The aim of this paper was to evaluate S-100 concentration in cerebrospinal fluid (CSF) from patients with different neurological disorders, and in subjects with no proven neurological pathology, in order to study possible differences in their protein concentrations. The total number of patient-samples examined was 119 (58 males and 61 females; mean age 35 yrs, 1-79 yrs). Based on the final diagnoses, nine patient groups were studied: a control group, meningitis, acute lymphatic leukemia (ALL), dementia, hydrocephalia, polyneuropathy-motor neuron disease, acute cerebral infarction (ACI), and patients diagnosed with multiple sclerosis. S-100 protein concentrations were measured by the Sangtec 100 two-site immunoradiometric assay. The highest S-100 levels in CSF were found in the dementia group, ACI group, bacterial-fungal and lymphocytic meningitis groups (Kruskal-Wallis test). The S-100 concentrations in these groups were significantly higher compared with the control group (Mann-Whitney U test, p<0.05, p<0.01) and the multiple sclerosis group (p<0.05, p<0.01). No other significant differences were found between groups. Our results suggest that the high protein levels in CSF found in these pathologies may reflect the presence of brain damage. However, the levels need to be considered individually, as they depend on several factors, such as age, severity of brain damage or interval between the onset of brain damage and the taking of the sample.

In order to evaluate the S-100 concentration in cerebrospinal fluid from subjects with nonischemic brain damage, a total of 33 samples were analyzed: 11 from subjects in whom no organic disease could be found; 14 from patients with a diagnosis of lymphocytic or bacterial-fungal meningitis, and 8 from patients with acute lymphatic leukemia but no demonstrable signs of meningeal involvement. In all cases, the subjects considered had no previous history of melanoma or ischemic brain damage. The mean levels ± SEM found for each study group were 1.00 ± 0.11, 1.67 ± 0.23 and 1.17 ± 0.14 μg/l, respectively. Significant differences appeared between the groups when applying the Kruskal-Wallis nonparametric test (p = 0.035). The highest levels were found in the meningitis group and were significantly different from those of the control group (p = 0.015). No significant differences were found with regard to age or sex. Based on the pathophysiology of meningitis and on previous studies, the results suggest the existence of brain damage caused by an infection as a possible cause of increased S-100 levels.

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