Transient MR changes and symptomatic epilepsy following gamma knife treatment of a residual GH-secreting pituitary adenoma in the cavernous sinus

Objective. To report a rare side effect of gamma knife treatment of pituitary macroadenoma. Case report. In a forty-one-year old female patient acromegaly was diagnosed due to a growth hormone secreting pituitary macroadenoma. Following transsphenoidal surgery the patient underwent gamma knife treatment for persistent uncontrolled acromegaly activity of residual tumor, infiltrating the left cavernous sinus. 15 months later, complex partial seizures were diagnosed and 17 months after gamma knife treatment a gadolinium enhancing lesion was detected in her left medial temporal lobe. Radiation induced changes, radiation necrosis or a glioma were considered. Neuropsychological testing indicated potentially significant post-surgical deficits. Therefore, surgical action was postponed and anti-epileptic treatment was started. Four months later she was free of seizures and an MR scan showed an almost complete regression of the gadolinium enhancing lesion, indicating that it had been due to radiation induced changes. Conclusion. Gamma knife surgery of a pituitary adenoma may cause radiation induced MR changes of the mesial temporal lobe mimicking glioma or radionecrosis and cause symptomatic epileptic seizures. The awareness of this rare complication is important to avoid unnecessary and potentially harmful diagnostic or therapeutic interventions.