title: Intracranial aneurysms in previously irradiated fields: literature review and case report.
abstract: OBJECTIVE
  Radiotherapy is a common treatment for a variety of disease processes in the central nervous system; it has an ever-increasing number of indications and applications. With the life expectancy of cancer patients increasing, delayed complications of radiation have become more apparent. One such potential complication is the appearance of intracranial aneurysms in the irradiated field. The incidence and natural history of these aneurysms is not well understood. To this end, we performed a review of the literature to analyze the current state of knowledge of these rare aneurysms. Furthermore, we present a case treated at our center.
  
  
  METHODS
  We reviewed the literature for all reported cases of intracranial aneurysms appearing in an irradiated field, including any available histopathologic analysis. All papers were included irrespective of the language in which it was published. We calculated the mean age at radiation exposure, the interval between radiation exposure, and aneurysm development and the rate of presentation. Herein we also present a case of an intracranial aneurysm in a 38-year-old patient detected in an irradiation field 33 years after the patient underwent craniospinal irradiation for a medulloblastoma.
  
  
  RESULTS
  A total of 46 patients with 69 intracranial aneurysms in irradiation fields were reported between 1978 and 2013. The mean age at radiation exposure was 34 years, and the mean lag time between exposure and diagnosis was 12 years (range, 4 months to 50 years). The median lag time between exposure and diagnosis was shorter in patients older than 40 (6 years). Among the reported aneurysms, 83% were saccular, 9% were fusiform, and 9% were considered pseudo-aneurysms. The Median lag time was 20 years for brachytherapy, 8 years for focused radiation, 9 years for whole brain radiation, and 6 years for SRS. Among reported aneurysms, 55% presented with some form of hemorrhage: intracranial rupture with subarachnoid hemorrhage, epistaxis, or otorrhagia. Only 13% were discovered on routine follow-up or were found incidentally for work-up of unrelated neurologic symptoms.
  
  
  CONCLUSIONS
  Although rarely reported, intracranial aneurysms in irradiation fields may warrant special attention when diagnosed. These aneurysms may have an inherently weaker structure and may be more prone to rupture. Their repair may also be complicated by more fragile and irregular morphology. The increasing longevity of cancer patients suggests that screening for aneurysms at irradiation sites may be warranted, but further studies are needed to validate this approach.
authors.affiliation: Department of Neurological Surgery, Northwestern Memorial Hospital, Chicago, Illinois, USA.
authors.forename: Allan D
authors.initials: AD
authors.lastname: Nanney
authors.affiliation: Department of Neurological Surgery, Northwestern Memorial Hospital, Chicago, Illinois, USA.
authors.forename: Najib E
authors.initials: NE
authors.lastname: El Tecle
authors.affiliation: Department of Neurological Surgery, Northwestern Memorial Hospital, Chicago, Illinois, USA.
authors.forename: Tarek Y
authors.initials: TY
authors.lastname: El Ahmadieh
authors.affiliation: Department of Neurological Surgery, Northwestern Memorial Hospital, Chicago, Illinois, USA.
authors.forename: Marc R
authors.initials: MR
authors.lastname: Daou
authors.affiliation: Department of Pathology, Northwestern Memorial Hospital, Chicago, Illinois, USA.
authors.forename: Esther N
authors.initials: EN
authors.lastname: Bit Ivan
authors.affiliation: Department of Radiation Oncology, Northwestern Memorial Hospital, Chicago, Illinois, USA.
authors.forename: Maryanne H
authors.initials: MH
authors.lastname: Marymont
authors.affiliation: Department of Neurological Surgery, University of Texas Southwestern, Dallas, Texas, USA.
authors.forename: H Hunt
authors.initials: HH
authors.lastname: Batjer
authors.affiliation: Department of Neurological Surgery, Northwestern Memorial Hospital, Chicago, Illinois, USA; Department of Radiology, Northwestern Memorial Hospital, Chicago, Illinois, USA. Electronic address: bbendok@nmff.org.
authors.forename: Bernard R
authors.initials: BR
authors.lastname: Bendok
mesh_terms: D000328:Adult; D002528:Cerebellar Neoplasms / Q000532:radiotherapy*; D006801:Humans; D002532:Intracranial Aneurysm / Q000209:etiology*; D008297:Male; D008527:Medulloblastoma / Q000532:radiotherapy*; D011832:Radiation Injuries / Q000175:diagnosis*; D011878:Radiotherapy / Q000009:adverse effects*; D013997:Time Factors
keywords: Intracranial aneurysms; Irradiation; Radiation-induced aneurysms; Stereotactic radiosurgery; Subarachnoid hemorrhage