Split-hand index in amyotrophic lateral sclerosis: an F-wave study

Abstract

Objective: Split-hand sign is a useful clinical and electrophysiological feature in the diagnosis of amyotrophic lateral sclerosis (ALS). We proposed a novel split-hand index (SI) using F-wave persistence (FP) and assessed its diagnostic utility in ALS. Methods: Eighty-three consecutive ALS patients were recruited, and 50 healthy, age-, and height-matched volunteers were used as a control group. Compound muscle action potentials (CMAP) and FP were recorded from the abductor pollicis brevis (APB), first dorsal interosseous (FDI), and the abductor digiti minimi (ADM) muscles. The SI derived from FP was calculated using the following formula: SI_FP = (FP_APB ×FP_FDI)/FP_ADM. The sensitivity and specificity of SI_FP and SI_CMAP in differentiating ALS from healthy controls (HCs) were derived from receiver-operating characteristic (ROC) curve analysis. Results: Both SI_FP and SI_CMAP were significantly reduced in ALS patients. The ROC curve analysis indicated that both SI_FP and SI_CMAP reliably differentiated ALS from HCs [0.92 (95% CI: 0.88–0.95); 0.86 (95% CI: 0.82–0.91)], but SI_FP showed better diagnostic accuracy than SI_CMAP (p = 0.04), with a high sensitivity (81.2%) and specificity (97%). In subgroup analyses, SI_FP appeared to be a better variable than SI_CMAP for differentiation of ALS patients with normal CMAP from HCs, with an area under the curve of 0.87 (95% CI: 0.80–0.93), sensitivity of 69.4%, and specificity of 94%. Conclusion: The SI_FP reliably distinguished ALS patients from HCs and may be more sensitive for determining the split-hand pattern of ALS than SI_CMAP, particularly in the early stage of the disease.

Keywords:

• Amyotrophic lateral sclerosis
• compound muscle action potential
• F-wave
• split hand
• split hand index

Acknowledgments

We would like to thank the patients and their families for their kind participation in this study.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.

Additional information

Funding

This work was supported by the National Key Research and Development Program of China under Grant (2016YFC0905103); the Chinese Academy of Medical Sciences (CAMS) Innovation Fund for Medical Sciences (CIFMS) under Grant (2016-12M-1-004); the Strategic Priority Research Program (Pilot study) ‘Biological basis of aging and therapeutic strategies’ of the Chinese Academy of Sciences under Grant (XDPB10).