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Ionising radiation in infancy and adult cognitive function

Editor—Hall et al did not give a detailed description of the patients they studied; the boys had cutaneous haemangiomas in the head region, and they were in 1930-59 younger than 18 months.1 
 
How many of these boys had Sturge-Weber syndrome with cutaneous and cerebral haemangiomas? In a typical case the cutaneous lesions are in the territory of the trigeminal nerve and the cerebral in the hemispheral cortex of the same side, but there are many variations. The neurological symptoms, if present, include epileptic seizures, hemiparesis, and some mental retardation. Cortical calcifications may be seen on skull radiography. 
 
Possible cortical haemangioma was not diagnosed at the time of radiation. In 1930-59 none of the current neuroradiological examinations was available, and skull radiography, if performed, was of little help because cortical calcifications are rare at such a young age. 
 
The study found an inverse association between the estimated radiation dose and high school attendance, and frontal radiation dose and military test results. In Sturge-Weber syndrome the cutaneous lesions are predominantly in the forehead, and the sizes of the cutaneous and cortical lesions are often correlated. Therefore, large frontal doses of radiation are likely to be associated with larger cerebral cortical lesions. 
 
Sturge-Weber syndrome may have affected only some of the boys who had radiation treatment for cranial haemangiomas, but it could explain the poorer (mean) results in both high school attendance and military tests. This probability should be examined before frightening lay readers more about the hazards of computed tomography and x ray examinations.