Dementia What is Dementia ?Dementia is an organic brain syndrome which results in global cognitive impairments. Dementia can occur as a result of a variety of neurological diseases.
Some of the more well known dementing diseases include Alzheimer’s disease (AD), multi-infarct dementia (MID), and Huntington’s disease (HD). Throughout this essay the emphasis will be placed on AD (also known as dementia of the Alzheimer’s type, and primary degenerative dementia), because statistically it is the most significant dementing disease occurring in over 50% of demented patients (see epidemiology). The clinical picture in dementia is very similar to delirium, except for the course. Delirium is an acute transitory disorder.
By contrast Dementia is a long term progressive disorder (with the exception of the reversible dementias). The course of AD can range anywhere from 1.5 to 15 years with an average of about 8.1 years (Terry , 1988).
AD is usually divided into three stages mild, moderate, and severe.Throughout these stages a specific sequence of cognitive deterioration is observed (Lezak, 1993). The mild stage begins with memory, attention, speed dependent activities, and abstract reasoning dysfunction. Also mild language impairments begin to surface.
In the moderate stage, language deficits such as aphasia and apraxia become prominent. Dysfluency, paraphasias, and bizzare word combinations are common midstage speech defects. In the severe stage the patient is gradually reduced to a vegetative state. Speech becomes nonfluent, repetitive, and largely non-communicative.
Auditory comprehension is exceedingly limited, with many patients displaying partial or complete mutism. Late in the course of the disease many neuropsychological functions can no longer be measured. Also primitive reflexes such as grasp and suck emerge. Death usually results from a disease such as pneumonia which overwhelms the limited vegetative functions of the patient.
Dementia is commonly differentiated along two dimensions: age and cortical level. The first dimension, age, distinguishes between senile and presenile dementia. Senile dementia is used to describe patients who become demented after the age of 65, whereas presenile dementia applies to patients who become demented prior to that age. Late onset AD (LOAD) also known as senile dementia Alzheimer’s type (SDAT) is the predominant cause of senile dementia.
Early onset AD (EOAD) is the most frequent cause of presenile dementia, but HD, Pick’s disease and Creutzfeldt-Jakob disease though not as frequent are also important causes in presenile dementia.The second dimension, cortical level, differentiates between cortical and subcortical dementia. Corticaldementia is used to describe dementia which results from brain lesions at the cortical level, whereassubcortical dementia describes dementia resulting from subcortical brain lesions. AD and Pick’s disease arethe best known examples of cortical dementia; whereas HD, Parkinson’s disease (PD), and progressivesupranuclear palsy (PSP) are good examples of subcortical dementia (Mayke, 1994).
Dementia with bothcortical and subcortical features is also possible, in that case the term mixed dementia is used. MID is acommon example of mixed dementia. Historical developments in dementia Pre-Modern Developments The use of the term dementia dates back to Roman times. The Latin word demens did not originallyhave the specific connotation that it does today.
It meant ‘being out of one’s mind’ and, as such, was ageneral term for insanity (Pitt, 1987). It was the encylopedist Celsus who first used the worddementia in his De re medicina, published around AD 30. A century later the Cappadocian physicianAretaeus first described senile dementia with the word dotage (i.e.
, “The dotage which is the calamity of oldage…dotage commencing with old age never intermits, but accompanies the patient until death.
“).Curiously, dementia was mentioned in most systems of psychiatric classification throughout pre-moderntimes, though the precise meaning of the word is often unclear (Pitt, 1987).Nineteenth Century It can be argued that the origins of the scientific study of dementia date back to the early nineteenth century. The initial steps were undertaken by the great French psychiatrist Pinel at the beginning of that century.
Pinel’s observations led him to the conclusion that the term dementia should be applied in relation to the”progressive mental changes seen in some idiots” (Pitt,3). Furthermore, Pinel thought that dementiawas a distinct abnormal entity, and thus he used the term dementia to designate one of the five classes ofmental derangement. However, by applying the term dementia to ‘idiots’, Pinel failed to differentiatebetween dementia and mental subnormality. This was accomplished by Pinel’s student Esquirol in his 1838 textbook Mental maladies-A treatise on insanity.
Esquirol summed up the difference between the dementedand the mentally handicapped in the following epigram: “The dement is a man deprived of the possessionshe once enjoyed, he is a rich man who has become poor. But the defective has been penniless and wretchedall his life” (Mahendra, 10). Furthermore, Esquirol was also instrumental in the popularization of the termsenile dementia. Remarkably, his description of senile dementia is very similar to our present day definition.
Interestingly, in 1845 Griesinger proposed that senile dementia was due to a disease of the cerebralarteries, a faulty view which persisted until Alzheimer’s time. Much of today’s basic knowledge about dementia was accumulated throughout the second half of the nineteenth century, and the first decade of the twentieth century. 1872 saw Huntington present a papercalled “On chorea”, in which he discussed a typical case of what is now known as Huntington’s disease.Twenty years later in 1892 two significant events occurred.
First Pick in a paper called “On the relationbetween aphasia and senile brain atrophy” described the case of August H. a 71 year old patient with seniledementia. Although the case is not typical of our present day conception of the disease Pick was givencredit for discovering a new disease. The other more significant event in 1892 was Blocq and Mariensco’sdescription of scattered silver staining plaques in the cortex of senile patients.
These plaques weresubsequently named senile plaques (SP) by Simchowitz in 1911.The year 1894 saw Alzheimer’s first major contribution , a differentiation between senile and vascular(arteriosclerotic)dementia. Alzheimer described the specific changes observed in arteriosclerotic atrophy ofthe brain, which resemble what we might call vascular dementia. In 1898 another milestone occurred whenBinswanger introduced the term presenile dementia.
