Features of Dementia

Dementia is a devastating condition that deprive the individual of his most cherished mental and physical skills. Memory, dexterity and behaviour fade away. Life is not the same anymore and the individual is not the same person. Dementia has profound effect on the lives of those inflicted by the disease. It is a common condition that has implications for the provision of health and social services care for the elderly.

Dementia encompasses a number of diseases. All these conditions share features in common like ongoing increasing deterioration in higher brain functions. Nothing would stop that progression of loss of those skills. The consciousness is intact and awareness of surroundings is maintained but memory deficiency is not the only defect.

Alzheimer's disease is the commonest cause of dementia affecting approximately 5% of the population over the age of 65 and 20% of those over 85. Age is the prominent risk factor, Alzheimer's disease incidence increase with age, it is exceedingly rare in middle age.

The Main Features of Dementia

1. Loss of Memory (Amnesia)

Memory is the ability of the brain to store and retrieve information. There various types of memory. The two main types are short-term or long-term memory. Short-term memory is the working memory where sensory information from the outside world is examined and dealt with before storage. Long-term memory is the durable lasting form of memory.

If you are asked to repeat a long phone number, you repeat it because you recall it soon after you hear it. This does not last long and you may forget the number if you do not need to keep it in memory. This process use the short-term or immediate memory. If asked to memorise the number, you try to find pattern in the number to keep it in your long-term memory. Short-term memory allow recall of information within 30 seconds. It is also limited to four to seven items. When trying to manage a bigger piece of information, the person may divide it into chunks. So, a number like 345778823 may be chunked into 345-77-88-23.

On the other hand long-term memory is limitless and can last for the whole life span. It is consolidated into the brain cells in the form of change to the brain proteins. There is no specific area for storage of memory like a memory disk, but it is widespread throught the brain. Memory can be semantic in the form of language or abstract information like principles or facts. Episodic memory is the store of events occuring in time and sapce. There is another form of memory: procedural memory deals with ow to do things like your ability to ride a bike or tie shoelaces.

Memory can also be consious or unconscious. A football player or musician do not recall each movement or action during playing but react cleverly and unconsciously.

Sensory information can take several forms: hearing, vision, touch, movement, smell and taste, etc. These sensations are integrated into memories about an event and distributed in its corresponding area of the brain: the hearing area in the temporal lobe and the visual area in the occipital lobe.

Calling back a memory can be aided by clues, like in case of recognition of a picture or a face of a person, you recognise a distinctive part such as a beard or moustache. If that is changed, you may look for another feature to recognise the face. Memory tends to fade away with time but can be revived with repeated learning of the same material once again.

What happend to memory in Alzheimer' disease?

In Alzhiemer's disease, short-term memory is intact. Long-term memory is also not affected in the early stages of the disease. What does occur is the failure of transfer of new information learnt from short-term memmory to the long-term storage. Later in the illness, recall of old memories is also poor. Recall of information and recognition of facts, events and the way to do things or the direction in the space around the person may fail later.

The hippocampus, shaped like a seahorse hence the name, is an area deep in the brain. Hippocampus is involved in conscious memory and spatial orientation. Another part in the limbic system, amygdala, is involved in emotional memory. These areas manage the distribution and integration of new memories to their stores in the various areas of thr brain. Damage to these particular parts of the brain occurs early in the disease and is resposnible for failure of learning new information.

Failure of spatial memory lead to disorientation and difficulty in finding direction during travelling in the surrounding environment. Failure of episodic events and time or place of events is clearly evident in patient's denial of recent events in his life.

2. Inability to find words (Aphasia)

Early in dementia, the person may find difficulty finding words, and his eloquence may suffer. This may be overlooked by the patient himself or his family. Later the inability to express self may be more prominent. Understanding of people's communication become a problem at some stage. Not only naming an object may be difficult, but answering requests may be misunderstood. The person may avoid naming an object and call it "that thing out there" and misunderstand a request like "open your mouth" by closing his eyes. Complete loss of comprehensible language may be the end result later in dementia.

3. Apraxia

In dementia, there is progressive inability to perform complex tasks. This is a result of damage to cortical areas of the brain and not due to any defect in movement like cases of paralysis or stroke. Motor functions may be intact but the performance is poor and deficient. The patient might become unable to dress or wash, prepare his food or do any house chores. Inability to perform relatively straightforward tasks around the home make it neccessary to provide these needs by others when the patient become incapacitated. Early on in dementia, clumsy, awkward and unskillful actions may be noticed but overlooked.

