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Mental Retardation: Clinical Classification of Mental Retardation are as follows: 1. Mongolism 2. Cretinism 3. Microcephaly 4. Hydrocephaly 5. Phenylketonuria (PKU) 6. Turner Syndrome.
Mental retardation can be classified not only on the basis of the level of intelligence, but also on the basis of their clinical symptoms.
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This classification helps for easy diagnosis and treatment. These types are basically related to biological or genetic factors. Important among them are:
1. Mongolism:
These children will have physical features resembling Mongolian race, hence called mongolism. This is otherwise called ‘Down’s syndrome’ named after the doctor by name Langdon Down (1886) who recognized this disorder for the first time.
The physical features of this disorder include small stature, small head size, short neck and short fingers of hands, almond shaped eyes, flat nose, small mouth, fissured tongue, broad and curved palms and foot, deep voice, lack of muscular coordination, approximately about 50% will have eye cataract problem.
Usually these children are prone to suffer from disorders of heart, lungs, stomach and intestine. They remain backward in learning and training. It is presumed that this disorder is caused due to chromosomal aberration or metabolic disorder or trisomy (where the two chromosomes join with the single 21st chromosome from the father forming an abnormal condition) and variation in secretion of pituitary gland. These children will have IQ level approximately in between 20-50.
2. Cretinism:
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This condition is caused due to lack of iodine in thyroxin hormone during childhood. The severity of the condition depends upon the amount of deficiency of thyroxin hormone. Rate of mental retardation ranges from moderate to severe.
The physical features include short stature, thick skin, short but fat hands and legs, rough hairs, fatty eyelids, broad and flat nose, broad and drooped ears, bulged abdomen, sexual immaturity, un-shining(dull) eyeballs, etc.
3. Microcephaly:
This condition is otherwise called small headedness. The size of the skull is smaller than the normal size- approximately about 17 inches instead of 22 inches of normal size. The other features include stunted body growth, almond shaped skull, recessed forehead and chin, etc. There are more chances of death shortly after birth.
According to studies the growth of head stops at the 4th or 5th month of pregnancy. The cause may be genetic factors, infection in mother’s womb, pelvic irradiation (mother undergoing X-ray during pregnancy). It is observed that many children born in Nagasaki and Hiroshima after world war had this problem.
4. Hydrocephaly:
This is otherwise called large headedness. The size of the skull is larger than the normal size. This condition is caused due to excess secretion or lack of absorption of cerebrospinal fluid. The brain is pressed due to accumulation of CSF, causing mental retardation.
The size of the skull at the same time increases because the bones of the skull are not ossified yet. This disease is said to cause due to brain tumor or meningitis. This may start before birth or immediately after birth of the child. Rate of MR depends upon the damage to the brain. It may range approximately from moderate to profound.
5. Phenylketonuria (PKU):
It appears very rarely and estimated to appear one in 20,000 children. It was first recognized by a doctor by name As Bjorn Foiling from Norway in the year 1934. He observed this condition when a mother reported to him that her baby was foul smelling (smelling badly) and inactive.
He found that the baby was having problem with metabolism of phenylalanine. The phenylalanine quantity increases in the blood due to lack of a catalytic enzyme helps digestion of proteins.
The disease appears from 6-12 months after birth. The rate of MR ranges from moderate to severe. The other physical features include lack of muscular coordination, paleness of skin and hairs, etc.
6. Turner syndrome:
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Chromosomes are 45.XO. Diagnosis is evident at birth. Short length of hands and feet, short neck, anomalous ears, small mandible, broad chest, lack of sexual maturation, adult stature is less than 145 cm, etc. Associated defects in kidneys, hearing and intellectual deterioration. This disorder is caused only in females.
The other clinical types of mental retardation include galactosemia, Klinefelter’s syndrome, cerebral palsy, etc.