Mechanism of micturition syncope

Daroff: Bradley’s Neurology in Clinical Practice, 6th ed.
Copyright © 2012 Saunders, An Imprint of Elsevier
Chapter 2 – Episodic Impairment of Consciousness
Joseph Bruni

Micturition syncope most commonly occurs in men during or after micturition, usually after arising from bed in the middle of the night to urinate in the erect position. There may be a history of drinking alcohol before going to bed. The syncope may result from sudden reflex peripheral vasodilatation caused by the release of intravesicular pressure and bradycardia. The relative peripheral vasodilatation from recent alcohol use and a supine sleeping position is contributory because blood pressure is lowest in the middle of the night. The syncopal propensity may increase with fever. Rarely, micturition syncope with headache may result from a pheochromocytoma in the bladder wall. Defecation syncope is uncommon, but it probably shares the underlying pathophysiological mechanisms responsible for micturition syncope. Convulsive syncope is an episode of syncope of any cause that is sufficiently prolonged to result in a few clonic jerks; the other features typically are syncopal and should not be confused with epileptic seizures. Other causes of situational syncope include diving and the postprandial state. Syncope during sexual activity may be due to neurocardiogenic syncope, coronary artery disease, or the use of erectile dysfunction medications.