Dynamic muscle ultrasound identifies upper motor neuron involvement in amyotrophic lateral sclerosis

The aim of the present study was to elucidate the pattern of change in bulbar muscles using ultrasound in patients diagnosed with amyotrophic lateral sclerosis (ALS).

Changes in the mylohyoid and geniohyoid muscle complex (mylohyoid-geniohyoid-muscle-complex) thickness were recorded while swallowing 5 ml of water using M-mode ultrasound in 30 ALS patients compared to 20 healthy controls. The ratio of mylohyoid-geniohyoid-muscle-complex thickness as determined by the maximum thickness of mylohyoid-geniohyoid-muscle-complex during swallowing divided by thickness at rest, was compared between ALS patients and controls, with the correlation between thickness ratio, echogenicity and clinical parameters assessed.

Overall, the thickness ratio in ALS patients was 1.39 ± 0.23 (mean ± SD) compared to 1.55 ± 0.17 in controls (p < 0.05). In sub-analysis, the thickness ratio was significantly decreased in ALS patients with bulbar-onset disease compared to those with limb-onset disease (p < 0.01) and controls (p < 0.01). Thickness ratio negatively correlated with the severity of upper motor neuron involvement in the bulbar region (p < 0.05).

Bulbar muscle ultrasound represents a novel method to detect impaired mobility and thereby provides an objective assessment of upper motor neuron involvement in the bulbar region of ALS patients.