Neurologic Manifestations of Glioblastoma Multiforme Workup

Updated: Nov 07, 2021
  • Author: Gaurav Gupta, MD, FAANS, FACS; Chief Editor: Stephen A Berman, MD, PhD, MBA  more...
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Workup

Laboratory Studies

Routine laboratory workup results in glioblastoma multiforme (GBM) often are negative, but excluding a metabolic or infective process is important in an otherwise healthy patient who presents with new-onset seizures or mental status changes for the first time.

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Imaging Studies

The preferred workup for glioblastoma multiforme (GBM) is diagnostic neuroimaging studies. 

MRI

Brain MRI with and without gadolinium contrast is the most sensitive and specific study. GBM tumors characteristically have low-signal intensity on T1-weighted images and high-signal intensity on T2-weighted images. With contrast, the tumors usually enhance. The enhanced T1-weighted images typically have a central hypodensity surrounded by a thick enhancing rim of the tumor. See the images below.

T1-weighted axial gadolinium-enhanced MRI demonstr T1-weighted axial gadolinium-enhanced MRI demonstrates an enhancing tumor of the right frontal lobe. Image courtesy of George Jallo, MD.
T2-weighted image demonstrates notable edema and m T2-weighted image demonstrates notable edema and midline shift. This finding is consistent with a high grade or malignant tumor. Image courtesy of George Jallo, MD.

CT scan

CT scan can be ordered with or without contrast when MRI is contraindicated or unavailable. Consider the following:

  • On CT scan, GBMs have a variable, inhomogeneous hypodense or isodense appearance with surrounding edema.

  • GBMs tend to infiltrate along the white matter tracts and frequently involve and cross the corpus callosum.

  • Approximately 4–10% of GBMs and 30–50% of AAs do not enhance, while a significant percentage of low-grade gliomas do not enhance.

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Other Tests

Functional neuroimaging such as positron emission tomography (PET scan), single-photon emission computed tomography (SPECT), or MR spectroscopy may help differentiate a glioblastoma multiforme (GBM) tumor from other benign mass lesions, brain abscess, or toxoplasmosis. However, the definitive diagnosis is confirmed by stereotactic or open brain biopsy. See the image below.

Magnetic resonance spectroscopy is representative Magnetic resonance spectroscopy is representative of a glioblastoma multiforme.

Consider the following:

  • Functional imaging is commonly used to differentiate between treatment-related radiation necrosis and tumor recurrence.

  • Functional imaging is also used in defining the margins of the tumor for surgical resection and planning for the radiation fields.

  • Additionally, functional imaging may be helpful in determining the most abnormal region of the tumor to improve the diagnostic accuracy in case a small biopsy sample is taken.

Direct or indirect ophthalmoscopy is used to look for papilledema and secondary optic atrophy.

Neuropsychological evaluation can help to localize the pathology as well as rule out psychiatric diseases.

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Histologic Findings

High-grade astrocytomas (HGAs) are extremely heterogeneous tumors characterized by varying degrees of increased cellularity, pleomorphism, mitoses, microvascular proliferation, and necrosis.​See the image below.

The 2021 WHO grading of gliomas has significantly changed the way glioblastomas are diagnosed. Instead of solely relying on histological characteristics, both histological and molecular characteristics are considered to diagnose glioblastoma. In adults, any IDH-wildtype diffuse and astrocytic glioma with microvascular proliferation or necrosis or TERT promoter mutation or EGFR gene amplification or +7/-10 chromosome copy number changes is considered as glioblastoma, IDH wildtype. IDH mutant-type gliomas are no longer considered glioblastoma irrespective of the suggestive histological features. Also, the term "glioblastoma" is no longer used in the pediatric setting. [26]

Histopathologic slide demonstrating a glioblastoma Histopathologic slide demonstrating a glioblastoma multiforme.
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