Full Scale IQ (FSIQ) changes in children treated with whole brain and partial brain irradiation. A review and analysis.

PURPOSE

Neuropsychological impairment has been reported following whole brain and partial brain irradiation in children. The purpose of this analysis was to assess current knowledge, with focus on correlation with radiation dose, irradiated volume and age.

METHOD

Full Scale IQ (FSIQ) data, representing 1,938 children, were derived from 36 publications and analyzed as to radiation dose, irradiated volume, and age.

RESULTS

FSIQ after whole brain irradiation showed a non-linear decline as dosage increased. The dose-effect relationship was age-related, with more pronounced FSIQ decline at younger age. FSIQ test results below the normal level (< 85) were found at doses higher than 24 and 36 Gy in children under age 3, and older than age 6, respectively. Mean FSIQ test result after 18 Gy was 100, thus at the mean standard value; a minor decline was detectable only when compared to test results of a control group. Young children scored at this dose in the low normal range. Partial brain irradiation caused minor FSIQ decline, with measurable effects at dose levels > 50 Gy.

CONCLUSION

The collected data suggest that whole brain irradiation doses of 18 and 24 Gy have no major impact on intellectual outcome in children older than age 6, but may cause impairment in younger children. Doses > 24 Gy comprise a substantial risk for FSIQ decline, even in older children. At equal dose levels, partial brain irradiation is less damaging than whole brain irradiation. The authors are well aware of limitations in the interpretation of data collected for the current review. Thus, further research is required to evaluate the effect of low-dose whole brain irradiation as well as partial brain irradiation on FSIQ development.