Researchers recently identified a new sub-type of multiple sclerosis: myelocortical MS. This additional sub-type of multiple sclerosis adds clarity to the growing understanding of MS.
It was nearly 20 years ago that an international gathering of multiple sclerosis experts established the then-current classifications of MS. At that time, MS classifications included four types:
- Relapsing-remitting MS
- Primary progressive MS
- Secondary progressive MS
- Progressive relapsing MS
Since then, even more is understood about multiple sclerosis. For example, progressive relapsing MS (PRMS) no longer exists as a category. Instead, patients previously considered to have PRMS are now categorized as having primary progressive MS (with disease activity).
In addition, clinically isolated syndrome (CIS) has been added as a stand-alone classification. CIS is the first clinical presentation of MS, yet the type of MS is not yet known in these patients. Over time, as the CIS symptoms progress, the patient will be further diagnosed.
Now, back to the latest new sub-type: myelocortical MS. This form of MS is unique since it causes the loss of neurons, but there’s no accompanying damage to the brain’s white matter. All other types of MS are associated with white matter damage. This discovery has been somewhat perplexing to researchers, considering that the previous understanding was that neuron loss and demyelination occurred together. In this new sub-type, those processes are not necessarily connected. Unfortunately, this sub-type of MS can currently only be determined in a post-mortem examination of the brain.
The key takeaway from this research relates to future medication decisions. If a patient can be determined to have this type of MS (which is currently not possible) that would inform the selection of medications, with such a patient benefiting from a more tailored medication.
Trapp BD, Vignos M, Dudman J, et al. Cortical neuronal densities and cerebral white matter demyelination in multiple sclerosis: a retrospective study. The Lancet Neurology DOI:https://doi.org/10.1016/S1474-4422(18)30245-X