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Imaging in Glioblastoma Multiforme

Overview

Glioblastomas (malignant glioma) are the most common adult malignant brain tumors, and 20% of all primary brain neoplasms are glioblastoma multiforme tumors. Glioblastoma multiforme (GBM; malignant glioma) is the highest-grade form (grad IV) of astrocytoma and makes up about two thirds of all brain astrocytomas.
Mortality associated with GBM is greater than 90% at 5 years, with a median survival of 12.6 months.
The prognosis for this tumor is at the extreme worst end because of its high-grade status.

See the images below

T1-weighted axial gadolinium-enhanced magnetic res

T1-weighted axial gadolinium-enhanced magnetic resonance image demonstrates an enhancing tumor of the right frontal lobe. Image courtesy of George Jallo, MD.

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T2-weighted image demonstrates the same lesion as

T2-weighted image demonstrates the same lesion as in the previous image, with notable edema and midline shift. This finding is consistent with a high-grade or malignant tumor. Image courtesy of George Jallo, MD.

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Preferred examination

Computed tomography (CT) scanning can demonstrate the tumor and associated findings; however, in making the glioblastoma multiforme (GBM; malignant glioma) diagnosis, CT scanning may cause small tumors to be missed. A small low-grade glioma that is missed with a screening study may eventually progress to glioblastoma multiforme (GBM; malignant glioma). In addition, this modality may not depict all multifocal lesions. Cerebrospinal fluid (CSF) spread, particularly early spread, may also be difficult to diagnose with CT scanning.

Magnetic resonance imaging (MRI) is significantly more sensitive to the presence of tumor, as well as its associated findings, in the inclusion of peritumoral edema, and is the modality of choice for the examination of a patient with suspected or confirmed glioblastoma multiforme (GBM; malignant glioma).
This lesion is a highly infiltrative tumor; thus, tumor cells are usually found beyond the margins of an area of abnormal signal intensity on MRIs. Central nervous system (CNS) metastases are frequent, but extracerebral metastases are rare.

After surgery, differentiating between recurrent tumor and scar tissue on the basis of MRI findings alone may be difficult. Positron emission tomography (PET) scanning is useful in this regard.

Because of the highly variable appearance of the tumor, it may sometimes mimic other conditions, such as an infarct, an abscess, or even a tumefactive plaque in multiple sclerosis, and thereby delay diagnosis. In terms of the imaging appearance and the appearance of a mass in the spectrum from low-grade astrocytoma to glioblastoma multiforme (GBM; malignant glioma), the following generalizations can be made (although some exceptions apply):

The incidence of calcification decreases in the spectrum from low-grade astrocytoma to glioblastoma multiforme (GBM; malignant glioma).

The incidence of enhancement increases in the spectrum from low-grade astrocytoma (preserved blood-brain barrier [BBB], low enhancement frequency) to glioblastoma multiforme (GBM; malignant glioma) (disrupted BBB).

Hemorrhage, necrosis, mass effect, and edema incidence patterns are the same as those for enhancement.

Unless hemorrhagic changes are present, most tumors are hypointense on T1-weighted MRIs and hyperintense on T2-weighted MRI.

Enhancement on CT scans means enhancement on MRIs.

Some forms of glioblastoma multiforme (GBM; malignant glioma) are considered variants. Giant cell glioblastoma (monstrocellular GBM) is a variant of GBM but has the same imaging findings as those of GBM.

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