Thus by the twentieth century significant changes weretaking place in our understanding of dementia. The nineteenth century view that there was only one mentaldisease-insanity-and that dementia was its terminal stage was dispelled by Kraepelin in the 6th edition of histextbook Psychiatrie, published in 1899 (Pitt, 4). Kraepelin separated dementia praecox (a concept heproposed in 1898 in relation to Schizophrenia) from the other dementias (paralytica and organic), and Seniledementia was included under another category called involution psychosis (Pitt, 4).Twentieth Century In 1907 Alzheimer published his landmark case “A unique illness involving the cerebral cortex” in which he described a fifty-five year old demented woman.
The case was very unusual for two reasons its clinical course, and the discovery of a striking microscopic lesion in the woman’s brain (Beach, 1987). The clinicalcourse was unusual because of the young age of the patient and the rapidity of degeneration (the patient diedwithin four and a half years of symptom onset). At autopsy neuropathological findings were even moreunusual. One quarter to one third of cerebral cortical neurons had disappeared, and many of the remainingneurons contained thick, coiled masses of fibers within their cytoplasm (Beach, 1987).
Alzheimer speculatedthat a chemical change had occurred in the neurofibrils. Thus Alzheimer described for the first timeneurofibrillary tangles (NFT), which togther with SP are considered to be the neuropathologocal halmarksof AD (See Appendix 1 for Alzheimer’s original drawing of NFT). Alzheimer concluded that hediscovered a unique entity separate from senile dementia as it was known at that time. However, it was notuntil 1910 when Kraepelin discussed the condition in the 8th edition of his textbook Psychiatrie that ADgained official recognition.
The second decade of the twentieth century witnessed the end of the golden period in dementia research (this only lasted until the 1960’s when a renaissance occurred). U’Ren cites two reasons as the principalcauses (Pitt, 6). First the rise of Freud’s Psychodynamic theory caused American psychiatry to swerve in thedirection of psychological explanations. Second Kraepelin’s descriptions and classifications seemed to leavelittle room for therapeutic efforts or optimism.
Notwithstanding, several key contributions have been made in the ‘Dark Ages’ of dementia research. In1920 Creutzfeldt, and in 1921 Jakob, described cases of dementia with pyramidal and extrapyramidal signs.Although it is now thought that only Jakob’s case was typical of the disease the Creutzfeldt-Jakob disease(CJD) was given to the world. The year 1936 saw an important change with regards to the diagnosis of AD.
Before 1936 it was common practice to provide a diagnosis based on both clinical and pathologicalcharacteristics. However, when it became clear that many non-demented people had some senile plaquesand neurofibrillary tangles, Jervis and Soltz advised that only clinical criteria would suffice for a diagnosis ofAD (Mahendra, 14). In 1948 Jervis published his landmark paper called “Early senile dementia inMongoloid idiocy.” Jervis described three individuals with Down’s syndrome (DS), aged 37, 42 and 47years, each of whom had shown a profound emotional and intellectual deterioration in the last few years oflife.
At autopsy, all were found to have SP and two also displayed NFT (Beach, 39). This was the firstdemonstration of NFT in DS and the first full clinical and pathological correlation supporting an Alzheimer- like syndrome in DS (Beach, 39). Research in dementia began to revive in the early sixties. New causes of the dementia syndrome have been recognized including, depression, which in the form of psuedodementia may mimic dementia (Kiloh,1961), progressive supranuclear palsy (Steele et al, 1964) and normal pressure hydrocephalus (Adams et al, 1965) , (cited in Pitt, 6).
Prior to the 1960’s dementia was still viewed as a chronic, irreversible anduntreatable condition (Mahendra, 14). Accordingly, in the 1960s, several writers in Europe called for arevision of the concept and emphasized that irreversibility should not be viewed as an essential feature ofdementia. Another important change that took place in the 1960’s concerned epidemiology. Prior to thesixties arteriosclerosis was thought to be the predominant cause of dementia, whereas AD was thought to berare (Pitt, 12).
However, arteriosclerosis was decisively challenged as the prime cause of dementia byseveral reports between 1960 and 1970 (i.e.,Tomlinson, Blessed, and Roth, 1968 and 1970). These reportsdemonstrated that arteriosclerosis was greatly overestimated as a cause of dementia, and that the majority ofpatients dying with dementia in fact showed the characteristic plaques and tangles of AD.
Furthermore,Katzman, in 1976 argued that because of similarity in the clinical picture and the identical nature of thehistopatholgy, distinctions between AD and senile dementia were arbitrary and no longer useful (Pitt, 12).Thus when it was understood that AD and senile dementia are similar, it was clear that AD is a commonillness.In the mid-1970’s two important contributions were made. First, Butler in his 1975 book Why survive? Being old in America criticized the widespread notion that senility was a normal part of aging.
Butlerargued that, senility, was a result of brain disease or depression and was potentially treatable. The extensionof this view was that senility was abnormal, and that its usual causes were diseases, not just aging(Pitt, 1987).Second, three different labs (Bowen et al, 1976; Davies & Maloney, 1976; and Perry et al,reported low levels of choline acetyltransferase, the marker enzyme for acetylcholine 1977) (ACh), in thebrains of patients who died from AD. ACh deficiency has since been the target of most therapeutic efforts inAD (see treatment).
