We report the case of a nonobese and nonsmoking 51-year-old man with n
octurnal arterial oxygen desaturation that returned to normal after sp
henoidal meningioma resection, He presented an important daytime hyper
somnia and episodes of nocturnal apnea, without snoring, His arterial
blood gases, mechanical properties of the respiratory system, pulmonar
y diffusing capacity and chemosensitivity were normal, The most freque
nt causes of nocturnal hypoxemia are examined.