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On Difficulties of Equilibrium Control in Down Children (A Preliminary Note)
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Renato Cocchi M.D., Ph.D. (Sociology)
Italian Journal of Intellective Impairment 4 (2): 267-270 (1991)
Reprinted with the permission of Renato Cocchi|
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The possible reasons of frequent troubles of the equilibrium in the Down child were examined. They were primarily suggested in a cerebellar dysfunction, also responsible of the hypotonicity; In a specific vestibular dysfunction, which shows itself even with the increased nystagmus presence; In a dysfunction of nuclei areas of eyes motor muscles, to which one can refer the high incidence of convergent not refractive squint, these subjects suffer from.
Key words: Down syndrome, Equilibrium, Vestibule, Cerebellum, Oculo-motor nuclei, Squint, Nystagmus.
Problems of his equilibrium controlling in the Down child did never have a clear separation in a specific way from all the motor aptitudes of these subjects. Within a clumsy and awkward motility, enough similar to that of the children with mental retardation of other origin, without any motor lesion, the aspects of the control of his equilibrium of the Down seem introducing peculiar features worthy of a more exact investigation.
Following preceding epidemiological and clinical investigations made on this topic, (Cocchi and Branchesi, 1988; Cocchi, 1989; Cocchi, 1990), and waiting for a clinical report on the constant relief of the equilibrium in the subject Down treated by drugs, I considered no outside place to start with delineating a frame of neurophysiological and neuropathological, and rehabilitative reference as regard to the trisomy 21.
It is known that the equilibrium maintenance is the result of a complex functioning that finds in the vestibule the main brain structure. The vestibular apparatus is made by the receptors of the back membranous labyrinth, by the vestibular component of the eighth pair of the cranial nerves (the "acoustic" nerves), by nuclei of the bulb-prutuberential region related to it, and by pathways linking those nuclei with other structures of the nervous system, in particular with the cerebellum, the reticulate formation, the oculo-motor nuclei, the spinal motor-neurons.
The receptors of the membranous labyrinth are stimulated by the acceleration of head movements, either rotatory or linear. The neural impulses coming from it are transferred to the four vestibular nuclei, where converge even fibres deriving from the spinal cord, from the reticulate formation, from the cerebellum and from the brain cortex.
From the vestibular nuclei have origin fibres that go to the oculo-motor nuclei, to motor-neurons going to the head muscles, to the neck, to the trunk, to superior and inferior limbs, with the possibility of influencing the postural tone of these muscles. Always from the vestibular nuclei other fibres originate which are going to the cerebellum, and with probable mediation of the ascending pars reticulata, these nuclei are in connection with the parietal brain cortex.
So, it is therefore evident that, in this tangled connections system, alterations of the functionality of the vestibule, or of the cerebellum or of the parietal cortex (or of more than one of these structures), is the more probable cause of the equilibrium troubles.
The troubles of the equilibrium in the Down child manifest themselves with:
If the first three symptoms, and perhaps, in part, even the quarter, can be common to children with mental retardation other than the trisomy 21, I have the clear impression (to be confirmed) that the fear of oscillating plates is a specific feature.
The ligamentous laxity, the squint, and the nystagmus, when present, would add their own contribution to the difficulty in maintaining the equilibrium. It remains however to annotate that the troubles of the equilibrium are not found in all Down children. Felicioli and Moretti, 1984, found again a varying percentage from the 41.4 to the 48.9% out of an altogether modest casuistry. They think that the smaller percentage, as related on subject persons born a five-year period later, is already the result of a wider and earlier neuro-psychomotor rehabilitation intervention.
From it they argue that the trouble is not stabilized, but malleable, a fact that I completely agree. More interesting is the problem why over 50% of Down children do not have troubles of the equilibrium. To answer by recalling the phenotype difference among subjects with the same chromosomal anomaly is a non-response. With other words, it is a way to say that Down subjects, although the same for the trisomy 21 anomaly, are different because they are different.
We can look for the presence of other pathological symptoms as signals of brain areas dysfunctioning of such complex system that supports a suitable expression of the equilibrium ability. Even if it doesn't assure that these symptoms are the results of the same event, their presence may at least direct towards a more fertile pathway of the search.
