Brainstem gliomas consist of a heterogeneous group that varies greatly in histology and prognosis. Unless otherwise specified, the term brainstem glioma usually refers to the most common histology of a diffuse midline glioma H3 K27-altered although 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 vague.
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Clinical presentation
Although the exact presentation will vary according to the location and size of the tumour, 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 gliomas (in contrast to focal gliomas), in which 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 tumours tend to be of a lower grade than those in the pons and medulla 3.
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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
focal dorsally exophytic brainstem glioma is an uncommon variant accounting for only 10% of pontine tumours, and has a much better prognosis, as it usually represents a pilocytic astrocytoma
overall 5-year survival of pontine gliomas is 10%
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mesencephalic
includes diffuse, focal, exophytic and tectal variants
focal brainstem gliomas are more common here than elsewhere in the brainstem
tectal plate gliomas are typically indolent
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medullary
least common location
includes focal dorsally exophytic, focal, diffuse and cervicomedullary junction variants
cervicomedullary junction tumours usually represent upper cervical tumours extending superiorly
most common location for NF1 associated tumours
Radiographic features
MRI
MRI is the imaging modality of choice. The appearance will vary with the tumour type, thus please refer to individual articles.
Angiography (DSA)
May show anterior displacement of the basilar artery.
Treatment and prognosis
Again, both treatment and prognosis are significantly influenced by tumour type, morphology and location. Radiation is a key part of treatment as surgical resection is usually not possible.
As a general rule, dorsal exophytic tumours and cervicomedullary tumours tend to do best with surgery, whereas surgery has no role in the management of diffuse brainstem gliomas.