THE HYPOTONIA IN DOWN
CHILDREN: AN EPIDEMIOLOGICAL SURVEY.
Marco Favuto and Renato Cocchi
Summary.
To evaluate the presence of hypotonia as
isolated from the joint laxity in Down children, from the clinical cards of a
consecutive not selected series of 490 Ss we extracted those of anyone who aged
13-78 months at first consultation.
In the outcoming sample (153 M + 116 F; M/F
ratio = 131.90; chrososomal anomalies: only clinical diagnosis: M = 0.00 and F
= 3.45 %; standard trisomy 21: M = 94.12% and F = 91.38%; mosaicisms M = 2.61%
and F = 0.86 %; translocations: M = 3.27% and F = 4.31%) the presence of
hypotonia seen during the first consultation, was found in 22 M (14.38% of
males) and in 21 F (18.10% of females), without any gender differences as for the
chromosomal distribution, and age stratification, but both genders show a
statistically significant decreasing of the hypotonia as related to the age.
The hypotonia prevalence we have found seems
lesser than usually noticed.
Key words: Hypotonia; Down syndrome;
children; prevalence; gender, age.
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The problem of the hypotonia is already, by
itself, a complex problem.
If we follow what Adams and Victor, 1985,
outlined, the hypotonia is a decrease of the muscular tone. This one is that
light resistance that a relaxed normal muscle offers to the passive movement.
The tone at rest comes in part from the active action of gamma motoneurons
which influence, throughout the spinal cord, the activity of both agonists and
antagonists alpha motoneurons.
Both the alpha motoneurons and the gamma
ones, undergo even an influence by descending neuronal systems. The hypotonia
is evident in the inspection of the buttock and of the calf, with a tendency to
a smaller evidence of the Achilles' tendon.
It is more apparent in acute affections than
in chronic ones. The preferential way to pointing out the hypotonia is that to
strike the wrist or the wrists of a standing individual, with his arms
lengthened forward. From it, it follows a movement of a greater excursion than
the normal, for the difficulty of the muscle to keep it fixed the limb to the
shoulder.
In Down children, a hypotonia of cerebellar
origin (Adams and Victor, 1985), a great deal probable for the cerebellar
anatomical deformity in these Ss (Crome, Covie and Slater, 1966; Adams and
Victor, 1985) and for the presence of other cerebellar symptoms (Cocchi, 1991)
becomes of difficult evaluation for the contemporary setting of joint laxity.
An investigation on the hypotonia in Down
children by Nagata and coll., in 1982, pointed out it by the dorsal flexing of
the ankle, the bending of the thigh with the extension of the leg, the
extension of the wrist, and the sign of the foulard. All these tests, as for
us, are clearly debatable because the presence of the joint laxity.
In the little Down child, who cannot still stand
up and has difficulty to understand the orders, the only possibility of the
hypotonia evaluation becomes what based on the palpation of the calf in a rest
condition. Even so there is the risk that a part of the perceived
"softness" is due to the greater possibility of the excursion of the
muscular insertions, because of the contemporary joint laxity.
Moreover, as the Down syndrome is a chronic
disease, the hypotonia could be more difficult to appraise.
In a so fleeing picture becomes
understandable how the presence of the hypotonia in Downs produced rates enough
different (Benda, 1956; Mcintire and Dutch, 1964; Magner, 1962). In the
international literature controlled till the whole 1991, we did not
successfully find other investigations specifically dedicated to the hypotonia
in Down children.
So, though it is quoting too as the factor
that mostly influences their motor development (Melyn and Harrobin, 1972;
Harris, 1981; Rast and Harris, 1985). An Italian paper on the motor development
of these children (Felicioli and Moretti, 1984) ignores all that matter.
This contribution has the aim to appraise
the hypotonia presence exclusively as the reduced muscular tone, without any
joint laxity, or (a rare case) leaving aside it.
Materials and method.
