Electromyography of respiratory muscles in amyotrophic lateral sclerosis

We reviewed the records of 52 amyotrophic lateral sclerosis (ALS) patients examined between 1995 and 2000 who had needle electromyography (EMG) of the ir respiratory muscles, including the diaphragm, at or near the time of the ir diagnosis. With respiratory function testing, patients with abnormal dia phragmatic EMG at diagnosis (Group 1, n = 23) had significantly lower force d vital capacity (FVC), lower daytime arterial PO2 and higher PCO2 measurem ents (p < 0.05) than patients with normal diaphragmatic EMG (Group 2, n = 2 9). Twenty-eight percent of the patients without symptoms or signs of respi ratory insufficiency at the time they were examined had an abnormal diaphra gm EMG. Mean survival of Groups 1 and 2 were similar. However, sub-analysis of patients within each group, comparing those treated with non-invasive p ositive pressure ventilation (NIPPV) with those not treated, showed that tr eated patients in Group 1 (abnormal diaphragm EMG) survived significantly l onger (p < 0.05) than untreated patients. They also started NIPPV earlier t han treated patients in Group 2. We conclude that respiratory muscle EMG wa s simply and safely performed on ALS patients at or around the time of diag nosis. The procedure can detect sub-clinical respiratory muscle dysfunction . The technique used for EMG of the respiratory muscles, its pitfalls and c ontraindications are also reviewed. (C) 2001 Elsevier Science B.V. All righ ts reserved.