Mental retardation, also known as mental retardation, is a syndrome that can be caused by a variety of brain developmental disorders, mainly characterized by mental retardation and social adjustment difficulties, and may be accompanied by some kind of mental or physical illness. It starts during the developmental period and progresses slightly with age, but moderate and severe cases still pose a heavy burden to the family and society. Mild patients have no obvious physical developmental abnormalities and are often overlooked in the recruitment experience and selected, causing difficulties in troop training and management, which should be taken into account.
The disease is relatively common, with foreign reports of an overall prevalence of 8 per 1,000 (UK) to 10 per 1,000 (US), with 2 per 1,000 for both moderate and severe cases. The results of the 1982 joint survey of twelve regions in China: the prevalence of moderate and severe is 3.33‰, and there is no data on the prevalence of mild patients. The prevalence rates reported outside China are higher in rural than in urban areas, and higher in men than in women.
Etiology pathology pathogenesis
The etiology is complex. According to foreign data, about 20% of mental retardation is caused by environmental factors, 25% by chromosomal or genetic abnormalities, and more than half of the patients cannot find the cause. It is also found that 85% of severe patients can identify biological causes, such as chromosomal abnormalities, congenital diseases, metabolic and endocrine abnormalities, infections, poisoning, trauma and other physical factors. The psychosocial factors causing mental retardation are difficult to analyze and summarize, and the more certain causes are summarized as follows.
1, genetic abnormalities: mainly refers to neurological dysplasia, malformation or congenital metabolic Down syndrome, Turner syndrome caused by genetic or chromosomal abnormalities; phenylketonuria, galactosemia, familial nigrostriatal dementia; neurofibromatosis, tuberous sclerosis and congenital hydrocephalus, cerebral penetrating malformation, microcephaly, etc.
2.Acquired abnormalities in fetal period: The first trimester of pregnancy is the initial formation stage of fetal nervous system structure, which is vulnerable to damage by pathogenic factors and leads to obvious malformations. Maternal infections (viruses, spirochetes, toxoplasma), abdominal trauma or radiation exposure, psychoactive substance poisoning, endocrine diseases such as hypothyroidism, gestational toxemia, malnutrition, hypoxia and other serious diseases during the fetal period are among the causes of mental retardation.
3, perinatal diseases: including premature birth, obstructed labor, brain injury during delivery, neonatal asphyxia and nuclear jaundice, etc.
4.Postnatal diseases: In the first 2 years after birth, brain development is the fastest, and the brain damage caused by pathogenic factors during this period is also serious. Preschool age is the most critical period, followed by elementary school age. There are many causative factors, such as infection (especially infection of the central nervous system), cranial trauma, poisoning, epilepsy, malnutrition, endocrine or metabolic diseases and post-vaccination encephalitis.
Recent studies have shown that stimulation of various sensory organs is an important factor in promoting the developmental proliferation of brain nerve fibers. Social and environmental factors during development, especially education during infancy and early childhood, can affect brain development. Studies on wolf children and monkey children prove that the deprivation of cultural education opportunities in infancy and early childhood brings damage to normal brain development that cannot be remedied by any careful education later. Epidemiological surveys have found that low IQ is often associated with low socioeconomic and cultural levels, crowded housing, and unstable family environments.
Clinical manifestations
Mental retardation is mainly manifested by low intelligence and social maladjustment. The level of intelligence is generally measured by intelligence tests, while the measure of social adaptation is more complex and often related to age, occupational requirements, and socio-cultural background. The degree of mental retardation is not always consistent with the degree of social adjustment ability, and some people with low IQ can still be socially adjusted; therefore, it is not appropriate to diagnose mental retardation based solely on the level of intelligence. In the past, there were three levels according to the severity of symptoms: stupid, demented and idiotic. The Chinese Classification of Mental Disorders uses a 4-level classification.
1. Mild: IQ of 50-69. accounts for most of the mental retardation. In preschool, intellectual development, speaking and walking are slower than children of the same age. They can barely graduate from elementary school, but they cannot enter secondary school. They do not have much difficulty in speaking in daily life. However, the content of speech is monotonous and childish. Emotional development is also immature, and the ability to distinguish moral concepts such as good and evil is poor. There are no special abnormalities in physical development, and they can perform simple work and learn simple techniques under guidance, but they lack initiative. Some patients show signs of hyperactivity. The former is quiet, easily educated, has certain skills, can still adapt to the social environment, and is easily sympathetic and cared for; the unstable type, also known as the excitable type, is excited, hyperactive, chattering, lacking self-awareness, poor social adaptation, and often annoying or teased. The “equivalent” is “foolishness”.