Throughout the 1980’s and 1990’s two trends emerged. First, with regards to diagnosis, criteria have been made stricter. Classification systems like the Diagnostic and Statistical Manual have evolvedtowards a more precise and comprehensive definition of dementia. Moreover, neuoroimaging techniquesare becoming more and more standard, allowing in some cases for a more accurate diagnosis.
Second,the past fifteen years have witnessed a substantial growth in genetically based research. For instance one of the genes involved in AD, the amyloid precursor protein (APP), has been localized to a specific segmentof chromosome 21 (see risk factors).Epidemiology Dementia is known as the quiet epidemic, but it affects a significant proportion of our population. In1989 the Canadian consensus conference on the assessment of dementia reported that Canada had about250,000 cases of dementia (which at the time comprised about 1% of the population), with 25,000 newcases occurring annually (Clarfield, 1989).
Jorm et al. (1988) project that until the year 2025 Canada willexperience a growth in the prevalence of dementia, more rapid than the rise if the number of elderly agedover 65. The majority of dementia cases are attributable to AD, vascular dementias, or a combination ofthese (Table 1). In the past there were hopes that up to 40% of dementias had reversible causes.
However, recent reports (Clarfield, 1988; Barry and Moskowitz, 1988) suggest that the true incidence of reversibledementias is at the most 11% and is probably far lower, with drugs, metabolic causes and depression accounting for about two thirds of the cases (Clarfield, 1989).Overall, there are no significant gender differences in prevalence and incidence rates for dementia as awhole. However, for AD, there is an increased prevalnce in females. Jorm et al.
(1987) estimate a female tomale AD prevalence ratio of 1.6. Ethnically there seem to be important differences in both prevalence andsubtype of dementia. Prevalence wise, Heyman et al.
(1991) found that out of a random sample of 411616% of African Americans had dementia compared to only 3.1% of Caucasians. The same study also found that mixed and MID were more likely to occur in African Americans (26% of dementias in African Americans compared to 14% in Caucasians). Moreover, in both Europe and North America most studiespoint to AD as the most common dementing illness; whereas in Asia (especially Japan) MID predominates(Morris, 1994).
The observed high rate of stroke in Japan is consistent with a high MID rate. Possibly thehigher level of stress in Japan leads to more strokes and therefore a higher incidence of MID.Table 1. Etiology of Progressive Dementia and Approximate Incidencesenile dementia of the Alzheimer type50%Multi-infract dementia10-15%Mixed SDAT and MID 10-15%Alcoholic-nutritional dementia5-10%Normal pressure hydrocephalus 5%Miscellaneous: Huntington’s disease, neoplasms, chronicsubdural hematomas, Parkinson’s disease,Cruetzfeldt-Jakob disease, AIDS, unknown cause5-20%Life Expectancy and Mortality Estimates The following summary is based on Terry’s (1988) review of the Wang (1978) and Barclay et al.
(1985) studies. The Wang study examined senile dementia (mean age of onset 71.3 years) and presenile dementia (mean age of onset 53.8 years) survival rates during the 1960s.
Senile dementia patients survivedon the average 6.0 years, close to half of the expected survival rate (11.1 years) of similarly aged nondemented people. Presenile demented patients survived slightly longer an average of 6.
9 years, against an expected survival of 22.3 years. The Barclay et al. Studies examined survival rates in AD and MID patientsin the 1980s.
The mean survival rates for AD and multi-infarct dementia were 8.1 and 6.7 yearsrespectively. Interestingly, the survival rate of demented women on the whole is significantly higher than that of men.
Terry (1988) suggests that the lower survival rate of demented men is due to a higher incidence of MID in men. Risk Factors Age Age is the biggest risk factor for developing dementia. According to a model proposed by Jorm et al.(1987) a doubling of the prevalence rate occurs every 5.
1 years. (1987) For the elderly population aged 65and above the prevalence of dementia is estimated at about 10%. Whereas in the very elderly it can reach upto 40% (Clarfield, 1989).Genetics Genetic factors are important in some dementing diseases.
In HD an autosomal dominant gene onchromosome 4 is directly responsible for the disease. The genetic evidence in AD is less conclusive. On theone hand there are studies (i.e.
, Breitner et al. , 1988) which have reported a cumulative risk of AD amongrelatives of patients approaching 50%, thus implying an autosomal dominant mode of transmission(Morris, 1994). But, on the other hand, genetically transmitted diseases should be concordant inmonozygotic twins, this does not appear to be the case in AD. For instance both Creasey et al.
(1989) andKumar et al. (1991) have reported three pairs of monozygotic twins who were discordant. Whereas Nee etal. (1987) only found a 41% concordance rate for AD in 17 monozygotic twins.
Farrer et al. (1990) suggest that AD appears as an autosomal dominant in families in which the averageage of onset among kindreds is under 58. Supporting evidence for this comes from studies which havelinked EOAD with DS (Lezak, 1993). Individuals who are afflicted with Down syndrome and who surviveto age 40 almost invariably develop Alzheimer like dementia.
During the intermediate and terminal stages ofDS the individual suffers from recent memory loss, apraxia, temporal disorientation, and mutism, all ofwhich are also common in AD (Morris, 1994). Thus it is not surprising that four studies have found anincreased risk for AD with late maternal age (Morris, 1994). The increased risk of AD to patients born tomothers over 40 is consistent with Down syndrome risk curve (Rocca et al. , 1991).
Both EOAD and DS have been localized to chromosome 21. However, chromosome 21 does not appear to be a very good genetic marker for EOAD (Green book, 104). Recent studies have shown that a defectin chromosome 14 is more likely to be associated with EOAD, but the specific gene(s) have not yet beenisolated (Green book, 104). Evidence for genetic predisposition to LOAD has only emerged over the lasttwo years.