4. Inability to recognise people and faces (Agnosia)

One of the most distressing symptoms to families of the patient is inability to recognise persons. Many things around the Alzheimer's patient seems strange. He or she may take one person for another or deny that they know that person. Inability to reconise a spouse is most distressing after many years of marriage. Difficulty in recognising the place may make the person try to leave or become angry and resistive to stay in a new place away from his familar home. Confusion about time make some patients wander about during the night when light is dimmed.

5. Other symptoms

The change in the personality is common and frequent. Calm persons make become agitated and irritable. Those with life-long good judgement and controlled emotions may become capricious and child like or emotionally labile. Many become suspisicous or panaroid, accusing others of plannig harm or stealing their money or belongings. Hallucinations may be evident in times of confusion at night. changes Misidentifying someone for another person is a cause for embarrassment or upset. It is also possible to identify a place for another. May patients have depressive symptoms in addition to cognitive impairment. This complicates the picture and must be dealt with in its own right. Most dementia patient lack awareness of their defective behaviour and deny their failings.

The distictive feature of dementia is memory failure. As a progressive illness, short-term memory is affected first. This makes it difficult to learn new things. Information is not stored. Events are never recorded and persons were never there. A simple test to show this defect in short-term memory is to mention three unrelated objects to the patient and ask them to recall it in five minutes or even after two distractions like asking another two questions. So, if you tell the patient:

  • "I want you to remember three things and will ask you to recall them later: An Apple, A Horse and Hotel".

You may think this is so simple, but it may be difficult for someone with dementia to recall, because he cannot register these three unrelated things.

Long-term memory also may be affected. A patient may not recall important past personal information, like where he met his wife the first time, when he visited a particular country, what was his first job and so on. Generl information too may be fading away and patchy. Asked about past wars, name of presidents, prime ministers, current affairs and events can be hard for a dementia patient to recall. Other cognitive areas may be impaired. Abstract thinking becomes a problem. The simplest form of abstract thinking is dealing with numbers. Dementia patients find great difficulties dealing with numbers and calculations. They may misjudge their possessions and this can cause troubles to others in addition to tendency to suspisicious and paranoid about theft and conspiracy to rob him of his assets.

In a typical case of Alzheimer's disease, the onset is so subtle, slow and sneaking, which makes family members underestimate the personality change and decline. They may be unable to tell exactly when the impairment began.

More than one deficiency of cognitive functions can work together to produce signs of dementia. Disturbed coordination of movements, together with disorientation, loss of spactial memory and imapired navigation make the person unable to drive. Motor skills deteriorate to hinders the person's ability to dress himself, wash himself, prepare simple meal, use the stove or the microwave. Disorientation to time, place and person contributes to getting lost on the way to a familiar place which has been frquently visited for many years. The individual is initially aware of the difficulty and this make him confused, sad and afraid of going out or mixing with others.

The diagnosis of dementia is often missed or delayed. Prevalence studies of community samples also detect many undiagnosed cases. Unfortunately, sometimes a physician may apply a dementia diagnosis incorrectly when it does not exist, or overlooking it when it is there. Such errors may result from a lack of attention to cognitive functioning during medical screening examinations, or a lack of knowledge about the normal aging process.

Essential in diagnostic evaluation are things like: a complete history from someone who knows the patient well, physical and neurological examinations, and a mental status examination.

Brief standardized mental status tests (e.g., the Mini-Mental State Examination) are useful to quantify the degree of cognitive impairment, and more extensive neuropsychological batteries provide details on the nature of the cognitive deficits.

Examination of Alzhimer's patient may show: - apraxia (inability to carry out motor commands, even though comprehension and motor function are intact) - agnosia (inability to recognize objects, despite intact sensory function) - difficulties in visual-spatial skills (inability to copy two-dimensional and three-dimensional figures or to assemble blocks).

A variety of behavioral changes may accompany the cognitive deficits, including paranoia, agitation, insomnia, anxiety, and depression.

Symptoms are similar across dementia types and it is difficult to diagnose by symptoms alone. Diagnosis is aided by brain scanning techniques. In many cases, the diagnosis requires a brain biopsy to become final, but this is rarely recommended (though it can be performed at autopsy). In those who are getting older, general screening for cognitive impairment using cognitive testing or early diagnosis of dementia has not been shown to improve outcomes. However, screening examination is useful in the over 65 persons with memory complaints.

Normally, symptoms must be present for at least six months to support a diagnosis. Cognitive dysfunction of shorter duration is called delirium. Delirium can be easily confused with dementia due to similar symptoms. Delirium is characterized by a sudden onset. The symptoms are changeable and fleeting over tme and it is usually of short duration, often lasting only from hours to weeks. Delirium is primarily related to a somatic condition or a medical disturbance like fever or infection. In comparison, dementia has typically a long, slow onset (except in the cases of a stroke or trauma), slow decline of mental functioning, as well as a longer duration (from months to years).

