Objective: The palmomental reflex (PMR) is commonly interpreted as a frontal release sign, but it has also been discussed as a clinical marker of motoneuron affection in amyotrophic lateral sclerosis (ALS). The aim of this study was to investigate the impact of motor dysfunction versus neurocognitive impairment on the appearance of PMR in amyotrophic lateral sclerosis (ALS). Methods: 97 patients with ALS and ALS-variants were enrolled in this prospective, cross-sectional study. PMR was examined in a standardized procedure and the neurocognitive profile was assessed using the Edinburgh Cognitive and Behavioral ALS Screen (ECAS). Disease severity and motor function were recorded using ALS Functional Rating Scale revised (ALSFRS-R) and standardized clinical assessment. Results: 52% of all patients had a positive PMR (PMR+). These patients showed more frequently signs of motor dysfunction in the bulbar region (p < 0.001), impaired cognitive performance in the ECAS ALS-specific score (p < 0.05), predominantly in executive functions (p < 0.01), as well as lower scores in ALSFRS-R (p < 0.05) compared to patients without PMR (PMR-). A multivariate logistic regression analysis revealed that bulbar involvement, executive function impairment, and a lower motor and respiratory (non-bulbar) ALSFRS-R significantly predicted PMR+ (all p < 0.05), with bulbar involvement being a stronger predictor than executive function impairment. Discussion: In this study, we showed that bulbar involvement is a much stronger predictor on the appearance of PMR compared to executive function impairment. PMR is therefore primarily a sign for bulbar involvement, rather than a sign for executive dysfunction in ALS patients.
Keywords: Amyotrophic lateral sclerosis; cognitive dysfunction; motoneuron disease; palmomental reflex.