Diffuse intrinsic pontine gliomas are diagnosed by their clinical signs and symptoms on presentation and their appearance on imaging. Since the publication of the Children’s Cancer Group (CCG) report in 1993 (32) that outlined the typical presentation and radiographic appearance of these brainstem tumors, most believe that these findings are diagnostic and a biopsy is unnecessary. If, however, the clinical or radiological presentation is not typical, or if brainstem encephalitis or an inflammatory process of the pons cannot be ruled out, many would argue for a stereotactic biopsy before initiating radiation therapy and chemotherapy.
A CT scan is not the ideal study for the imaging of diffuse tumors. It may suggest a tumor if there is a hypodense and expanded pons.
- Diffuse intrinsic pontine gliomas infiltrate widely: Diffuse intrinsic pontine gliomas are typically diagnosed by their clinical presentation and imaging. MRI shows infiltrative expansion of the pons that is typically hypointense on T1-weighted images, hyperintense on T2-weighted and FLAIR images, and has no significant dorsal exophytic component. Involvement of adjacent levels of brainstem and/or cerebellum is common.
- Diffuse intrinsic pontine gliomas can encase basilar artery: Envelopment of the basilar artery is common.
- Gadolinium enhancement is uncommon and has no prognostic significance: Enhancement with gadolinium is variable, with no enhancement being common (95). Enhancement, if present, is usually patchy, without known prognostic significance.
- Neuraxis dissemination common during progression: During progression, neuraxis dissemination can be seen in more than 50% of patients on MRI (31).
- MRS is helpful in differential diagnosis: Increased Cho/NAA and Cho/Cre ratios are helpful in differentiating diffuse intrinsic pontine gliomas from brainstem encephalitis, demyelination, and other inflammatory processes when clinical and MRI presentations are atypical (96, 97). However, the differentiating power of MRS is limited in NF1-associated diffuse intrinsic pontine gliomas (97).