BREATHING PATTERN AWAKE AND ASLEEP IN PATIENTS WITH MYOTONIC-DYSTROPHY

Patients with myotonic dystrophy often have an irregular pattern of br eathing at rest, implying abnormality of breathing control No central medullary defect has been found in such patients, We postulated that i rregular breathing in myotonic dytrophy due to abnormal central respir atory output would persist during slow-wave sleep, We examined the pat terns of breathing whilst awake and asleep in seven patients with myot onic dystrophy, seven similarly weak nonmyotonic subjects and seven no rmal controls, Polysomnography was performed, and the coefficients of variation (CoV) of the breath intervals were analysed during different stages of sleep, The myotonic group showed significantly greater vari ation in breath intervals than the other two groups whilst awake (medi an CoV 37 vs 18% for nonmyotonics) and during light sleep (31 vs 13%). This difference was not evident during slow-wave sleep (median CoV 12 vs 9% in nonmyotonic) We conclude that irregular breathing in patient s with myotonic dystrophy whilst awake and during light sleep, does no t persist during slow-wave sleep, These results suggest that ''behavio ural'' influences play a role in the abnormal breathing pattern found in myotonic dystrophy, The source of the irregular breathing is unlike ly to be found in the medulla, but may originate from forebrain influe nces.