Systematic Review of the Literature on Definitions and Characterisation of MS Lesions

While inspecting the brain magnetic resonance imaging (MRI) scans from a sample of Multiple Sclerosis (MS) patients, blind to any clinical, cognitive and demographic information, it caught our attention the presence of ovoidal or circular, partially stellate, regions of signal intensities similar to that of the normal brain parenchyma in Fluid Attenuated Inversion Recovery (FLAIR) surrounded by hyperintensities in the periventricular region in a reasonable number of scans, seemingly corresponding in all cases to hypointense regions (i.e. with the same signal level of the cerebrospinal fluid) in T1-weighted. The ovoidal shape of these features, clearly distinctive due to their homogeneously lower signal with respect to their surroundings in the FLAIR sequence prompted us to refer them as FLAIR ‘pseudocavities’. The idea that they could be differentially distinctive and indicative of an underlying process of different aetiology from their surroundings is not implausible. Inversion recovery imaging can potentially discriminate among tissues based on subtle differences in T1 characteristics. Specifically, the FLAIR sequence exploits the fact that many types of pathology have elevated T1 and T2 values resulting from increased free water content compared to background tissue. Higher specific absorption rate due to additional 180 degrees, together with the increased dynamic range, and the additive T1 and T2 contrast, make FLAIR highly susceptible to differentially reflect subtle pathological processes (Bydder & Young, 1985).

We, hence, systematically reviewed the literature in the last 10 years (i.e. from March 1999 up to March 2019) to investigate the definitions of MS lesions used up to date and their characterisation, to establish if what we called “FLAIR ‘pseudocavities’” have been described previously. This dataset is conformed by an excel file (Microsoft excel 97-2003 (.xls)) with multiple worksheets which contain all the references found in the two databases explored (i.e. Medline and EMBASE), as well as the data extracted and the results of the analyses. Briefly, from just over a hundred studies that defined MRI lesions in MS, more than half characterised lesions based on the criteria that they were hyperintense on T2-weighted, FLAIR and PD-weighted series, and more than a quarter of the studies characterised lesions based on the criteria that they were hyperintense on T2-weighted, FLAIR and PD-weighted and that they were hypointense on T1-weighted series. The literature review confirmed that what we refer to as FLAIR ‘pseudocavities’ have not yet been acknowledged in the MS literature.
Note: The dataset contains a master excel spreadsheet with multiple worksheets. The data from each worksheet in the excel file is also provided as a .csv file

Shukru, Filiz; Valdés Hernández, Maria. (2019). Systematic Review of the Literature on Definitions and Characterisation of MS Lesions, 1999-2019 [dataset]. University of Edinburgh. Centre for Clinical Brain Sciences. https://doi.org/10.7488/ds/2715.