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Updated: May 1, 2026
Quantifying Cognitive Decrements Caused by Cranial Radiotherapy
Published on: October 18, 2011
No clinically relevant effect on cognitive outcomes after low-dose radiation to the infant brain: a population-based
Malin Blomstrand1, Erik Holmberg, Maria A I Aberg
1Department of Oncology, Institute of Clinical Sciences, University of Gothenburg , Sweden.
Insights
Low-dose ionizing radiation to the brain in infancy did not affect most cognitive functions. A subtle decrease in verbal scores was observed at higher hippocampal doses, but this had questionable clinical relevance for long-term educational outcomes.
Area of Science:
- Neuroscience
- Radiation Oncology
- Pediatric Oncology
Background:
- Cranial radiotherapy is known to harm developing brains.
- Effects of low-dose ionizing radiation on cognitive function are less understood.
- Infant brain radiation exposure may have long-term cognitive consequences.
Purpose of the Study:
- To investigate if low-dose ionizing radiation to the brain in infancy impacts later cognitive function.
- To determine if hippocampal radiation dose predicts cognitive side effects better than other brain regions.
Main Methods:
- Population-based cohort study of 3860 boys treated for hemangiomas (1950-1960) before 18 months of age.
- Analysis of military test scores (N=3030) at age 18 and highest educational level (N=2559).
- Dose assessment to hippocampus, anterior, and posterior brain regions.
Main Results:
- No significant effect on logical, spatial, or technical test scores with increasing irradiation doses.
- A trend for decreasing verbal test scores with increasing hippocampal doses (p=0.005) was observed, but the effect size was small.
- No impact on educational level; hippocampal dose better predicted cognitive effects than anterior/posterior brain doses.
Conclusions:
- Ionizing radiation doses up to 250 mGy showed no cognitive decline.
- A subtle verbal score decrease occurred at higher hippocampal doses (median 680 mGy), but clinical relevance is questionable.
- No long-term educational impact was found, suggesting limited clinical significance of observed subtle cognitive changes.
Unlabelled:
While the detrimental effects of cranial radiotherapy on the developing brain are well known, the effects on cognitive performance of low doses of ionizing radiation is less studied. We performed a population-based cohort study to determine whether low doses of ionizing radiation to the brain in infancy affects cognitive function later in life. Further we hypothesized that the dose to the hippocampus predicts cognitive late side effects better than the anterior or the posterior brain doses.
Material And Methods:
During 1950-1960 3860 boys were treated with radiation in Sweden for cutaneous hemangiomas before the age of 18 months. Of these, 3030 were analyzed for military test scores at the age of 18 years and 2559 for the highest obtained educational level.
Results:
Logical, spatial and technical test scores were not affected by increasing irradiation doses. The verbal test scores displayed a significant trend for decreasing scores with increasing doses to the hippocampus (p = 0.005). However, the absolute mean difference between the zero dose and the highest dose category (median 680 mGy) was very small, only 0.64 stanine points, and the significance was dependent on the highest dose category, containing few subjects. The educational level was not affected by brain irradiation. Overall, the hippocampal dose was a better predictor of late cognitive side effects than the doses to the anterior or the posterior brain. In conclusion, there was no decrease in logical, spatial and technical verbal or global test scores after ionizing radiation doses up to 250 mGy, but a subtle decrease in verbal test scores if the highest dose category was included (median 680 mGy). However, the clinical relevance of this decline in the highest dose group is questionable, since we could not find any effect on the highest obtained educational level.
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