BACKGROUND: There are many theories, but the etiology of chronic
fatigue syndrome (CFS) remains unknown. Diagnosticians have
set guidelines to try to classify the condition, but its
clinical definition is one of exclusion rather than defined by
specific clinical testing. The primary goal of this
investigation was to find a diagnostic key to define CFS. CFS
patients and those diagnosed with the sympathetic
hypersensitivity condition called fibromyalgia syndrome (FMS)
exhibit identical brain single photon emission computerized
tomography (SPECT) images. Therefore, this investigation was
initiated to see if CFS patients also had denervation
hypersensitivity of the sympathetic system.
METHODS: A standardized supersensitivity test was performed
using an ocular instillation of two drops of 1.0% phenylephrine.
Sixty-two subjects (29 CFS patients and 33 normals)
participated in the study. Measurements of pupil size were
recorded by pupil gauge and flash photography. A pupillary
dilation of greater than 2.5 mm would suggest a sympathetic
RESULTS: For all participants, a
small, but statistically significant increase in pupil size
was found (mean of 0.788 mm in normals and 0.931 mm in CFS
patients). The change in pupil size in the CFS patients and
controls showed substantial overlap and was not statistically
significant (t = 0.83, p = 0.42, dF = 60).
CONCLUSION: In conclusion, the results suggest that a denervation
hypersensitivity of the pupil does not occur in CFS patients.
The use of 1.0% topical phenylephrine had no diagnostic value
in detecting CSF patients vs. normals.