We reexamined the clinical cards of non
selected, consecutive series of 490 Down Ss coming from all the Italian
regions, who came to consultation of one of the writers, between 1979 and all
April 1991. From them we get out all those of the children who, at first
examination had more of the 12 months and less of 79 months (between 1 year
finished and 6 years and half). We divided these cards by gender, and we
quantify them for the chromosomal anomaly of the related children.
Among the selected cards we selected all
that reported, at the first consultation, the presence of muscular hypotonia,
as evaluated by the palpation of the calf. Even of these latest, always divided
by gender, we reported the type of chromosomal anomaly and we sorted them as
stratified for age bands.
Then, we did the statistic comparisons with
the Chi Square test with the Yates' correction, when in need, and with the
linear correlation.
Results.
The first sorting by the age then separed by
gender did origin to a subgroup of cards with 153 males + 116 females, with M/F
ratio = 131.90.
The other results were summarized in the 1-3
tables.
Tab. 1: Distribution of the chromosomal
anomalies of children of 13-78 months.
|
Chrom. Anomalies |
Males |
% |
Females |
% |
|
Standard 21 trisomy |
144 |
94.12 |
106 |
91.38 |
|
Mosaicisms |
4 |
2.61 |
1 |
0.86 |
|
Translocations |
5 |
3.27 |
5 |
4.31 |
|
Not picked up |
0 |
0.00 |
4 |
3.45 |
|
Totals |
153 |
100.00 |
116 |
100.00 |
Chi Square: 6.991 NS
Tab 2: Distribution of the chromosomal anomalies
in Ss where hypotonia appeared during the first consultation.
|
Chrom. Anomalies |
Males |
% |
Females |
% |
|
Standard 21 trisomy |
20 |
90.91 |
19 |
90.48 |
|
Mosaicisms |
1 |
4.55 |
0 |
0.00 |
|
Translocations |
1 |
4.55 |
2 |
9.52 |
|
Totals |
22 |
100.00 |
21 |
100.00 |
Chi Square = 1.336 NS
The stratification for age bands of all
13-78 months children seen at the first examination, both non hypotonic and the
hypotonic ones divided by gender.
Tab. 3: Stratification for age bands.
|
Band age (months) |
Males |
Females |
||||||
|
Not hypot |
% |
Hypoton. |
% |
Not hypot |
% |
Hypoton. |
% |
|
|
13-18 |
22 |
16.79 |
8 |
36.76 |
16 |
16.84 |
9 |
47.62 |
|
19-24 |
14 |
10.69 |
3 |
13.64 |
10 |
10.53 |
2 |
9.52 |
|
25-30 |
17 |
12.98 |
4 |
18.18 |
16 |
16.84 |
2 |
9.52 |
|
31-36 |
16 |
12.21 |
2 |
9.09 |
11 |
11.58 |
2 |
9.52 |
|
37-48 |
18 |
13.74 |
3 |
13.64 |
13 |
13.68 |
3 |
14.29 |
|
49-60 |
25 |
19.08 |
1 |
4.55 |
16 |
16.84 |
2 |
9.52 |
|
61-72 |
17 |
12.98 |
1 |
4.55 |
9 |
9.47 |
1 |
4.76 |
|
73-78 |
2 |
1.53 |
0 |
0.00 |
4 |
4.21 |
0 |
0.00 |
|
Totals |
131 |
100.00 |
22 |
100.00 |
95 |
100.00 |
21 |
100.00 |
|
|
||||||||
|
Chi Square |
Males: Not hypot. vs. hypoton. 8.172 NS |
Females: Not hypoton. vs. hypoton. 9.001 NS |
||||||
|
Chi Square |
(Between hypotinic Ss of both genders) 1.236 NS |
|||||||
Linear correlation
between age and presence of hypotonia:
Years no. vs hypotonic
males; r = - 0.937 with t = - 4.642 with 3 df; p = .019;
Years no.vs hypotonic females;
r = - 0.978 with t = - 3.175 with 3 df; p = .050
There is an inverse correlation: In the
investigated sample, with age increasing, the hypotonia reduced, mainly in
males.
Discussion.
