Beyond Diagnosis: New Data Show Early Nerve Conduction Studies Predict Treatment Outcomes in CIDP

Thapat Wannarong, MD

Credit: US News

In a new analysis, findings show that early changes in nerve conduction study (NCS) variables can serve as reliable predictors of treatment outcomes in patients with chronic inflammatory demyelinating polyneuropathy. In addition, the study also showed that improvements in ulnar and fibular compound muscle action potentials (CMAPs), as well as fibular conduction velocity, were significantly associated with better neuropathy impairment scores and treatment response.¹

Overall, the study featured 39 individuals with CIDP who were identified through the 2021 European Academy of Neurology/Peripheral Nerve Society criteria, most of which received intravenous immunoglobulin (n = 36) as their first-line treatment. Results revealed that median neuropathy impairment scores (NIS) changes for patients considered responders and nonresponders on NIS were –28.0 versus 4.0 (P <.001) and ­–34.5 versus 12.0 (P <.001) at first and last follow-up, respectively.

The study was presented at the 2024 American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM) meeting, held October 15-18, in Savannah, Georgia, by Thapat Wannarong, MD, a neurologist in Rochester, Minnesota. Wannarong was among 10 others who received the President’s Research Initiative Award for the best submitted abstracts, chosen by the AANEM president each year.

"The changes in NCS parameters after treatment, particularly fibular CMAP amplitude changes, serves as both a robust indicator of current treatment response and a predictive biomarker for long-term outcomes," Wannarong told NeurologyLive. "This dual utility - diagnostic and prognostic - represents a significant advancement in CIDP management. The ability to predict treatment response through early NCS changes provides clinicians with an objective tool for treatment optimization and patient counseling."

Traditionally, the diagnosis of CIDP has been based on a combination of clinical symptoms, NCS findings that indicate demyelination, and other supportive criteria; however, prior to this study, there has been little work done on whether NCS can predict treatment outcomes. For context, the 2021 revision to the most widely adopted guideline on the diagnosis and treatment of CIDP included clinical and electrodiagnostic criteria for CIDP variants, updated supportive criteria, and sensory criteria as an integral part of the electrodiagnostic criteria.²

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In the new analysis, the patient cohort had a follow-up median of 39.5 months, with a median time to first follow-up of 4.9 months. Among those included, 26 had reduced NIS, considered responders, and 13 had either worsened or stable NIS, considered nonresponders.

Wannarong added, "The evidence strongly supports increased integration of early NCS monitoring in CIDP management. While baseline NCS studies are standard in diagnosis, our findings suggest that systematic early follow-up studies have significant prognostic value. The ability to predict treatment response through early NCS changes could facilitate more timely treatment modifications and improve patient outcomes. However, implementation would require standardization of testing protocols and timing to ensure reliable, reproducible results across different clinical settings."

Between the 2 groups, responders showed significant improvements in the amplitudes of CMAPs (1.0mV versus -0.4mV, p=0.036), fibular CMAPs (0.3mV versus -0.3mV, p=0.003), summated CMAPs (1.7mV versus -1.5mV, p=0.003), and fibular conduction velocity (3m/s versus -1m/s, p=0.034). Fibular CMAP amplitude changes were the only variable to show a negative correlation with NIS changes over the entire follow-up period (6 to ≥60 months, R -0.6 to -0.8, p≤0.003). Notably, three patients exhibited no fibular response at both baseline and follow-up despite improvements in their NIS, though all demonstrated ulnar and summated CMAP responses.

"The changes in CMAP amplitudes provide crucial insights into axonal function and reinnervation processes," Wannarong said. "Specifically, fibular CMAP amplitude emerges as a primary predictive biomarker, effectively differentiating between treatment responders and non-responders. In cases where fibular motor responses are absent, our data validates the use of ulnar and summated CMAP amplitudes as alternative markers. These findings have immediate clinical applications in:

• Optimizing immunotherapy protocols, particularly IVIG dosing and frequency
• Providing objective criteria for early identification of treatment non-responders
• Guiding timely introduction of second-line therapies
• Developing individualized treatment algorithms based on neurophysiological response patterns"

These improvements provide more detail, better structure, and clearer clinical implications while maintaining scientific accuracy."

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REFERENCE
1. Wannarong T, Skolka M, Swart G, et al. Early nerve conduction findings predict treatment outcomes in chronic inflammatory demyelinating polyradiculoneuropathy. Presented at: 2024 AANEM Annual Meeting; October 15-18; Savannah, GA. ABSTRACT 5
2. Doorn IN, Eftimov F, Wieske L, Schaik LN, Verhamme C. Challenges in the early diagnosis and treatment of chronic inflammatory demyelinating polyradiculoneuropathy in adults: current perpsectives. Ther Clin Risk Manag. 2024;14:20:111-126. doi:10.2147/TCRM.S360249