P44-T Axonal excitability properties of bulbar-dominant amyotrophic lateral sclerosis

Abstract

Background Isolated bulbar palsy (IBP) is a rare regional variant that can show a relatively benign course, while progressive bulbar palsy (PBP) has recently been regarded as a bulbar-dominant type of classical amyotrophic lateral sclerosis (cALS). This study aimed to identify differences in the excitability properties between IBP and PBP. Material and methods We consecutively collected both clinical and electrophysiological data of 22 ALS patients for 9 years at two university-based hospitals. An automated nerve excitability test (NET) utilizing the threshold-tracking technique was applied to measure the strength–duration time constant, parameters of threshold electrotonus (TE), the current–threshold relationship, and the recovery cycle. The axonal excitability properties were compared in 13cALS, 5PBP, and 4IBP patients to those in 25 normal controls. Results Compared to controls, the cALS group showed a more change in the depolarizing phase of TE (90–100 ms) (53.3 ± 1.3 [mean ± SEM] for the ALS group and 49.0 ± 0.7 for the control group, P Conclusions This study identified that the excitability properties of IBP and PBP differ from those of cALS. The pattern of NET in PBP was more similar to that in cALS than IBP. These findings suggest that IBP is a different entity to bulbar-dominant ALS or PBP.