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Oligodendroglioma

Summary

fleuron

  • Oligodendroglioma is a slow-growing, diffusely infiltrating glial tumour of the central nervous system
  • Typically affects adults in their 4th-5th decades of life
  • Characterised by classic "fried egg" appearance histologically and 1p/19q co-deletion genetically1

Pathophysiology

  • Typically occurs in the cerebral hemispheres, particularly the frontal lobes
  • Molecular markers include 1p and 19q co-deletion and IDH½ mutation
  • Typical findings of histopathological include "fried egg" oligodendrocytes, chicken-wire neovascularisation and microcalcification

Demographics

  • Accounts for approximately 5-20% of all gliomas and 5-10% of all intracranial tumours
  • Peak incidence in 4th-5th decades of life
  • Slight male predominance (M:F ratio 1.1-2:1)

Diagnosis

  • Clinical presentation:
    • Seizures (50-80% of cases)
    • Headaches
    • Focal neurological deficits
    • Cognitive changes

Imaging

  • CT:
    • Hypoattenuating cortical/subcortical mass
    • Calcifications in 50-90% of cases
    • May cause remodelling of the overlying skull (representing slow growth)
  • MRI:
    • ++T2/FLAIR++ hyperintense
    • ++T1++ hypointense to isointense
    • ++T1C++ Minimal to moderate enhancement with contrast
    • ++SWI++ Hypointensity/blooming due to calcification (or, more rarely, haemorrhage)
  • Advanced imaging:
    • MR spectroscopy: elevated Cho/NAA ratio, presence of lactate/lipid peak
    • Perfusion imaging: CBV may be elevated even in grade 2 lesions

panels-1

  • A 40-year-old patient presented after a tonic-clonic seizure.
  • MRI showed a relatively well-demarcated tumour in the left frontal lobe that involved cortex.
  • Phase data from SWI showed diamagnetic susceptibility artefact consistent with dystrophic calcification.
  • There was punctate enhancement and elevated CBV (ratio of 2.5 relative to contralateral normal-appearing brain tissue).
  • MRS showed elevated choline and reduced NAA (indicating the replacement of normal neurons with mitotically active cells).

Treatment

  • Maximal safe resection with radiotherapy and PCV chemotherapy for higher grade/risk
  • Defined by IDH mutation and 1p/19q codeletion (both required); this confers a better prognosis and chemosensitivity than astrocytoma

Differential diagnosis

Differential Diagnosis Differentiating Feature
Astrocytoma T2/FLAIR mismatch sign (bright T2 but suppressed on FLAIR) favours astrocytoma; less well-defined margins; calcification rare
Dysembryoplastic neuroepithelial tumour (DNET) "Bubbly" multinodular cortical architecture; no enhancement; typically in younger patients
Ganglioglioma Cystic lesion with mural nodule; mixed cystic-solid architecture; calcification less prominent
Glioblastoma Central necrosis; ring enhancement; elevated rCBV; marked DWI restriction

  1. M Smits. Imaging of oligodendroglioma. 2016. The British journal of radiology - Open in new tab. ↩