Signs of autonomic arousal precede tilt-induced psychogenic nonsyncopal collapse among youth

Characterizing the physiologic changes leading up to psychogenic nonsyncopal collapse (PNSC) may help to elucidate the processes that cause paroxysmal functional neurological symptom disorders and to clinically distinguish PNSC from syncope. Thus, we aimed to characterize preictal sweat rate, heart rate, and systolic blood pressure changes among patients with tilt-induced PNSC compared to patients with tilt-induced neurally mediated syncope. The presence of increased preictal sweating was compared between groups. Heart rates and systolic blood pressures were compared from the recumbent and tilted baselines to the periods 120 s and 30 s prior to PNSC and syncope. Patients with PNSC (n = 44) were more likely than patients with syncope (n = 44) to have preictal increases in sweating, n = 31 (70.5%) versus n = 21 (47.7%), p = 0.03, although all patients with syncope eventually developed a sweat response. Comparing the recumbent baseline to the period 30 s prior to PNSC, blood pressure (112 ± 9 versus 129 ± 13 mmHg, p < 0.001) and heart rate (76 ± 12 versus 119 ± 22 bpm, p < 0.001) increased. Similarly, comparing the tilted baseline to the period 30 s prior to PNSC, blood pressure (118 ± 12 versus 129 ± 13 mmHg, p < 0.001) and heart rate (95 ± 15 versus 119 ± 22 bpm, p < 0.001) increased. Preictal blood pressure and heart rate differed significantly between patients with PNSC and patients with syncope. In conclusion, signs of autonomic arousal (increased sweating, heart rate, and blood pressure) often precede tilt-induced PNSC. Sweating prior to fainting may not be useful in distinguishing PNSC from neurally mediated syncope.