It is now known that a gene which codes for a lipoprotein called ApolipoproteinE (APOE) inchromosome 19 is involved (Green book, 101). APOE is linked to the type 4 allele (e4). It has now been proven that an increase risk for dementia is dependent on a strong chemical binding between the mainingredient of SP, the Beta amyloid protein, and the APOE-e4 (Green book, 102). Table 2 summarizes the genetic findings that have been made thus far in EOAD and in LOAD.
Table 2. Alzheimer’s Disease GeneticsChromosome 21 Chromosome 14 Chromosome 19Onset EOAD EOAD LOAD Risk factor for developing AD Low Higher Highest Specific gene(s) APP Not yet isolated Not yet identified MarkerAPOE-e4 ________________________________________________________________________________ Note: Reproduced from Berger & Finkel, 1995, Treating Alzheimer’s and other dementias , New York: Springer publishingOther Risk Factors Corsellis and Brierly (1959) [as cited by Graves ; Kukull, 1994] have shown that dementia similar tothat seen in AD may occur following a single head injury. In addition, dementia puglistica, (the so called’punch-drunk syndrome’) develops in some boxers. Lower education has also been associated withdementia.
Animal studies demonstrate a positive relation between environmental stimulation and dendriticgrowth. It is also known that dendritic growth in humans continues throughout life. Possibly lowereducation is related to a lack of mental exercise, which could delay the onset of significant cognitive decline(Graves ; Kukull, 1994).Aluminum (Al) has been implicated as a possible neurotoxin, but the evidence is inconclusive (Carson ;Butcher, 1992)).
Proponents of the Al neurotoxin hypothesis argue that Al has been shown to accumulate inneurons with neurofibrillary degeneration, and that aluminosilicates accumulate in senile plaques. Criticsargue that the abnormal accumulation of Al is an effect, not a cause, of brain degeneration. Anothercontroversial risk factor is depression. Four studies have reported a statistically significant associationbetween a history of depression and AD (Graves ; Kukull, 1994).
The controversy revolves around theidea that depression is possibly an early manifestation of AD.There is some research suggesting that individuals with a weakened immune system may be more susceptible to develop AD. Heyman et al. (1984) [as cited by Graves ; Kukull, 1994] have found anincreased risk of AD associated with thyroid disease in women.
However, their findings have not beenreplicated. Interestingly, there is some evidence to suggest that smoking can have a protective effect fromAD. For instance, Duijn and Hofman (1991) [as cited by Graves ; Kukull, 1994] have found a negative correlation between smoking and AD in a study involving 198 individuals.Neuropathology For each dementing disease a specific neuropathological pattern is observed.
However, due to thelimited scope of this essay the discussion will be limited to the most important dementing disease, AD.Gross Features Several changes are observed at the gross neuropathological level in AD (Mirra ; Gearing, 1994).Cortical atrophy is generally observed in the frontal, temporal, and parietal cortex. Sectioning of the brainreveals variable enlargement of the lateral and third ventricles.
Disproportionate enlargement of thetemporal horn of the lateral ventricle is commonly encountered, with concomitant atrophy of the entorhinalcortex, amygdala, and hippocampus.Microscopic Features At the microscopic level the two most distinguishing neuropathological features are senile plaques (SP)and Neurofibrillary tangles (NFT).There are two types of SP, neuritic and diffuse, both plaques share antigenic determinants with the Betaamyloid 4 protein. Neuritic plaques can be distinguished by their abnormally thickened neurites ( i.
e., axonsor dendrites) arranged around a central core of amyloid (Mirra ; Gearing, 1994). By contrast the diffuseplaques lack the thickened neurites and the amyloid core seen in the neuritic plaques (Mirra ; Gearing,1994). Plaques of both types are found in varying degrees in the neocortex, entorhinal cortex, hippocampus,and in the amygdala.
SP also occur in the brains of healthy people. It is only when they exceed a certaincritical number that AD emerges.NFT are intraneuronal structures which occupy the cell body of the neuron. Usually NFT coexist withSP in the neocortex, but they may be absent there in up to 30% of AD patients (Mirra ; Gearing, 1994).
However, NFT are consistently found in the entorhinal cortex, hippocampus, amygdala, nucleus basalis ofMeynert, and dorsal raphe nucleus (Mirra ; Gearing, 1994). It is thought that the major antigeniccomponent in NFT is the protein tau.Neuronal Loss Neuronal loss is directly related to the degree of synaptic density, which has been found to be crucial indetermining the severity of cognitive decline. It is greatest in the temporal lobes, but is also significant in thefrontal and parietal lobes (Lezak, 1995).
The strongest correlation with a global measure of dementia is theloss of functional synapses in the midfrontal and lower parietal areas which surround the temporal lobes(Lezak, 1995). The effect of this pattern of neuronal cortical loss is twofold. First it disconnects thetemporal lobe structures from the rest of the cerebral cortex. This accounts for the prominence of memoryimpairments (Lezak, 1995).
Second this pattern also disconnects the prefrontal structures from the parietalones. This accounts for the compromised capacity for attentional tasks (Lezak, 1995). It is thought thatbesides the effects of SP and NFT, neuronal loss is chiefly related to the depletion of the neurotransmitteracetylcholine (see treatment).Overall Picture In a study conducted by Brun and Gustafson (1978) [as cited by Cummings, 1988], the regionaldistribution of SP, NFT, and neuronal loss, was examined in AD patients.
