Diffuse midline glioma

Case Discussion

All diffuse midline gliomas (DMGs) including diffuse intrinsic pontine glioma (DIPG) are WHO grade 4 regardless of the histopathologic grade which does not correlate with prognosis.

The diagnosis is mainly made on MRI imaging, rarely a biopsy is performed due to high complications and high mortality rate.

Diffuse midline gliomas typically have the following features on MRI ^2,3:

• T1: ill-defined hypointense mass expanding the brainstem (mainly the pone)

• T2: hyperintense mass (relative hypointense areas may indicate foci of higher cellularity or spared white matter tract)

• T1 C+ (Gd): usually non-enhancing, focal enhancing areas (correlated with relative hypointensity on T2 and low ADC values) may represent areas of higher grade

• DWI/ADC: typically no restriction, some areas of diffusion restriction may represent areas of higher grade (usually with relative hypointensity on T2 and/or enhancement on post-contrast T1)

• T2*/SWI: areas of marked hypointensity/blooming in cases of intralesional hemorrhage

• DTI: disruption of the white matter tracts indicates diffuse midline glioma rather than focal brain stem gliomas

The presence of restricted diffusion at non-enhancing DMG is called diffusion-weighted imaging-gadolinium enhancement mismatch sign (DWI-Gd mismatch sign) ¹, and it is found to be a very poor prognostic sign.

Due to high risk of biopsy, the diagnosis is made radiographically, and the patient was send to radiotherapy.