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Alzheimer's disease: clinical features and classification
In AD, as in most complex neurodegenerative diseases, there is a wide clinical heterogeneity of symptoms.
At the beginning of the disease, memory loss may go unnoticed or be mistaken for ordinary forgetfulness.
Gradually, cognitive impairments begin to limit everyday activity (conducting financial affairs, professional activities, driving a car, shopping and taking care of the house).
Some patients are not aware of these disorders ( anosognosia); in other cases, criticism remains intact, which causes severe experiences.
The reason for the differences in the course of the disease is unknown.
Patients get lost in a new environment and may get lost while walking or driving a car.
At the height of the disease, patients are not able to work, they are easily disoriented ; they need constant care.
At the same time, secular skills and stereotypical behavior can be preserved, and with a superficial conversation, you can not notice any violations.
At the same time , speech disorders are possible, especially understanding someone else's speech and naming objects .
In some cases, severe aphasia appears already at the beginning of the disease.
Difficulties in the selection of words and verbosity sometimes occur even in patients with satisfactory performance of special speech tests.
In addition to naming objects , fluency, understanding and repetition of speech may be impaired .
Various forms of apraxia are characteristic : dressing is difficult , patients cannot eat independently , they are not able to solve the simplest puzzles and copy geometric shapes .
The account is broken , patients can not determine the time by the clock .
Occasionally, cortical blindness develops , which the patients themselves deny.
In such cases, gross changes in the visual cortex are found during autopsy .
In the later stages, some patients can move independently, but their movements around the house are reduced to aimless wandering ; a complete loss of cognitive functions ( the ability to make judgments and conclusions, etc.) is possible.
Hallucinations or delusions often occur .
As a rule, they are simple in content and devoid of quirkiness.
For example, patients unreasonably suspect their spouse of infidelity , do not recognize old friends , take a visitor for a thief or are afraid of their reflection in the mirror .
Disinhibition and conflict can be replaced by apathy and alienation .
The sleep wake cycle may be disrupted ; at night, patients wander around the house, which further complicates the care of them by relatives.
Sometimes a shuffling gait and generalized muscle rigidity develop , movements become slow and clumsy , and in general the appearance of patients resembles that of Parkinson's disease ; however, a fast, rhythmic tremor of rest is rare.
For the late stage of Alzheimer's disease, as a rule (but not always), muscle rigidity , mutism , urinary incontinence, fecal incontinence are characteristic ; patients are bedridden.
Without outside help, they can not even eat, dress and recover.
Tendon reflexes can increase, there is a sucking reflex and a proboscis reflex .
Spontaneously or in response to stimuli (for example, loud sounds), myoclonic twitching of individual muscles or the entire body sometimes occurs.
These symptoms make it possible to exclude Creutzfeldt Jakob disease .
In contrast, Alzheimer's disease is characterized by a more protracted course.
Generalized epileptic seizures are possible .
Death in most cases occurs from exhaustion, secondary infection or heart disease.
The recent discovery of several AD genes explains the clinical heterogeneity of AD symptoms.
Being an etiologically heterogeneous disease, AD is characterized by one common pathological phenotype - progressive dementia, accompanied by the following pathomorphological signs [ Selkoe, 1991 ]: 1) intracellular accumulation of filaments forming neurofibrillary tangles in neurons;
2) education in the hippocampus, neocortex, and other parts of the brain of senile plaques that are composed of multiple proteins, including alpha antichymotrypsin , the ARI , beta amyloid (A?42) (the accumulation of A?42 in the parenchyma is observed at the beginning of the development of ad and, apparently, initiates the formation of protein aggregates [ Hardy, 1997 ; Pollen, 1996 ; Arnold et al, 1997 ]. 3) mass death of neurons, especially in the hippocampus and the temporal lobes of the cerebral cortex - the departments responsible for the processes of storage and active processing of memory .
There is still a debate about whether the accumulation of tau proteins and A?
42 are the direct causes that cause the death of neurons, or, conversely, the consequence of such death [Rogaev, 1999 ].
The general neurodegenerative process is accompanied, in addition, by a decrease in the activity of a number of enzymes, in particular, elements of signal transduction and neurotransmitter systems: choline acetyltransferase , norepinephrine, serotonin receptors, nicotine receptors, glutamate receptors and somatostatin receptors [ Myhrer, 1998 ; Talbot et al, 2000 ; de la Monte et al, 2000 ; Gattaz et al, 1996 ], - which may be associated with the death of the corresponding neurons [ Nakamura et al, 1984 ].
Identification of primary molecular disorders in AD is the main and most difficult task, especially since the first histopathological changes in AD can occur long before the first clinical symptoms appear [ Pollen, 1996 ].
There are various clinical forms and, accordingly, classifications of AD.
In Russia, a classification based on the features of the clinical manifestation of AD has been adopted [ Gavrilova et al, 1993 ].
Abroad, a simplified scheme is used, according to which Alzheimer's disease is divided into forms with early (younger than 65 years) and late (65 years and older) onset of development [ WHO, 1989 ].
The average life expectancy for Alzheimer's disease is 8-10 years, but it can range from 1 to 25 years.
For unknown reasons, in some cases, the disease progresses slowly and continuously, while in others, long periods of stabilization of the condition are characteristic.
See also: ALZHEIMER'S DISEASE (AD, AD)
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