The results indicated that themost severely affected areas were the medial temporal and the temporo-parieto-occipital junction region(see figure 1). Two positron emission tomography (PET) studies by Benson et al. (1983) and Foster et al.(1984) [as cited by Cummings, 1988] have confirmed this pattern.
[A1] Cognitive Deficits General Intelligence A profile of declining IQ scores reliably discriminates normals from AD patients. However, the utility ofIQ scores in other dementing diseases is unknown. In the early stages of the disease performance IQ tendsto decline at a faster rate than Verbal IQ which remains relatively unimpaired. Subsequently, as the diseaseprogresses the decline is evident in both performance and verbal IQ (Schmitt ; Sano, 1994).
Memory Memory dysfunction is often considered to be the distinguishing clinical feature of AD. Therefore, it is unlikely that a diagnosis of AD will be assigned unless a memory deficit is present. Hom’s (1992) study[as cited by Schmitt & Sano, 1994] compared the verbal and visual memory of elderly demented patientswith similarly aged normals, under two conditions, immediate and delayed recall. Memory performance inthe immediate recall condition was 29% for verbal memory and 31% for visual memory, of the averageperformance of the normals.
The deficit was even more pronounced in the delayed recall condition, wherethe figures were 11% for verbal recall and 6% for visual recall. Common examples of memory dysfunctionin mild dementia include misplacement of items without independent retrieval, failure to recall details of re cent conversations or events, and frequent repetition of questions. At a more advanced stage recent eventsare forgotten, and even knowledge of highly learned material erodes (Morris, 1994). It is thought that inAD, memory failure occurs as a result of improper encoding rather than due to retention failure (Schmitt &Sano, 1994).
Orientation dysfunction usually co-occurs with a memory deficit. There are difficulties with dates, temporal sequencing, day/night distinction, and navigating through familiar places (Morris, 1994).With regards to the last deficit it seems that an underlying visuospatial impairment is the critical causal factor(see other cognitive impairments).Language The most common language impairment in AD patients is dysnomia, the inability to name commonobjects.
Dysnomia emerges early in the course of AD, later on expressive and receptive aphasia are oftenpresent (Schmitt & Sano, 1994). Table 3 illustrates the linguistic impairments seen in each of the three ADstages (mild, moderate, and severe dementia). Table 3. Progressive Changes in Linguistic abilities in AD Stage I 1.
Dysnomia2. Empty, fluent speech 3. Poor word list generation 4. Mild anomia 5.
Lack of spontaneously initiated conversation Stage II 1. Anomia 2. Paraphasia with increasinglylittle relation to target word 3. Impaired auditory comprehension4.
Impaired comprehension ofwritten language 5. Aphasic agraphia6. Relative preservation of repetition and reading aloud 7. Poor engagement in conversation Stage III 1.
Incoherent verbal output 2. Echolalia, palilalia, logoclonia3. Diminished articulatory agility4. Terminal mutism 5.
Mechanical agraphia ____________________________________________________________________________________Note: Modified from Cummings & Benson, 1983, Dementia: A clinical approach, Boston: ButterworthsThe typical AD linguistic impairment pattern includes poor auditory comprehension, poor naming withparaphasia, writing impairment, and poor reading comprehension (Cummings, 1988). According to Benson(1979) [as cited by Cummings, 1988] the pattern of verbal output seen in AD resembles transcorticalsensory aphasia (which is associated with focal posterior left hemisphere damage). The difference is that inAD there is less paraphsia, echolalia, and the completion phenomenon, and more impairment of automaticspeech production.Other Cognitive impairments Several other cognitive impairments are commonly seen in AD patients.
Constructionaldyspraxia (impairment in constructional tasks) is often present. Additionally, many patients suffer frombasic visuospatial impairment. It is quite common for patients to find themselves lost in familiarneighborhoods, or drive in the wrong direction on a one way road (Cummings, 1988). Also common are attentional deficits, and disturbances of abstraction, calculation, problem solving and judgment.
The lattercluster of deficits points to an underlying frontal lobe dysfunction (Morris, 1994).Model for Overall Cognitive Deficit Picture Cummings (1988) has proposed a model to explain the above deficit picture observed in AD. Thefollowing discussion summarizes the main points. The combination of all of the cognitive deficits in AD is greater than the sum of the individual losses.
Forinstance a focal lesion which results in a memory defect has a small impact on verbal output, and an aphasicdisorder does not effect memory . By contrast, the dysfunction seen in AD results from multiple defectswhich interact to produce additive abnormalities. In AD a memory deficit directly contributes toimpoverished linguistic output and the aphasia in turn magnifies the memory problems. Furthermore, otherabnormalities such as visuospatial and calculation deficits are superimposed on these, and together theydisable various integrative abilities such as insight, strategy formulation, and anticipatory planning.
Taking into account these considerations, Cummings (1988) proposes a three-tired model of humanintellectual activity which applies to AD. The most basic activities (i.e., arousal, attention, motivation) aremediated by subcortical structures.
These fundamental functions are largely intact in AD. However, twoother aspects of intellectual activity are damaged in AD. First instrumental functions which are specificneuropsychological abilities (i.e.
, memory, language, calculation) mediated by the cerebral cortex aredamaged. More importantly, the distinguishing feature of AD involves damage to supraordinant functions (integrative abilities). These functions are dependent upon a proper interaction between the fundamental andinstrumental functions.Behavioral Problems and Psychopathology The gradual destruction of various brain structures, causes several maladaptive behavioral changes.
Typically dementia is viewed as a collection of negative symptoms, but positive symptoms are present as well. Tariot and Blazina (1994) suggest that these behavioral changes may be collectively present up to90% of the time during the course of a given dementing illness. Furthermore, they have determined thatcertain behaviors occur at a particularly high rate. Table 4 shows the eight different categories whichinclude these behaviors.
