The mechanism of cough syncope

Although described in 1876 by Charcot, 1 the syndrome of cough syncope has until recently been considered a rare form of fainting. However, the excellent reports by Baker,2 Sharpey-Schafer,3 and Kerr and Derbes,4 indicate that the condition may not be uncommon. Despite increasing recognition of the syndrome, the mechanism producing the syncope remains elusive.4 Earlier investigators have suggested that this form of syncope is an epileptic equivalent5–7 or the result of a laryngeal reflex.6,8 These theories, however, have generally been abandoned in favor of a circulatory mechanism producing cerebral anoxia.9 It has been suggested that the cerebral anoxia might be the result of marked reflex peripheral vasodilation3 or a decreased cardiac output secondary to a reduced inflow or marked pulmonary vasoconstriction.10 These theories, though attractive, fail to explain completely certain unique features of this form of syncope. For example, syncope may develop with remarkable rapidity (3 to 5 seconds) after the onset of cough. With the cessation of cough, consciousness is rapidly recovered without vasomotor or other sequelae. The syndrome is rarely observed in women and syncope may occur in the supine or standing subject. The present report, based on observations made on normal individuals and patients with cough syncope, suggests a more acceptable mechanism for this type of fainting.