Clinical Utility of Far-Field Potentials in Amyotrophic Lateral Sclerosis

Area of Science:

• Neurophysiology
• Neurology
• Biomarker Discovery

Background:

• Amyotrophic lateral sclerosis (ALS) diagnosis relies on clinical assessment and exclusion of mimics.
• Neurophysiological biomarkers are crucial for prognostic evaluation in ALS.
• Far field potentials (FFP) have emerged as potential reliable neurophysiological biomarkers in ALS.

Purpose of the Study:

• To evaluate the diagnostic utility of ulnar nerve FFP in distinguishing ALS from ALS-mimicking disorders.
• To assess the correlation of FFP amplitude with established neurophysiological and clinical markers of ALS progression.

Main Methods:

• Peripheral neurophysiological assessments in 62 ALS and 43 ALS-mimicking disorder participants.
• Ulnar nerve stimulation with recording of compound muscle action potentials (CMAP), FFP, and near field potentials.
• Analysis included split-hand index, neurophysiological index, MScanFit-MUNE, MUNIX, and receiver operating characteristic (ROC) analysis.

Main Results:

• FFP amplitude was significantly lower in ALS patients (5.07 mV) compared to ALS mimics (8.25 mV).
• FFP amplitude showed moderate-to-strong correlations with CMAP amplitude, split-hand index, neurophysiological index, MUNIX, and MScanFit-MUNE.
• ROC analysis indicated reliable distinction between ALS and mimics (AUC = 0.80), with consistent accuracy across ALS phenotypes.

Conclusions:

• Ulnar nerve FFP amplitude demonstrates diagnostic capability comparable to established neurophysiological biomarkers in ALS.
• FFP is a promising prognostic and diagnostic biomarker for ALS, with potential for clinical application.
• The simplicity and reproducibility of FFP complement traditional neurophysiological measures for ALS diagnosis and monitoring.