Autonomic reflexes (ie, with orthostatic vital sign test, Valsalva test, and ice-water immersion test) were intact at rest, and the former two were absent during the episodes. He had normal heart rate variability between episodes. Due to his extremis with the episodes, we were unable to test his orthostatic response during one. He had an appropriate response to an adrenocorticotropic hormone stimulation test. His serum histamine, serotonin, VDRL, and 24-h urine 5-HIAA levels were normal. An arterial line was placed, and serum norepinephrine, epinephrine, dopamine, and total catecholamine levels were measured both during an episode and during quiescence (Table 1
). The results of a paraneoplastic antibody panel (ie, Ach receptor [muscle] binding antibody, striational antibody, Ca channel binding antibody N-type, Ca channel binding antibody P/Q-type, parietal cell antibody Tr, CRMP-5-IgG antibody, anti-neutrophil nuclear antibodies 1, 2, and 3, parietal cell antibodies 1 and 2, amphiphysin antibody, and Achr ganglionic neuronal antibody) were negative.