During the early stages of the illness when the patient is only mildly impaired it is very common for individuals to avoid active participation in life. Patients tend to withdraw from social engagements, lackinitiative, and overall behave in an indifferent and apathetic manner. A possible explanation for this behavioris that these patients may be embarrassed by their cognitive deficits, and so they avoid interacting. As the illness progresses and the cognitive deficits increase patients may become more anxious andagitated.
Patients with preexisting psychological problems are prone to experiencing hallucinations anddelusions. In particular these patients exhibit paranoid delusions, for instance accusing the elderly spouse ofbeing unfaithful. Misperceptions, such as the inability to distinguish real people from television images, arealso common at this stage (Tariot & Blazina, 1994). Aggression, in particular verbal hostility tends toincrease as accurate perception declines.
According to Cohen-Mansfield et al. (1986) [as cited by Tariot &Blazina, 1994, P. 470] agitated and aggressive behaviors may represent “adaptive efforts to obtainstimulation and certain verbal behaviors may be frustrated efforts to communicate or obtain assistance.”Table 4.
Schematic Summary of Reported Frequencies of Behavioral disturbances Associated with Dementia (% of patients)Behavioral Disturbance Range Median 1. Disturbed affect/mood 0-86 19 2. Disturbed ideation (Delusions) 10-73 33.5 3.
Altered perceptionHallucinations 21-49 28Misperceptions 1-49 23 4. AgitationGlobal 10-90 44Wandering 1-49 23 5. AggressionVerbal 11-51 24Physical 0-46 14.3Resistive/uncooperative 27-65 14 6.
Anxiety 0-50 31.8 7. Withdrawn/passive behavior 21-88 61 8. Vegetative behaviorsSleep 0-47 27Diet/appetite 12.
5-77 34 _________________________________________________________________________________ Note: Reproduced from Morris, 1994, Handbook of Dementing Illnesses, New York, Marcel DekkerAssessment Interview The initial diagnostic procedure used in the assessment of dementia is the interview. The purpose of theinterview is twofold. First it is important for the clinician to gain an accurate picture of the case history.It is important to interview at least one significant other person, and if possible more, to gain an objectiveview.
Information should be collected about premorbid functioning, and about the nature, onset, and courseof the symptoms. Second during the interview the clinician evaluates whether the individual’s presentingcomplaints match the clinical profile for dementia. It is important to rule out other disorders that may mimicdementia. For instance self reported memory complaints correlate better with the presence of depressionthan with dementia ( Morris, 1994).
Brief Mental Status Examination Alongside the interview, a brief mental status examination is often used. The exam’s purpose is toindicate whether any gross cognitive deficits are present. According to Schmitt & Sano (1994, P. 94) thestrengths of such an exam are: “(1) the ability to rapidly screen a large number of people, and (2) the abilityto measure progression in those who have been identified with dementia”.
The problem with these exams isthat they are insensitive to mild dementia, particularly in highly educated individuals. Furthermore, they lackthe ability to assess specific neuropsychological functions, and thus are of little value in specifying the typeof dementia (Schmitt & Sano, 1994). Nevertheless, these brief exams can be very useful. In practice manyprimary care physicians do not routinely administer these tests.
For instance in a study by McCartney andPalmateer (1985) [as cited by Katzman et al. , 1988] it was found that these exams were carried out in only4 out of 165 patients in the United States. As a result 50 patients with cognitive impairments were missed. The two mental status tests which are in widest use are the information-concentration-orientation test ofBlessed et al.
and the mini-mental state exam of Folstein et al. The Blessed test is the most sensitive, and thus is used the most in very early cases. The mini-mental test is broader in that it also tests language,writing, and drawing. Both tests are inappropriate to use with mentally retarded individuals or those with apoor educational background.
Also the tests should be adjusted for individuals who are not fluent in Englishor for those who have a different cultural background (Katzman et al. , 1988). Another useful brief item isthe dementia rating scale. It is utilized to estimate the severity of dementia.
Neuropsychological Testing According to Morris (1994, P. 79) neuropsychological testing in demented patients serves threefunctions: “(1) to provide objective documentation of impaired cognition and therefore support the clinicaldiagnosis of dementia (2) to assess cognitive changes longitudinally, and (3) to identify selective patterns ofcognitive deficits for correlation with neuroimaging and postmortem findings”.The shortest battery for discriminating dementia patients from normals is the Iowa screening battery for mental decline. It consists of three neuropsychological tests, Temporal Orientation, Benton VisualRetention Test and the Controlled Oral Word Association Test.
This battery is used to determine if furtherevaluation is necessary. If further evaluation is necessary usually the Consortium to Establish a Registry forAlzheimer’s disease (CERAD) battery is used. The battery consists of seven tests, some of which areslightly modified from their original form (Lezak, 1995). These tests include the Word List Memory Testand the Boston Naming Test, which test for memory and language respectively.
The word List MemoryTest tests for memory by verifying how well a person can recall three lists of ten words. Whereas the Boston Naming Test tests for language by verifying how well the person can duplicate three lists of fivewords (Lezak, 1995). Sometimes it is useful to test for specific cognitive abilities. For instance theWechsler Memory Scale-Revised is often used to see if a memory impairment is present.
