Cerebrospinal fluid tau protein as a biomarker for severity of spinal cord injury in dogs with intervertebral disc herniation.

Intervertebral disc herniation (IVDH) is a common cause of spinal cord injury (SCI) in dogs. Microtubule-associated protein tau derives predominantly from neurons and axons, making it a potential marker of neuronal injury. A retrospective study, including 51 dogs with thoracolumbar or cervical IVDH and 12 clinically normal dogs, was designed to describe associations between cerebrospinal fluid (CSF) tau concentration, degree of neurological signs and motor functional recovery in dogs with IVDH. Signalment, degree of neurological dysfunction and outcome were recorded. Cisternal CSF tau values were determined by ELISA. Associations between CSF tau concentration and various clinical parameters were evaluated. Receiver-operating characteristics curve (ROC) analyses were performed to assess the validity of protein tau measurements. CSF tau concentrations were significantly higher in dogs showing plegia (median, 79.9 pg/mL; range, 0-778.7 pg/mL; P=0.016) compared to healthy dogs and dogs with paresis (median, 30.1 pg/mL; range, 0-193.1 pg/mL; P=0.025). Plegic dogs that improved by one neurological grade within 1 week had significantly lower tau protein levels compared to plegic dogs that needed more time for recovery or did not show an improvement (P=0.008). A CSF tau concentration >41.3 pg/mL had a sensitivity of 86% and specificity of 83% to predict an unsuccessful outcome in plegic dogs based on ROC analysis (area under the curve, 0.887; P=0.007, 95% confidence interval [CI] 0.717-1.057). CSF protein tau levels are positively associated with the severity of spinal cord damage and may serve as a prognostic indicator in dogs with IVDH.