Cerebral palsy is defined as a non-genetic disorder; a disorder which occurs because of non-genetic factors causing developmental brain damage (e.g.: lack of oxygen; infection; physical trauma; lack of thyroid hormone). Years of observation have indicated that cerebral palsy does not occur in family trees over time. However, it is recognized that there is an increased occurrence in ethnic groups (e.g.: Pakistani), racial groups (African Americans) and socio-economic groups (the poor).

A recent publication reopens the issue of the role of genetics in cerebral palsy¹. In a city in England, the prevalence of cerebral palsy in the Asian population (predominately from Northern Pakistan) was compared to that of non-Asians. The prevalence rate of cerebral palsy in the Asian population was 6.42 cases per 1,000 persons; in the non-Asian population, it was 3.18 per 1,000. This is a significant difference. Spastic cerebral palsy was the most common form of disability in both groups, with hemiplegic cerebral palsy being more common in the non-Asian group.

The study's authors were not able to study the socio-economic variables in these populations, either between ethnic groups or between families with and without cerebral palsy occurrence. However, first cousin marriages occurred in 51% of the Asian families and rarely in the non Asian families. In the Asian community, there was another member with a similar type of cerebral palsy in over half the families in which cerebral palsy occurred. This increased occurrence in families with close inter-marriages, led the authors to hypothesize that there was a genetic factor influencing the occurrence of cerebral palsy in the Asian population.

Comment:

Cerebral palsy is a condition characterized by a variety of causes, each resulting in non-progressive developmental brain damage resulting in a disorder of movement and/or posture. An environmental condition has generally been identified as the cause. Previous studies of a genetic factor as a cause have generally found no relationship to cerebral palsy. Thus cerebral palsy is considered an "acquired" rather than a "genetic" disorder.

However, recent knowledge of the role of genetics as either a primary cause or a contributing cause (a predisposition or susceptibility factor) is reopening the question of the contribution of genetics in a wide variety of disorders. This report on the occurrence of cerebral palsy in which there are marriages of close relatives is provocative. The question is being re-opened about the presence of genes in the genetic code which can either cause the developmental brain damage we identify as cerebral palsy or make an infant more susceptible to environmental factors. In special populations there might be both a "genetic" and an "acquired" type of cerebral palsy, as there is in other brain disorders such as Alzheimer’s Disease and Parkinson’s Disease. However, at this time in the U.S. there is no evidence that "a genetic form of cerebral palsy" occurs. The rapid growth of new information about the genetic code will undoubtably help us clarify this issue in the reasonably near future.

1Sinha, G. et al. Prevalence and Type of Cerebral Palsy in a British Ethnic Community: The Role of Consanguinity. Developmental Medicine and Child Neurology (1997) 39:259-261.