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Reasons for Performing Study: Infiltration of the equine maxillary nerve with local anaesthetic can be useful for both diagnostic and surgical procedures. The deep location and proximity of the nerve to surrounding vascular and orbital structures make an accurate, complication-free injection a challenge using traditional techniques reliant upon surface anatomical landmarks., Objectives: To develop an ultrasound-guided injection technique of the maxillary nerve in equine cadavers and to evaluate its efficacy and potential for complications in vivo., Study Design: Descriptive cadaver anatomical and clinical study., Methods: The relevant anatomy of the pterygopalatine fossa was reviewed in 6 cadaver heads from mature horses of a range of ages, breeds and genders. In an additional 13 cadaver heads, ultrasound-guided injection of 0.2 ml New Methylene Blue dye was performed on both left and right maxillary nerves (n = 26 attempts) in the pterygopalatine fossa. An independent observer dissected the area and recorded the number of times that dye successfully contacted the nerve, along with inadvertent penetration of other structures. The procedure was then performed on 8 clinical cases undergoing a variety of standing surgical procedures on the head., Results: Dye was successfully deposited in contact with the nerve during all attempts on cadaver heads, with no penetration of the orbital cone, deep facial vein and maxillary artery or associated branches. In a single cadaver, a unilateral gas artefact in the masseter muscle prohibited an injection attempt. Analgesia of the maxillary nerve was achieved in <15 min in all clinical cases, with complete loss of ipsilateral cutaneous sensation over the rostral face. No gross or ultrasonographic abnormalities were detected following the procedure., Conclusions: Using ultrasonographic landmarks of the pterygopalatine fossa, local anaesthetic can be deposited around the maxillary nerve without the inadvertent penetration of adjacent vital structures., Potential Relevance: The technique allows for vascular structures to be visualised and avoided, which is currently not possible using traditional blind approaches., (© 2013 EVJ Ltd.)

A 3-year-old Thoroughbred gelding presented with a history of neurological signs, including incoordination in his hindlimbs, of about 7 months' duration. On initial examination, the horse exhibited ataxia and paresis in all limbs with more severe deficits in the hindlimbs. Cervical radiographs displayed severe osteoarthritis of the articular processes between C5 and C6. On subsequent cervical myelography the dorsal contrast column was reduced by 90% at the level of the intervertebral space between C5 and C6. Cervical vertebral canal endoscopy, including epidural (epiduroscopy) and subarachnoid endoscopy (myeloscopy), was performed under general anaesthesia. A substantial narrowing of the subarachnoid space at the level between C6 and C7 was seen during myeloscopy, while no compression was apparent between C5 and C6. Epiduroscopy showed no abnormalities. After completion of the procedure, the horse was subjected to euthanasia and the cervical spinal cord submitted for histopathological examination. Severe myelin and axon degeneration of the white matter was diagnosed at the level of the intervertebral space between C6 and C7, with Wallerian degeneration cranially and caudally, indicating chronic spinal cord compression at this site. Myeloscopy was successfully used to identify the site of spinal cord compression in a horse with cervical vertebral stenotic myelopathy, while myelography results were misleading., (© 2011 EVJ Ltd.)

Reasons for Performing Study: Despite modern medical diagnostic imaging, it is not possible to identify reliably the exact location of spinal cord compression in horses with cervical vertebral stenotic myelopathy (CVSM). Vertebral canal endoscopy has been successfully used in man and a technique for cervical vertebral canal endoscopy (CVCE) has been described in equine cadavers., Objective: To determine the feasibility and safety of CVCE in healthy mature horses., Methods: Six healthy mature horses were anaesthetised. A flexible videoendoscope was subsequently introduced via the atlanto-occipital space into the epidural space (epiduroscopy, Horses 1-3) or the subarachnoid space (myeloscopy, Horses 4-6) and advanced to the 8th cervical nerve. Neurological examinations were performed after surgery and lumbosacral cerebrospinal fluid (CSF) analysed in horses that had undergone myeloscopy., Results: All procedures were completed successfully and all horses recovered from anaesthesia. Anatomical structures in the epidural space (including the dura mater, nerve roots, fat and blood vessels) and subarachnoid space (including the spinal cord, blood vessels, arachnoid trabeculations, nerve roots and the external branch of the accessory nerve) were identified. During epiduroscopy, a significant increase in mean arterial pressure was recognised, when repeated injections of electrolyte solution into the epidural space were performed. In one horse of the myeloscopy group, subarachnoid haemorrhage and air occurred, resulting in transient post operative ataxia and muscle fasciculations. No complications during or after myeloscopy were observed in the other horses. CSF analysis indicated mild inflammation on Day 7 with values approaching normal 21 days after surgery., Conclusions: Endoscopic examination of the epidural and subarachnoid space from the atlanto-occipital space to the 8th cervical nerve is possible and can be safely performed in healthy horses., Potential Relevance: Cervical vertebral canal endoscopy might allow accurate identification of the compression site in horses with CVSM and aid diagnosis of other lesions within the cervical vertebral canal., (© 2011 EVJ Ltd.)

Reason for Performing Study: Localisation of spinal cord compression in horses with cervical vertebral stenotic myelopathy is inexact. Vertebral canal endoscopy has been used in man to localise spinal cord lesions and has the potential to become a useful diagnostic technique in horses., Objective: To establish a surgical approach via the atlanto-occipital space to the cervical vertebral canal in equine cadavers and describe the endoscopic anatomy of the cervical epidural and subarachnoid spaces., Methods: The cadavers of 25 mature horses were used to assess 3 surgical methods to approach the cervical vertebral canal, including 2 minimally invasive and one open technique. Once the approach had been made, a flexible videoendoscope was inserted into the epidural space (epiduroscopy) or the subarachnoid space (myeloscopy) and advanced caudally until the intervertebral space between C7 and T1 was reached., Results: The epidural and subarachnoid spaces could not be accessed reliably using the minimally invasive techniques. Furthermore, damage to the nervous tissues was a frequent complication with these procedures. The open approach allowed successful insertion of the videoendoscope into the epidural and subarachnoid spaces in all horses and no inadvertent damage was observed. Anatomical structures that could be seen in the epidural space included the dura mater, nerve roots, fat and the ventral internal vertebral venous plexus. In the subarachnoid space, the spinal cord, nerve roots, blood vessels, denticulate ligaments and external branch of the accessory nerve were seen., Conclusions: Using the open approach, epiduroscopy and myeloscopy over the entire length of the cervical vertebral canal are possible in the mature horse., Potential Relevance: Cervical vertebral canal endoscopy may become a valuable tool to localise the site of spinal cord injury in horses with cervical vertebral stenotic myelopathy and could aid in the diagnosis of other diseases of the cervical spinal cord., (© 2010 EVJ Ltd.)