title: Changes mimicking new leptomeningeal disease after intensity-modulated radiotherapy for medulloblastoma.
abstract: OBJECTIVE
  Acute and late changes in magnetic resonance imaging of the pediatric brain have been described after radiotherapy (RT). We report the post-RT neuroimaging changes in the posterior fossa after intensity-modulated RT (IMRT) in children with medulloblastoma and contrast them with those of leptomeningeal disease.
  
  
  METHODS
  We performed a retrospective review of 53 consecutive children with medulloblastoma who were treated with craniospinal RT followed by IMRT to the posterior fossa and chemotherapy between 1997 and 2006.
  
  
  RESULTS
  After IMRT to the posterior fossa, 8 (15%) of 53 patients developed increased fluid-attenuated inversion-recovery signal changes in the brainstem or cerebellum and patchy, multifocal, nodular contrast enhancement at a median of 6 months. The enhancement superficially resembled leptomeningeal disease. However, the enhancement resolved without intervention at a median of 6 months later. The accompanying fluid-attenuated inversion-recovery signal changes occasionally preceded the enhancement, were often parenchymal in location, and resolved or persisted to a lesser degree. All 8 patients with transient magnetic resonance imaging changes in the posterior fossa were alive at last follow-up. In contrast, leptomeningeal disease occurred in 8 (15%) of our 53 patients at a median of 19.5 months after IMRT completion. Of these 8 patients, 7 demonstrated initial nodular enhancement outside the conformal field, and 7 patients died.
  
  
  CONCLUSIONS
  Magnetic resonance imaging changes can occur in the posterior fossa of children treated with IMRT for medulloblastoma. In our experience, these transient changes occur at a characteristic time and location after RT, allowing them to be distinguished from leptomeningeal disease.
authors.affiliation: Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA.
authors.forename: Jodi A
authors.initials: JA
authors.lastname: Muscal
authors.forename: Jeremy Y
authors.initials: JY
authors.lastname: Jones
authors.forename: Arnold C
authors.initials: AC
authors.lastname: Paulino
authors.forename: Alison A
authors.initials: AA
authors.lastname: Bertuch
authors.forename: Jack
authors.initials: J
authors.lastname: Su
authors.forename: Shiao Y
authors.initials: SY
authors.lastname: Woo
authors.forename: Donald H
authors.initials: DH
authors.lastname: Mahoney
authors.forename: Murali
authors.initials: M
authors.lastname: Chintagumpala
mesh_terms: D000293:Adolescent; D001932:Brain Neoplasms / Q000532:radiotherapy*; D002648:Child; D002675:Child, Preschool; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008297:Male; D008527:Medulloblastoma / Q000532:radiotherapy*; D008577:Meningeal Neoplasms / Q000175:diagnosis* / Q000209:etiology*; D008579:Meningioma / Q000175:diagnosis* / Q000209:etiology*; D011832:Radiation Injuries / Q000175:diagnosis* / Q000209:etiology*; D020266:Radiotherapy, Conformal / Q000009:adverse effects*