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Research Notes: Brain PlasticityRoger Lewin. "Is Your Brain Really Necessary?" Science 12 December 1980, page 1232. "Is your brain really necessary?" This was the question asked by British neurologist John Lorber when he addressed a conference of pædiatricians in 1980. Such a frivolous sounding question was sparked by case studies Lorber had been involved in since the mid-60s. The case studies involve victims of an ailment known as hydrocephalus, more commonly known as water on the brain. The condition results from an abnormal build up of cerebrospinal fluid and can cause severe retardation and death if not treated. Two young children with hydrocephalus referred to Lorber presented with normal mental development for their age. In both children, there was no evidence of a cerebral cortex. One of the children died at age 3 months, the second at 12 months. He was still following a normal development profile with the exception of the apparent lack of cerebral tissue shown by repeated medical testing. An account of the children was published in Developmental Medicine and Child Neurology. Later, a colleague at Sheffield University became aware of a young man with a larger than normal head. He was referred to Lorber even though it had not caused him any difficulty. Although the boy had an IQ of 126 and had a first class honours degree in mathematics, he had "virtually no brain". A noninvasive measurement of radio density known as CAT scan showed the boy's skull was lined with a thin layer of brain cells to a millimeter in thickness. The rest of his skull was filled with cerebrospinal fluid. The young man continues a normal life with the exception of his knowledge that he has no brain. Although anecdotal accounts may be found in medical literature, Lorber is the first to provide a systematic study of such cases. He has documented over 600 scans of people with hydrocephalus and has broken them into four groups:
Of the last group, which comprised less than 10% of the study, half were profoundly retarded. The remaining half had IQs greater than 100. Skeptics have claimed that it was an error of interpretation of the scans themselves. Lorber himself admits that reading a CAT scan can be tricky. He also has said that he would not make such a claim without evidence. In answer to attacks that he has not precisely quantified the amount of brain tissue missing, he added, "I can't say whether the mathematics student has a brain weighing 50 grams or 150 grams, but it is clear that it is nowhere near the normal 1.5 kilograms." Many neurologists feel that this is a tribute to the brain's redundancy and its ability to reassign functions. Others, however, are not so sure. Patrick Wall, professor of anatomy at University College, London states, "To talk of redundancy is a cop-out to get around something you don't understand." Norman Geschwind, a neurologist at Boston's Beth Israel Hospital agrees: "Certainly the brain has a remarkable capacity for reassigning functions following trauma, but you can usually pick up some kind of deficit with the right tests, even after apparently full recovery." Paul Pietsch. Brain shrinks, yet thinks. (from Science Digest, October 1983. vol. 91 No. 10) Anatomy textbooks contain detailed maps of "normal" human brain function. Sight, we are told, resides in one region, hearing in another. But one fascinating patient who was referred to the eminent British neurologist John Lorber demonstrates that there are exceptions to every rule. Lorber, who specializes in birth defects caused by fluid buildup within the interior of the brain, tells of a 26 year- old man referred to him for a brain scan. Ordinarily, the walls of the cerebrum are 4-5 millimeters thick. This man's cerebrum had been squashed by fluid pressure - a condition known as hydrocephalus - to a thickness of less than one millimeter. That Lorber's patient was alive at all seems incredible. But he was socially normal, had an IQ of 126 and had earned a first class honors degree in mathematics. His relative lack of gray matter had not apparently affected his intelligence. How could this possibly be? If the way the brain functions is similar to the way a hologram functions, that one-millimeter sliver might suffice. Certain holograms can be smashed to bits, and each remaining piece can reproduce the whole message. A tiny fragment of this page, in contrast, tells little about the whole story. Observations such as Lorber's suggest that input-output functions of different parts of the brain can be shifted and that there's a great deal of functional plasticity in it. Indeed, in recent years, plasticity has become a major topic among neuroscientists. That valid maps exist at all - and they do - suggests that there is a strong tendency as we mature for certain regions to assume particular chores. But that a brain one millimeter thick functions as well as its 4 to 5 millimeter counterpart illustrates that these tendencies are not etched in stone. Dev Med Child Neurol. 1992 Jul. Studies of 10 sets of twins discordant for hydrocephalus in early life revealed striking differences in degree and nature of development of verbal vs. non-verbal cognitive functions, birth order, and hand and eye preference. Despite similar (four dizygotic pairs) or identical (six monozygotic pairs) genetic endowment and grossly similar intra- and extra-uterine environmental and socio-economic influences, the consistency of the differences between the hydrocephalic children and their seemingly normal twins indicate systematic differences in pre-, peri- and/or early postnatal organization and development of hemispheric function. Follow-up studies also documented development of above-average intelligence, despite drastically reduced cerebral mantle size in hydrocephalus of early onset. The atypical patterns of development of the non-hydrocephalic twins also confirm previously described qualifications reported in studies of the significance of genetic vs. environmental factors in twins. Z Kinderchir. 1981 Dec. Of 10 children with macrocephaly in association with achondroplasia only two children had progressive hydrocephalus. They were treated with a shunt procedure. One of these is intellectually and neurologically normal, and one is wheelchair bound and mentally retarded, with a spastic quadraplegia. Three children showed mild dilatation of the ventricles and one of these died from severe constriction at the foramen magnum. The other two are neurologically normal; one is intellectually normal but below average (WISC 88) and the other is slow normal at 18 months of age. Four children with demonstrated megalencephaly and a fifth with probable megalencephaly are all intellectually and neurologically normal. Intelligence in achondroplasia appears to be mainly in the normal range. Dev Med Child Neurol Suppl. 1975. It has been suggested that the presence of lacunar skull deformity in infants with myelomeningocele and hydrocephalus is indicative of later lowered intelligence and therefore is a useful criterion in early selection for treatment. In the present study, retrospective investigations were made of the clinical records and skull X-rays of 169 surviving children who had been admitted immediately after birth with myelomeningocele and hydrocephalus to the Children's Hospital, Sheffield. Adequate X-rays were available for 131 of the children, of whom 97 per cent exhibited some degree of lacunar skull deformity. At five years of age or older, the 131 children were tested on the Wechsler Intelligence Scale for Children. The differences in mean IQ between the various degrees of severity were not large, and it was found that 82 per cent of children with the most severe degree of lacunar skull deformity had IQs above 70. These findings do not support the use of lacunar skull deformity as an important measure in selection for treatment of children with myelomeningocele and hydrocephalus. |