Multiple orofacial indices in amyotrophic lateral sclerosis

Abstract

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterized by significant speech and swallowing problems resulting from upper and lower motor neuron loss. Weakness is the primary ALS disease-related sign, and measures of muscle strength have revealed nonuniform patterns of muscle weakness in orofacial muscles. To a large extent, muscle strength measures in these studies have not been evaluated in terms of functional significance, and few researchers have addressed the relation between weakness and motor neuron loss. This study addressed whether multiple measures, including static isometric maximum voluntary contraction (MVC), a dynamic measure of the peak rate of change of force (PRCF), an upper motor neuron (UMN) index, and a functional disability score (FDS) might enhance understanding of speech dysfunction in ALS. Ten males diagnosed with sporadic ALS showing mild speech impairment and an equal number of matched controls were studied. Tongue MVC and PRCF were more impaired than those of the lip and jaw, irrespective of the time post onset and site of initial symptoms. Results also suggested that disproportionate tongue impairment may be related to UMN deficits. However, impairments in the rate of contraction did not appear to be related to UMN deficits. Tongue weakness and tongue and lower lip PRCF were related to the degree of speech severity, but none of the measures was related to speech intelligibility. The value of a functional outcome measure like speech intelligibility and its role in characterizing orofacial involvement in the early stages of ALS bulbar impairment are discussed.