Brainstem gliomas are primary tumors most frequently involving the pons and are typically diagnosed in children.
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Terminology
Brainstem glioma is not a formal diagnosis but rather a catch-all term encompassing a heterogeneous group that varies greatly in histology and prognosis. It was useful, along with other terms like diffuse intrinsic pontine glioma, particularly when histology was often not obtained. More recently, the combination of the need for formal histological and molecular diagnosis and the increased safety of stereotactic biopsy has meant that biopsy is now more frequently obtained 8.
Unless otherwise specified, the term brainstem glioma usually refers to the most common formal diagnosis of a diffuse midline glioma H3 K27-altered, which was largely analogous to the term diffuse intrinsic pontine glioma.
Importantly, however, many other gliomas can be encountered in the brainstem (e.g. pilocytic astrocytoma, ganglioglioma, etc.). As such, caution must be used when using this term as it is inherently vague.
Epidemiology
Epidemiology will depend upon the tumor type, but in general, brainstem gliomas are most often encountered in children 2-8.
Clinical presentation
Although the exact presentation will vary according to the location and size of the tumor, in general, patients will exhibit a combination of 4:
cranial nerve palsies
long tract signs
The duration of symptoms is usually much shorter in diffuse infiltrating tumors compared to more focal localized gliomas. In diffuse tumors, the history is typically very short (a few days) 4. Additionally, diffuse gliomas more frequently have multiple cranial nerve palsies.
Pathology
As a general rule, mesencephalic (midbrain) tumors tend to be of a lower grade than those in the pons and medulla 3.
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mesencephalic
focal gliomas (most commonly pilocytic astrocytomas) are more common
tectal plate gliomas are typically indolent
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pontine
most common location
classic location for the childhood "brainstem glioma" which tends to refer to a diffuse midline glioma, H3 K27–altered
overall 5-year survival of pontine gliomas is 10%
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medullary
least common location
cervicomedullary junction tumors usually represent upper cervical tumors extending superiorly
Radiographic features
MRI
MRI is the imaging modality of choice. The appearance will vary with the tumor type, thus please refer to individual articles.
Treatment and prognosis
Again, both treatment and prognosis are significantly influenced by tumor type, morphology and location. Radiation is a key part of treatment as surgical resection is usually not possible.
As a general rule, exophytic tumors and cervicomedullary tumors tend to do best with surgery, whereas surgical resection has no role in the management of diffuse infiltrating brainstem gliomas.