Neuroradiology #40

EDiR Holders

8 months ago

Clinical Data

19-year-old female presents to the neuro-emergency department with:

Right-sided hypesthesias and sensorimotor aphasia
Subacute onset: the symptoms did not develop extremely quickly as we would expect in a stroke
Unremarkable past medical history (mild gastroesophageal reflux)
Non-contrast CT was ordered

Describe the findings:

An ill-defined hypodense lesion primarily located in the deep white matter of the left parietal lobe.

MRI was performed:

FLAIR / T1 FFE / DWI / ADC / T2 / T1 FFE post-contrast AX / SAG / COR

MRI was performed (superior slices):

What are the top 3 differential diagnoses for lesions involving the corpus callosum?

Glioblastoma (formerly known as glioblastoma multiforme/GBM).
Primary CNS lymphoma.
Demyelinating disorders (multiple sclerosis…).

Did the MRI help in narrowing your differential?

A T2/FLAIR hyperintense lesion with enhancement was seen in the mentioned location and it was reported as representing either lymphoma or GBM in the conclusion of the MRI by the neuroradiologist.

Does the lesion have a complete or incomplete rim of enhancement?

The lesion has an incomplete rim of enhancement.

What type of enhancement would you expect in the top 3 differential diagnoses?

Glioblastoma: complete ring, irregular enhancement.
Primary CNS lymphoma: homogeneous enhancement. (In immunocompetent patients)
Demyelinating disease: incomplete ring enhancement.

A small digression:

A well-known mnemonic for remembering ring-enhancing CNS lesions is…

MAGICAL DR

M = Metastasis
A = Abscess
G = Glioblastoma (or other high-grade gliomas)
I = Infarct (subacute phase may show enhancement)/Infections (others – non-pyogenic pathogens: Mycobacteria, Toxoplasmosis, Cysticercosis, Cryptococcus)
C = Contusion and resolving hematomas
A = AIDS related: again, non-pyogenic infections (Cysticercosis, Cryptococcus)
L = Lymphoma
D = Demyelinating disease
R = Radiation necrosis

Can demyelinating disease simulate CNS tumors?

These lesions can closely resemble CNS tumors, and in such cases, they are referred to as tumefactive demyelinating lesions.

Back to our case:

Another odd thing was overlooked.

Do you notice it on the T2-weighted image?
Does it additionally help narrowing the differential?

We see concentric rings at the periphery of the lesion.
Alternating hyper- and hypo-intense bands. Resembling the layers of an onion bulb.

Meanwhile:

The patient was admitted to neurosurgery.
Thinking it was a tumor, the neurosurgeons resected most of the lesion.
The histological diagnosis was not consistent with GBM or lymphoma. It mentioned a focus of leukoencephalitis with fiber destruction.
While ad definitive diagnosis was not provided by the pathologists: it was presumed, however, that the lesion represented “some sort of demyelinating disease or MS”.

The bands were seen on multiple MRIs

2 weeks after the initial MRI, before surgery (performed as part of pre-op MR tractography).
T1 GRE sag and ax, without contrast.

After surgery (2 days after the previous MRI).
T2WI sag and ax.

1 year after the first presentation, after surgery.
T2WI ax and FLAIR cube sag.

The bands are quite obvious on all MRI examinations.

The alternating bands are characteristic of what disease?

The “onion bulb” or “bullseye” appearance is characteristic of Baló concentric sclerosis.

This is a case of Baló concentric sclerosis, a rare demyelinating disease, often considered a variant of multiple sclerosis (MS).
Unlike conventional MS, the clinical course of Baló’s sclerosis is typically monophasic, with more severe symptoms during a single episode of demyelination. Our patient has not developed additional focal neurological deficits or new lesions outside of the previously operated area.
The hallmark MRI findings are the “onion bulb” or “bullseye” appearance, most clearly seen on pre-contrast T1- and T2-weighted images. Similar to other demyelinating disease, contrast enhancement usually appears as an incomplete open ring. DWI might show diffusion restriction during the episode of active demyelination (representing in most part intramyelinic edema).
This case serves as a reminder thta, when faced with a complex diagnosis, it‘s important to pause,reflext and ask key questions.
Asking the right questions at the right time might help you to narrow the list of your differential diagnoses and rule out other possibilities.
In our case, if the possibility of tumefactive demyelination had been considered based on the pre-operative imaging, the extensive surgery could have been avoided.
The three most common tumor or tumor-like lesions of the corpus callosum are glioblastoma, primary CNS lymphoma and demyelinating disorders. Corpus callosum is composed of dense white matter tracts, that make it hard for hematogenous metastases to deposit in that area, so they are rarely seen in this region and not on the top of your differentials. The abundance of white matter tracts probably explains, however, why predominantly white matter diseases affect this region – namely glioblastoma and demyelinating diseases. CNS lymphoma has a predilection for periventricular regions, corpus callosum being one of those regions.
Enhancement can help in differentiating the three entities, with classically glioblastoma having irregular ring enhancement or heterogeneous enhancement, lymphoma having homogenous enhancement and demyelinating diseases having the open ring enhancement.
Knowing the epidemiology can also be helpful. Glioblastoma and CNS lymphoma are seen in slightly older/older patients (>40 years), with a slight male predominance. Tumefactive demyelinating lesions have, similar to other demyelinating disorders, a younger age of onset (<40 years) with a female predominance. Our patient was a female in her late teens.