The Clinical and Electroencephalographic Spectrum of Tilt-Induced Syncope and "Near Syncope" in Youth

BACKGROUND: The aim of the study was to characterize the clinical and electroencephalographic (EEG) patterns associated with tilt-induced reflex syncope and delayed orthostatic hypotension without syncope in youth. METHODS: We conducted a prospective observational study of 95 patients referred to a pediatric neurology clinic for head-upright tilt testing. Clinical signs, symptoms, video EEG, and continuous blood pressure and heart rate were monitored. RESULTS: Eighty patients had reflex syncope, and 15 had delayed-onset hypotension without syncope. The mean age was 15.3 (standard deviation +/- 2.3) years; 75 (78.9%) were female. All patients with hypotension only had corresponding signs and symptoms; 13 (86.7%) had corresponding EEG slowing. The duration of EEG slowing with hypotension far exceeded the presyncope interval from onset of slowing to loss of consciousness among patients with syncope (P < 0.001). Although prior near-syncope and presyncope episodes were reported commonly in both groups, patients with delayed hypotension without syncope were less likely to have experienced loss of consciousness during episodes of orthostatic intolerance (P < 0.001). Patients with syncope had either slow-flat-slow (n = 23) or slow-only (n = 57) EEG patterns. Compared to those with slow-only EEG patterns, patients with the slow-flat-slow pattern had greater rates of asystole (P < 0.001), myoclonic movements (P < 0.001), facial grimace (P = 0.003), vocalizations (P = 0.002), and arm flexion (P < 0.001) or extension (P = 0.006) during tilt-induced syncope. CONCLUSIONS: Among otherwise healthy youth, orthostatic signs and symptoms vary across the spectrum of tilt-induced reflex syncope and delayed hypotension without syncope. Delayed hypotension without syncope may represent the poorly defined phenomenon of "near syncope" in some patients.