3111 Spontaneous bilateral vertebral artery dissection causing young adult ischaemic stroke: a case study of a novel <i>SMAD3</i> variant-related loeys-dietz syndrome

with alpha-synucleinopathy, 46 with autoimmune autonomic disorders, and 194 with peripheral neuropathy.Results Of 642 patients, 477 had nOH on AST or HUT (74.3%).Of these, 8.6% were identified only on HUT and 4% only on AST.Delayed OH was identified in 8.5% of cases on AST and in 4.5% of cases on HUT.Delayed OH was more commonly identified in patients with peripheral neuropathy and less commonly seen in patients with AAD.Patients with dOH had lower supine blood pressure (BP), smaller drop in last BP, lower orthostatic intolerance ratio, and greater rise in noradrenaline levels on upright tilt.Conclusion HUT and AST are complementary techniques in the recognition of nOH in patients with autonomic failure.Prolonged orthostatic challenges are useful for the detection of dOH, which appears to reflect milder sympathetic dysfunction in patients with autonomic failure.