Commercial cytokine assay on equine cerebrospinal fluid does not distinguish equine degenerative myeloencephalopathy from cervical vertebral stenotic myelopathy

Objective To measure and compare CSF cytokine concentrations among horses with equine neuroaxonal dystrophy (eNAD)/ equine degenerative myeloencephalopathy (EDM), horses with cervical vertebral stenotic myelopathy (CVSM), and control horses and to evaluate for associations with clinical parameters. Methods Banked equine CSF samples from horses with neurologic disease that underwent a complete neurologic examination and postmortem diagnosis confirmation of CVSM or eNAD/EDM or from control horses were included. Cytokines were measured with an equine-specific cytokine/chemokine magnetic bead multiplex panel (23-cytokine multi-plex). Results were compared between groups, and correlations with clinical parameters were evaluated. Results Cerebrospinal fluid samples from 35 horses with CVSM, 35 horses with eNAD/EDM, and 8 control horses were ana-lyzed. Most cytokines analyzed were below the lower limit of detection in the majority of samples. Eotaxin, IL-10, interferon-γ–induced protein 10, granulocyte colony-stimulating factor, and tumor necrosis factor–α were detect-able in 5 or more samples; however, concentrations were not different between groups. Increasing sample volume or using a commercial protein-concentrating column did not enhance cytokine recovery. In horses with eNAD/EDM, IL-10 concentrations correlated with CSF phosphorylated neurofilament heavy concentrations. Conclusions This commercial cytokine assay was unable to distinguish between CVSM and eNAD/EDM based on CSF cytokine profiles in this population. Clinical Relevance Optimization of a more sensitive assay is warranted as CSF cytokine concentrations have high potential to be used as biomarkers to characterize neuroinflammation in equine neurological diseases.