Skip to content

Low Grade Glioma

Summary

fleuron

  • Low-grade gliomas (LGGs) are slow-growing primary brain tumours originating from glial cells
  • Typically affect young adults and present with seizures or subtle neurological deficits
  • Characterised by diffuse infiltration on imaging and require long-term follow-up due to potential for malignant transformation1

Pathophysiology

  • Arise from glial cells (astrocytes, oligodendrocytes, or mixed)
  • Under WHO 2021, adult-type grade 2 diffuse gliomas are astrocytoma (IDH-mutant) or oligodendroglioma (IDH-mutant, 1p/19q-codeleted); "oligoastrocytoma" is no longer used
  • IDH mutation is near-universal; 1p/19q codeletion defines oligodendroglioma, ATRX loss defines astrocytoma
  • Slow growth rate but infiltrative nature

Demographics

  • Peak incidence: 30-40 years of age
  • Slight male predominance (M:F ratio 1.3:1)
  • Accounts for approximately 15% of all primary brain tumours
  • More common in Caucasians compared to other racial groups

Diagnosis

  • Clinical presentation:
    • Seizures (most common initial symptom, 80-90% of cases)
    • Headaches
    • Subtle neurological deficits
    • Cognitive changes
  • Neurological examination may be normal or show mild focal deficits
  • Neuropsychological testing may reveal cognitive impairments
  • Definitive diagnosis requires histopathological examination and molecular testing

Imaging

  • MRI is the imaging modality of choice:
    • T1-weighted: hypointense to isointense
    • T2-weighted/FLAIR: hyperintense
    • Minimal or no enhancement on post-contrast T1
    • Diffusion restriction typically absent
  • Advanced MRI techniques:
    • Perfusion imaging: usually shows no increased cerebral blood volume
    • MR spectroscopy: elevated Cho/NAA ratio, reduced NAA peak
  • PET imaging:
    • Hypometabolism on FDG-PET
    • Increased uptake on amino acid PET (e.g., 11C-methionine)

panels-1 panels-2

Treatment

  • Maximal safe resection, with radiotherapy/chemotherapy (PCV or temozolomide) for higher-risk disease
  • IDH inhibitors (vorasidenib) are an emerging option; long-term surveillance is needed for malignant transformation

Differential diagnosis

Differential Diagnosis Differentiating Feature
Multiple sclerosis Multiple ovoid periventricular lesions; calloso-septal interface; Dawson's fingers on sagittal FLAIR
Brain abscess Ring enhancement with smooth thin capsule; restricted central DWI; surrounding vasogenic oedema
Metastasis Multiple lesions at grey-white junction; surrounding vasogenic oedema disproportionate to size; nodular or ring enhancement
Subacute infarct Follows vascular territory; wedge-shaped; cortical gyral enhancement; resolves on follow-up
Primary CNS lymphoma Homogeneous enhancement; periventricular; restricted DWI; hyperdense on non-contrast CT
Encephalitis Cortical/limbic T2 signal; temporal lobe predilection; may show restricted DWI in active areas
Cortical dysplasia Congenital malformation; transmantle sign on MRI; blurring of grey-white junction; no mass effect
Ganglioglioma Calcification more common, often presents with long-standing epilepsy
DNET (Dysembryoplastic neuroepithelial tumour) Cortical location, often associated with drug-resistant epilepsy

  1. Fangusaro et al. Response assessment in paediatric low-grade glioma: recommendations from the Response Assessment in Pediatric Neuro-Oncology (RAPNO) working group. 2020. The Lancet. Oncology - Open in new tab. ↩