The adoption of a very restricted evaluation
criteria, in this investigation had, as a result, the finding of poor presence
of pure hypotonia or even hypotonia clearly separable from the joint laxity. We
think that they are two different problems, the first of cerebellar origin, and
then a neurologic one, the other of biochemical origin (a possible peripheral
deficit of SAMe). This is the first footstep for following research on both
symptoms of a motor disability.
For what concerns the choice of the age
limits within we did the investigation, the superior limit is about that where
it is appraised the motor deficit in the subjects with cerebral palsies. It is
few up the maximum limit of the onset of walking in Downs (74 months according
to Melyn and Mhite, 1972).
For the down limit instead, we are dealing
with the consequence of a personal choice of refusing to examine children with
less than 13 months of age. So, to avoid that one can attribute to the drug
therapy regimen, the rare, but possible, West syndrome onset, which when it
appears, in the 97% of the cases appears within the first year of life. In all
the picked cases this band of 0-12-months age results therefore much
under-represented.
The two subgroups of Down Ss males and
females between 13 and 78 months at the first examination came from every part
of Italy. They have a distribution of the chromosomal anomalies that is not far
from what normally known in Italy and abroad. We can say the same about the
males/females ratio. Therefore, these two samples can be considered as
representative of the Italian population of Down between 13 and 78 months.
The analysis of results, divided by gender,
showed that did not exist statistically significant differences on the
hypotonia presence, on the distribution of the chromosomal anomalies of the
hypotonic children, and on their distribution for age bands. Even the
comparison by the age bands of the remaining Down children of the same gender
did not show statistically significant differences of distribution. There
exists a statistically significant negative correlation for both genders
between age bands and hypotonia presence, which inclines to reduce or disappear
with age increasing.
We do not know whether this is a possible
natural development, or it is the result of the rehabilitation regularly
applied, in Italy, to these age subjects.
References.
Adams R.D.: Victor M.; Principles of
neurology. International edition. McGraw Mili. Singapore 1985.
Benda C.E.: Mongolism; A comprehensive
review. Arcb. Pediatr. 1956, 73; 391-407.
Cocchi R.: Difficoltà di controllo
dell'equiibrio nel bambino Down. Nota preliminare. Riv. It. Disturbo Intellet.
1991, 4: 267-270. English translation <www.stress-cocchi.net/Down30.htm>
Crome L., Cowie V., Slater E.: A statistical
note on cerebellar and brainstem weight in mongolism. J. Ment. Defic. Res:
1966, 10; 69-72.
Felicioli F., Moretti A.: Sviluppo motorio,
comunicazionale linguistico ed evoluzioni dei livelli di apprendimento. In;
Ce.Pi.M.; Aspetti epidemiologic!, genetici, clinici, riabilitativi e sociali
della sindrome di Down. Ce.Pi.M., Genova 1984: 307-342.
Harris S.R.: Relationship of mental and
motor development in Down's syndrome infants. Phis. Occup. Therap. Pediat.
1981, 1: 13-18.
Mcintire M.S., Dutch S.J.: Mongolism and
generalized hypotonia. Amer. J. Ment. Defic. 1964, 68: 669-670.
Melyn M.A., White D.T.: Mental and
developmental milestones of noninstitutionalized Down's syndrome children.
Pediatrics 1973, 52: 542-545.
Magata K., Higurashi M., Ishikava N., Ikeda
Y.: The hypotonia and passive ROM (range of motion) in children with Down
syndrome. Pubblicato in giapponese in Brain. Develop. 1982, 14: 456-464.
Abstract in Excerpta Medica, Psychiatry 1983, 48: 464.
Rast M.M., Harris S.R.: Motor control in
infants with Down syndrome. Develop. Med. Child Neurol. 1985, 27, 682-685.
Wagner H.: Mongolism in Orientals. Amer. J.
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Printed in Italian on Riv. It. Disturbo Intellet. 1992, 5: 113-117.
Posted on internet 19 February 2005. Copyright by Renato Cocchi, 2005.
Author's address: dr Renato Cocchi, via Rabbeno, 3
42100 Reggio Emilia (Italy)
renatococchi@libero.it
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