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Is dementia classification confusing? That's enough to read this!

 Last Update: 2022-10-21
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Diagnostic ideas are 3 steps

Dementia is a syndrome
with acquired cognitive impairment at its core and a marked decline in the patient's ability to live daily life, socialize, and work.
The cognitive impairment of patients involves memory, learning, orientation, comprehension, judgment, calculation, language, visuospatial and other functions, analysis and problem-solving skills, and is often accompanied by mental, behavioral and personality abnormalities
at some stage of the course of the disease.

Classification of dementia ^[1]

1.
According to whether it is a transsexual: it is divided into transsexualism and non-transsexuality dementia
.

Degenerative dementia: including Alzheimer's disease (AD), Lewy body dementia (DLB), Parkinson's disease dementia (PDD), frontotemporal dementia (FTD);

Non-degenerative dementia: includes vascular dementia (VD), normal pressure hydrocephalus, and other secondary conditions such as dementia caused by infections, tumors, toxicity, and metabolic diseases
.

2.
According to the lesion site: divided into cortical dementia, subcortical dementia, cortical and subcortical mixed dementia and other
dementias.

Cortical dementia: including AD and FTD;

Subcortical dementia: including VD, extrapyramidal lesions, hydrocephalus, white matter lesions, etc.
;

Cortical and subcortical mixed dementia: multiple infarcted dementia, infectious dementia, toxicity, and metabolic encephalopathy, also seen in DLB;

Other dementias: dementia after brain trauma and subdural hematoma
.

Diagnosis

of dementia Dementia is a syndrome whose diagnosis requires a comprehensive analysis
based on history, neurological physical examination, neuropsychological evaluation, laboratory and imaging findings.

1.
Determine whether it is dementia: 2.
Medical history collection:
The patient's medical history should be collected in detail, and if possible, in addition to the medical history provided by the patient himself, the medical history information provided by the insider must also be obtained (A level recommendation).

3.
Cognitive and mental examination: The first step in the examination of consciousness, cognition and mental state is to carefully examine and judge the ideology
of the patient at the time of examination.
Consciousness is a function of the brain, the highest form of human reflection of objective reality, which is expressed through human language, body movements and behavior
.

Abnormal consciousness can be clinically abnormal from two aspects:

(1) Awakening inhibition or awakening fluctuations, that is, impaired awakening levels, caused by brainstem reticular structural lesions, manifested as drowsiness, lethargy, coma, etc
.

(2) Disorders of consciousness content, patients can not insist on concentration under the condition that the level of consciousness is generally normal, and abnormal thinking, orientation, emotion and other aspects occur
.

How to correctly check and judge the status of a variety of advanced neural functions, such as consciousness, memory, orientation, calculation, use, language, generalization, visuospace, etc.
, is very important
for the correct diagnosis of dementia.

Differential diagnosis of dementia^[2]

1.
AD Differential

from VD2.
FTD
The morphological feature of FTD is atrophy
of the frontal and temporal poles.
However, in the early stage of the disease, these changes are not obvious, the pattern of cognitive impairment of FTD belongs to the "frontal lobe type", in the visual space short-term memory, word immediacy, delay, cue recall and rerecognition, implicit memory, attention persistence test, FTLD patients perform better than AD patients, while Wis-consin card sorting test, Stroop test, wiring test B and other executive function tests perform worse
than AD patients 。 In addition, non-cognitive symptoms, such as lack of social awareness and self-awareness, inhibition, interpersonal dysfunction, antisocial behavior, apathy, and lack of will, are important bases for
distinguishing FTD from AD.

3.
Compared with AD patients, DLB patients with DLB
have relatively retained recall and recognizance functions, and more serious
impairments in speech fluency, visual perception and executive function.
In the case of comparable cognitive level, DLB patients have more severe functional impairment, more serious motor and neuropsychiatric disorders, and worse
self-care ability than AD patients.
The characteristic clinical presentation of DLB patients with fluctuating cognitive impairment, parkinsonism, and recurrent visual hallucinations helps differentiate from AD
.

