Objective: To determine cerebrospinal fluid levels of osteopontin (OPN), a proinflammatory cytokine that was found to be overexpressed in multiple sclerosis lesions and increased in plasma during relapses and in secondary progressive multiple sclerosis.

Methods: Case series. Osteopontin, interleukin 12p40 (IL-12p40), IL-10, and matrix metalloproteinase 9 were measured by enzyme-linked immunosorbent assay by an investigator unaware of the patients' diagnoses. Methods: Consecutive patients with multiple sclerosis (n = 27), or other inflammatory (n = 11) or non-inflammatory (n = 23) neurological diseases, undergoing lumbar puncture, were investigated.

Results: Osteopontin was significantly elevated in the cerebrospinal fluid of patients with multiple sclerosis (mean [SD], 415 [186] ng/mL) and other inflammatory diseases (563 [411] ng/mL) compared with those with noninflammatory neurological diseases (286 [150] ng/mL). Cerebrospinal fluid OPN levels were slightly higher than plasma OPN levels. Cerebrospinal fluid OPN levels positively correlated with the ability to detect cerebrospinal fluid IL-12p40.

Conclusions: Osteopontin in the cerebrospinal fluid may be, in part, of central nervous system origin, and may play an important role in central nervous system inflammation.