Clinical Features of Isolated Bulbar Palsy of Amyotrophic Lateral Sclerosis in Chinese Population

BACKGROUND Progressive bulbar palsy (PBP) is a classic phenotype of bulbar onset amyotrophic lateral sclerosis (ALS) with more rapid progression and worse prognosis. However, as an often under-understood variant of ALS, isolated bulbar palsy (IBP) appears to progress more slowly and has a relatively benign prognosis. This study aimed to investigate the natural course and clinical features of IBP in Chinese population and to compare them with those of PBP. METHODS The clinical data of patients with bulbar onset ALS were collected from January 2009 to December 2013. Revised ALS Functional Rating Scale (ALSFRS-R), forced vital capacity (FVC), and follow-up evaluation were performed, and the differences in basic clinical features, ALSFRS-R, FVC, and primary outcome measures between IBP and PBP were analyzed. The independent t-test, Chi-square test, Mann-Whitney U-test, and Kaplan-Meier analysis were used. RESULTS Totally 154 patients with bulbar onset ALS were categorized into two groups, 33 with IBP and 121 with PBP. In the IBP group, the male to female ratio was 0.7 to 1.0, and the mean onset age was 58.5 years. The mean duration from the onset was 16.0 months, and the mean ALSFRS-R score was 43.4 at patients' first visit to our hospital. In 14 IBP patients performing FVC examination, the mean FVC value was 90.5% and there were only two cases with abnormal FVC. In 26 IBP patients completing follow-up, 15 (58%) suffered death or tracheotomy and the mean survival time was 40.5 months. Significant differences were noted in sex ratio, onset age, ALSFRS-R score, upper motor neuron limb signs, pure lower motor neuron (LMN) bulbar signs, FVC, and survival time between IBP and PBP. CONCLUSIONS IBP was evidently different from PBP, which was characterized with the predominance of female, pure LMN bulbar signs, an older onset age, a relative preservation of respiratory function, and a better prognosis.