Technical note on cervical epidural catheterization in two adult horses: Injectate distribution and epidural space effects.

Cervical epidural catheters can deliver injectate to the brachial plexus level with acceptable short-term tissue tolerance.

This pilot study investigated cervical epidural catheterization (CEC) in two adult horses, evaluating injectate distribution via contrast radiography and pathological changes associated with indwelling catheters maintained for up to 17 days. Catheters were placed under ultrasound guidance, and 5 mL aliquots of 50% Iohexol contrast solution were injected up to a total of 15 mL, with laterolateral radiographs taken every 5 minutes. Results demonstrated notable variability between subjects: in one horse, contrast reached the cranial C6 level at 25 minutes following 15 mL total volume, while in the other horse, cranial C6 was reached within 1 minute of the initial 5 mL injection. The caudalmost extent of contrast diffusion was consistently achieved after 15 mL and within 20-25 minutes. These findings suggest that volumes of 10-15 mL are capable of reaching the cranial extent of the brachial plexus, which has meaningful implications for managing pain or disease processes in the caudal cervical region. Gross necropsy at 16-17 days post-placement revealed mild inflammation and fibrosis surrounding the catheter in the epidural space, findings consistent with previously reported changes associated with sacrococcygeal and lumbosacral epidural catheters in horses. The authors conclude that CECs are a potentially viable route for drug administration targeting caudal cervical vertebral pathology and call for further studies to evaluate therapeutic efficacy and safety of this approach in clinical equine patients.

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