age and abnormalities of memory do not always occur. Mental retardation Opens in new window must be considered in the differential diagnosis of dementias of childhood and adolescence along with such disorders as Wilson’s disease (hepatolenticular degeneration), lead intoxication, subacute sclerosing panencephalitis, HIV spectrum disorders, and abuse of substances, particularly inhalants.
Patients with schizophrenia Opens in new window may also exhibit a variety of cognitive abnormalities, but this condition also has an early onset, a distinctive constellation of symptoms, and does not result from a medical condition or the persisting effects of a substance.
Factitious Disorder Opens in new window must be distinguished from dementia. Unlike dementia, this condition presents with inconsistent symptoms that, although similar in some respects, are not totally consistent with those of a dementia. For example, a patient with Factitious Disorder with Predominantly Psychological Signs and Symptoms (in this case dementia) might have equal impairment in all phases of memory, while patients with dementia usually have better remote than recent memory.
Dementia must also be distinguished from benign senescence (normal aging). Only when such changes exceed the level of altered function to be expected for the patient’s age is the diagnosis of dementia warranted.
The course of a particular dementia is influenced by its etiology. Although historically the dementias have been considered progressive and irreversible, there is, in fact, significant variation in the course of individual dementias. The disorder can be progressive, static, or remitting. In addition to the etiology, factors that influence course of the dementia include
- the time span between the onset and the initiation of a prescribed treatment,
- the degree of reversibility of the particular dementia,
- the presence of comorbid mental disorders, and
- the level of psychosocial support.
The previous distinction between treatable and untreatable dementias has been replaced by the concepts of reversible, irreversible, and arrestable dementias. Most reversible cases of dementia are associated with a shorter duration of symptoms, mild cognitive impairment and superimposed delirium. Specially, the dementias caused by drugs, depression, and metabolic disorders are most likely to be reversible. Other conditions such as normal pressure hydrocephalous, subdural hematomas, and tertiary syphilis are more commonly arrestable.
Although potentially reversible dementias should be aggressively investigated, in reality, only 8% of dementias are partially reversible and about 3% fully reversible.
There is some evidence to suggest that the early treatment of demented patients, particularly those with Alzheimer’s type, with such agents as donepezil (Aricept), which acts as an inhibitor of acetylcholinesterase, and galanthamine (Reminyl) may slow the rate of progression of the dementia, although some investigators doubt the ability of these agents to slow the rate of progression.
The management of dementia involves
- the identification and, if possible, correction of the underlying cause;
- environmental manipulation to reorient the patient;
- intervention with the family by means of education, peer support, providing access to community organization, discussing powers of attorney, living wills, and institutionalization if appropriate, and arranging therapy if indicated; and
- pharmacological management of psychiatric symptoms and behavior.
For psychotic patients, low-dose antipsychotics with minimal anticholinergic potential and occasionally short-acting benzodiazepiens (e.g. lorazepam) are the drugs of choice.
Because depression with antidepressants of low anticholinergic and hypotensive potential is often indicated. For patients with dementia secondary to abuse of drugs or alcohol, appropriate referral for rehabilitation is essential. Some elderly patients may be further disinhibited by benzodiazepines.
- Delirium Opens in new window
- Dementia of the Alzheimer’s Type (DAT)Opens in new window
- Vascular Dementia Opens in new window
- Dementia due to HIV DiseaseOpens in new window
- Dementia due to Pick's DiseaseOpens in new window
- Dementia due to Parkinson's DiseaseOpens in new window
- Dementia due to Huntington's DiseaseOpens in new window
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