P38. Longitudinal sonographic alterations of the peripheral nerve structure in ALS

Abstract

Background We aimed to examine whether there are time-dependent alterations of the upper limb peripheral nerves’ structure in amyotrophic lateral sclerosis (ALS) applying high-resolution sonography and calculating various gray-scale measures. Material and methods This analysis included 69 ALS patients (mean [SD] age 63.9 [10.4] years, 62% male) that underwent at least two sonographic follow-up exams (FUs) (2 FUs n = 69, 3 FUs n = 31, 4 FUs n = 20, 5 FUs n = 11, 6 FUs n = 8, 7 FUs n = 4) of various distal and proximal segments of the median and ulnar nerve. Cross-sectional nerve area (CSA) and distinct gray-scale measures comprising median echo intensity (EI), echo variance (EV), hypo echogenic fraction (HF) and textural correlation (TCOR) were calculated. Repeated-measures ANOVA was conducted contrasting the first against the last available sonographic exam and comprising timespan between those two measures as a covariate. P-values were deemed to be significant at ⩽0.05. For every variable the slope β was calculated giving the unit and direction of change with respect to the timespan (in months) between last and baseline sonographic exam. Results During a mean [SD] disease duration of 6.6 [8.1] months ALS patients displayed alterations of all sonographic markers affecting various nerve segments comprising CSA (median nerve upper arm [UA] F(1) = 6.3, p = 0.02, β = −0.005), EI (ulnar nerve wrist [WR] F(1) = 6.1, p = 0.02, β = 0.1), EV (median nerve forearm [FA]; F(1) = 4.0, p = 0.05, β = 0.5; ulnar nerve WR F(1) = 13.2, p = 0.001, β = 0.5), HF (ulnar nerve WR F(1) = 3.2, p = 0.083, β = 0.01 [trend]) and TCOR (median nerve UA F(1) = 7.7, p = 0.009, β = −0.01; ulnar nerve FA F(1) = 6.3, p = 0.02, β = −0.005; ulnar nerve WR F(1) = 4.6, p = 0.04, β = −0.01). Conclusion In ALS, sonographic measures displayed peripheral nerve atrophy, EI and EV increase together with TCOR loss over the course of disease especially affecting nerve segments predominantly containing motor branches such as the upper arm median nerve or the wrist ulnar nerve. Findings seem to reflect peripheral nerve degeneration in terms of myelinated fiber loss and fibrous texture increase in ALS.