Ultrasonography-Guided Perineural Injection of the Ramus ventralis of the 7 and 8th Cervical Nerves in Horses: A Cadaveric Descriptive Pilot Study

Abstract

To describe the feasibility and dye diffusion of selective perineural injection of the 7 and 8th cervical nerve (C7 and C8) ramus ventralis under ultrasonographic guidance in horses. Study design: Prospective experimental pilot cadaver study. Animals: Four equine cadavers of similar body weight (420-480 kg) and neck conformation. Methods: Five C7 and five C8 rami were perineurally injected with a dye solution. Anatomic dissections including vertebral canal opening were conducted to confirm nerve dye staining and describe the extent of color diffusion. Results: The ramus ventralis of the spinal cervical nerves was visualized in all cadavers. All the injections were successful in staining a portion of the nerve trunk. Eight rami had a uniform transversal staining of the nerve trunk that longitudinally covered a distance >2 cm. One C7 and one C8 nerve trunk showed incomplete transversal staining with a more concentrated color on its half cranial aspect and a longitudinal coverage of <2 cm. Five injections resulted in dye extending proximally and medially into the epidural space. Volume had no appreciable effect on the extent of nerve staining. A greater proportion of epidural diffusion was found with injections done within less than one cm distally to the articular processes. All injections were considered to be selective for the targeted nerve. Conclusion and clinical relevance: Ultrasonography-guided perineural injection of C7 and C8 ramus ventralis is a feasible technique that may have multiple applications in multimodal analgesia in horses. Further clinical study will be necessary to determine the appropriate drug, dosage, and volume to inject and to confirm its usefulness.

Ultrasonographic guidance for perineural injections of the cervical spinal nerves in horses

“…Similar studies in which ultrasonographicguided approaches to intra-articular injection of the cervical APJ have been described have provided evidence of comparable success rates of 72% and 89%. 10,11 Touzot-Jourde et al 12 concluded that perineural injection of the ventral ramus was feasible and the technique described by the authors. The study shares similarities with regard to the general technique and landmarks for injection.…”

“…4 A cadaveric pilot study has recently been published in which researchers demonstrated that ultrasonographic-guided cervical perineural injection is feasible in horses. 12 In this study, 12 a micro convex probe was used in a longitudinal plane, and 7 to 14 mL of methylene blue was injected into 10 sites. There were issues relating to dye diffusion, which the authors found in their pilot study in which methylene blue was injected.…”

“…Nerve root medication is performed in man for the treatment of radiculopathy primarily with the use of fluoroscopy but also under ultrasonographic guidance 4 . A cadaveric pilot study has recently been published in which researchers demonstrated that ultrasonographic‐guided cervical perineural injection is feasible in horses 12 . In this study, 12 a micro convex probe was used in a longitudinal plane, and 7 to 14 mL of methylene blue was injected into 10 sites.…”

Ultrasound-guided injections of the equine head and neck: review and expert opinion

“…This study highlighted the feasibility of perineural injection techniques as a potential treatment option for cervical radiculopathy in the horse. Touzot-Jourde et al (2020) published a pilot cadaver study of four horses in which they described an US-guided perineural injection technique for the ramus ventralis of the 7th and 8th cervical nerves in the horse [50]. A total of 10 injections were performed, and all were deemed accurate using a large volume of injection (7 ml or 14 ml), as demonstrated by evidence of dye staining a portion (2/10) or the entire (8/10) cross section of the ramus ventralis nerve trunks [50].…”

“…(2020) published a pilot cadaver study of four horses in which they described an US-guided perineural injection technique for the ramus ventralis of the 7th and 8th cervical nerves in the horse [ 50 ]. A total of 10 injections were performed, and all were deemed accurate using a large volume of injection (7 m l or 14 m l ), as demonstrated by evidence of dye staining a portion (2/10) or the entire (8/10) cross section of the ramus ventralis nerve trunks [ 50 ]. Some diffusion was noted in the epidural space in 5/10 injections [ 50 ].…”