EMG and Ultrasound of Respiratory Muscles and Respective Nerves and to Predict Respiratory Insufficiency in ALS

Amyotrophic lateral sclerosis (ALS) is a rare condition with progressing degeneration of upper and lower motor neurons. Main symptoms include muscle weakness, spasticity, atrophy and fasciculations, which lead to gait impairment, dysphagia, dysarthria and loss of hand dexterity. Currently no disease modifying treatment is available and the condition leads to death, usually within three to five years. Respiratory insufficiency is a common complication, especially in later stages of the disease. It results from weakness of respiratory muscles and in some cases also from chronic aspiration pneumonia. It decreases significantly quality of life and may shorten the survival. Not infrequently it is not accompanied by feeling of dyspnea but may be associated with other symptoms like tiredness, sleepiness, and depression. Survival and the quality of life can be improved with noninvasive ventilation (NIV), but the timing of detection of respiratory insufficiency and starting the therapy is crucial to achieve the best possible efficacy. The goal of this study is to assess the value of electromyography of respiratory muscles as well as the ultrasound of the diaphragm and nerves involved in respiration in predicting the onset of respiratory insufficiency. Electromyography is a method commonly used to confirm the diagnosis and neuromuscular ultrasound it is increasingly used along with electromyography to exclude mimics, especially in atypical cases. Investigators hypothesize, including nerves and muscles involved in respiration into electrophysiological and ultrasonographic testing may yield additional benefit of detecting actual or antecedent respiratory failure. The study will recruit 80 patients with definite or probable ALS. Investigations include electromyography of bilateral sternocleidomastoideus and rectus abdominis with assessment of presence of acute and chronic denervation. Ultrasonographic measurements include cross-sectional area and diameter of bilateral phrenicus, vagus and accessory nerves as well as diameter of diaphragm. Respiratory insufficiency is assessed with slow vital capacity and partial pressure of arterial oxygen and arterial carbon dioxide. Furthermore, ALS severity is assessed with revised ALS Functional Rating Scale and the symptoms which may reflect respiratory insufficiency even in the absence of dyspnea such as sleepiness, fatigue and depression are assessed with Fatigue Severity Scale, Epworth Sleepiness Scale and Hamilton Depression Rating Scale respectively. SVC and blood gases will be compared between group with and without denervation in investigated muscles. SVC and blood gases will be correlated with corssectional areas and diameters of investigated nerves and diaphragm as well as with the scores obtained in used scales and questionnaires.