Blood Flow to the Head in a Person With Myalgic Encephalomyelitis Experiencing Postexertional Malaise: A Case Report

Purpose: Reduced cerebral blood flow (CBF) may play a role in the pathophysiology of postexertional malaise (PEM) in myalgic encephalomyelitis (ME). This case report aimed to determine the feasibility of measuring differences in blood flow to the head occur during PEM induced by 2-day cardiopulmonary exercise testing (CPET). Methods: One individual with ME and 1 nondisabled individual underwent a 2-day CPET to induce PEM. Blood flow was assessed using a novel in-ear device (Lumia Health), using photoplethysmography to estimate a relative flow index while participants were supine and during a 10-minute standing test before CPET. The person with ME showed a 34% decrease in work at the ventilatory anaerobic threshold (VAT), confirming PEM on day 2. During PEM, flow index decreased by 17% while supine and 23% during orthostasis compared to day 1. The nondisabled individual did not exhibit subjective or objective PEM (1% reduction in work at VAT) and experienced less than a 5% reduction in flow index while supine. Results and Conclusions: Reduced blood flow to the head during PEM may partially explain ME symptomatology. The novel in-ear device shows promise as a diagnostic and biofeedback tool, warranting further research in larger studies.