所有的智力障碍都是涉及中枢神经系统的问题。遗传性神经系统疾病的症状及体征繁多,其中一部分,如智力障碍、抽搐等,具有普遍性,见于多种疾病。 习惯上,智）低下是指智能发育不全或称精神发育迟缓（Mental retard- ation）等,系一组因为先天的或儿童期的疾病引起的精神活动发育受阻,特别表现为智力及社会适应能力低下。智力低下实质上是一个症状群,它可由多种原因引起,但如果在智力充分发育之后,由各种致病因素引起的智力退化,则不应称为智力低下。至于“智力充分发育” 的年龄,西方国家习惯于定在18岁,我国则常定在12岁左右,因此两 All mental retardation is a problem involving the central nervous system. Hereditary nervous system diseases, many symptoms and signs, some of them, such as mental retardation, convulsions, etc., is universal, found in a variety of diseases. Habitually, wisdom) Low refers to mental retardation, or mental retardation, which is a group of mental activity due to congenital or childhood disorders blocked development, especially for the mental and social adaptability low. Mental retardation is essentially a group of symptoms that can be caused by a variety of causes, but should not be considered mental retardation if the mental deterioration is caused by a variety of causative factors after full mental development. As for the age of “full development of intelligence”, the western countries are accustomed to being set at 18 years old and our country is always around 12 years old. Therefore, two