Clinical History
Previously healthy 54-year-old man saw his family physician complaining of a one-month presentation of spatial disorientation, auditory hallucinations, and short-term memory-loss.
Upon physical examination, the patient presents subtle right paresthesias, right hemianopsia and dyscalculia. Blood-analysis shows no relevant anomalies.
Brain imaging is indicated to discard organic cause.
Imaging Findings
Non-enhanced CT (NECT) demonstrates an area of hypodensity that affects bilateral occipital white matter through the corpus callosum splenium. An area of hyperdensity in the occipital horn of the left-lateral ventricle represents intraventricular haemorrhage.
A complementary multiparametric MRI shows the corresponding area to be hypointense in T1WI, hyperintense in T2WI and FLAIR. Mottled areas of signal drop in T2*WI, especially in the left-hemispheric component, correlate with the area of haemorrhage in NECT. DWI shows dispersed areas of diffusion-restriction.
Post-contrast imaging shows peripheral enhancement with no internal enhancement. An area of peripheral non-enhancement can be seen between the mass and the left-lateral atrium, probably corresponding to leakage of tumour necrosis/haemorrhage to ventricles. Perfusion-imaging shows increased rCBV in the periphery of the mass, with decrease in the central aspect.
MR-Spectroscopy (MRS) shows abundant lipids and lactate, increased Cho/Cr-ratio, and Myoinositol/glycine and Glx peaks.
Discussion
A. Background:
Glioblastoma multiforme (GBM), or grade IV-WHO astrocytoma, is the most malignant form of neuroepithelial tumour, and also the most common (especially in adults) [1, 2].
GBM may be primary, "de novo"; or secondary, as a malignization of lower-grade glial tumour. The differences between the two are both genetical and clinical. Summarizing, primary tumours frequently (40-50%) present EGFR-amplification, whilst this is rare in secondary tumours. The contrary happens with p53 mutation [1].
Clinical presentation of primary GBMs is more abrupt, probably originating from non-differentiated stem-cells, whilst secondary tumours arise in a more insidious manner, as a complication of a slower-growing lower-grade tumour [1].
Pathologically, GBMs have a high mitotic rate and are composed of different types of neuroepithelial cells with bizarre differentiation, along with necrosis and neovascularization [1, 2].
B. Clinical-Perspective:
The tumour may appear at any age, with slightly different forms of presentation depending on the time of onset. Primary GBMs incidence peaks at an older age (60-75 years) than secondary GBMs [1].
Most common symptoms at presentation include seizures, neurologic deficits and altered mental-status.
C. Imaging-Perspective:
On NECT, GBMs present as a centrally hypodense mass, with a higher-density periphery, often with changes of internal haemorrhage. Extensive peritumoral oedema might represent both vasogenic oedema and microinfiltration. Contrast-enhanced-CT (CECT) shows irregular peripheral enhancement with profuse vascularization [1, 2].
MRI shows as centrally necrotic mass, with high, heterogeneous signal intensity in FLAIR and T2WI. Internal T2*WI signal-voids often represent haemorrhage, vascularization and tumour-debris. Enhancement correlates with that of CECT, peripheral and delineating areas of necrosis [1-3].
Diffusion is commonly restricted in areas of the mass. Satellite foci of diffusion restriction or enhancement may represent tumoral dissemination, commonly following white matter tracts. This white-matter tract dissemination justifies the common bihemispheric trans-callosal "butterfly-glioma" presentation [1-3].
In MRS, the presence of lipids and lactate represents necrosis, suggesting GBM or metastasis. The presence of glial markers, such as Glx (glutamine-glutamate complex), and myoinositol will suggest a tumour of glial origin. In GBM, glycine is part of the lipid-necrosis component; this glycine superimposes itself with the myoinositol peak forming a Gly/Myo peak, typical of GBM [4].
D. Outcome;
Average survival is under one year, prolonged slightly in secondary GBMs. Tumour resection, followed by radio-chemotherapy is the standard management option when possible. This somewhat prolongs survival, with certain repercussions on quality-of-life [1].
E. Teaching-Points:
-High-grade aggressive tumour with terrible prognosis
-Typical: highly-cellular, enhancing and restricting periphery, with internal necrosis.
-White-matter-tract dissemination is typical, often through corpus callosum resembling a "butterfly"
Differential Diagnosis List
Glioblastoma multiforme
Primary CNS lymphoma
Corpus callosum metastasis
Cerebral toxoplasmosis (AIDS)
