Dementia: when is the diagnosis made?

The diagnosis of dementia is based on an interview with the patient and a physical examination (cognitive functions, neurological examination, autonomy, mental health).

Examinations: the first step in diagnosing dementia

It includes basic and clinical examinations. The clinical examination includes a history and physical examination.

A. Maintenance

From the start of the interview, the doctor must establish a climate of trust, by speaking directly to the patient whenever his condition allows. The physician must ensure that the patient hears, sees and speaks clearly (wearing glasses, hearing aids and dental appliances). The office in which the interview takes place should be quiet and well lit. Questioning of a relative is necessary if the patient has problems communicating. The doctor must nevertheless continue to question the patient, interpreting his words.

The anamnesis consists of questioning the patient to collect as much information as possible:

What is the personal history provided by the subject and corroborated by those around him: does he have a medical history, has he stayed in hospital, does he have a family history of illness (for example Does a close relative have Alzheimer’s disease A medical history may be important if a late-onset genetic disease such as Alzheimer’s disease is suspected.

Does he take any prescribed or over-the-counter medications? Certain medications (anxiolytics, hypnotics, certain antidepressants) are likely to cause cognitive disorders.
What are the symptoms frequently reported by the patient?

Is the patient still independent (eg does he take the bus alone?, does he dress himself)? A test is carried out to assess the subject’s ability to perform tasks of daily living (using the questionnaire on instrumental activities of daily living) and self-care (questionnaire on functional activities).
Has he lost weight, does he feel listless, depressed or confused, does he have memory loss, has he recently had falls, does he suffer from gait disturbances and posture, sleep (nightmares)? The observations made by the patient’s entourage describing, for example, the patient’s cognitive decline, are taken seriously into account by the doctor.

B. Physical examination

The doctor assesses mental and functional abilities (that is, their ability to perform physical activities of daily living).

B1. Examination of cognitive functions

It is done using the following assessment tests:

The Mini-Mental State Examination
The clock test
The five-word test
Grober and Buschke’s free and cued recall tests

B2. Neurological examination

The neurological examination includes examination of motor skills, tone and posture. The search for a parkinsonian syndrome (tremor at rest, akinesia, parkinsonian hypertonia) or frontal syndrome (reduction of the capacity to carry out a simple movement up to akinesia) must be sought systematically. The tremors at rest – at the rate of 5 per second – appear for a certain degree of muscular relaxation, and disappear during the execution of a voluntary movement.

It is at the end of the upper limb that it begins and is most characteristic. Akinesia is characterized for example by a rarity of blinking and the reduction of mimicry, giving the patient a frozen appearance, and a reduction in the associated swinging of the arms when walking. The examination highlights a difficulty in executing alternating movements quickly. For example, in strumming movements, there is a rapid decrease in the amplitude of the movements which can lead to a real blockage. Akinesia can disappear temporarily under the influence of an emotion.

The examination of reflexes is not only an exploration of the afferent and efferent elements of the reflex arc. It is also a test that evaluates the responsiveness of the nervous system as a whole at a specific time. Inhibition of Achilles tendon reflexes, caused by stimulation of the Achilles tendon, is frequently observed in very old people. It does not necessarily indicate peripheral neuropathy.

B3. Autonomy Review

The most widely used tool for assessing autonomy is the Activities of Daily Living (ADL) scale , which explores the basic activities of daily living: continence, eating, dressing , hygiene care, mobility, grooming.

If the subject appears to be autonomous, the doctor pursues the evaluation further using the scale of instrumental activities of daily living (AIVQ, in English Instrumental Activities of Daily Living or AIDL).

In France, the AGGIR grid (gerontological autonomy, isoresource groups) gives an overall score of autonomy that includes the patient’s ability to carry out the various acts of daily living independently. Patients are thus divided into six ‘iso-resource’ groups (GIR), which allows them to receive a social benefit for autonomy. The AGIR grid does not make it possible to accurately assess the specific needs of the patient.

The presence of a loss of functional autonomy must evoke the existence of dementia because these daily utilitarian tasks (for example managing one’s finances, using one’s telephone, driving a car, making purchases, etc.) are essentially governed by functions cognitive (judgment, language, orientation, calculation, memory, praxis, planning).

B4. Mental examination

The doctor must detect the signs reflecting a mood disorder or anxiety, corroborated by the patient’s entourage.

Psychiatric disorders are also important to identify because they are often inaugural in certain dementias such as frontotemporal dementia, Alzheimer’s disease and vascular dementia.

