Presentation
The patient, with no past medical history, presents with severe headache and new left visual changes over a 24-hour period. She reports preceding symptoms, including 1 week of developing cough with associated fever, headache, lightheadedness, and intermittent blurry vision.
Patient Data
Unenhanced CT of the head displays marked edema centered in the right parietal and occipital lobes. The swelling extends subtly across the splenium of the corpus callosum and into the ipsilateral mesial temporal lobe.
There is an extensive regional mass effect with effacement of the adjacent cortical sulci and partial effacement of the right lateral ventricle. There is no evidence of hemorrhage or calcification.
MRI better delineates the extent of the disease. We see a marked mass-like T2/FLAIR signal abnormality centered in the right parieto-occipital white matter. Signal abnormality extends across the splenium of the corpus callosum and into the posterior right mesial temporal lobe. Mass effect is similar to the same-day head CT, with regional cortical and lateral ventricular effacement.
On diffusion, we see mostly T2-shine through effects, as evidenced by hyperintensity on ADC maps.
Following contrast administration, we see marked heterogeneous enhancement, particularly along the periphery of the lesion. The post-contrast MP RAGE better characterizes the speckled and linear perivascular enhancement of the lesion than the post-contrast with fat suppression. SWI shows subtle punctate and fine linear hypointensity corresponding to the areas of enhancement, suggesting of microhemorrhage.
The next day, contrast-enhanced brain MRI with advanced imaging techniques shows marked interval progression from the prior study obtained 24 hours ago. T2/FLAIR signal abnormality has progressed, now extending across the body of the corpus callosum, into the left parietal white matter, along the posterior left mesial temporal lobe, as well as into the right gangliocapsular and thalamocapsular regions. The mass effect has also worsened, with greater cortical and ventricular effacement, a new leftward midline shift, and right uncal herniation. Additionally, new temporal horn enlargement is suggestive of early ventricular entrapment.
Diffusion imaging shows dominant T2 shine-through effects with minimal speckled true diffusion restriction along the superoanterior margin. No GRE or SWI sequence was obtained for this study.
Following contrast administration, we better characterize the extensive speckled and perivascular enhancement along the periphery of the mass.
The advanced imaging techniques show no elevation in relative cerebral blood volume during perfusion. Permeability scan shows mild elevation in distribution volume (Ve) corresponding to the areas of enhancement.
The GRE obtained on the post-operative MRI shows speckled and fine linear hypointensity along the periphery of the lesion, and corresponding to previous areas of enhancement seen on the prior MRI. The findings on GRE are in a pattern and distribution not expected for post-operative change from the interval right parietal biopsy and decompressive hemicraniectomy.
We also see improved mass effects following decompressive hemicraniectomy.
Case Discussion
The imaging appearance is typical of a fulminant and hemorrhagic demyelinating disease. The key feature, in this case, to separate the diagnosis of acute hemorrhagic leukoencephalitis from the tumor is the rapid change in 24 hours. This rapid progression is too fast for malignancy such as lymphoma or glioblastoma. Other key imaging features include the speckled and perivascular peripheral enhancement (rather than solid or heterogeneous enhancement with necrosis), lack of elevation in cerebral blood volume (as expected in high-grade glioma and to a lesser extent lymphoma), lack of any central diffusion restriction with mild true restriction along the margin, and hypodensity on CT rather than density expected with lymphoma or heterogeneity usually seen with glioblastoma.
The patient went on to biopsy.
Histology:
Perivascular neutrophilic inflammation and macrophage infiltration with spreading into the brain parenchyma. There was associated destruction of the intraparenchymal venules obliterated by vascular necrosis, fibrin exudates, and neutrophilic debris. Ring-like perivascular hemorrhages encasing damaged small blood vessels and axonal damage were also seen.
No evidence of multinucleated giant cells, viral cytopathic effect/inclusions, or spongiform changes are noted. No parasitic organism is identified. No evidence of a hematolymphoid neoplastic process is seen.
Immunohistochemistry:
Immunohistochemical stains with adequate controls were performed. Neurofilament stains neuronal processes and highlights areas of axonal damage. CD68 and CD163 stains abundant macrophages and microglia. Luxol fast blue and neurofilament stains performed show both myelin loss and axonal loss, respectively, in areas with inflammation, consistent with tissue damage.
All positive and negative controls performed are adequate.
Final diagnosis: acute hemorrhagic leukoencephalitis.