A New Look at Demyelination and White Matter Density in Multiple Sclerosis

Myelocortical multiple sclerosis (MS), a subtype of MS, is set apart by demyelination of the spinal cord and the cerebral cortex but not of cerebral white matter. Cortical neuronal loss may be enhanced in myelocortical MS cortex compared with typical MS cortex, according to study results published in The Lancet Neurology.

Researchers examined the brains and spinal cords of deceased individuals with MS selected from the Cleveland Clinic rapid autopsy protocol. Brains were scanned using an MRI and then divided into hemispheres and matching slices. Of these, 12 brains did not have visible lesions in cerebral white matter or myelocortical MS. These brains and spinal cords were compared with those from 12 individuals with typical MS and 13 brains from individuals who did not have MS.

Cerebral white-matter lesions per hemisphere were considerably greater in the typical MS group (10.0 (4.5 to 19.0) compared with the myelocortical MS group (0.5 (0.0 to 1.0). The typical size of individual white-matter lesions was also considerably larger in typical MS hemispheric slices than in myelocortical MS hemispheric slices. Researchers found a significant increase in the spinal cord demyelinated area in typical MS compared with myelocortical MS. Compared with controls, neuronal densities in typical MS cortices were considerably decreased in layer V. However, this was not the case in layers III or VI. None of the 3 layers were considerably different in typical MS compared with myelocortical MS.

“We propose that myelocortical multiple sclerosis is a subtype of multiple sclerosis that is characterised by demyelination of spinal cord and cerebral cortex but not of cerebral white matter. Cortical neuronal loss is not accompanied by cerebral white-matter demyelination and can be an independent pathological event in myelocortical multiple sclerosis,” researchers concluded. Investigators also stressed the need for further studies on the molecular mechanism of MS.

Multiple authors declare associations with the pharmaceutical industry. Please see original reference for a full list of authors’ disclosures.

Reference

Trapp BD, Vignos M, Dudman J, et al. Cortical neuronal densities and cerebral white matter demyelination in multiple sclerosis: a retrospective study. Lancet Neurol. 2018;17:870-874.