Genetic factors reported to play major role in cerebral palsy
DANVILLE, PA - Cerebral palsy is the most common physical disability of childhood; it is considered to be a group of disorders that can involve brain and nervous system functions such as movement, learning, hearing, seeing, and thinking. It has commonly been attributed to a variety of environmental factors, most commonly birth asphyxia (lack of oxygen at birth). However, a new study notes that a growing body of evidence points to a genetic source for many cases of cerebral palsy.
The study, which was conducted by Genomic Medicine Institute of the Geisinger Health System, Danville, Pennsylvania, was published in the March 2012 edition of Lancet Neurology. The authors note that cerebral palsy is probably caused by multiple genetic factors, similar to other neurodevelopmental disorders such as autism and intellectual disability. They note that recent technologic advances have facilitated rapid and cost-effective sequencing of the entire human genome. They predict that genes responsible for the disorder will probably be identified as more geneticists and clinicians use this approach to study individuals with undiagnosed neurological disorders. They predict that knowledge of the underlying mechanisms of cerebral palsy will evolve to the point that genomically-guided therapeutic interventions can be established.
Lead author Dr. Andres Moreno-De-Luca MD noted that a number of well-designed studies have clearly demonstrated that birth asphyxia accounts for less than 10% of cerebral palsy cases and at present, six different genes are known to be involved in the disorder. He added that many more genes can produce symptoms resembling cerebral palsy if they mutate. He defines these symptoms as cerebral palsy spectrum disorders, which encompasses the condition in a similar manner as that of the term autism spectrum disorder.
The authors note that multiple gene mutations increase the risk of congenital abnormalities (11-32%) compared to the general population (2-3%). These include cardiac (heart) malformations (29%), cerebral (brain) malformations (72%), facial clefts (i.e., cleft palate; 18%), microcephaly (small brain; 26%), hydrocephaly (excess fluid within the brain) (19%), musculoskeletal disorders (14%), and urinary disorders (9%).
The researchers note that a number of studies have reported a significantly increased rate of cerebral palsy among monozygotic (single egg or identical) twins compared to dizygotic (fraternal) twins. They add that the risk for cerebral palsy is approximately 2.5 times higher in consanguineous families (“inbred” families with common ancestors) compared to families with unrelated ancestors. Some research has suggested that paternal age is a risk factor: older fathers are more likely to sire a child with cerebral palsy.
This study should prove to be of value on two fronts: (1) Parents with a child with cerebral palsy; and (2) Obstetricians. If a genetic cause is responsible for the condition, ongoing research may be able to improve function in affected children. Research is ongoing for known genetic disorders such as cystic fibrosis and Tay-Sachs disease. Advances in genetic research could also lead to genetic testing of the parents as well as intrauterine testing (i.e., an amniocentesis) early in pregnancy.
A constant worry for an obstetrician is to be involved in the delivery of a child with cerebral palsy. Compensation for a brain damaged child is a major factor in the high cost of malpractice insurance for this specialty. If tests can prove a genetic origin for the disorder, the physician can be relieved of liability. Conversely, if the genetic tests are negative, it would supply evidence that the cerebral palsy was due to birth trauma.
Reference: The Lancet Neurology