4.
PDD PDD
refers to the degree of cognitive impairment in patients with Parkinson's disease to the level of
dementia.
Executive function is particularly impaired
in patients with PDD relative to impairment in other cognitive domains.
Deficiencies in visuospatial function are also common, and their degree is more severe
than AD.
PDD patients have decreased short-term memory and long-term memory, but the severity is less
severe than AD.

PDD and DLB have many overlaps
in both clinical and pathologic manifestations.
Recurrent episodes of visual hallucinations are common
in both disorders.
However, dementia in people with Parkinson's disease usually does not appear
until 10 years or more after the onset of motor symptoms.

However, with the exception of differences in the order of symptoms, age of onset, and response to levodopa preparations, dementia with Lewy bodies is very similar to PDD in many aspects such as cognitive impairment, neuropsychological manifestations, sleep disturbance, autonomic impairment, Parkinson's disease symptoms, neuroleptic hypersensitivity, and efficacy of cholinesterase inhibitors
。
Therefore, some scholars have pointed out that it is
unscientific to separate the two.
DLB and PDD may be different manifestations
in the generalized Lewy body disease spectrum.

5.
Normal intracranial pressure hydrocephalus
is characterized by
three main characteristics: progressive mental decline, ataxia gait and urinary incontinence.
Some elderly normal pressure hydrocephalus can be confused with VD, but the former has an insidious onset and no clear history
of stroke.
Normal pressure hydrocephalus is a common cause of treatable dementia, and in addition to medical history consultation and detailed physical examination, determining the type of hydrocephalus requires CT, MRI and other examinations to make a judgment
.

6.
Huntington's disease (HD)
is an autosomal dominant genetic disease, more than 35~40 years old.

Initially manifested as involuntary movements or athetes throughout the body, accompanied by behavioral abnormalities such as irritability, apathy, depression, etc
.
After a few years, intelligence gradually declined
.
Early intellectual impairment is mainly memory, visuospatial dysfunction and language fluency, and later develops into general cognitive decline, especially use impairment
.
Diagnosis
is not difficult based on typical family history, movement disorders, and progressive dementia, combined with imaging tests.

7.
Progressive nuclear ascending paralysis (PSP)
PSP is a neurodegenerative disease, and the cause is still unclear
.
Pathological neurofibril tangles, granular vacuolar degeneration, neuronal loss, etc
.
can be seen in the subcortical structure.
Clinically it is mostly insidious in onset, manifested as personality changes, emotional abnormalities, gait instability, visual and language disorders
.
The main features are supranuclear ophthalmoplegia, axial myotonia, parkinsonism, pseudobulbar palsy, and dementia
.
Typical patients are not difficult to diagnose, but early in the disease and atypical symptoms need to be differentiated
from Parkinson's disease, cerebellar disease, and basal ganglia disease.

8.
Infection, poisoning, metabolic diseases dementia may also be one of the manifestations of a variety of central nervous system infectious diseases
such as HIV, neurosyphilis, proteinopathy, encephalitis, etc.

Vitamin B₁₂ deficiency, hypothyroidism, alcoholism, carbon monoxide poisoning, heavy metal poisoning, etc
.
can occur dementia.
For the diagnosis of dementia and its subtypes, comprehensive clinical, imaging, neuropsychological, laboratory examination, pathology and other aspects of examination are required
.

Summary:
The diagnosis of dementia and its subtypes requires comprehensive clinical, imaging, neuropsychological, laboratory tests, pathology and other aspects of examination
.

References:

[1] Chinese Dementia and Cognitive Impairment Guidelines Writing Group, Cognitive Impairment Disease Professional Committee, Neurologist Branch of Chinese Medical Doctor Association.
2018 Chinese Guidelines for the Diagnosis and Treatment of Dementia and Cognitive Impairment (I): Dementia and its classification and diagnosis criteria[J].
Chinese Medical Journal,2018,98(13):965-970.
)

[2] Gale S A,Acar D,Daffner K R.
Dementia[J].
Am J Med,2018,131(10):1161-1169.

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