Canadian Medical Guide > Diseases > Nervous System Diseases > Neurologic Manifestations > Neurobehavioral Manifestations > Mental Retardation Terms and Definitions

Mental Retardation

Medical Definition:	Subnormal intellectual functioning which originates during the developmental period. This has multiple potential etiologies, including genetic defects and perinatal insults. Intelligence quotient (IQ) scores are commonly used to determine whether an individual is mentally retarded. IQ scores between 70 and 79 are in the borderline mentally retarded range. Scores below 67 are in the retarded range. (Joynt, Clinical Neurology, 1992, Ch55, p28)
Guide Notes:	use Cat C qualif; /rehabil permitted: do not equate with EDUCATION OF MENTALLY RETARDED
Also Called:	Mental Retardation, Psychosocial,Deficiency, Mental,Idiocy

Mental Retardation Categories.

	Cri-du-Chat Syndrome - An infantile syndrome characterized by a cat-like cry, failure to thrive, microcephaly, MENTAL RETARDATION, spastic quadriparesis, micro- and retrognathia, glossoptosis, bilateral epicanthus, hypertelorism, and tiny external genitalia. It is caused by a deletion of the short arm of chromosome 5 (5p-).
	De Lange Syndrome - A syndrome characterized by growth retardation, severe MENTAL RETARDATION, short stature, a low-pitched growling cry, brachycephaly, low-set ears, webbed neck, carp mouth, depressed nasal bridge, bushy eyebrows meeting at the midline, hirsutism, and malformations of the hands. The condition may occur sporadically or be associated with an autosomal dominant pattern of inheritance or duplication of the long arm of chromosome 3. (Menkes, Textbook of Child Neurology, 5th ed, p231)
	Down Syndrome - A chromosome disorder associated either with an extra chromosome 21 or an effective trisomy for chromosome 21. Clinical manifestations include hypotonia, short stature, brachycephaly, upslanting palpebral fissures, epicanthus, Brushfield spots on the iris, protruding tongue, small ears, short, broad hands, fifth finger clinodactyly, Simian crease, and moderate to severe MENTAL RETARDATION. Cardiac and gastrointestinal malformations, a marked increase in the incidence of LEUKEMIA, and the early onset of ALZHEIMER DISEASE are also associated with this condition. Pathologic features include the development of NEUROFIBRILLARY TANGLES in neurons and the deposition of AMYLOID BETA-PROTEIN, similar to the pathology of ALZHEIMER DISEASE. (Menkes, Textbook of Child Neurology, 5th ed, p213)
	Mental Retardation, X-Linked - A class of genetic disorders resulting in mental retardation that is associated either with mutations of GENES located on the X CHROMOSOME or abberations in the structure of the X chromosome (SEX CHROMOSOME ABERRATIONS).
	Prader-Willi Syndrome - A chromosomal disorder associated with a deletion of the proximal portion of the long arm of chromosome 15 (15q11-q13) in the majority of affected individuals. The abnormalities occur exclusively on the paternally derived chromosome 15. Clinical manifestations include MENTAL RETARDATION, muscular hypotonia, OBESITY, hyperphagia, short stature, hypogonadism, strabismus, and hypersomnolence. (Menkes, Textbook of Child Neurology, 5th ed, p229)
	Williams Syndrome - A contiguous gene syndrome associated with a heterozygous microdeletion in the chromosomal region 7q11.23, encompassing the ELASTIN gene. Clinical manifestations include supravalvular aortic stenosis (AORTIC STENOSIS, SUPRAVALVULAR), MENTAL RETARDATION, elfin facies, impaired visuospatial constructive abilities, and transient hypercalcemia in infancy. The condition affects both sexes, with onset at birth or in early infancy.

Mental Retardation Medical Definitions and Terms

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