George H Kraft1, Katie T Singsank1*, Sarah B Simmons1 and James D Bowen2
Background: This Multiple Sclerosis (MS) is a Central Nervous System (CNS) disease characterized by demyelination or axonal loss encompassing several clinical subtypes—Relapsing-Remitting MS (RRMS), Secondary-Progressive MS (SPMS), and Primary-Progressive MS (PPMS). Strategies for treating progressive forms are limited, and better understanding of underlying pathophysiology is essential.
Method: Somatosensory Evoked Potentials (SEP) were analyzed for CNS conduction slowing caused by myelin impairment defined as 3 or more standard deviations, in 109 people with MS (16 with PPMS compared to 93 with RRMS and/or SPMS).
Results: People with RRMS and SPMS have a higher prevalence of CNS conduction slowing compared to PPMS (83.9% compared to 12.5% respectively, P<.001). Subgroup analysis suggests this is not due to differences in age at SEP, timing of SEP in disease course, or differences in disease severity at time of SEP.
Conclusion: CNS demyelination can be assessed by SEP and tends to be significantly less in patients with PPMS compared to RRMS or SPMS, despite similar levels of disability. This has important implications for underlying pathophysiology, suggesting that demyelination and axonal degeneration may independently contribute to disease progression.