Autonomic Function in CFS

The autonomic nervous system affects virtually every aspect of body functioning. It regulates most involuntary functions such as heart rate (HR), blood pressure (BP) and gut and bladder function. Autonomic symptoms are not included in the diagnostic criteria of CFS. Never the less many CFS patients have clinical symptoms which suggest autonomic dysfunction. These include: increases heart rate, dizziness, fainting, delayed gastric emptying, urinary frequency and orthostatic intolerance. Orthostatic intolerance refers to symptoms caused or worsened by standing. There are two types of OI. Neurally Mediated Hypotension (NMH) is a neurally mediated sudden drop in BP which causes fainting upon standing. Postural Orthostatic Tachycardia Syndrome (POTS) is an increase in HR of over 30 bpm from sitting to standing without loss of consciousness. The gold standard of diagnosis for OI is the onset of dizziness or fainting during tilt table testing. Bou Holaigah et al from Johns Hopkins in 1995 were the first to note the connection between CFS and OI. They found that 22/23 CFS patients had abnormal responses on tilt table testing (Bou-Holaigah et al, 1995). Since then the finding of autonomic dysfunction has been validated as occurring in a subset of CFS patients. Research findings include: · increased incidence of abnormal tilt table response in CFS (30- 95%) (Bou-Holaigah et al, 1995;Freeman & Komaroff, 1997;Gibson et al, 1993;Stewart et al, 1999;De Lorenzo et al, 1997) Not all agree (Duprez et al