Relationships between cerebrospinal fluid characteristics, injury severity, and functional outcome in dogs with and without intervertebral disk herniation.

BACKGROUND Cerebrospinal fluid (CSF) is commonly acquired in dogs with intervertebral disk herniation (IVDH) and is a common method to assess inflammatory responses following spinal cord injury (SCI). OBJECTIVES The purpose of the study was to describe relationships between cisternal CSF characteristics, behavioral measures of SCI, T2- weighted (T2W) hyperintensity on magnetic resonance imaging (MRI), and long-term outcome in dogs with IVDH. Diagnostic accuracy of CSF for differentiating IVDH from other myelopathies was also assessed. METHODS The retrospective case series included 727 dogs, 443 with thoracolumbar IVDH, 103 with cervical IVDH, and 181 with other spinal cord diseases. Signalment, initial neurologic function, ambulatory function at long-term follow-up, T2W MRI, and CSF variables were recorded for dogs with IVDH. Signalment, etiology, and CSF data were retrieved for dogs with other myelopathies. Associations between CSF predictors, diagnosis, and outcomes were assessed. RESULTS CSF total nucleated cell count (TNCC) increased with SCI severity (rho -0.256, P < .001) in dogs with IVDH, TNCC was significantly higher in the presence of T2W hyperintensity (P = .001) in dogs with thoracolumbar IVDH, but TNCC, RBC count, microprotein, and percent neutrophils decreased with increasing injury duration (rho -0.253, P < .001; rho -0.269, P < .001; rho -0.141, P = .004, and rho -0.356, P < .001, respectively). CSF characteristics were not accurate for differentiating IVDH from other spinal cord diseases. CONCLUSIONS In dogs with IVDH, CSF TNCC, RBC count, microprotein, and percent neutrophils are correlated with clinical aspects of SCI such as injury severity and duration, but cannot differentiate IVDH from other etiologies.