Building upon the above study, the authors compared GW veterans with the most severe symptoms of Syndromes 1, 2, and 3 (cases) with two groups of veterans with no serious health problems, deployers and non-deployers to the Persian Gulf (20 controls). The 23 cases had more evidence of brain dysfunction by several neuropsychological tests. Neurophysiological and audiovestibular tests among cases generally did not exceed normal limits for the testing laboratory, but the results were significantly more in the abnormal direction in the cases than in the controls. Neurological examinations disclosed no difference between cases and controls in the proportions with abnormalities. The distribution of blood test abnormalities was not significantly different between cases and controls. Six neurologists and the investigators who reviewed the findings on each subject concluded that clinical and laboratory findings were nonspecific and not sufficient to diagnose any known syndrome in any subgroup of the subjects. The authors conclude that the cases’ scores "more in the abnormal direction on objective tests of neurologic function" support their hypothesis that "a subset of veterans with Gulf War-related illnesses appears to have a subtle neurologic injury or illness contracted in the war." The authors suggest that future screening of Gulf War veterans should include a combination of neuropsychological, neurophysiological, and audiovestibular tests similar to those used in this study. Limitations of the study are the low rate of participation (see above study), the small sample sizes (23 cases divided among the 3 syndromes), the interpretation of test results that were generally within normal limits, the inclusion of veterans with known diseases among the cases, and the speculative nature of the putative exposures with which the veterans’ symptoms are associated.