RESPIRATORY ELECTROPHYSIOLOGICAL STUDIES IN GUILLAIN-BARRE-SYNDROME

Respiratory failure is a common and potentially life threatening compl ication in patients with Guillain-Barre syndrome. The incidence of phr enic nerve involvement and the predictive value of phrenic nerve condu ction and diaphragmatic needle EMG were studied in 40 patients with Gu illain-Barre syndrome within the first three days of admission to hosp ital. The negative peak onset latency of the diaphragmatic compound mu scle action potential (CMAP), and its amplitude, duration, and area we re abnormal in 83%. The need for ventilation was correlated with diaph ragmatic CMAP amplitude (P = 0.005), and area (P = 0.001), but not wit h latency or duration. Abnormalities in diaphragmatic needle EMG were found in 45%, mainly a decreased number of motor unit potentials. The abnormalities correlated with the need for ventilation (P = 0.013). Of the 40% who required ventilation, all had either abnormal phrenic con duction, abnormal diaphragmatic needle EMG, or both. Eighty one per ce nt of the ventilated patients had abnormal forced vital capacity on th e day of the electrophysiological examination. The results indicate th at phrenic nerve conduction studies and diaphragmatic EMG are useful i n detecting respiratory involvement in patients with Guillain-Barre sy ndrome and in identifying those at risk of respiratory failure.