eFIGURE 75.1 Lateral neck radiograph of a child with epiglottitis Note the swollen epiglottis, often referred to as the “thumb sign” (arrow ) and ballooning of the hypopharynx (A ) eFIGURE 75.2 Lateral neck radiograph of a child with a retropharyngeal abscess Note the widened prevertebral/retropharyngeal space (A ) CHAPTER 76 ■ SYNCOPE THOMAS B WELCH-HORAN, ROHIT SHENOI INTRODUCTION Syncope is a sudden, brief loss of consciousness and postural tone caused by transient global cerebral hypoperfusion and characterized by complete recovery Presyncope is a feeling of impending sensory and postural changes without loss of consciousness Syncope is a common condition in childhood In the United States, it accounts for about 3% of pediatric emergency department (ED) visits The incidence peaks during the second decade of life, and about 30% to 50% of children experience syncope by the end of adolescence Girls are more commonly affected than boys The most common cause of syncope in children is vasovagal syncope, which is related to a loss of vasomotor tone and is generally benign Occasionally, the etiology may be a life-threatening cardiac condition When evaluating a child who presents to the ED with syncope, the goal is to assess whether high-risk conditions are present, or whether the symptoms can be attributed to a more benign etiology When normal individuals assume an upright position, cardiac output and cerebral arterial blood pressure (BP) are maintained by a combination of mechanical pumping activity of the skeletal muscles on venous return to the right atrium, the presence of one-way valves in the veins that facilitate venous return, arterial vasoconstriction caused by the baroreceptor reflex, and cerebral blood flow autoregulation If stroke volume is not maintained, then reflex sinus tachycardia develops Vasovagal syncope (also known as neurocardiogenic syncope) is believed to begin with excessive peripheral venous pooling that leads to a sudden decrease in peripheral venous return This results in increased cardiac contractility and baroreceptor and left ventricular mechanoreceptor firing, followed by an efferent response consisting of peripheral α-adrenergic withdrawal and enhanced parasympathetic tone The hallmark is vasodilatation and bradycardia with hypotension Sudden activation of a large number of mechanoreceptors in the bladder, rectum, esophagus, and lungs may also provoke such a response In orthostatic hypotension, often caused by fluid depletion, the compensatory responses and ensuing sinus tachycardia are insufficient to maintain brain perfusion, and syncope develops when the patient stands Syncope on exertion suggests a cardiac or cardiopulmonary cause, such as obstruction to left or right ventricular outflow or pulmonary hypertension In these conditions, cardiac output is unable to meet increased peripheral tissue needs Failure to increase cardiac output sufficiently, together with a fall in peripheral resistance during exercise, may lead to syncope on exertion There are three main categories of syncope: autonomic (vasovagal or neurocardiogenic), cardiac, and others ( Table 76.1 ) AUTONOMIC (VASOVAGAL OR NEUROCARDIOGENIC) SYNCOPE Autonomic syncope is the most common cause of syncope in children and adolescents, and accounts for almost 80% of cases It belongs to a group of neurally mediated syncope conditions in which there is a brief inability of the autonomic nervous system to keep BP and sometimes heart rate at a level necessary to maintain cerebral perfusion and consciousness Other conditions in this group include “situational” syncope, which may occur after micturition, defecation, hair grooming, coughing, or sneezing The precipitating causes for vasovagal syncope include prolonged standing, a crowded and poorly ventilated environment, brisk exercise in a warm environment, severe anxiety, perceived or real pain, and fear There are three clinical types In the first, there is marked hypotension (vasodepressor syncope) The second type is characterized by marked bradycardia (cardioinhibitory syncope) and in the third form, there is a combination of hypotension and bradycardia Some symptoms that herald a syncopal event include feelings of weakness, lightheadedness, blurring of vision, diaphoresis, and nausea Breath-holding spells, a type of vasovagal syncope, occur in older infants and toddlers and may be triggered by anger, pain, or fear There are two forms: cyanotic or pallid In the cyanotic form, the child holds his or her breath, turns cyanotic, and then loses consciousness In the pallid form, the loss of consciousness occurs before breath-holding Occasionally the child may have associated tonic or clonic motor activity CARDIAC SYNCOPE There are several cardiac conditions that can lead to syncope in children ( Table 76.1 ) They account for 1.5% to 6% of pediatric syncope The most important causes that may be associated with significant morbidity or death are discussed here Long QT Syndrome (LQTS) This is an important cause of syncope and sudden cardiac death in children without structural heart disease An abnormal electrocardiogram (ECG) obtained ... Syncope is a common condition in childhood In the United States, it accounts for about 3% of pediatric emergency department (ED) visits The incidence peaks during the second decade of life, and... cardiac conditions that can lead to syncope in children ( Table 76.1 ) They account for 1.5% to 6% of pediatric syncope The most important causes that may be associated with significant morbidity or