Necrosis of the brain due to radiation therapy; clinical and pathological observations.

In treating intracranial tumours with deep x rays or radium the aim is to direct the largest possible dose of radiation to the tumour within the limits of safety for the normal tissues. Even with the standard dosages in current use, irradiated areas of the scalp suffer temporary or permanent epilation. Excessive radiation is known to cause burns and necrosis of the scalp and skull, and harmful effects on the underlying brain. These complications are usually manifest within a short, time of treatment and they may be largely avoided by using multiple portals of entry so that no one area of the overlying or surrounding tissues receives more than a fraction of the total dose brought to bear on the tumour. In fact the technique of therapy is so well developed that serious damage to normal structures is regarded as a rare occurrence. Nevertheless we have encountered in recent years a series of cases in which harmful effects to the brain have followed standard dosages and technique without serious superficial damage, and at long intervals after the termination of treatment. Although the effects were not strictly uniform in every case, the similarity was close enough in each, and so different from other pathological processes, that it seems reasonable to relate them to the single common feature of radiation treatment. In brief, the lesion was an extensive subcortical necrosis, maximal in the field which received the most radiation. In some cases the clinical effects came on after a long latent interval with the suddenness of a vascular accident; inothers they were slowly progressive, clinically suggesting a recurrence of the tumour for which the radiation treatment had been given. In the fatal cases the lesion seemed to be largely responsible for death. Nine cases have been examined. Eight of these had had various surgical procedures for cerebral neoplasms followed by one or more courses of radiation treatment. The other case is of particular interest because so far as can be known the brain was normal before radiation treatment was instituted for a rodent ulcer of the scalp. This case will be described first, followed by four others which are representative of the remainder.