Mental retardation

Mental retardation Mental retardation is a chronic disease that affects approx. 2-3% of the population and which involves the following three criteria (American Psychiatric Association 1994 definition): 1. Reducing the importance of intellectual function (IQ <70). Determination of intelligence is through standardized cognitive tests (Stanford-Binet, Wechsler). Intelligence quotient (IQ) is the ratio of mental age and chronological. Like other multifactorial character has a normal Gaussian distribution (Gauss bell). 2. Significant limitation of adaptive function relative to chronological age as follows: - For infant and toddler mental retardation are highlighted (actually only suspected barely school age and underline) as a developmental delay - Preschool occur if use of language and communication difficulties, as well as autoingrijirii - Formal abstract thinking is embodied in the deficiencies of poor results at school. - Teen and young adults can not achieve economic independence and not be satisfactorily integrated into society. 3. The appearance of these changes before the age of 18.
The prevalence estimated by WHO for Europe and North America is approximately 3% of the general population. Over 85% of all cases are mild mental retardation. Males are more frequently affected (sex ratio 1, 5), a fact explained in part by the existence of some form of mental retardation caused by mutations in genes located on chromosome X.
At the opposite end is mental retardation as a restricted category (2% of world population) consists of the smartest people on earth. Most of them are found in a company - called MENSA, whose sole criterion for acceptance as a member is very high IQ. If mental retardation (at least for the untrained patients with severe retardation) is a safe assumption for failure and addiction specialist care, a very high IQ is no guarantee of success.

Classification of mental retardation - very useful in adopting a suitable therapeutic strategy of prevention and especially - can be done according to several criteria:
After severity there are two main forms: - Easy mental retardation (IQ = 70-50) is most often the consequence of a poor family environment, social, interested mainly the disadvantaged and has a high risk of recurrence, medical causes are rare and patients are educated and can gain a degree of independence. Represents approx. 85% of all cases of mental retardation. - Severe mental retardation (IQ <50) It can be further subdivided into mild (IQ = 50-35), severe (IQ = 35-20) and profound (IQ <20). It has a uniform distribution of all social classes , biomedical causes are most frequent, low risk of recurrence, require special care. A particularly important aspect of genetic counseling is to compare the intelligence of the patient with parents and siblings.
After etiology exists: - Mental retardation caused by genetics: monogenic or chromosomal diseases. - Environmental causes mental retardation (negenetice) nutritional factors, infectious, immunologic, etc.. - Idiopathic mental retardation (represents about 50% of all cases, the etiology can not be identified with precision is probably multifactorial).
Phenotypically there are two forms of mental retardation: - Isolation or non-specific mental retardation patient shows no other physical or neurological damage, - Specific syndrome or mental retardation. Cognitive deficiencies associated with other events occurring phenotypic (congenital anomalies) in some syndromes.
An educational classification distinguishes three categories of mental retardation: - Learners can learn simple things in school, but not exceeding grade level will - Coach can learn to care, but few can learn to read and write - Untrained care are totally dependent on others.
The etiology of mental retardation Establishing the causes of mental retardation is a very difficult but necessary action to establish a prognosis and proper genetic counseling. The Pathogenesis of environmental factors contribute to mental retardation and / or genetic.
Environmental factors are represented by different agents trauma (intracranial hemorrhage), toxic (especially maternal alcoholism / fetal alcohol syndrome), infections (cytomegalovirus, toxoplasma, rubella, etc.), pregnant women's nutritional deficiencies (iodine, selenium). These factors can act both during pregnancy and after birth. Prematurity and its complications explain nearly 10% of the forms of mental retardation easy. The factors most easily preventable nutritional deficiency of iodine. Iodine participate in CNS development both as such (elemental iodine) and through hormones tiroidieni.Deficitul pregnant severe iodine (endemic goiter), especially in the first trimester when fetal thyroid is not yet developed, leads to cretinism product design . cerebrospinal tract organ of Corti and are particularly vulnerable to iodine deficiency in the first weeks of intrauterine life. Genetic causes chromosomal abnormalities consist either be transmitted in Mendelian monogenic mutations. The determinism of multifactorial idiopathic retardation are involved with environmental factors of several gene mutations.
