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Prenatal exposure to ionizing radiation and subsequent development of seizures
1Radiation Effects Research Foundation, Hiroshima, Japan.
Insights
Prenatal radiation exposure during the 8-15 week window after fertilization increased seizure risk in atomic bomb survivors. Higher fetal radiation doses correlated with a linear increase in seizure incidence, particularly unprovoked seizures.
Area of Science:
- Medical Science
- Radiation Biology
- Developmental Neuroscience
Background:
- Seizures are a common outcome of impaired brain development.
- Prenatal radiation exposure can lead to brain damage and increase seizure risk.
- Understanding the timing and dose-dependency of radiation effects on fetal brain development is crucial.
Purpose of the Study:
- To investigate the incidence and types of seizures in individuals prenatally exposed to atomic bombings.
- To determine the association between seizure occurrence and specific stages of prenatal development during irradiation.
- To analyze the relationship between fetal radiation dose and seizure risk.
Main Methods:
- Utilized clinical records of atomic bomb survivors with prenatal exposure.
- Assessed seizure history through biennial examinations starting around age 2.
- Classified seizures as febrile or unprovoked based on clinical records.
- Correlated seizure incidence with estimated fetal radiation dose and gestational age at exposure.
Main Results:
- No seizures were observed in subjects exposed 0-7 weeks post-fertilization at doses >0.10 Gy.
- Seizure incidence peaked with irradiation between 8-15 weeks post-fertilization for doses >0.10 Gy.
- A linear relationship was found between fetal radiation dose and overall/unprovoked seizure incidence.
- Excluding severe mental retardation cases, the seizure increase was suggestively significant for unprovoked seizures.
Conclusions:
- The 8-15 week period after fertilization is a critical window for radiation-induced seizure risk.
- Fetal radiation dose is linearly associated with increased seizure incidence during this sensitive developmental period.
- Later stages of prenatal development showed no increased risk of recorded seizures following radiation exposure.
Abstract:
Seizures are a frequent sequela of impaired brain development and can be expected to affect more children with radiation-related brain damage than children without such damage. This report deals with the incidence and type of seizures among survivors prenatally exposed to the atomic bombing of Hiroshima and Nagasaki, and their association with specific stages of prenatal development at the time of irradiation. Fetal radiation dose was assumed to be equal to the dose to the maternal uterus. Seizures here include all references in the clinical record to "seizure," "epilepsy," or "convulsion." Histories of seizures were obtained at biennial routine clinical examinations starting at about the age of 2 years. These clinical records were used to classify seizures as febrile or unprovoked (without precipitating cause). No seizures were ascertained among subjects exposed 0-7 weeks after fertilization at doses higher than 0.10 Gy. The incidence of seizures was highest with irradiation at the eighth through the 15th week after fertilization among subjects with doses exceeding 0.10 Gy and was linearly related to the level of fetal exposure. This obtains for all seizures without regard to the presence of fever or precipitating causes, and for unprovoked seizures. When the 22 cases of severe mental retardation were excluded, the increase in seizures was only suggestively significant and only for unprovoked seizures. After exposure at later stages of development, there was no increase in recorded seizures.