Table 5 illustratessome of the more common neuropsychological tests utilized in the assessment of dementia.Table 5. Assessment of Neuropsychological Functions for Dementia Diagnosis Function(s) assessed Examples of useful clinical testsGlobal mental statusMini Mental State, Mattis Dementia Rating Scale, Information-Memory Concentration Test, Syndrome Kurtz Test Premorbid functioningNational Adult Reading Test, Wide-Range Achievement Test-Reading General intellectual functioningWechseler Adult Intelligence Scale-Revised, Ravens Progressive Matrices, Test of Nonverbal Intelligence MemoryWechsler Memory Scale Revised, Benton Visual Retention Test, Rey-Osterreith Complex Figure, Rey Auditory Verbal Learning Test, Selective Reminding Test, California Verbal Learning Test, Rivermade Behavioral Memory Test Language (naming and fluency)Boston Diagnostic Aphasia Examination, Western Aphasia Battery, Holland Communicative Abilities in Daily Living, Halstead-Wepman Aphasia Screening Test, Boston Naming Test, Controlled Oral Word Association, Semantic Category Naming Problem solving (and executive functioning)Halstead-Reitan Category Test, Wisconsin Card Sorting Test, Trailmaking A ; B, Stroop Praxis and constructional abilityRosen Drawing Test, Rey-Osterreith Complex Figure (copy), Benton 3-Dimensional Blocks, Beery Test of Visual Motor Integration, WAIS-R Block Design, BDAE Stick Test MotorFinger Oscillation, Grooved and Purdue Pegboards, Diadokinesis Attention/concentration WAIS-R Digit Span, Reaction Time Tests, Cancellation Tasks, Syndrome Kurtz Test ______________________________________________________________________________________ Note: Reproduced from Morris, 1994, Handbook of Dementing Illnesses, New York: Marcel DekkerClinical Diagnosis and Related Problems A definitive diagnosis of AD and many other dementing diseases can only be made either throughcerebral biopsy, the surgical removal of a small piece of the cerebral cortex, or when the patient dies and anautopsy is performed. The two most widely used criteria for the diagnosis of dementia are the Diagnosticand Statistical Manual Third Edition-Revised (DSM-IIIR) and the National Institute of Neurological andCommunicative Disorders and Stroke/Alzheimer’s Disease and Related Disorders Association(NINCDS/ADRDA).
DSM-IIIR is more often used for research purposes and the NINCDS/ADRDA forclinical purposes. There are several problems in diagnosing dementia, most notably differentiating dementia from normalaging and from depression. In general, the cerebral processing resources needed for attention demandingtasks and secondary memory functions are adversely affected by age (Morris, 1994). Clinically, these impairments result in limited attentional capacity and diminished speed of information processing and retrieval.
But unlike in dementia these symptoms are largely nonprogressive, and do not interferesubstantially with everyday life (Morris, 1994). In patients with mild cognitive changes it is almostimpossible to make an exact diagnosis even with the best neuropsychological tests. Only the likelihood ofdeveloping dementia can be estimated. There can be a great deal of symptom overlap between dementia and depression especially in the earlystages of dementia.
Depression presenting as dementia is often called pseudodementia. The termpseudodementia implies that the dementia is reversible, and is not caused by an organic disorder but ratherit is caused by a psychiatric disorder (Clarfield, 1989). Currently there are no definitive tests to differentiatebetween dementia and depression.Clinical Subgroups of Alzheimer’s Disease Blenow, Wallin ; Gttfries (1994) have proposed a model for clinical subgroups in AD based upondifferential clinical symptomatology and neuropathology.
Their findings indicate that there are two distinctsubtypes which they have termed Alzheimer’s disease type I and type II. Alzheimer’s disease type I ischaracterized by dominant temporoparietal symptoms, low frequency of vascular factors, normal blood-brainbarrier function, low frequency of CT indicated leukoaraiosis (white matter lesions), and relatively youngerage of onset. These characteristics correspond to the classic description of AD. Therefore AD type I appears to constitute classical or pure AD (Blenow et al.
, 1994).Alzheimer’s disease type II is characterized by general cognitive symptoms, absence of or mild temporo- parietal symptoms, high frequency of confusional symptoms, relatively high frequency of vascular factors,mildly impaired blood-brain barrier function, high frequency of CT indicated leukoaraiosis, and relatively late age of onset. These characteristics suggest that vascular changes are responsible for the production ofdementia symptoms in AD type II (Blenow et al. , 1994).
Markers Markers Reflecting Brain Changes Markers which belong to this category utilize cerebral spinal fluid (CSF) changes to reflect alteredneurotransmitter levels or abnormal proteins (Katzman et al. , 1988). The enzyme Acetylcholinesterase(which regulates the neurotransmitter Achetylocholine, see treatment) is known to be decreased in thecerebral cortex of demented patients. Several investigators have found it decreased in the CSF, while othershave failed to confirm this.
According to Thal (1985) [as cited by Katzman et al. , 1988] the apparentdecrease in some studies may be a dilutional effect secondary to ventricular enlargement. SimilarlySomatosatin and Norepinephrine are also reduced in the cerebral cortex of demented patients. However, inthe CSF Somatosatin is only decreased in some patients, whereas Norepinephrine is actually increased in theCSF.
A good area for future research is to investigate whether any of the abnormal proteins associated withAD can be found in the CSF (Katzman et al. , 1988).Peripheral Markers Peripheral markers are markers which reflect changes in the skin or blood cells (Katzman et al. , 1988).
Most of the findings in this category are either inconclusive or have not been replicated. For instanceDiamond et al. (1983) [as cited by Katzman et al. , 1988] have found that the sodium-lithium counter- transport rates in red blood cells were elevated in AD patients, but this finding has not been replicated.
