Researchers uncover myelocortical multiple sclerosis, a new subtype of the disease that features neurodegeneration but lacks white matter myelin loss in the brain.
Multiple sclerosis (MS) is typically characterized as a disease of demyelination, in which immune cells destroy myelin and cause irreversible damage. For the first time, new findings have identified a novel subtype of MS that occurs without cerebral white matter demyelination.
Although it was previously believed that demyelination of cerebral white matter drives neuronal degeneration and disability in patients with MS, the findings provide evidence that demyelination and neurodegeneration may occur independently.
In the study, published in Lancet Neurology, researchers from the Cleveland Clinic identified a subtype of MS, called myelocortical MS (MCMS), that features neuronal degeneration but no white matter myelin loss in the brains of patients. In MCMS, part of the neurons become swollen and appear to be typical MS lesions indicative of white matter myelin loss on MRI, the researchers noted. Because it is indistinguishable from traditional MS on an MRI, MCMS was only diagnosed in post-mortem tissues.
Brains and spinal cords were collected from 100 patients between May 1998 and November 2012, and the retrospective study was conducted between September 2011 and February 2018. The researchers found the subtype by analyzing the brain tissue from patients with MS after death and identifying 12 brains that did not have white matter demyelination. They compared microscopic tissue characteristics from the brains and spinal cords of 12 patients with MCMS, 12 traditional patients with MS, and individuals without neurological diseases.
Both MCMS and traditional MS patients had lesions in the spinal cord and cerebral cortex, but only traditional MS patients had lesions in the brain white matter, the researchers noted. Despite the lack of cerebral white matter demyelination, the researchers observed that MCMS brains had reduced neuronal density and cortical thickness, which is indicative of the brain degeneration also seen in traditional MS.
“We propose that myelocortical multiple sclerosis is a subtype of multiple sclerosis that is characterized by demyelination of spinal cord and cerebral cortex, but not of cerebral white matter,” the researchers concluded in the study.
The researchers further emphasized that the findings provide a better understanding of the individualized nature of the disease and may lead to more personalized diagnosis and treatments. More sensitive MRI imaging techniques could help identify this new subtype of MS in patients and allow treatment plans to be tailored more effectively.
“The importance of this research is 2-fold. The identification of this new MS subtype highlights the need to develop more sensitive strategies for properly diagnosing and understanding the pathology of MCMS,” Daniel Ontaneda, MD, clinical director of the brain donation program at Cleveland Clinic’s Mellen Center for Treatment and Research in MS, said in a press release. “We are hopeful these findings will lead to new tailored treatment strategies for patients living with different forms of MS.”
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Chen J, Nakamura K, Rudick RA, et al. Cortical neuronal densities and cerebral white matter demyelination in multiple sclerosis: a retrospective study. The Lancet Neurology. 2018. Doi: https://doi.org/10.1016/S1474-4422(18)30245-X
Cleveland Clinic Researchers Discover Novel Subtype of Multiple Sclerosis [news release]. 2018. https://newsroom.clevelandclinic.org/2018/08/21/cleveland-clinic-researchers-discover-novel-subtype-of-multiple-sclerosis/. Accessed August 22, 2018.