A 69-year-old woman suffering from Parkinson's disease for 22 years was admitted 
because of frequent occurrence of paroxysmal dyspnea for 3 months. Her dyspneic 
attacks consisting of inspiratory stridor and cyanosis occurred mainly during 
the wearing-off time and continued for less than 30 min. During nonictal period 
her respiration and phonation were normal and endoscopic investigation of the 
vocal cord and upper respiratory tract revealed no abnormality. Based on these 
findings, she was diagnosed to have focal laryngeal dystonia. The 24-hr 
monitoring with pulseoxymeter recorded frequent occurrence of paroxysmal 
asymptomatic hopoxemia during both daytime and sleep. With the treatment of 
tracheostomy and the reduction and alteration of anti-Parkinsonian drugs, 
dyspneic attacks disappeared gradually. We also confirmed the complete 
disappearance of paroxysmal asymptomatic hopoxemia with the 24-hr monitoring by 
pulseoxymeter, which is considered to be a useful method for early detection of 
asymptomatic focal laryngeal dystonia.