What is Dementia ?

Dementia is an organic brain syndrome which results in global cognitive impairment. 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 all 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

years (Katzman, Lasker & Bernstein, 1988). AD is usually divided into three stages mild, moderate,

and severe. Throughout these stages a specific sequence of cognitive deterioration is observed (Lezak,

1995). The mild stage begins with memory, attention, speed dependent activities, and abstract reasoning

dysfunction. Mild language impairments also begin to surface at this period. In the moderate stage,

language deficits such as aphasia and apraxia become prominent. Dysfluency, paraphasias, and bizarre word

combinations are common midstage speech defects. In the severe stage the patient is gradually reduced to a

vegetative state. Speech becomes non-fluent, repetitive, and largely non-communicative. In addition,

Auditory comprehension becomes 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.

Furthermore, primitive reflexes such as grasp and suck emerge as well. 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, serves to distinguish 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 of the 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. Cortical

dementia is used to describe dementia which results from brain lesions at the cortical level, whereas sub-

cortical dementia applies to dementia which results from subcortical brain lesions. AD and Pick's disease

are amongst the best known examples of cortical dementia; whereas HD, Parkinson's disease (PD), and

progressive supranuclear palsy (PSP) are good examples of subcortical dementia (Derix, 1994). When

dementia with both cortical and subcortical features occurs, the term mixed dementia is used. MID is a

common 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 originally

have the specific connotation that it does today. It meant ?being out of one's mind' and as such was a

general term for insanity (U'Ren, 1987). It was the encylopedist Celsus who first used the word dementia in

his De re medicina, published around AD 30. A century later the Cappadocian physician Aretaeus first

described senile dementia with the word dotage: ?The dotage which is the calamity of old age?dotage

commencing with old age never intermits, but accompanies the patient until death? (U'Ren, 1987, P. 1).

Curiously, dementia was mentioned in most systems of psychiatric classification throughout pre-modern

times, though the precise meaning of the word is often unclear (U'Ren, 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 conclude that dementia is caused by ?idiotism'. He used the term

dementia in relation to the ?progressive mental changes seen in some idiots? (U'Ren, 1987,3). Furthermore,

Pinel thought that dementia was a distinct abnormal entity, and thus he used the term dementia to designate

one of the five