Barts-MS rose-tinted-odometer: ★★★★★ (neon tennis ball green #dfff4f)
Yet another study showing that there are abnormalities in the so-called normal-appearing white matter (NAWM) that precede the development of new MS lesions.
This supports the hypothesis that there is something in the brain tissue that triggers the development of lesions and relapses. Could this be a virus, like an isolated seed or flower in a field of wheat? Why do I say this? Firstly, when pwMS were treated with interferon-gamma, a cytokine that stimulates immune responses, they all had relapses. The interesting thing about these interferon-gamma-induced relapses is that they occurred in sites previously affected by MS. When I discussed this observation with the late Hillel Panitch, who was the principal investigator on the gamma-interferon trial, he thought that this observation was a fundamental observation and was telling us something important about MS.
Another observation that supports the abnormal field hypothesis is the rebound post-natalizumab. This suggests that whilst you keep T and B cells out of the nervous system with natalizumab the field (brain and spinal cord) becomes more abnormal and when you let these cells back in they detect the abnormal field and run amok trying to clear the field of the offending agent. This is what happens with IRIS (immune reconstitution inflammatory syndrome) and PML. When natalizumab is washed out the immune system finds the JC virus and tries to clear it by initiating an inflammatory process. Some of us think that rebound post natalizumab is simply IRIS in response to the virus that causes MS.
Other serial MRI studies have shown subtle changes in the white matter many weeks or months before a gadolinium-enhancing lesion appears.
These studies all suggest that the primary pathology is smouldering MS and is due to something in the nervous system that takes weeks or months to trigger a focal inflammatory lesion. The inflammation is secondary to what is causing the disease. The challenge for us all is to find out what the abnormality is that is causing these changes in the NAWM. I think the best chance we have of doing this is to study the brains of pwMS on natalizumab. To do this we will need someone with MS to die whilst on natalizumab treatment and to donate their brain to a unit with the necessary techniques to look for viruses. I think this will work because the viral load is likely to be higher in the absence of inflammation. This is why it is so important for pwMS to donate their brains for medical research.
If you are interested in more musing about the field hypothesis please read a previous post of mine from 2012 on this subject.
Well done to Emma Raducanu, whose US Open victory was a joy to watch. But best of all is her Twitter bio which contains just four words “london|toronto|shenyang|bucharest”. Another example of the pros of diversity, similar to the author list of the paper below “Colm Elliott, Parya Momayyezsiahkal, Douglas L Arnold, Dawei Liu, Jun Ke, Li Zhu, Bing Zhu, Ilena C George, Daniel P Bradley, Elizabeth Fisher, Ellen Cahir-McFarland, Peter K Stys, Jeroen J G Geurts, Nathalie Franchimont, Arie Gafson, Shibeshih Belachew”.
Brain Communications, Volume 3, Issue 3, 2021, fcab176.
Normal-appearing white matter is far from normal in multiple sclerosis; little is known about the precise pathology or spatial pattern of this alteration and its relation to subsequent lesion formation. This study was undertaken to evaluate normal-appearing white matter abnormalities in brain areas where multiple sclerosis lesions subsequently form, and to investigate the spatial distribution of normal-appearing white matter abnormalities in persons with multiple sclerosis. Brain MRIs of pre-lesion normal-appearing white matter were analysed in participants with new T2 lesions, pooled from three clinical trials: SYNERGY (NCT01864148; n = 85 with relapsing multiple sclerosis) was the test data set; ASCEND (NCT01416181; n = 154 with secondary progressive multiple sclerosis) and ADVANCE (NCT00906399; n = 261 with relapsing-remitting multiple sclerosis) were used as validation data sets. Focal normal-appearing white matter tissue state was analysed prior to lesion formation in areas where new T2 lesions later formed (pre-lesion normal-appearing white matter) using normalized magnetization transfer ratio and T2-weighted (nT2) intensities, and compared with overall normal-appearing white matter and spatially matched contralateral normal-appearing white matter. Each outcome was analysed using linear mixed-effects models. Follow-up time (as a categorical variable), patient-level characteristics (including treatment group) and other baseline variables were treated as fixed effects. In SYNERGY, nT2 intensity was significantly higher, and normalized magnetization transfer ratio was lower in pre-lesion normal-appearing white matter versus overall and contralateral normal-appearing white matter at all time points up to 24 weeks before new T2 lesion onset. In ASCEND and ADVANCE (for which normalized magnetization transfer ratio was not available), nT2 intensity in pre-lesion normal-appearing white matter was significantly higher compared to both overall and contralateral normal-appearing white matter at all pre-lesion time points extending up to 2 years prior to lesion formation. In all trials, nT2 intensity in the contralateral normal-appearing white matter was also significantly higher at all pre-lesion time points compared to overall normal-appearing white matter. Brain atlases of normal-appearing white matter abnormalities were generated using measures of voxel-wise differences in normalized magnetization transfer ratio of normal-appearing white matter in persons with multiple sclerosis compared to scanner-matched healthy controls. We observed that overall spatial distribution of normal-appearing white matter abnormalities in persons with multiple sclerosis largely recapitulated the anatomical distribution of probabilities of T2 hyperintense lesions. Overall, these findings suggest that intrinsic spatial properties and/or longstanding precursory abnormalities of normal-appearing white matter tissue may contribute to the risk of autoimmune acute demyelination in multiple sclerosis.
General Disclaimer: Please note that the opinions expressed here are those of Professor Giovannoni and do not necessarily reflect the positions of the Barts and The London School of Medicine and Dentistry nor Barts Health NHS Trust and are not meant to be interpreted as personal clinical advice.