Evaluation of neurologic function in Gulf War veterans: A blinded case- control study

Objective. - To determine whether Gulf War-related illnesses are associated with central or peripheral nervous system dysfunction. Design. - Nested case-control study. Participants. - Twenty-three veterans with factor analysis-derived syndromes (the cases), 10 well veterans deployed to the Gulf War (the deployed controls), and 10 well veterans not deployed to the Gulf War (the nondeployed controls). Method. - With investigators blinded to group identities, participants underwent objective neurophysiological, audiovestibular, neuroradiological, neuropsychological, and blood tests. Main Outcome Measures. - Evidence of neurologic dysfunction. Results. - Compared with the 20 controls, the 23 cases had significantly more neuropsychological evidence of brain dysfunction on the Halstead Impairment Index (P=.01), greater interside asymmetry of the wave I to wave III interpeak latency of brain stem auditory evoked potentials (P=.02), greater interocular asymmetry of nystagmic velocity on rotational testing, increased asymmetry of saccadic velocity (P=.04), more prolonged interpeak latency of the lumbar-to-cerebral peaks on posterior tibial somatosensory evoked potentials (on right side, P=.03, and on the left side, P=.005), and diminished nystagmic velocity after caloric stimulation bilaterally (P values range from .02 to .04). Cases (n=5) with syndrome 1 ('impaired cognition') were the most impaired on brain stem auditory evoked potentials (P=.005); those (n=13) with syndrome 2 ('confusion-ataxia') were the most impaired on the Halstead Impairment Index (P=.006), rotational testing (P=.01), asymmetry of saccadic velocity (P=.03), and somatosensory evoked potentials (P≤.01); and those (n=5) with syndrome 3 ('arthro-myo-neuropathy') were the most impaired on caloric stimulation (P≤.01). Conclusions. - The 3 factor-derived syndromes identified among Gulf War veterans appear to represent variants of a generalized injury to the nervous system.