Pertreatment radiation induced oedema causing acute hydrocephalus after radiosurgery for multiple cerebellar metastases.

Background: Most complications of radiosurgery occur after 6-12 months and some long term complications up to after 5-10 years. Although severe, immediate side effects are rare, we report a patient who shows that this possibility should be taken into account when large volumes are treated especially in the posterior fossa.

Case Report: A patient was treated with radiosurgery for multiple brain metastases, of which 5 were located in the posterior fossa. Deterioration occurred, radiosurgery was halted abortion and CT showed acute hydrocephalus caused by a significant edema in the posterior fossa, not present in an MR examination performed some 6 hours earlier. After intubation and external ventricular CSF drainage, a permanent shunt was inserted, the edema resolved, and the patient recovered to her pretreatment condition within 10 days. The remaining metastases were treated during the first session and MR images showed the hydrocephalus resolved when all the radiated tumors had significantly decreased in size.

Interpretation: Care should be taken when treating with radiosurgery patients posterior fossa metastases and signs of compressed CSF pathways. Exceptionally, an acute radiation induced edema could result in a block of the CSF pathways, necessitating a surgical intervention. Prophylactic shunt insertion or hospitalization the night following the treatment should be considered.