P5344Paradigme shift to disequilibrium in the genesis of orthostatic intolerance in patients with chronic fatigue syndrome

Abstract

Abstract Background Chronic fatigue syndrome (CFS) characterized by severe disabling fatigue and prolonging post-exertional malaise. The dysfunction of the central nervous system associated with myalgic encephalomyelitis (ME) has been postulated as the main cause of CFS. Orthostatic intolerance (OI) causes a marked reduction in the activities of daily living and impairs the quality of life in patients with ME/CFS. OI has been surmised to be a cardiovascular symptom with cerebral hypo-perfusion and exaggerated sympathetic nervous activation. Purpose Postural instability or disequilibrium may be involved in the etiology of OI because postural stability is an essential element for static balance. Methods The study comprised 72 patients with ME/CFS (18 men and 54 women; mean age, 37±10 years), who underwent neurological examinations and the active 10-min standing test. Results Disequilibrium defined as instability on standing with their feet together and eyes shut, was detected in 23 (32%) patients while postural orthostatic tachycardia in 16 (22%). Compared with 49 patients without disequilibrium, patients with disequilibrium more prevalently failed to complete the 10-min standing test (74% vs. 4%, p<0.01) and body sway was significantly more prevalently observed during the test (100% vs. 12%, p<0.01). The performance status score was significantly higher in patients with disequilibrium than those without it (median: 7 vs. 5, p<0.01), suggesting more severely restricted activity of daily living in the former. The prevalence of postural orthostatic tachycardia during the standing test was comparable between the patients with disequilibrium (23%) and those without it (22%, p=1.00). The 19 (26%) patients who failed to complete the 10-min standing test had disequilibrium more prevalently than those who completed it (89% vs. 11%, p<0.01). Performance status score was significantly higher in patients who failed to complete it than those who completed it (median: 6 vs. 5, p<0.01), suggesting more severe restriction of activity of daily living in the former. Significantly higher rates of disequilibrium (89% vs. 11%, p<0.01), unstable standing on one leg (84% vs. 17%, p<0.01) as well as abnormal tandem gait (79% vs. 11%, p<0.01) were noted in patients who failed to complete it than those who completed it. Body sway during the standing test was significantly more prevalently observed in the patients who failed to complete it than those who completed it (89% vs. 23%, p<0.01). The prevalence of postural orthostatic tachycardia during the standing test was comparable between the patients who failed to complete it and those who completed it (21% vs. 23%, p=1.00). Among the patients who failed to complete it 8 had the previous study records which revealed that 6 of them had completed it 6–24 months before when all the 6 patients had had no disequilibrium. Conclusion Disequilibrium should be recognized as an important cause of OI in patients with ME/CFS.