LAHORE, Jan 4: Contrary to the myth that abnormal smallness of head or microcephaly has anything to do with wearing iron-cap, a joint study by two universities reveals that the abnormality is ‘altogether a genetic disorder’.
The research is aimed at tracing the causes of the small head disorder and how to treat and prevent it. It also serves as an answer to the popular myth that the abnormality is caused by covering a child’s head with an iron-cap at the shrines. Some people ‘donate’ their first child to those with professed knowledge of spirituality under the belief that such an act will bring good luck to the family and will be a source of benediction.
A six-member team of the University of Health Sciences, Lahore, and the Quaid-i-Azam University, Islamabad, picked some 40 families having persons with microcephaly in the parts of Punjab and the NWFP for the purpose. Some persons at the shrines in Gujrat, Kasur and Northern Areas also were included in the study.
The Department of Genetics and Bio-Technology of UHS’ Associate Professor Dr Saqib Mahmood, who headed the project, told Dawn on Sunday that this was the first local research and it would certainly help control and prevent the abnormality in the future generation. He maintained that its victims could be in thousands in Pakistan, however, to know the exact number of such people a thorough population-based study was required.
The study says: “Microcephaly is a congenital abnormality characterised by severe underdevelopment of the brain, particularly the cerebral cortex. Clinically, microcephaly refers to a head circumference (HC) significantly less than expected for an individual’s age and sex.“The patients with primary microcephaly have head smaller than normal at birth.
This is because the brain fails to grow to the correct size during the first 32 weeks of pregnancy, resulting in an abnormally small brain. There are many non-genetic and genetic causes of primary microcephaly with mental retardation. The non-genetic causes may include congenital infections that affect the brain (such as cytomegalovirus), intrauterine exposure to teratogenic agents, and birth asphyxia. Chromosomal defects, single gene defects and syndromes of undetermined etiology are the genetic causes of primary microcephaly”.
The study further says Autosomal Recessive Primary Microcephaly (ARPM) is the most predominant form of microcephaly caused by genetic defect and is defined by an absence of identifiable environmental causes.
“All these individuals have mild to moderate degree of mental retardation and a majority of them have normal height, weight, appearance, chromosome analysis and brain scan. Motor and social milestones are mildly delayed but speech development is consistently delayed. In rare cases patients may present with fits. There are no major abnormal physical features except sloping forehead, which is not always present. Brain weight in these persons is typically 430 gram compared with 1,450 gram in normal males, and the cerebral cortex is disproportionately small.”
Primary microcephaly, says the study, can be viewed as an example of evolutionary retrogression whereby, the brain dimensions of affected individuals revert to a level resembling that of the very early hominids. This raises the attractive possibility that genes implicated in primary microcephaly, which are clearly involved in regulating brain size during development, may also play a role in the expansion of the brain during evolution.
“There are six possible genes in human cells which are responsible for the proper growth of brain cerebral cortex during early fetal life. Inherited defect in any one of these genes results in child being born with a small head.”
The study further points out that a key biological basis for this is huge brain size of humans relative to other existing species. “Human brain is considered to be over five times as large as the average brain of a mammal with the same body size. This is particularly true for the cerebral cortex which is the outer layer of the major part of brain. This region of the brain is most prominently involved in higher cognitive functions such as ability to think, reason, analyse, solve problems, memorise, learn and speak in human beings. “It is generally believed that the brain expansion sets the stage for the emergence of human language and other high-order cognitive functions and it was caused by adaptive selection during the process of evolution.”