For example, anosognosia (the individual’s lack of knowledge of his disease) appears in certain Alzheimer’s patients (it is detected by the Cornell scale) and in other dementias.

Depression is considered a differential diagnosis of dementia (a condition called pseudodementia). It is often difficult to differentiate the two pathologies (dementia and pseudodementia) characterized by the presence of depressive symptoms. The diagnosis is made by prescribing the patient an antidepressant (if the antidepressant has no effect on cognitive disorders, this means that the patient suffers from dementia).

The existence of behavioral disorders should prompt the physician to assess cognitive functions and make a diagnosis of dementia. But he must avoid mistakenly evoking dementia. Indeed, some disorders such as hallucinations can be caused by drugs or delusional manifestations (eg Charles Bonnet syndrome with visual hallucinations).

The rating scales are:

Penn State Questionnaire
Geriatric depression scale
Hamilton Depression Scale
The Neuropsychiatric Inventory

Dementia diagnostic criteria

The diagnostic criteria of the Diagnostic and Statistical Manual of Mental Disorders 4th Edition (DSM IV) will be used to make the diagnosis dementia, or to make a differential diagnosis, that is to say find another cause at the origin of these cognitive disorders /behavioural; mental confusion may be one such cause.

A. Appearance of multiple cognitive deficits, as evidenced by both:

Memory impairment (impaired ability to learn new information and/or recall previously learned information).
One (or more) of the following cognitive disturbances:
Aphasia: language disturbance (difficulty naming objects or people, vague speech with long convolutions, and excessive use of imprecise words like “thing” and “it.
Apraxia: Impaired ability to perform motor activity despite intact motor functions (subjects cannot imitate gestures such as combing their hair or correctly perform symbolic gestures such as waving their hands. Apraxia can lead to impossibility of essential independent tasks dressing, etc.).
Agnosia: inability to recognize or identify objects despite intact sensory functions (objects, family members or even their own image in the mirror).
Disturbance of executive functions (making plans, organizing, ordering in time, thinking abstractly).
Both criteria A1 and A2 cognitive deficits cause significant impairment in social or occupational functioning and represent a significant decline from the previous level of functioning.
Demonstration from the history of the disease, physical examination or complementary investigations that the disturbance is the direct physiological consequence of one of the general medical conditions listed below.
Deficits do not occur exclusively during the course of delirium.

Reference: American Psychiatric Association, DSM-IV, Diagnostic and Statistical Manual of Mental Disorders. French translation, Paris, Masson, 1996.

The etiology of dementia

When the diagnosis of dementia is made, it is necessary to seek the etiology, that is to say the causes and factors at the origin of the disease.

The doctor studies the way in which the disorders have settled, their evolution since the appearance of the first signs, the existence of accompanying signs (motor, psychological and behavioral disorders such as hallucinations), the profile of the neuropsychological disorders, the detection of cerebral abnormalities by neuroimaging (in particular cerebrovascular lesions characteristic of vascular dementia). Other complementary examinations can be useful for the etiological diagnosis.

Dementia Diagnosis Reliability

If the doctor is in doubt about the diagnosis of dementia, another diagnosis can be made within 6 months.

However, and despite a rigorous clinical approach, a quarter of the diagnoses made are invalidated by the post-mortem study of the patient’s brain, which ultimately determines the diagnosis.

Laboratory tests and neuroimaging

Neuroimaging and laboratory examinations are then carried out when the diagnosis of dementia is probable, in order to exclude any reversible form of cognitive decline and to refine the diagnosis.

The laboratory tests thus are intended to identify the reversible causes, the focal (localized) lesions affecting the white matter observed in vascular dementia, as well as atrophy of the medial temporal lobe characteristic of Alzheimer’s disease.

MRI (magnetic resonance imaging) makes it possible to observe cerebral atrophy whose topography points to the etiology of dementia:

Alzheimer’s disease: predominantly medial temporal atrophy.
Frontotemporal dementia: Marked frontal and anterior temporal atrophy, as well as less medial temporal atrophy than seen in Alzheimer’s disease.
Vascular dementia: presence of focal lesions (lacunae), small bleeding (infarction) and white matter signal abnormalities.

Positron emission tomography (PET) or single photon emission tomography (SPECT) are useful in differentiating Alzheimer’s disease (marked functional abnormalities of the bilateral parietal and temporal lobes) from normal aging or degeneration fronto-temporal (Figure 3), but they are not necessary in the assessment of dementia. Single-photon emission tomography (SPECT) and PET are also used to distinguish dementia with Lewy bodies from Alzheimer’s disease, using the dopamine transporter (DATscan®).