Some mental illnesses, including depression and psychosis, may produce symptoms that must be differentiated from both delirium and dementia. Therefore, any dementia evaluation should include a depression. Screening tests exist such as the Geriatric Depression Scale. Physicians used to think that people with memory complaints had depression and not dementia, because they thought that those with dementia are generally unaware of their memory problems. Depression manifesting with cognitive and memory difficulties is called pseudodementia. However, in recent years researchers have realized that many older people with memory complaints in fact have Mild Cognitive Impairment, the earliest stage of dementia. Depression should always remain high on the list of possibilities.

Changes in thinking, hearing and vision are associated with normal ageing and can cause problems when diagnosing dementia due to the similarities.

Cognitive testing

Various brief tests (5-15 minutes) for dementia exists and reasonable reliabe to screen for Alzheimer's disease. The mini mental state examination (MMSE) is the best studied and most commonly used. The MMSE is a useful tool for helping to diagnose dementia if the results are interpreted along with an assessment of a person's personality, their ability to perform activities of daily living, and their behaviour.

Other cognitive tests include: - Abbreviated Mental Test Score (AMTS) - Modified Mini-Mental State Examination (3MS) - Cognitive Abilities Screening Instrument (CASI) - Trail-making test - The clock drawing test

The MoCA (Montreal Cognitive Assessment) is a reliable screening test and is available online for free in 35 different languages. The MoCA has also been shown somewhat better at detecting mild cognitive impairment than the MMSE.

Sensitivity and specificity of common tests for dementia

Test Sensitivity Specificity
MMSE 71%-92% 56%-96%
3MS 83%–93.5% 85%-90%
AMTS 73%–100% 71%-100%

The AD-8 a screening questionnaire used to assess changes in function related to cognitive decline is potentially useful, but is not diagnostic, is variable, and has risk of bias. Brief cognitive tests may be affected by factors such as age, education and ethnicity.

Another approach to screening for dementia is to ask an informant (relative or other supporter) to fill out a questionnaire about the person's everyday cognitive functioning. Informant questionnaires provide complementary information to brief cognitive tests. Probably the best known questionnaire of this sort is the - Informant Questionnaire on Cognitive Decline in the Elderly IQCODE.

Evidence is insufficient to determine how accurate the IQCODE is for diagnosing or predicting dementia.

  • The Alzheimer's Disease Caregiver Questionnaire is another tool. It is about 90% accurate for Alzheimer's when completed by a caregiver.

The General Practitioner Assessment Of Cognition combines both a patient assessment and an informant interview. It was specifically designed for use in the primary care setting.

Clinical neuropsychologists provide diagnostic consultation following administration of a full battery of cognitive testing, often lasting several hours, to determine functional patterns of decline associated with varying types of dementia. Tests of memory, executive function, processing speed, attention and language skills are relevant, as well as tests of emotional and psychological adjustment. These tests assist with ruling out other etiologies and determining relative cognitive decline over time or from estimates of prior cognitive abilities.

Laboratory tests

Routine blood tests are usually performed to rule out treatable causes. These include tests for vitamin B12, folic acid, thyroid-stimulating hormone (TSH), C-reactive protein, full blood count, electrolytes, calcium, renal function, and liver enzymes. Abnormalities may suggest vitamin deficiency, infection, or other problems that commonly cause confusion or disorientation in the elderly.

Magnetic resonance imaging study of the early Alzheimer's patient was normal, and the late Alzheimer's patient had some nonspecific atrophy.

Laboratory assessments of Alzheimer's disease should at least include some blood tests to screen out thyroid disease, vitamin B 12 deficiency, anemia, liver disease, and various metabolic disturbances, which could possibly cause memory change. The combination of increased tau and decreased β-amyloid has been found in the CSF of patients with Alzheimer's disease, but the sensitivity and specificity of this profile have not been studied in large clinical populations.


A CT scan or MRI scan is commonly performed, although these tests do not pick up diffuse metabolic changes associated with dementia in a person who shows no gross neurological problems (such as paralysis or weakness) on a neurological exam. CT or MRI may suggest normal pressure hydrocephalus, a potentially reversible cause of dementia, and can yield information relevant to other types of dementia, such as infarction (stroke) that would point at a vascular type of dementia.

The functional neuroimaging modalities of SPECT and PET are more useful in assessing long-standing cognitive dysfunction, since they have shown similar ability to diagnose dementia as a clinical exam and cognitive testing. The ability of SPECT to differentiate vascular dementia from Alzheimer's disease, appears superior to differentiation by clinical exam.