As I said, if we are dealing with one not always present symptom that can show different severity, it comes out from it that we have to think to a dysfunction rather than to a lesion.
Skipping for now the symptoms' search of the parietal syndrome, that nobody has still noticed in the Down syndrome, the survey of the cerebellar level and of the areas where have their room the nuclei of the oculo-motor nerves (mesencephalon and pons) get immediately interesting findings.
Symptoms of cerebellar dysfunction are the hypotonicity, reported as an excitatory symptom, and the dysmetria. Both are present in several Down persons.
The squint is a symptom of the mesencephalon and the pons dysfunction, found in about 30%, according to our survey (Cocchi and Branchesi, 1988).
The nystagmus is a known vestibular symptom, and we found it in little more than 6% of our cases (Cocchi and Branchesi, 1989 ). Following a recent exhaustive review, its incidence in Downs accounts, instead, between 9% and 22%.
The nystagmus, in Down and not Down subjects, got relief, till its disappearance, by a treatment with drugs (Cocchi and Branchesi, 1989; Cocchi and Maniscalco, 1989), and the same occurred for the squint in Downs (Cocchi, 1991). Those facts show that even these two symptoms are, somehow, malleable, ie. Modifiable.
Felicioli and Moretti, 1984, asserted that the hypotonicity and the dysmetria profit of rehabilitative and neuro-psychomotor treatments.
I agree with them, although till now not having had the chance to publish the data that confirm this fact, even by using the drug treatment. From all that we can argue that it appears a great deal that the equilibrium troubles in the Down child are somehow related to the cerebellum, the vestibule and the mesencephalon and pons areas dysfunctioning. We can argue also that such troubles can be reduced in various ways, the drug treatment inclusive. [see: Post scriptum].
This preliminary note on the troubles of the equilibrium in the Down child had the aim to trace a neurophysiological, neuropathlogical, clinical and rehabilitative frame where we can place these troubles and their treatment possibilities.
Then, I pointed out the dysfunctionality of vestibular, mesencephalon-pontine and cerebellar areas as possible cause for the presence of the reduced equilibrium, which, at least following a rehabilitative intervention, have been asserted as manageable. In following works to be published, I shall report the results I obtained, with drug treatments, already effective on the nystagmus and on the squint.
PS. After I had this article printed, I got out several papers on this topic (anticipation of walking, bike riding, ligamentous laxity)
Cocchi R.: The anticipation of walking in drug treated Down infants: a controlled study. It. J. Intellect. Impair. 1989, 2: 15-19.
Cocchi R.: Paralisi cerebrali infantili in bambini Down: 3 casi. Riv. It. Disturbo Intellet. 1990, 327-330.
Cocchi R.: Drug therapy of squint in Down syndrome subjects. Results according to the length of drug taking: Report on 125 cases. It. J. Intellect. Impair. 1991, 4: 9-14.
Cocchi R., Branchesi R.: Is there a causal non-connection between squint and cerebral palsy through prematuruty and/or low birthweight in Down syndrome children? It. J. Intellect. Impair. 1988, 1: 141-144.
Cocchi R., Branchesi R.: Il nistagmo nel bambino Down: presenza, implicazioni ed esiti dopo farmacoterapia. Riv. It. Disturbo Intellet. 1989, 2: 213-217.
Cocchi R., Maniscalco M.: Scomparsa del nistagmo spontaneo in 3 bambini cerebropatici trattati con farmaci. Riv. It. Disturbo Intellet. 1990, 3: 321-326.
Felicioli F., Moretti A.: Sviluppo motorio, comunicazionale linguistico ed evoluzioni dei livelli di apprendimento. In: Ce.Pi.M.: Aspetti epidemiologici, genetici, clinici, riabilitativi e sociali della Sindrome di Down. Ce.Pi.M., Genova 1984: 307-342.
Shapiro M.B., France T.D.: The ocular features of Down's syndrome. Am. J. Ophthalmol. 1985, 99: 659-663.