For years it was thought that a difficult birth and other perinatal factors were the leading causes of cerebral palsy (CP), a group of disorders that can involve brain and nervous system functions such as movement, learning, hearing, seeing and thinking. Now, researchers at Geisinger Health System find that the majority of cerebral palsy causes may in fact be caused by genetic abnormalities.
Published in the The Lancet Neurology, Geisinger researchers find that CP -- the most common physical disability of childhood -- is probably caused by multiple genetic factors, similar to other neurodevelopmental disorders such as autism and intellectual disability. The paper suggests physicians should consider performing genetic testing when children present with CP and CP-like conditions.
"There is a widespread misconception that most cases of CP are caused by difficult delivery leading to birth asphyxia," said Andres Moreno De Luca, M.D., research scientist at the Genomic Medicine Institute, Geisinger Health System, and lead author of the paper. "What we're finding is a growing body of evidence that suggests mutations in multiple genes are responsible for CP. In fact, we suspect these genetic abnormalities may also be the cause of some difficult births to begin with."
Despite substantial improvements in obstetric and neonatal care, the paper finds the worldwide prevalence of cerebral palsy has remained stable at 2 to 3 per 1,000 livebirths for more than 40 years. Inadequate oxygen supply to fetuses, known as birth asphyxia, remains the most studied factor associated with CP, though electronic fetal monitoring and other technologies have been developed to detect fetal distress.
"What we're finding is even though more preventative efforts have been put in place, like fetal monitoring, the incidence of CP has not decreased," said David Ledbetter, Ph.D., chief scientific officer, Geisinger Health System. "We've seen a five-fold increase in the rate of caesarean sections, which are done in part to avoid potentially difficult delivery, and again, the CP rates remain steady. These findings lead us to believe genetics play a much bigger role than previously thought."
The paper also reports that even though most cases of CP are not caused by birth asphyxia and those that are can rarely be prevented by obstetric intervention, between 1999 and 2003 an estimated 76 percent of obstetricians in the U.S. faced medical malpractice litigation, most often for alleged birth mismanagement resulting in CP.
"We now know of six genes that can cause CP when disrupted, and we estimate that many other developmental brain genes probably contribute to the genetic heterogeneity of this disorder," said Dr. Moreno De Luca. "Many capable obstetricians face legal action even though research is telling us genetics is the likely cause of most cases of CP."
As the paradigm shift continues and more researchers, clinicians, and the general population start to consider the cerebral palsies as a group of neurogenetic disorders, the paper states we will probably witness an increase in research efforts, a change in the diagnostic approach, and eventually novel therapies for treating CP.
- Andres Moreno-De-Luca, David H Ledbetter, Christa L Martin. Genomic insights into the causes and classification of the cerebral palsies. The Lancet Neurology, 2012; DOI: 10.1016/S1474-4422(11)70287-3
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