Posterior fossa ependymomas: new radiological classification with surgical correlation

Childs Nerv Syst. 2010 Dec;26(12):1765-72. doi: 10.1007/s00381-010-1251-6. Epub 2010 Aug 3.

Abstract

Purpose: The key determinant of long-term outcome in infratentorial ependymomas remains the extent of surgical resection. We describe a new radiological classification system which is validated against surgical findings and correlated with risk of post-operative residual tumour.

Methods: Twenty-five consecutive patients (12 females, mean age 4.9 years, range 0.5-17 years) with infratentorial ependymomas were studied. Lesions were classified on pre-operative MRI according to the pattern of extension, brainstem displacement and involvement of the obex, as lateral-type or midfloor-type tumours. Twenty-one operative records were reviewed with respect to the microanatomical tumour origin by a paediatric neurosurgeon, blinded to MRI findings. Follow-up imaging studies were evaluated for residual tumour.

Results: There were 15 cases of midfloor-type tumour (anterior displacement of brainstem, infiltration of obex) and 10 cases of lateral-type tumour (lateral displacement of brainstem, obex free of tumour). Extension into prepontine or cerebellopontine cisterns was more common in lateral-type tumours. Agreement between the radiological classification and tumour origin, as defined by operative records, was seen in 18 out of 20 cases. Risk of residual tumour in lateral-type tumours was more than twice that of midfloor-type tumours (80% vs. 33%, p=0.04). Risk of tumour residual was also significantly higher when vessel encasement or prepontine extension was observed.

Conclusions: Infratentorial ependymomas can be pre-operatively classified as lateral-type or midfloor-type tumours. This correlates well with operative findings. Lateral-type tumours have significantly increased risk of residual tumour compared to midfloor- type tumours and this may influence intensity of imaging surveillance.

MeSH terms

  • Adolescent
  • Child
  • Child, Preschool
  • Ependymoma / classification*
  • Ependymoma / pathology
  • Ependymoma / surgery
  • Female
  • Humans
  • Infant
  • Infratentorial Neoplasms / classification*
  • Infratentorial Neoplasms / pathology
  • Infratentorial Neoplasms / surgery
  • Magnetic Resonance Imaging
  • Male