Brain Stem Gliomas MRI

On MRI brain, diffuse brainstem glioma is characterized by decreased intensity on T1, heterogenously increased on T2. Focal brainstem glioma is characterized by iso- to hypointense to grey matter on T1, and hyperintense to grey matter on T2.

MRI brain is the imaging modality of choice for brainstem gliomas. The findings will vary with the tumor type.^[1]

Diffuse brainstem gliomas

The pons is enlarged, with the basilar artery displaced anteriorly against the clivus and potentially engulfed. The floor of the fourth ventricle is flattened (“flat floor of fourth ventricle sign”) and obstructive hydrocephalus may be present. Occasionally the tumor is exophytic, either outwards into the basal cisterns or centrally in the fourth ventricle. Usually the tumor is homogenous pre-treatment, however in a minority of patients areas of necrosis may be present.

• T1: Decreased intensity
• T2: Heterogeneously increased
• T1 C+ (Gd): Usually minimal (can enhance post radiotherapy)
• Diffusion weighted imaging (DWI): Usually normal, occasionally mildly restricted

Focal brainstem glioma

• Tectal glioma subtype

Typically the tumors demonstrate expansion of the tectal plate by a solid nodule of tissue.

• T1: Iso- to slightly hypointense to grey matter
• T2: Hyperintense to grey matter
• T1 C+ (Gd): Usually no enhancement

With time the mass can develop small cystic spaces (sometimes associated with neurological deficits) or calcification. Higher grade tumors tend to be larger and tend to enhance more vividly.

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