General Neurology

Electrodiagnostic Clustering Identifies Prognostic Patient Subgroups in CIDP

Neurology Advisor Contributing Writer
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Demyelinated nerve. Coloured transmission electron micrograph (TEM) of a section through an axon (a structure that transmits nerve impulses to other nerve cells) that has lost its myelin sheath. The axon (red) has only its Schwann cell (brown) surrounding it. The Schwann cell would normally produce the myelin sheath. A nerve’s myelin sheath increases the speed at which it conducts electrical impulses and when the myelin sheath is lost, nerve function is impaired. This is seen in nerve disorders such as multiple sclerosis (MS), where patches (lesions) of myelin sheath are destroyed.
Electrodiagnostic data-driven clustering may help differentiate EDX features with prognostic implications in chronic inflammatory demyelinating polyneuropathy.

The use of electrodiagnostic, data-based clustering may be able to distinguish electrodiagnostic feature patterns among those with chronic inflammatory demyelinating polyneuropathy (CIDP), according to a study recently published in the Journal of Neurology, Neurosurgery & Psychiatry. Poor treatment response may not be predicted by reduced distally evoked compound muscle action potentials (CMAPs).

This retrospective study included electrodiagnostic and clinical data from 56 individuals with confirmed CIDP at 2 teaching hospitals. Standard surface electrode recording with electromyography technology and percutaneous supramaximal stimulation were performed for nerve conduction studies. Individuals were clustered into subgroups of similar electrodiagnostic features through the use of a hierarchical agglomerative clustering algorithm.

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Predictors of long-term outcome were analyzed using a stepwise logistic regression analysis. A chi-squared or Fisher’s exact test was used to compare categorical variables, while a Mann-Whitney U test was used to compare continuous variables.

The clustering algorithm resulted in two clusters, one of which was distinguished by significant conduction slowing and coexistent reduced distally evoked CMAP amplitudes.

Distal-acquired demyelinating symmetric polyneuropathy significantly overrepresented this cluster compared with the other (70% vs 26.1%; P =.042).

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This cluster was associated with 100% successful long-term treatment outcome, compared with 63% in the other cluster (P =.023). Poor long-term outcome was predicted by initial disability (odds ratio [OR] 6.1; 95% CI, 2.4-25.4), distal CMAP duration (OR 0.96; 95% CI, 0.91-0.99), and F-wave latency (OR 0.93; 95% CI, 0.86-0.98).

Limitations to this study include a retrospective and uncontrolled design, a lack of information on arm function in the modified Rankin scale, potential type I error inflation, and the potential for information loss due to a combination of values from multiple nerves.

The study researchers conclude that “clinical subtypes and long-term treatment outcomes were significantly different between the two [electrodiagnostic] data-based patient clusters, indicating the phenotypic and prognostic implications of the unsupervised approach.”

Reference

Baek S-H, Hong Y-H, Choi S-J, et al. Electrodiagnostic data-driven clustering identifies a prognostically different subgroup of patients with chronic inflammatory demyelinating polyneuropathy [published online March 23, 2019]. J Neurol Neurosurg Psychiatry. doi:10.1136/jnnp-2018-319758

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