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Brainstem glioma

Brainstem gliomas are primary tumors most frequently involving the pons and typically diagnosed in children aged 2-8 years presenting with ataxia, cranial nerve palsies, long tract signs, and/or hydrocephalus.

Key Images

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Patient A

Patient B

Patient B

Patient C

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Patient C

Look For First
  • Intrapontine or diffuse brainstem mass in a child with short symptom duration (days)
  • Expansion and hyperintense T2/FLAIR signal within the pons with or without exophytic component
  • Associated obstructive hydrocephalus from fourth ventricle compression
  • Multiple cranial nerve palsies on clinical presentation suggesting infiltrative rather than focal disease
Key Image Findings
  • MRI is the imaging modality of choice for brainstem gliomas evaluation and characterization
  • Diffuse infiltrating tumors typically show short clinical history (days) in contrast to focal gliomas which present with longer symptom duration
  • Mesencephalic (midbrain) tumors tend to be lower grade and are more commonly focal gliomas, particularly pilocytic astrocytomas, whereas pontine tumors are more frequently diffuse midline gliomas H3 K27-altered
  • Tectal plate gliomas in the mesencephalon are typically indolent with favorable prognosis
  • Pontine gliomas represent the classic location for childhood brainstem glioma with overall 5-year survival of only 10%, making them the most common and most aggressive location
  • Medullary gliomas are least common and often represent cervicomedullary junction tumors with upper cervical extension
  • Exophytic and cervicomedullary tumors have better surgical candidacy and prognosis, while diffuse infiltrating gliomas are generally not amenable to surgical resection
  • The term brainstem glioma is now increasingly supplemented with formal histological and molecular diagnosis via stereotactic biopsy to establish precise tumor type and H3 K27 mutation status
Differential Diagnosis
  • Pilocytic astrocytoma - typically focal, well-circumscribed, lower grade lesion more common in mesencephalon with better prognosis than diffuse midline glioma
  • Tectal plate glioma - indolent lesion at tectal plate with prolonged clinical course and favorable outcome
  • Brainstem lymphoma - typically enhances more homogeneously and occurs in different age group
  • Ependymoma - may arise from fourth ventricle or central canal, often has different imaging characteristics
  • Ganglioglioma - can occur in brainstem but typically more focal with different histological grade
  • Cervicomedullary junction tumor - upper cervical origin extending into brainstem rather than primary brainstem origin
Discussion

Brainstem glioma is now recognized as a heterogeneous group requiring formal histological and molecular diagnosis rather than imaging-based diagnosis alone, with diffuse midline glioma H3 K27-altered being the most common formal diagnosis

Clinical presentation duration is critically important: diffuse infiltrating tumors present acutely (days) with rapid symptom progression, while focal gliomas have more gradual symptom onset

Multiple concurrent cranial nerve palsies suggest diffuse infiltrating disease, whereas single or limited nerve involvement suggests more focal tumor

Location strongly predicts prognosis and treatment approach: mesencephalic tumors are lower grade, pontine tumors are most common with worst prognosis (10% 5-year survival), and medullary tumors are rare

Surgical management depends critically on tumor morphology: exophytic and cervicomedullary tumors may be surgically resectable with better outcomes, but diffuse infiltrating pontine gliomas are not surgical candidates and rely on radiation therapy

Stereotactic biopsy is now more frequently obtained to establish H3 K27 mutation status and grade, guiding prognosis and treatment decisions

Reporting Pearls

When reporting a brainstem mass, clearly distinguish between diffuse infiltrating glioma (intraaxial expansion without well-defined margins, likely diffuse midline glioma H3 K27-altered with poor prognosis) versus focal/exophytic lesion (better-circumscribed, surgically amenable, potentially lower grade), and document compression of the fourth ventricle and presence of obstructive hydrocephalus, as these affect management strategy.

Pitfalls
  • Overusing the vague term 'brainstem glioma' without attempting to distinguish tumor type, morphology (diffuse vs. focal), and location, which critically impact prognosis and treatment planning
  • Misinterpreting focal pilocytic astrocytomas or other lower-grade tumors as having the poor prognosis of diffuse midline glioma H3 K27-altered based on location alone
  • Failing to recognize that diffuse infiltrating brainstem gliomas with short symptom duration (days) and multiple cranial nerve palsies are not candidates for surgical resection
  • Assuming all brainstem tumors in children have equally poor outcomes without considering location (midbrain vs. pons vs. medulla) and morphology (diffuse vs. focal/exophytic)
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