Chapter 13. Neuro-oncology
A 78-year-old woman is brought from a nursing home facility with an 8-month history of worsening daily headaches, occasional nausea and emesis, and a 10-day history of worsening gait and recurrent falls. The family further reports progressive decline in cognitive function. Neurological examination reveals bradylalia but no focal motor or sensory abnormalities.
An MRI of the brain shows an irregular mass with a heterogenous intensity crossing the corpus callosum to involve both cerebral hemispheres. The mass has thick margins, areas of necrosis, and surrounding vasogenic edema. Which of the following is the most likely diagnosis?
(B) Arteriovenous malformation
(D) Low-grade astrocytoma
(E) High-grade astrocytoma
(E) High-grade astrocytoma. Cerebral malignant primary tumors account for approximately 1.4% of all types of cancer in the United States. The most common malignant primary brain tumors arise from the glia and include astrocytomas, oligodendrogliomas, and ependymomas. The World Health Organization uses histological criteria to classify primary brain tumors into four grades, with an increasing severity of malignancy. Prognosis is generally less favorable with grades III and IV.
The highest grade-classified astrocytoma is glioblastoma multiforme (GBM), with typical tumor necrosis on pathological evaluation, as seen in the patient described in this clinical vignette. Hemorrhage is also a common finding, occurring in 19% of patients.
On T2 sequences, a GBM appears as a mass with heterogeneous intensity as a result of central necrosis, hemorrhage, hypervascularity, and edema. The neovascularization of a GBM contributes to its contrast enhancement on MRI. A GBM disseminates along the white matter tracts and may cross the corpus callosum to involve the contralateral hemisphere, generating the classically described butterfly lesion.
On MRI, a cerebral abscess (choice A) has true restricted diffusion with a low signal on apparent diffusion coefficient. On T2/FLAIR, the core of an abscess is hyperintense, with an intermediate to slightly low signal rim. On T1 imaging, the center of the abscess is hypointense, with ring-enhancement after gadolinium administration. Arteriovenous malformation (choice B) is better demonstrated on a angiographic studies, showing feeding arteries, nidus, and draining veins in what is deemed a “bag of worms” appearance. Meningiomas (choice C) typically appear as extra-axial masses with a broad dural base or tail. Meningiomas typically appear isointense on both T1 and T2 imaging, with vivid homogeneous enhancement. (Hartmann, 1738–1742; Rosenfeld, 406–408; Lee JH)
Hartmann M, Jansen O, Heiland S, et al. Restricted diffusion within ring enhancement is not pathognomonic for brain abscess. AJNR Am J Neuroradiol. 2001;22:1738–1742.
Rosenfeld M, Pruitt A. Management of malignant gliomas and primary CNS lymphoma: standard of care ...