Case studyDe novo superior cerebellar artery aneurysm following radiosurgery for trigeminal neuralgia

•Radiosurgery is a common effective treatment for trigeminal neuralgia.•Radiation treatment has been associated with formation of cerebral aneurysms.•An occurrence of a cerebral aneurysm occurring adjacent to the target of a trigeminal radiosurgery treatment.

Stereotactic radiosurgery is a commonly used method for treatment of trigeminal neuralgia. Radiation has been known to be a factor in the later development of aneurysms. Aneurysms have been reported to occur after radiation delivered in a variety of methods including both externally delivered radiation radiosurgery and brachytherapy. We report here an incidence of a de novo aneurysm presenting following radiosurgery treatment for trigeminal neuralgia. The patient was treated using frame-based LINAC radiosurgery receiving 90 Gy to the mid cisternal extent of the nerve via a 4 mm conical collimator. The patient presented with progressive hypoesthesia 11 years after treatment. Imaging evaluation demonstrated the presence of an aneurysm abutting the treated trigeminal nerve. The aneurysm was successfully coil embolized. The patient's facial hypoesthesia, however, did not improve following embolization. We believe that this is the first report of such an aneurysm occurring after radiosurgery for trigeminal neuralgia. De novo aneurysms are a recognized long term complication of radiotherapy and radiosurgery treatment. This report shows such aneurysms can occur with very small treatment volumes. Late sensory changes following radiosurgery for trigeminal neuralgia should prompt workup for de novo aneurysms as well as other late adverse radiation effects.