Genes involved in the development of cognitive processes in humans are divided into four groups: - Genes that encode proteins on the surface membrane of the cell synapse (tetraspaninele, IL1 IL1 receptor accessory protein Rapla = like, - Regulators of protein coding genes of translation (protein FMRP) - Gene encoding protein constituents of signaling pathways. Signaling protein involved in part of two categories: GTP-Aze (oligofrenina 1, GDP dissociation inhibitor type 1-GDI1) and kinases (kinases superfamily RAS components such as kinase PAK3, RSK2 cytosolic effector, LIMK1 kinase). - Genes that encode transcription factors (located on the X chromosome gene MECP2, located on the site of gene FRM2 FRAXE fragile, ATRX gene located on X psi FOXP2 gene located on chromosome 7).
Chromosomal abnormalities are the most common cause of severe mental retardation (about 40% of the total cases). Down Syndrome is about. 65% of chromosomal abnormalities associated with mental retardation. Chromosome microdeletions are found in Williams-Beuren syndrome, Angelman and Prader-Willi syndrome. The remaining cases is different partial trisomies or monosomy. In the last perioadao attention is identified subtelomeric abnormalities over 5% of patients previously considered as having idiopathic mental retardation. Mutations in this category included monogenic syndromes with multiple congenital anomalies (ACM) associated with mental retardation (JMA / MRI), metabolic diseases (1-5%), neuromuscular diseases (Duchenne muscular dystrophy), developmental disorders (holoprosencefalia) CNS malformations mental retardation involves an abnormal brain functional without necessarily associate the existence of anatomical abnormalities. However frequent brain malformation in patients with mental retardation ranging from 7-17%. The most common are lisencefalia, cerebellar hypoplasia, agenesis of the corpus callosum was Apart from this it is possible to exist other more subtle errors in neuronal migration, myelination of axons and neurons orientation can not be evidenced by normal investigative techniques.
Clinical evaluation 1) The history aims to obtain information on pre-, peri-and postnatal insisting on the circumstances of hypoxia, fetal movements, psychomotor development, seizures, hypotonia and hipoactivitatii in the first months after birth. As a particular history must gather data on three generations of existing targeting chronic diseases, birth defects, other cases of mental retardation, etc.. Ricare have examined patient ill family member. 2) Physical examination is considering several principles: - To assess both patient and close relatives; - Is carefully investigating neurological signs (bone-tendon reflexes, muscle tone, movements, muscle mass); - Emphasis on exam skull (size, shape), face, hair, skin, skeleton; - Must be rigorously described abnormal items (photos, measurements, audio / video). 3) Consult interclinic (neurologist, ophthalmologist, psychologist, etc.) within which it has a special role neuro exam, to assess the severity of mental retardation as well as directions for recovery.
Laboratory tests that are required to be performed include: - Cytogenetic analysis. All children with mental retardation but without a diagnosis of certainty requires a karyotype with 500 marker bands. To detect defects submicroscopical resort to subtelomeric analysis, but which is extremely expensive, require prior preselection of cases. - Molecular analysis of fragile X (FRAXA) is mandatory in all patients regardless of sex with unexplained mental retardation - Assess the structural integrity of CNS imaging (CT, MRI) is required in patients with microcephaly, abnormal brain stem stroke, seizures. MRI is the method of choice in most cases. - Metabolic screening. Many disorders of metabolism (metabolism of phenylalanine, bilirubin -> neonatal jaundice) have as consequence the appearance of mental retardation in general by the CNS accumulation of toxic metabolites. In 2003 two American specialists (Battaglia and Carey) have developed an algorithm for the evaluation of patients with developmental delay and / or mental retardation, but which unfortunately is not accessible to the great majority of hospitals. However this should not in any way hinder the clinician's freedom to conduct tests as it deems to be necessary.
Once put a definite diagnosis of mental retardation is on the one hand, the recovery and educating children to gain a larger degree of independence and secondly the problem of transmission of cognitive deficits in offspring.