Neurophysiological indices in amyotrophic lateral sclerosis correlate with functional outcome measures, staging and disease progression

Objective: This study examined neurophysiological (NI), split-hand (SI) and split-leg (SLI) index in patients with amyotrophic lateral sclerosis (ALS), and their correlation with functional status, disease duration, staging and survival.

Methods: Eighty-two patients underwent nerve conduction study to analyze NI, SI and SLI. Amyotrophic Lateral Sclerosis Functional Rating Scale-Revised (ALSFRS-R), disease progression rate (ΔFS), Milano-Torino (MiToS) and King's staging systems, Forced Vital Capacity (FVC), and survival data were collected.

Results: Both NI and SI indices were significantly associated with ALSFRS-R, MiToS, King's and FVC. Slow progressor patients (ΔFS < 0.5) reported a significantly higher NI and SI values compared to both normal (0.5 ≤ ΔFS < 1.00) and fast progressors (ΔFS ≥ 1.0). After dichotomizing patients in slow progressors (ΔFS < 0.5) and not-slow progressors (ΔFS ≥ 0.5), a combination of SI index and disease duration revealed to be the best prediction model to discriminate patients in accordance with their disease progression (c-index: 0.92), leading to a new prognostic index: the 'Split-Hand prognostic index' (SHpi).

Conclusion: SI and NI are correlated with functional status and FVC. SHpi index could represent an useful tool to discriminate patients in accordance with their disease progression.

Significance: These data provide novel evidence of neurophysiological indices as promising biomarkers in ALS.