Abstract

Background: Diffuse Midline Glioma (DMG) H3 K27M-mutant of the pons is the most common brainstem tumor of childhood, leading to poor outcome. Radiotherapy is the only proved and consensual therapeutic option that just offers temporary benefit, while co-adjuvant chemotherapy is still controversial. Although MRI allows for the diagnosis of DMG, biopsy is the gold standard as it offers additional molecular biology information that can be useful for future targeted immune or chemotherapy, improving diagnostic accuracy, prognostic stratification and potentially unveiling more treatment options.

Case: A 6-year-old girl presented with a 6-month history of vomits, ataxia with frequent falls, left peripheral facial palsy and headache along with irritability. Brain MRI showed an intra-axial lesion located in the mesencephalon and pons, hypointense in T1, hyperintense in T2 and FLAIR, without contrast enhancement. The dysmorphic pons partly surrounded the basilar artery, obstructing the upper part of the 4th ventricle and aqueduct, with supratentorial ventricular dilatation. A trans-frontal stereotactic biopsy of the lesion was performed followed by an Endoscopic Third Ventriculostomy (ETV), through two different burr holes and transcortical approaches. Histology and biology confirmed the diagnosis of H3 K27M-mutant DMG.

Conclusion: Biopsy is an invasive procedure; however, it should be offered to children with presumptive imaging of DMG. It shows low morbidity, confirms the diagnosis and has potential utility for research on targeted chemotherapy or immunotherapy for secondary treatment approach.

Keywords: Diffuse Midline Glioma; Stereotactic Biopsy; Molecular Diagnosis; Targeted Chemotherapy

Abbreviations: BBB: Blood-brain Barrier; CSF: Cerebrospinal Fluid; CT: Computerized Tomography; DMG: Diffuse Midline Glioma; DNA: Deoxyribonucleic Acid; ETV: Endoscopic Third Ventriculostomy; MRI: Magnetic Resonance Imaging; PFS: Progression-free Survival; RNA: Ribonucleic Acid; VP: Ventriculo Peritoneal; WHO: World Health Organization