Comparison of 2 collection methods for cerebrospinal fluid analysis from standing, sedate adult horses

Background Cerebrospinal fluid (CSF) analysis is an important component of the evaluation of horses with neurologic disease. Lumbosacral (LS) centesis is routine, but CSF is also collected from the space between the first and second cervical vertebrae (C1-C2). Objectives To compare collection times, CSF cytology results, and equine protozoal myelitis (EPM) titers of CSF collected from the C1-C2 and LS sites. Animals Fifteen university-owned adult horses with no evidence of neurologic disease, and 9 horses with signs of neurologic disease: 3 university-owned and 6 client-owned. Methods Prospective study. Cerebrospinal fluid collection from the LS space and C1-C2 space of each horse was performed in randomized order. Continuous data were analyzed using mixed-effects linear models and count data using mixed-effects negative binomial regression. Statistical significance was set at P < .05. Results Cerebrospinal fluid collected from the C1-C2 site had a significantly lower mean protein concentration (49 [95% CI: 43-55.8] mg/dL C1-C2 versus 52.1 [95% CI: 45.7-59.3] mg/dL LS; P = .03) and red blood cell count (6 [95% CI: 2-16] cells/mu L versus 33 [95% CI: 13-81] cells/mu L; P = .02). Collection time, total nucleated cell count, EPM titers, and serum:CSF EPM titer ratios were not significantly different between collection sites. Conclusions and Clinical Importance Cerebrospinal fluid from the C1-C2 space provides an acceptable alternative to LS CSF collection with decreased likelihood of clinically important blood contamination of samples.