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Introduction/Aims: While amyotrophic lateral sclerosis (ALS) is primarily characterized as a motor system disorder, there is a growing body of evidence indicating sensory involvement. This study aimed to examine the hypothesis that somatosensory processing is impaired in ALS. Methods: Study participants were ALS patients followed at the Neuromuscular Outpatient Unit, as well as healthy volunteers, from March 2021 to July 2023. The Medical Research Council (MRC) sum score was calculated for nine muscle groups bilaterally. The clinical status of patients was evaluated with the ALS Functional Rating Scale‐Revised (ALSFRS‐R) and the Penn Upper Motor Neuron core. Somatosensory temporal discrimination thresholds (STDTs) were recorded on the medial and lateral parts of both hands. Somatosensory cortex excitability was investigated with the paired somatosensory evoked potentials (SEP) paradigm in a subgroup. Results: Increased STD values were detected in ALS patients compared to controls in both medial (107.66 ± 35 ms vs. 82.7 ± 32.5 ms, p =.001) and lateral (106.5 ± 34.5 ms vs. 82.9 ± 31.3 ms, p =.002) hands. There were no significant differences in STDTs among ALS patients across four regions (medial and lateral parts of the right and left hands). Amplitude ratios obtained from the paired‐pulse SEP paradigm were approximately 1 for all interstimulus intervals (ISIs). STDTs did not show any correlations with motor findings or scales. Discussion: Somatosensory processing appears to be compromised among ALS patients. The lack of correlation between impaired STDT and motor findings implies that it is a purely sensory deficit in ALS. [ABSTRACT FROM AUTHOR]

Objective: There is a need for sensitive biomarkers in amyotrophic lateral sclerosis (ALS), to enable earlier diagnosis and to help assess potential treatments. The main objective of this study was to compare two potential biomarkers, threshold‐tracking short‐interval cortical inhibition (T‐SICI), which has shown promise as a diagnostic aid, and neurofilament light chains (NfL). Methods: Ninety‐seven patients with ALS (mean age 67.1 ± 11.5 years) and 53 ALS mimics (aged 62.4 ± 12.9) were included. Mean disease duration was 14 months ±14.1. Patients were evaluated with revised ALS functional rating score (ALSFRS‐R), Penn upper motor neuron score (UMNS), muscle strength using the Medical Research Council (MRC) score and examined with T‐SICI, quantitative electromyography (EMG), and NfL measured in spinal fluid. Results: NfL increased with increasing UMNS (rho = 0.45, p = 8.2 × 10−6) whereas T‐SICI at 2.5 ms paradoxically increased toward normal values (rho = 0.53, p = 1.9 × 10−7). However, these two measures were uncorrelated. Discrimination between ALS patients and mimics was best for NfL (area under ROC curve 0.842, sensitivity 84.9%, specificity 83.5%), compared with T‐SICI (0.675, 39.6%, 91.8%). For the patients with no UMN signs, NfL also discriminated best (0.884, 89.3%, 82.6%), compared with T‐SICI (0.811, 71.4%, 82.6%). However, when combining NfL and T‐SICI, higher AUCs of 0.854 and 0.922 and specificities of 93.8 and 100 were found when considering all patients and patients with no UMN signs, respectively. Interpretation: Both T‐SICI and NfL correlated with UMN involvement and combined, they provided a strong discrimination between ALS patients and ALS mimics. [ABSTRACT FROM AUTHOR]

Introduction/Aims: The transcranial magnetic stimulation tests of short‐interval intracortical inhibition (SICI) by both conventional amplitude measurements (A‐SICI) and threshold‐tracking (T‐SICI) are important methods to investigate intracortical inhibitory circuits, and T‐SICI has been proposed to aid the diagnosis of amyotrophic lateral sclerosis. Beverages containing caffeine are widely consumed, and caffeine has been reported to affect cortical excitability. The aim of this study was to determine whether these SICI tests are affected by caffeine. Methods: Twenty‐four healthy subjects (13 females, 11 males, aged from 19 to 31, mean: 26.2 ± 2.4 years) were studied in a single fixed‐dose randomized double‐blind placebo‐controlled cross‐over trial of 200 mg caffeine or placebo ingested as chewing gum. A‐SICI and T‐SICI, using parallel tracking (T‐SICIp), were performed before and after chewing gum. Results: There was no significant change in SICI parameters after placebo in A‐SICI (p >.10) or T‐SICIp (p >.30), and no significant effect of caffeine was found on A‐SICI (p >.10) or T‐SICIp (p >.50) for any of the interstimulus intervals. Discussion: There is no need for caffeine abstention before measurements of SICI by either the T‐SICI or A‐SICI measurements. [ABSTRACT FROM AUTHOR]

Objectives: To compare the utility of conventional amplitude measurements of short-interval intracortical inhibition (A-SICI) with two threshold-tracking (T-SICI) methods, as aids to early diagnosis of amyotrophic lateral sclerosis (ALS). The new parallel threshold-tracking method (T-SICIp) was compared with the previously used serial tracking method (T-SICIs). Methods: 112 consecutive patients referred with the suspicion of ALS and 40 healthy controls were prospectively included. Based on clinical follow-up, patients were divided into 67 patients with motor neuron disease (MND) comprising progressive muscular atrophy (PMA) as well as ALS, and 45 patient controls. SICI was recorded from first dorsal interosseus muscle using the three different protocols. Results: MND patients had significantly reduced T-SICIp, T-SICIs and A-SICI, compared with healthy controls and patient controls, while healthy and patient controls were similar. Paradoxically, T-SICIp was least affected in MND patients with the most upper motor neuron (UMN) signs (Spearman ρ = 0.537, P < 0.0001) whereas there was no correlation for T-SICIs or A-SICI. T-SICIp also provided the best discrimination between patient controls and MND as determined by the receiver operating characteristic (ROC) curves. For patients with no UMN signs, area under ROC curve for 2-3ms inter-stimulus intervals was 0.931 for T-SICIp, 0.771 for T-SICIs and 0.786 for A-SICI. Conclusions: SICI is a sensitive measure for detection of cortical involvement in ALS patients. T-SICIp has higher sensitivity and specificity than T-SICIs and A-SICI, particularly in patients without any upper motor neuron signs. [ABSTRACT FROM AUTHOR]