Purpose: To report the occurrence, degree, frequency, and duration of contrast enhancement in the craniopharyngioma cyst wall as caused by irradiation.
Material and methods: Eight patients with cystic craniopharyngiomas had comparable CT or MR studies before and after either external irradiation of the cyst (n = 5) or 32P instillation into the cyst (n = 3).
Results: A minimal to marked increase in cyst-wall enhancement was seen at 66-157 days after 32P instillation in 3/3 cases and at 112-495 days after external irradiation in 3/5 cases. The increased enhancement was always associated with a variable interim increase in the thickness of the enhanced cyst wall.
Conclusion: CT or MR imaging after the irradiation of cystic craniopharyngiomas usually demonstrated an increase in thickness and enhancement in the cyst wall. Such changes may be due to the irradiation alone and do not necessarily represent infection or increased neoplastic activity. The timing is uncertain as to the earliest possible development of such changes and their maximum duration, but they were seen as early as 66 days post-irradiation and as late as 495 days post-irradiation.