2.Moderate: IQ 35-49. About 10-20% of mental retardation. They can learn simple language in pre-school, but their vocabulary is poor and they cannot express more complex contents, and it is not easy for them to establish group relationship with children of the same age. With appropriate training, they can learn some simple tasks, but they need supervision and care in life and lack spontaneity. Emotional fluctuations, not easy to control. The body is small and the face is special, so it is easy to find out that the child is mentally retarded, which is equivalent to “demented”.
3.Severe: IQ is 20-34, accounting for about 1% of mental retardation, and physical and motor delays are found at an early age. After training and learning to eat on their own and basic hygiene habits, they live under supervision and cannot perform productive work, often accompanied by other congenital diseases and seizures; they may die at an early age due to infections or physical diseases.
4. Very severe: IQ of 20 or less, very rare, accounting for less than 1% of mental retardation. They are born with physical and neurological abnormalities, usually unable to learn to walk and talk, and can only make simple sounds similar to calling. They are not able to learn to walk and talk, and can only make simple sounds like screaming. They are sensory retarded and cannot avoid danger. Complete inability to care for oneself. Severe and very severe cases are comparable to the previously diagnosed “idiots”. In terms of personality traits, there is a dull, stupid type and an excitable, unrestrained and irritable type.
Physical symptoms: In mild cases, the incisors may be irregularly cut, the teeth may be misaligned, the skin may be loose and dry, and there may be no positive neurological signs. In moderate and severe cases, there are mostly somatic and neurological signs, such as general developmental disorders; gigantism, dwarfism or morbid obesity, etc.; cranial deformities; giant head, pointed head, long head, oblique head, navicular head, etc.; in addition, there are finger and toe deformities, abnormal palmoplantar skin lines, widening of the distance between the two eyes, auricular deformities, etc.; and neurological signs such as motor paralysis, hypertonia, ataxia, speech disorders or deafness.
Diagnosis and differential diagnosis
Since there are individual differences in the rate of mental and physical development in infancy and early childhood, it is necessary to make a comprehensive judgment by taking into account the detailed parenting history and family environment, social environment and other factors, in addition to the developmental criteria of normal children. The diagnostic criteria for mental retardation in the Chinese Classification and Diagnostic Criteria for Mental Disorders, Second Edition.
1. The onset of the disease is before the age of 18;
2.IQ is below 70;
3. Different degrees of social adaptation difficulties.
Diagnostic criteria for mild mental retardation
1, IQ 50-69;
2.No obvious speech impairment;
3, learning ability can not successfully complete elementary school education, can learn certain livelihood skills.
Diagnostic criteria for moderate mental retardation: 1.
1.IQ 35～49;
2.Can master the language of daily life, but the vocabulary is poor;
3.Can’t adapt to normal school study, but can learn to take care of themselves and simple work.
Diagnostic criteria for severe mental retardation.
1.IQ 20-34;
2.Seriously impaired speech function, unable to communicate effectively;
3, unable to take care of themselves.
Diagnostic criteria for very severe mental retardation: 1.
1.IQ below 20;
2.Lack of speech function;
3. Complete inability to take care of oneself.
To diagnose the etiology of this disease, it is necessary to know whether the patient’s parents have any bad habits, whether the mother has any viral infection during pregnancy, or other chronic diseases or mental illnesses, whether there is a history of acute or chronic poisoning, exposure to radioactive substances, whether there is a tendency to endemic diseases and drug use, etc. Detailed physical examination, neurological examination, chromosomal examination and other relevant auxiliary examinations should also be performed. Organic brain diseases, schizophrenia and childhood autism should be excluded.
Prognosis
The prognosis varies depending on the cause and severity of the disease. Mild and moderate cases may improve gradually with age, but still lower than normal people of the same age. The prognosis is related to factors such as brain disorders, low resistance, and low adaptability to life, and severe cases usually die early.