Brainstem Gliomas Workup

Updated: Jun 09, 2016
  • Author: Joseph C Landolfi, DO; Chief Editor: Tarakad S Ramachandran, MBBS, MBA, MPH, FAAN, FACP, FAHA, FRCP, FRCPC, FRS, LRCP, MRCP, MRCS  more...
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Workup

Laboratory Studies

Lab studies of blood chemistry and related body fluids are not helpful as a rule, though cerebrospinal fluid (CSF) examination is often important for differential diagnosis. The protein content of CSF may be elevated. Because of the risk of increased intracranial pressure due to obstructive hydrocephalus, caution in clinical and imaging assessment prior to lumbar puncture is stressed.

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Imaging Studies

MRI

MRI of the head is the diagnostic test of choice. MRI can differentiate vascular malformations and other processes that can be misdiagnosed as a brainstem glioma on CT scan. [6]

The typical MRI appearance of a brainstem glioma is an expansile, infiltrative process with low-to-normal signal intensity on T1-weighted images and heterogeneous high-signal intensity on T2-weighted images, with or without contrast enhancement (see the images below).

T2-weighted image of a diffuse intrinsic pontine g T2-weighted image of a diffuse intrinsic pontine glioma.
T2-weighted image of a right tectal glioma. T2-weighted image of a right tectal glioma.

MR spectroscopy has been used to help distinguish between tumor and nontumor lesions in the brain. An elevated choline peak suggests neoplasm.

MRI can delineate the extent of infiltration of the leptomeninges and the surrounding structures.

High midbrain tumors, especially those arising in the tectum, are typically low-grade lesions by histologic criteria. They commonly appear hypointense on T1 and hyperintense on T2 images even without contrast enhancement.

The occurrence of contrast enhancement in a tectal lesion should raise suspicion of a metastatic lesion, especially in an adult, with or without a known history of cancer.

CT scan

Although CT imaging is an appropriate choice when MRI is not available, the appearance of brainstem gliomas is variable on CT scan, and the sensitivity of and characterization of tumors by CT are poorer.

CT identifies calcifications, cystic changes, and displacement of the ventricular system; however, lower brainstem lesions are often not apparent on CT scan.

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Other Tests

Arteriography occasionally is useful in differentiating vascular lesions, including tumors, from gliomas.

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Procedures

Typically, biopsy is not required for diagnosis of diffuse intrinsic pontine or tectal gliomas, and cannot be recommended routinely; diagnosis can be made by MRI alone. Especially in clinical trials, however, biopsy of diffuse intrinsic pontine gliomas can be used to ascertain biological characteristics of the tumor, which may enhance understanding and targeting of treatments.

Tissue confirmation is frequently not feasible with infiltrating, expansile tumors unless an exophytic component exists. Even then, a biopsy cannot always be obtained.

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Histologic Findings

The histopathology is variable; most gliomas in the brain stem are fibrillary, pilocytic astrocytomas, or the more malignant glioblastoma multiforme. Hemorrhage and necrosis are associated with the more malignant forms. Cysts may be seen with either the high- or low-grade forms.

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