Tuesday, 29 July 2014

MRI of tumefactive lesions

Did you present with tumefactive MS? #MSBlog #MSResearch

"In recent years I have become interested in the science and philosophy of how we define a disease. This may seem esoteric to you, but it is not and it has many practical implications. For example, saying someone has MS, or not, may affect their ability to get life-insurance or a pay-out from a critical illness policy."

"The paper below tackles the thorny issue of whether someone who presents with a tumefactive lesion that turns out on biopsy not to be a tumour, but an inflammatory demyelinating lesion. Another term for these lesions is pseudotumoural; i.e. the lesion mimics a tumour. The paper is trying to better define the so called clinico-pathological correlate, or more specifically the radiological-pathological correlate; i.e. what features on MRI can be used to predict the underlying pathology? Seven out of 9 of the cases went onto develop MS, i.e. they developed new lesions that fulfilled the McDonald diagnostic criteria for dissemination in time and space and no other aetiology could explain the presentation. One case was labelled as having acute hemorrhagic leukoencephalitis (AHLE) and another acute disseminated encephalomyelitis (ADEM). Unfortunately, the MRI findings were not specific enough to identify these latter two cases; hence there is no specific radiological-pathological correlate that can be used to help make a diagnosis. In short, this paper tells us that the MRI findings are non-specific when it comes to MS vs. ADEM/AHLE. The number of cases studied is small and hence the field may benefit from an International effort to pool cases."

"What does this mean for those of you reading this blog who presented with tumefactive MS? Unfortunately, nothing regarding your management or prognosis. What this paper highlights is that we academics like to describe and classify things. Sometimes we do this without a sound philosophical perspective. I would have designed this study differently and come at it from a different perspective. For one, I would have include a large number of cases who turned out to have tumours as a comparative group; the real question that needs answering is can we define any imaging features specific to mono-focal tumefactive MS that suggest the lesion is not a tumour? This may prevent unnecessary biopsies and hence has a clinical application. The second question is to differentiate those who will go onto to develop MS from those with ADEM or AHLE, which are monophasic MS. The latter will only Be answered by increasing the number of cases studied and by possibly looking at other biomarkers, e.g. CSF findings. "

J Neurol. 2014 Jul.

Background: Tumefactive demyelinating lesions (TDLs) can mimic brain tumors on radiological images. TDLs are often referred to as tumefactive multiple sclerosis (TMS), but the heterogeneous nature and monophasic course of TDLs do not fulfill clinical and magnetic resonance imaging (MRI) criteria for multiple sclerosis. 

Objective: Redefining TDLs, TMS and other inflammatory brain lesions is essential for the accurate clinical diagnosis of extensive demyelinating brain lesions. 

Methods: We retrospectively analyzed MRI from nine TDL cases that underwent brain biopsy. Patterns of gadolinium enhancement on MRI were categorized as homogenous, inhomogeneous, patchy and diffuse, open ring or irregular rim, and were compared with pathological hallmarks including demyelination, central necrosis, macrophage infiltration, angiogenesis and perivascular lymphocytic cuffing. 

Results: All cases had coexistence of demyelinating features and axonal loss. Open-ring and irregular rim patterns of gadolinium enhancement were associated with macrophage infiltrations and angiogenesis at the inflammatory border. An inhomogeneous pattern of gadolinium enhancement was associated with perivascular lymphocytic cuffing. Central necrosis was seen in cases of severe multiple sclerosis and hemorrhagic leukoencephalopathy. 

Conclusions: These results suggest that the radiological features of TDLs may be related to different pathological processes, and indicate that MRI may be useful in understanding their pathophysiology. Further investigation is needed to determine the precise disease entity of these inflammatory demyelinating brain lesions.

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