Intracranial meningiomas related to external cranial irradiation.

Three cases are presented of meningiomas following small-dose external cranial irradiation in which several features clearly indicate a causal relationship between radiotherapy and tumour development. In two of them, multiple meningiomas followed X-ray treatment for Tinea capitis. The length of the latent period separates meningiomas following high-dose irradiation, usually administered for intracranial tumours, from those which followed small-dose irradiation. Therefore the oncogenic mechanism seems to act differently in the two groups. This demonstration that multiple meningiomas can occur in patients irradiated for Tinea capitis should enable other similar cases to be recognized.