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Diffuse intrinsic pontine glioma (DIPG) is a high-grade, infiltrative glioma located in the pons, primarily affecting children. It is classified as a midline glioma, H3K27-altered in the 2021 WHO CNS tumor classification, reflecting its molecular hallmark and poor prognosis.

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WHO 2021 Classification

Diffuse midline glioma, H3K27-altered (Grade IV)
Replaces “DIPG” terminology in diagnostic coding
Can occur in thalamus, spinal cord, or pons (DIPG = brainstem form)

Epidemiology

Feature	Details
Age group	Children 5–10 years
Prevalence	~10–15% of all pediatric CNS tumors
Sex	Slight male predominance
Outcome	Very poor prognosis; median survival ~9–12 months

Pathogenesis

Arises from glial precursor cells in the pons
Most cases show a H3K27M mutation in histone H3 genes (H3F3A, HIST1H3B), leading to:
- Epigenetic dysregulation
- WHO Grade IV designation regardless of histologic features

Clinical Presentation

Symptom	Mechanism
Cranial nerve palsies	Especially CN VI, VII – facial weakness, diplopia
Ataxia and dysmetria	Cerebellar pathway involvement
Long tract signs	Hemiparesis, hyperreflexia, Babinski sign
Dysphagia, dysarthria	Bulbar involvement
Headache, vomiting	Raised ICP if hydrocephalus develops
Rapid progression	Over weeks, occasionally days

Radiology

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Classic appearance:

Expansile, diffusely infiltrative pontine mass (>50% of the pons)
Blurs margins with basilar artery draped over the surface
Often encases the 4th ventricle, but rarely causes early hydrocephalus
Extensions: Midbrain (superior extension), medulla (inferior extension) & cerebellar peduncles </aside>

MR Brain: Modality of Choice

Sequence	Findings
T1-weighted	Hypo- to isointense, often ill-defined
T2/FLAIR	Hyperintense, diffuse expansion of the pons
Post-contrast	Minimal or patchy enhancement (in ~30%)
DWI	Mild or no restriction (high-grade nature not always reflected in diffusion)
SWI	May show microhemorrhages
MR Spectroscopy	Elevated choline, reduced NAA, increased lactate (aggressive profile)