Neurological Aspects of Reading Disability.

The author, a neurologist, looks at the nature of reading disabilities. He suggests that many reading disabilities are the result of normal constitutional differences and that the term "minimal brain dysfunction" is rarely appropriate and does not help the remediation process. Noted are various theories which relate neurology and reading ability. (DB) *********************************************************************** Documents acquired by ERIC include many informal unpublished * materials not available from other sources. ERIC makes every effort * * to obtain the best copy available. Nevertheless, items of marginal * * reproducibility are often encountered and this affects the quality * * of the microfiche and hardcopy reproductions ERIC makes available * * via the ERIC Document Reproduction Service (EDRS). !DRS is not * responsible for the quality of the original document. Reproductions * * supplied by EDPS are the best that can be made from the original. *********************************************************************** NEUROLOGICAL ASPECTS OF READING DISABILITY Louis R. Nelson, M.D. Division of Neurological Surgery Albany Medical College Albany, New York U S DEPARTMENT OF HEALTH. EDUCATION WELFARE NATIONAL INSTITUTE OF EDUCATION THIS DOCUMENT HAS SEEN REPRO DUCED EXACTLY AS RECEIVED FROM THE PERSON OR ORGANIZATION ORIGIN ATING IT POINTS OF VIEW OR OPINIONS STATED DO NOT NECESSARILY REPRE SENT OFFICIAL NATIONAL INSTITUTE OF EDUCATION POSITION OR POLICY presented at A.E.R.A., Chicago April 18, 1974 The act of reading as one form of human communication is clearly a complex act that requires the highest level functioning in the central nervous system. It is ,----___ not surprising then that numerous factors such as constitutional differe,, s, br injury, biochemical abnormalities, disease states, delayed /opment, i.e. maturational lag, etc., may result in various levels of function or dysfunction in those systems critical for the reading act and thus result in some degree of reading disability. The term reading disability is a descriptive term that would imply that the child is not succeeding in learning to read commensurate with his ,intellectual abilities. As such,,, it is a less specific term than developmental or specific dyslexia, which, according to the definition of the World Federation of Neurology, is "A disorder manifested by difficulty in learning to read despite conventional instruction, adequate intelligence and social-cultural opportunity. It is dependent on fundamental cognitive disabilities which are frequently of constitutional origin." Although the incidence of reading disability depends on many factors, probably at least 10% of the population of schoolchildren have a significant degree of reading disability. It would appear that the incidence of specific dyslexia is considerably lower, but again, the incidence depends on how strictly one applies the term. I would now like to discuss in detail some of those factors which may be important in reading disability from a neurological standpoint. The first of these is constitutional differences which may or may not be determined on a hereditary basis. Certainly, we are all aware of people who are "gifted" in art or music; which are both forms of human communication, and likewise probably some of us in this audience would be considered as art disabled or music disabled were that the primary means of communication. Excellence in one area of human communication does not necessarily imply excellence in another. There are cases of children who are reading disabled but excel in music.. Thus, when one deals with language and reading, it is reasonable to assume that there are those who are "gifted" when it comes to reading and those at the other end of the spectrum who we label as disabled. It is unfair, however, in the majority of cases to further stigmatize the child with reading disability with inappropriately applied labels such as minimarbrain'dysfunCtion;'brain'damaged, brain injured, hyperkinetic syndrome etc., implying there is more to the child's difficulty than constitutional differences This is not to say that there are not specific instances in which brain damage or minimal brain dysfunction is the cause of the reading disability, put in all likeliho this is the exception rather than the rule. :P. This brings me to the subject of brain damage, brain injury, and so-called minimal brain dysfunction in relation to reading disability. 040 Children who have so-Called soft neurological signs and/or EEG abnormalities O may be labeled as having minimal brain dysfunction. Certainly, some of these may very wellihave a degree of brain damage as a cause of their reading disability, however, tae must bear in mind that a significant percentage of children without any reading 9r other disability have abnormal EEG's and/or soft neurological signs. k) Thus.,. although there is a slight tendency for the children with learning disability -k( to have 4 higher incidence of abnormal EEG's and soft neurological signs, one is not necessarily justified in jumping to a cause and effect relationship except perhaps in selected cases in which there is documented organic abnormalities. One must also bear in mind the observation that the developing nervous system is highly plastic and,1 as such, has tremendous capabilities to recover from injury with other areas taking over. This is especially true in young children. Thus, children with injury to the dominant hemisphere at an early age will usually develop language function in the non-dominant hemisphere. There are numerous other theories that have been proposed in relation to reading disability and I will briefly comment on these. The first is the so-called maturational lag theory which basically says that certain areas in the brains of children with reading disability may develop more slowll than normals. Evidence for this comes from the observation that the angular gyrus 'of I the brain which is crucial for the reading process is one of the last areas to become rryelinated and myelination is generally thought to be associated with an area becoming functional. In addition, some children with reading disability tend to outgrow it as I they get older. This theory is not necessarily inconsistent with the constitutional differences theory since rate of development or maturation of the brain may be I constitutionally deterndned. Another popular theory of reading disability relates to either failure or late development of cerebral dominance. There are many problems related to tests of cerebr dominance and certainly results of'studies of this factor have'not been clear-cut. There may be some relationShip between maturational lag and c7.flayed development of dominance. Certainly, one factor relating to development of dominance is myelination of the corpus rallosum which generally is rmt completed until age 2-3 and, until this occurs, the two hemispheres must function relatively independently. This probably accounts for the fact that the non-dominant right hemisphere develops primitive language function. This is demonstrated by the ability of a person who has had their corpus callosum divided to select and point to an object out of a group of objects after the name of the object is shown to the left half of gthe visual field. This visual field projects exclusively to the right hemisphere Land with division of the corpus callosum the right hemisphere is isolated from the left. This person is unabl to say the name of the object, however, since the information cannot be transmitted to the dominant left hemisphere which subserves speech. There is one theory I would like to bring up only to discourage its use. This theory attempts to explain was-saw and b-d reversals by the concept that a mirror image of the word is seen by the non-dominant right hemisphere which, because of delayed or impaired development of dominance, competes with the dominant hemisphere image. From an anatomical basis alone one can discount this theory since, if this, were the case, all images arising in the left half of the visual field would be reversed, not just selected images such as was-saw, and there would be a discontinuit across the visual midline. Again, I mention this only to discourage its use since the concept violates known anatomic and physiologic facts. This brings me to the question of what type of medical)evaluation, if any, is indicated in-a child with reading disability. Certainly, both from a logistics and cost effectiveness standpoint it is not reasonable or practical for each child with reading disability to have a medical-neurological and EEG woxk-up. There are, howeve certain situations in which a complete reJical evaluation would be advisable. Examp of this include a child whose performance level'and intellectual capabilities appear to be deteriorating, a child who is suspected of having seizures, a child who has hearing or visual impairment, or a child who has or develops frank neurological abnormalities or complaints referable to the central nervous system. In addition, a complete medical evaluation may be advisable in selected cases to reassure the parents. Children who suffer from learning or reading disability in association with behavioral abnormalities may benefit from a psychological or psychiatric evaluation and treatment, if indicated. To summarize, it is apparent that there is a significant percentage of school age children in whom acquisition of reading and language skills is impaired or delaye Although numerous factors may be involved in each case, it is apparent that in the