title: Radiologic Dilemma in an Extra-Axial Petroclival Lesion: Low Grade versus High Grade.
abstract: BACKGROUND
  Radiologic differentiation between a low-grade and high-grade lesion is crucial when deciding extent of resection and prognostication. Occasionally, imaging features can be confusing between the 2 lesions. We report a case that presented such a radiologic dilemma. The lesion appeared benign and extra-axial on routine magnetic resonance imaging sequences. However, subtle clinical and imaging clues pointed to a high-grade lesion.
  
  
  METHODS
  A 27-year-old woman presented with multiple cranial nerve palsies, gait ataxia, and features of increased intracranial pressure. Computed tomography and magnetic resonance imaging showed a petroclival extra-axial contrast-enhancing lesion with areas of chunky calcification. Although choline peak on spectroscopy raised suspicion of a high-grade lesion, the primary differential diagnosis included meningioma and schwannoma considering its characteristic imaging appearance. Postoperative histopathology showed the lesion to be giant cell glioblastoma.
  
  
  CONCLUSIONS
  Apart from reporting a rare variant of glioblastoma in an unusual location, this case highlights atypical imaging in a glioblastoma. Brainstem edema may be a subtle indicator of the infiltrative nature of a tumor. Magnetic resonance spectroscopy may be a useful adjunct in such circumstances.
authors.affiliation: Department of Neurosurgery, Post Graduate Institute of Medical Education and Research, Chandigarh, India. Electronic address: karthigeyanm82@gmail.com.
authors.forename: Madhivanan
authors.initials: M
authors.lastname: Karthigeyan
authors.affiliation: Department of Radiodiagnosis, Post Graduate Institute of Medical Education and Research, Chandigarh, India.
authors.forename: Chirag Kamal
authors.initials: CK
authors.lastname: Ahuja
authors.affiliation: Department of Histopathology, Post Graduate Institute of Medical Education and Research, Chandigarh, India.
authors.forename: Debjyoti
authors.initials: D
authors.lastname: Chatterjee
authors.affiliation: Department of Neurosurgery, Post Graduate Institute of Medical Education and Research, Chandigarh, India.
authors.forename: Pravin
authors.initials: P
authors.lastname: Salunke
mesh_terms: D000328:Adult; D001929:Brain Edema / Q000000981:diagnostic imaging; D001932:Brain Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D003937:Diagnosis, Differential; D005260:Female; D005909:Glioblastoma / Q000000981:diagnostic imaging* / Q000473:pathology; D006801:Humans; D008279:Magnetic Resonance Imaging; D060787:Neoplasm Grading; D014057:Tomography, X-Ray Computed
keywords: Extra-axial; Giant cell; Glioblastoma; Meningioma; Petroclival