MEPs and MRI Motor Band Sign as Potential Complementary Markers of Upper Motor Neuron Involvement in Amyotrophic Lateral Sclerosis

Abstract

Background

Amyotrophic lateral sclerosis (ALS) is characterized by the degeneration of both upper and lower motor neurons (UMNs and LMNs). Recognizing the involvement of UMNs is challenging because of the absence of reliable biomarkers beyond clinical evaluation.

Aim

To identify a reliable marker of UMN damage in a cohort of patients with ALS referring to the Motor Neuron Disease Clinic of the University Hospital of Padova.

Methods

We retrospectively evaluated the clinical records of 79 patients with ALS and compared the results of various investigations, including the motor-evoked potentials (MEPs), positron emission tomography–magnetic resonance imaging (MRI) and light neurofilaments (NfLs), with the degree of UMN clinical involvement, as assessed by the Penn Upper Motor Neuron Score (PUMNS).

Results

MEPs, considering the central motor conduction time (CMCT) values in both the upper and lower limbs, showed a significant correlation with the relative PUMNS subscores (p = 0.01, ρ = 0.4; and p = 0.005, ρ = 0.45, respectively). Additionally, there was a positive correlation between NfLs and PUMNS values (p = 0.04, ρ = 0.33). The presence of the motor band sign on MRI was associated with higher PUMNS values. Receiver operating characteristic analysis revealed that PUMNS accurately predicted abnormalities in CMCT values (specificity 86%, sensitivity 62%) and the presence of the motor band sign (specificity 58%, sensitivity 80%).

Interpretation

In our cohort of patients with ALS, CMCT values proved to be the most reliable test for assessing UMN involvement, albeit the presence of the motor band sign on MRI showed higher sensitivity.