Olfactory deficit Markers Several investigators have found that AD patients have olfactory recognition and threshold deficits.Peabody and Tinklenberg (1985) [as cited by Katzman et al. , 1988] have found that 8 out of 18 AD patientshad these deficits compared to only 1 out of 26 normals. Katzman et al.
(1988) discuss increased carbondioxide production, increased superoxide dismutase, and decreased calcium uptake as possible causes forthese deficits in AD patients.Pharmacological TreatmentCholinergic Drugs There is no known cure for AD or many other dementing diseases. Several medications are available but their effectiveness is limited. The most promising group of drugs work by potentiating the cholinergicsystems in the brain.
During the 1970’s several studies have shown that demented patients have low levels of the neurotransmitter Acetylocholine (ACh). This has led to the development of the cholinergic hypothesisfor dementia. It has since been established that the enzyme from which ACh is synthesized, CholineAcetyltransfearse (ChAT), is severely decreased in AD patients.There are three mechanisms by which these drugs work (1) precursor loading , (2) preventing thebreakdown of ACh , and (3) the direct stimulation of the postsynaptic receptors.
Precursor loading in AD is similar to Parkinson’s disease (PD). The difference is that instead of using the precursor L-dopa for dopamine in PD, the precursors choline and lecithin are used in AD to synthesize ACh. Generally this treatment when used alone fails to improve cognitive performance (Schneider, 1994). Preventing the breakdown of ACh involves inhibiting the enzyme Acetylocholinesterase (AChE).
Theprincipal drugs which utilize this mechanism are Physostigmine, Tacrine, and Valancrine. The problem with Physostigmine is that the duration of its therapeutic effect is very short, usually about one to two hours,whereas Tacrine and Valancrine have serious side effects (Schneider, 1994). A second generation ofcholinesterase inhibitors which are longer acting and more selective are currently being developed, and the initial results are encouraging. In AD the postsynaptic M-1 cholinergic receptors are relatively intact.
It is the presynaptic M-2cholinergic receptors which regulate ACh release that are damaged. Therefore, it makes sense to try todirectly stimulate the postsynaptic receptors (Schneider, 1994). These cholinergic agonists includeBethanechol, Oxotremorine, Pilocrapine, RS-86, and Arecholine. When these drugs are given orally theyare not very effective.
They are more effective when administered through an implant of anintracereroventricular pump. But the risks of such an implant are not insignificant. For instance in one trialout of 68 implants 16 resulted in surgical complications, including one death, two hemorrhages, and sevenseizures (Schneider, 1994). Other Drugs There are several other drugs used in the treatment of dementia, although their therapeutic mechanismsare not understood very well.
Hydergine is the longest used and most extensively studied antidementia drug.Hydergine is an ergoloid derivative which effects the alpha-adrenergic, dopaminergic, and sertoninergicreceptors. There have been conflicting reports about its efficacy, but overall it seems that it is only slightlybetter than a placebo in relieving symptoms (Schneider, 1994).Nootropics are a group of drugs derived from the neurotransmitter GABA.
But instead of having GABAeffects they have a neuroprotective effect on the central nervous system, and they may stimulate centralcholinergic activity. Still, the specific mechanism of action relevant for dementia has not been established for these drugs. Overall results with Nootropics such as Piracetam, and Oxiracetam have not been veryencouraging (Schneider, 1994). Summary As the human race marches forward into the new millennia, one of the challenges that will remained to be solved is the dementia epidemic.
The continuous increase in life span means that the number of peoplewhich are afflicted with dementia will continue to grow. Notwithstanding, we have come along way in ourunderstanding of the dementia syndrome since the days of Pinel or even since the days of Alzheimer. We now know that dementia (senility) is not the natural outcome of aging, rather it is the result of a varietyof possible abnormal brain processes. For instance in AD (the most important dementing disease) theformation of SP and NFT in the brain have been proven to be the main causal factors of the disease.
Furthermore, in AD these processes have been shown to occur mainly in the cerebral cortex, and inparticularly in the temporal lobes.The effects of these brain lesions are mainly manifested in various cognitive and behavioral impairments.With regards to cognition, memory and language dysfunction are the most commonly encountered deficits in AD. In fact memory impairment is so crucial, that a diagnosis of AD will almost never be made unless it is present.
With respect to behavior, anxiety disturbances tend to predominate in the earlier stages of AD,whereas aggression is encountered in the latter stages.Significant progress has also been made in the assessment of dementia. Standard interviewing methods are now used alongside brief mental status examinations. Although the mental status exams have a limited diagnostic usefulness (they are only used as initial screening devices), they are nevertheless importantbecause of their relative low cost and quick administration time.
When further confirmation is required or more detail is desired neuropsychological testing is performed. Neuropsychological testing allows for the assessment of specific cognitive functions (i.e. memory, language, attention) thus discovering which brain areas are affected.
This is useful because not only is it possible to judge if the person suffers from dementia, but with a high degree of accuracy it is possible to say which dementing disease is responsible.Notwithstanding, even the best neuropsychological tests may run into difficulties at times. For instance differentiating dementia from depression is extremely difficult since people who are depressed may display many of the clinical symptoms observed in dementia.As our understanding of dementia grows it is conceivable that an effective treatment will be found within the next century.
Genetically several important breakthroughs have occurred recently in AD.Abnormalities in chromosomes 14 and 19 have been added to chromosome 21 as causal factors.Furthermore, investigators are now close to localizing the specific genes involved in these chromosomes (it is already known that in chromosome 21 the specific gene involved is the APP gene). With regards to pharmacological treatment the ACh hypothesis for dementia has led to the development of three groups of cholinergic drugs, some of which show great promise.
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