title: Paediatric PNET: pre-surgical MRI features.
abstract: OBJECTIVE
  To describe the preoperative magnetic resonance imaging (MRI) characteristics of primitive neuroectodermal tumours (PNETs), in particular the diffusion-weighted imaging (DWI), MR spectroscopy (MRS) features and cerebrospinal fluid (CSF) tumour dissemination.
  
  
  METHODS
  Twelve patients with PNETs were reviewed: nine with medulloblastoma and three with supratentorial PNETs (SPNETs). The MRI examination included contrast-enhanced intracranial and spinal MRI, and in some patients, gradient recalled echo, fluid-attenuated inversion recovery (FLAIR), DWI, and MRS.
  
  
  RESULTS
  All PNETs were either hypointense or isointense on T1-weighted images. Ten of the 12 tumours were either isointense or hypointense on T2-weighted images, and 11 were isointense on FLAIR images. Patients with SPNETs had large, vascular and haemorrhagic tumours. On DWI, all PNETs were hyperintense and had restricted apparent diffusion coefficient. MRS (two patients with medulloblastoma and one with a SPNET), showed elevated choline, decreased N-acetyl aspartate, and a small taurine peak in all three patients. Intraspinal tumour dissemination, visible as uniform or nodular enhancement coating the conus medullaris, was detected in six of 12 patients, two of whom also had intracranial dissemination.
  
  
  CONCLUSIONS
  PNETs have a characteristic imaging appearance on FLAIR, DWI and MRS, which may help in differentiating these highly cellular neoplasms from other tumours. There is CSF tumour dissemination in a high proportion of patients, and spinal imaging is important for disease staging and to formulate treatment protocols.
authors.affiliation: Department of Neuroradiology, National Neuroscience Institute, Singapore.
authors.forename: A
authors.initials: A
authors.lastname: Chawla
authors.forename: J V
authors.initials: JV
authors.lastname: Emmanuel
authors.forename: W T
authors.initials: WT
authors.lastname: Seow
authors.forename: J
authors.initials: J
authors.lastname: Lou
authors.forename: H E
authors.initials: HE
authors.lastname: Teo
authors.forename: C C T
authors.initials: CC
authors.lastname: Lim
mesh_terms: D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000032:analysis; D002555:Cerebrospinal Fluid; D002648:Child; D002675:Child, Preschool; D002794:Choline / Q000032:analysis; D003401:Creatine / Q000032:analysis; D016208:Databases, Factual; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D007089:Image Enhancement; D007223:Infant; D019344:Lactic Acid / Q000032:analysis; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008527:Medulloblastoma / Q000175:diagnosis*; D009362:Neoplasm Metastasis; D018242:Neuroectodermal Tumors, Primitive / Q000175:diagnosis*; D015173:Supratentorial Neoplasms / Q000175:diagnosis*; D013654:Taurine / Q000032:analysis
chemical_list: D013654:Taurine; D001224:Aspartic Acid; D019344:Lactic Acid; C000179:N-acetylaspartate; D019786:Gadolinium DTPA; D003401:Creatine; D002794:Choline