Equine cerebrospinal fluid: reference values of normal horses

Cerebrospinal fluid (CSF) samples were collected from the atlanto-occipital (AO) and lumbosacral (LS) subarachnoid spaces of 24 horses and 21 ponies that had no clinical evidence of neurologic disease. Depth of needle insertion, pressures, refractive index, rapid reagent strip test (protein, glucose, blood, pH) results, cell counts, content of protein, glucose, sodium, potassium, chloride, calcium, phosphorus, urea nitrogen, and cholesterol, and activities of creatine phosphokinase, aspartate transaminase, lactic dehydrogenase, and alkaline phosphatase were determined. The resulting clinical reference values obtained were discussed in light of the published normal values for CSF from horses, other animals, and man. White cell counts in CSF were found to be from 0 to 6/microliters. Values for protein content were distributed between wider limits than previously reported values. The LS-AO difference is proposed as a criterion for clinical evaluation of CSF protein content. Ponies were found to have more protein in their CSF than did the horses, and CSF from the LS site contained more glucose than that from the AO site. The CSF electrolyte composition was similar to that of previous reports. Enzyme activities in equine CSF are reported for the 1st time.