Cerebral palsy (CP)
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Cerebral palsy is characterized by damage to the motor components of the central
nervous system (brain damage), and it manifests as muscle weakness or spastic muscle
paralysis (rigidity of muscles). In most cases, CP is defined as damage to brain
tissue that occurs in the perinatal period, due to environmental rather than genetic
causes.
A number of neurological diseases are caused by hereditary metabolic disorders (inborn
errors of metabolism). Here involvement of the nervous system tissue can result
in a clinical picture that is similar to that occurring in classical cerebral palsy.
It is important to differentiate between the metabolic disorders and classical CP
that occurs as a result of environmental damage, even though this may not always
be possible.
In most cases, the cause is unknown. Only in a few cases is there a clear history
of disruption of the oxygen supply to the fetus before or during birth, or of another
external cause that can explain brain damage, such as an infection or brain hemorrhage.
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Clinical signs
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The increase in the number of very small premature infants has resulted in an increase
in the number of babies with CP in recent years. Some already have neurological
signs in the first month of life, but in most cases the condition is only detected
during the first year when the infant fails to develop motor skills commensurate
with his or her age. Later, the muscle weakness and rigidity can be discerned. Tendon
reflexes are increased.
Usually the condition does not progress, and improves with physiotherapy. In about
50% of cases there is mental retardation in addition to motor problems.
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There are a number of genetic diseases whose clinical manifestations are similar
to those of CP.
These constitute about 10% of the cases of children with a clinical picture of muscle
weakness and rigidity.
The risk that the child has a hereditary, genetic type of CP is increased in the
following cases: absence of an environmental factor indicating acquired damage,
progression and deterioration of the neurological damage over time, the presence
of involuntary dystonic movements, the presence of mental retardation that is more
severe than the motor problems, the absence of signs indicating environmental damage
in brain scans (CT or MRI), or the presence of signs indicating a genetic disease
in an examination of the child or in laboratory and/or imaging tests.
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Cerebral hypertension secondary to hydrocephalus and also chromosome disorders must be ruled out. It is especially important
to test for metabolic disorders such as leukodystrophy. All these conditions must
be considered by the geneticist.
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Inheritance pattern
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Most cases of CP are not genetically transmitted. However, in the approximately
10% of cases that are due to genetic causes rather than environmental, there may
be recurrence in future children of the couple.
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Penetrance
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In the metabolic disorders, this varies according to the specific disease.
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Associated features that can be demonstrated by imagery
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Usually there are no defects that can be identified by ultrasound examination during pregnancy.
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What is the risk of recurrence in a subsequent pregnancy?
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The incidence of classical CP is 1 in 350 births. The risk that siblings will also
be affected is low, but according to a number of studies, in certain types of CP,
such as those with dystonic movements and instability, or those with signs indicative
of a metabolic disorder, there is a risk of recurrence of up to 10%.
If there are 2 siblings with the condition, a metabolic disorder must be suspected.
Since these are usually transmitted by autosomal recessive inheritance, the risk
that the parents of an affected child will have another affected child is 25% in
every pregnancy. More distant relatives do not have a significantly increased risk
of having a child with this condition - as noted, the frequency in the general population
is up to 1% depending on the definition used.
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Cerebral palsy
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Molecular genetic information
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The gene for the disease
Only in the genetic cases, depending on the specific condition.
The location of possible genes
Depends on the specific condition.
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Genetic testing
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Diagnostic testing
Tests for specific genetic syndromes should be carried out, and also a blood test
to check for chromosome disorders. Definitive tests for specific metabolic diseases
may be recommended according to the clinical findings and the decision of the geneticist.
Carrier testing
This usually cannot be performed unless the child has a specific syndrome. See above
under "Diagnostic testing".
Fetal testing
This usually cannot be performed unless the child has a specific syndrome. See above
under "Diagnostic testing".
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