Paediatric PNET: pre-surgical MRI features

Chawla, A.; Emmanuel, J.V.; Seow, W.T.; Lou, J.; Teo, H.E.; Lim, C.C.T.

doi:10.1016/j.crad.2006.09.008

« Previous Next »Clinical Radiology
Volume 62, Issue 1 , Pages 43-52, January 2007

Paediatric PNET: pre-surgical MRI features

A. Chawla
- Department of Neuroradiology, National Neuroscience Institute, Singapore
J.V. Emmanuel
- Department of Neuroradiology, National Neuroscience Institute, Singapore
W.T. Seow
- Department of Neurosurgery, National Neuroscience Institute, Singapore
J. Lou
- Pediatric Medicine, KK Women's and Children's Hospital, Singapore
H.E. Teo
- Department of Diagnostic Imaging, KK Women's and Children's Hospital, Singapore
C.C.T. Lim
- Department of Neuroradiology, National Neuroscience Institute, Singapore
- Diagnostic Radiology, Yong Loo Lin Medical School, National University of Singapore, Singapore
- Guarantor and correspondent: T. Lim, National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore 308433. Tel.: +65 6357 7021; fax: +65 6358 1259.

Received 17 July 2006; received in revised form 7 September 2006; accepted 14 September 2006.

Aim

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.

Material and 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.

Conclusion

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.