Intracavitary irradiation with colloidal phosphorus-32 for treatment of an arachnoid cyst: a new approach.

Intracavitary irradiation is reported as an additional treatment for intracranial arachnoid cysts that do not communicate with the subarachnoid space. A 46-year-old woman with a large suprasellar arachnoid cyst that had enlarged over a 4-year interval presented with new onset headaches. Stereotactic intracavitary irradiation was performed using colloidal phosphorus-32 as an alternative to craniotomy or insertion of a shunt. Total regression of the cyst occurred within one month with resolution of her headaches. After three years of follow-up, imaging studies showed only an empty sella appearance, and no cyst recurrence. No early or delayed morbidity occurred. Intracavitary irradiation may be a useful therapy for arachnoid cysts, in an attempt to alter the biology of the cyst lining.