In December 2000, researchers convened for two days of intense discussions on orthostatic intolerance (OI) in chronic fatigue syndrome (CFS), exploring the evidence for autonomic nervous system dysfunction, outlining the limits of current knowledge, and seeking to improve and accelerate future research.

The meeting was organized as a “scientific court,” a format used by the National Institutes of Health (NIH) to develop consensus statements on scientific issues, including research priorities for Gulf War illnesses.

Following a full day of presentations by recognized experts, an independent panel representing the fields of endocrinology, epidemiology, pediatrics, rheumatology, neurology, psychology, allergy, and internal medicine, as well as two CFS patients, developed a consensus statement on five key questions about CFS and OI.

Key findings of the panel included:

There is evidence of an altered autonomic nervous system (ANS) and/or circulatory system in CFS patients.  The panel noted that the symptoms of OI are often seen in CFS patients and that the physiological stressors that exacerbate OI may also intensify symptoms in CFS patients.

The exact relationship between OI and CFS is unclear. Although both may be preceded by a viral-like illness, patients with OI but not CFS often do not report the characteristic symptoms of CFS, including severe fatigue, postexertional malaise, joint and muscle pain, recurrent sore throat, and painful lymph nodes.

Methods for studying ANS dysfunction in CFS are available. Although a number of conditions such as OI, Addison’s disease, and acute Epstein-Barr infection have clinical features in common with CFS, there are no human research models that sufficiently reflect the spectrum of CFS symptoms.

However, the panel pointed out that animal models and tests measuring a patient’s response to a specific activity or pharmacologic challenge can be used to study aspects of autonomic regulation in CFS.

There are relationships between ANS dysfunction and other abnormalities seen in CFS patients. Data suggest that CFS patients have altered relationships among the ANS and the cardiovascular, neuroendocrine, and immune systems. The panel recognized that the extensive interdependence of these systems makes discovery of the primary cause of CFS a challenge for the research community.

More research is needed to further define the possible interaction between OI and CFS. The panel outlined future research needs, including more studies of autonomic function and altered brain perfusion, examination of the relationships between the ANS and other body systems, and testing of therapeutic interventions to directly impact patient care in CFS.

The panel also suggested ways to overcome some of the methodological barriers researchers have faced, including subgrouping CFS patients to handle the heterogeneity of the patient base and creating standard definitions of OI terms to ensure that future study results can be compared against one another.

The scientific court on OI in CFS was organized   by The CFIDS Association of America, which supports and facilitates research  seeking to uncover the mechanisms and potential cause of CFS. This was the first meeting in a symposia series to explore and assess in-depth key questions facing CFS researchers.

The symposia are designed to identify the most promising next steps for research; define research and funding priorities; provide
scientific evaluation of current research findings; use the synergy of exchange to identify possible links, mechanisms, and causalities; and foster research collaboration teams.

Future Association research symposia topics will include neuroendocrinology, immunology, and diagnostic methodologies.

The panel’s consensus statement has been submitted to a peer-reviewed scientific publication to communicate the stimulating findings and opportunities in CFS research, and to encourage researchers to bring their knowledge and interests to bear on this area.

To preserve the ability to publish the statement in the medical literature, the complete statement is not yet available for distribution.

Vicki Walker is Research and Public Policy Project Manager for The CFIDS Association of America. Renée Brehio is Director of Communications for the Association.