Diffuse midline glioma, H3 K27-altered, is the WHO classification for a family of tumors that arise along the brain's midline, most often in the pons, the part of the brainstem that gives this tumor its older name, DIPG. These tumors are defined less by where exactly they sit than by how they grow: instead of forming a single mass with a clear edge, the tumor cells spread through and mix with the normal fibers of the brainstem. That growth pattern, not the tumor's grade in the traditional sense, is what makes it so difficult to treat.
It's a disease of childhood far more often than of adulthood, and the pons is involved in the large majority of cases. Because the pons controls basic functions like eye movement, facial sensation, swallowing, and motor pathways to the limbs, even a tumor of modest size can produce significant symptoms early on.
Because the pons is packed with cranial nerve nuclei and the major pathways connecting the brain to the rest of the body, symptoms tend to appear over just weeks rather than months, and often come as a cluster rather than one isolated complaint. Families frequently describe:
In most children, the MRI appearance alone, a tumor expanding the pons diffusely rather than sitting within it, is distinctive enough that a confident diagnosis can be made without tissue. Even so, we routinely add perfusion imaging, spectroscopy, and diffusion tensor imaging (DTI). Beyond confirming what the standard sequences already suggest, these techniques map the exact position of critical fiber tracts, which is what allows a biopsy needle, or occasionally a resection, to be planned along the safest possible corridor.
Radiotherapy is the backbone of treatment, and for most patients it remains the single most effective way to shrink the tumor and relieve symptoms, sometimes dramatically, for a period of months. What has changed in recent years is what happens around it.
We now take a stereotactic needle biopsy in essentially every patient before radiotherapy begins. Removing the whole tumor isn't possible given how it grows, but a small tissue sample is enough to run a full molecular workup, including next-generation sequencing, alongside standard pathology. That workup doesn't just confirm the diagnosis; it identifies specific mutations that, in a subset of patients, open the door to a targeted drug or a clinical trial that wouldn't otherwise be an option, and it gives us something concrete to fall back on if the tumor progresses and a second round of treatment is needed.
Surgical resection is the exception rather than the rule. A small number of these tumors grow with an exophytic component, a portion that bulges outward from the brainstem rather than infiltrating it, and in that specific setting partial or complete removal can be safely attempted. For the majority of patients, though, the plan is biopsy, radiotherapy, and molecular-guided therapy where the biology allows it.
Here's how we think through the decision for DIPG, and what to expect from biopsy through radiotherapy and beyond.
MRI, together with perfusion, spectroscopy, and DTI sequences, establishes the diagnosis and maps the safest corridor through the brainstem.
Neurosurgery, pediatric neuro-oncology, radiation oncology, and radiology review the imaging together and agree on a biopsy or, in select cases, a resection.
Almost every patient follows the same core path; a small minority are candidates for something more. Tap either one below.
Once radiotherapy finishes, we start any targeted or chemotherapy agents the molecular results support, and the tumor is followed with regular imaging. The molecular data stays on file, and it becomes relevant again if further treatment is ever needed.
Full MRI protocol, anesthesia clearance, and a joint plan between neurosurgery and radiation oncology for how the biopsy and treatment will proceed.
Done under general anesthesia through a needle-sized opening, guided in real time by neuronavigation. There's no large incision to recover from.
A neurological check the following morning is usually all that stands between the biopsy and discharge.
Pathology and the molecular panel are finalized, and radiotherapy is scheduled to begin.
Daily sessions over several weeks on our adaptive LINAC platform, with any indicated drug therapy layered in once the molecular results are complete, and imaging follow-up continuing afterward.
Shown for a typical case. Individual course may vary.