The etiologic relation between disequilibrium and orthostatic intolerance in patients with myalgic encephalomyelitis (chronic fatigue syndrome)

Abstract

Background: Orthostatic intolerance (OI) causes a marked reduction in the activities of daily living in patients with myalgic encephalomyelitis (ME) or chronic fatigue syndrome. Most symptoms of OI are thought to be related to cerebral hypo-perfusion and sympathetic activation. Because postural stability is an essential element of orthostatic tolerance, disequilibrium may be involved in the etiology of OI.

Methods and results: The study comprised 44 patients with ME (men, 11 and women, 33; mean age, 37±9 years), who underwent neurological examinations and 10-min standing and sitting tests. Symptoms of OI were detected in 40 (91%) patients and those of sitting intolerance were detected in 30 (68%). Among the 40 patients with OI, disequilibrium with instability on standing with their feet together and eyes shut, was detected in 13 (32.5%) patients and hemodynamic dysfunction during the standing test was detected in 19 (47.5%); both of these were detected in 7 (17.5%) patients. Compared with 31 patients without disequilibrium, 13 (30%) patients with disequilibrium more prevalently reported symptoms during both standing (100% vs. 87%, p=0.43) and sitting (92% vs. 58%, p=0.06) tests. Several (46% vs. 3%, p<0.01) patients failed to complete the 10-min standing test, and some (15% vs. 0%, p=0.15) failed to complete the 10-min sitting test. Among the seven patients with both hemodynamic dysfunction during the standing test and disequilibrium, three (43%) failed to complete the standing test. Among the 6 patients with disequilibrium only, 3 (50%) failed while among the 12 patients with hemodynamic dysfunction only, including 8 patients with postural orthostatic tachycardia, none (0%, p=0.02) failed.

Conclusions: Patients with ME and disequilibrium reported not only OI but also sitting intolerance. Disequilibrium should be recognized as an important cause of OI and appears to be a more influential cause for OI than postural orthostatic tachycardia in patients with ME.

Keywords: Chronic fatigue syndrome; Disequilibrium; Myalgic encephalomyelitis; Orthostatic intolerance; Postural orthostatic tachycardia.