Cervical vertebral canal endoscopy in the horse: intra- and post operative observations

A novel surgical technique for treatment of cervical vertebral stenotic myelopathy (wobbler syndrome) in a filly

Cervical vertebral stenotic myelopathy (CVSM), also known as equine wobbler syndrome or cervical ataxia, is a devastating neurological syndrome resulting from compression of the spinal cord at the cervical region. This report describes a novel surgical technique for treatment of 16-month-old Arabian filly with CVSM. The filly showed grade 4 ataxia, hypermetria, weakness of the hind limbs, stumbling during walking, and abnormal gait. Case history, clinical signs and myelography revealed spinal cord compression between the C3 and C4 and C4-C5. The filly underwent a novel surgical interference for decompression and stabilization of the point of stenosis using specially designed titanium plate and intervertebral spacer. Evidence of arthrodesis with absence of complications was confirmed by periodic radiography over eight months of postoperative care. The new technique applied in this cervical surgery was efficient for the decompression and stabilization of the vertebrae, allowing arthrodesis development and remission of the clinical signs. The obtained results encourage further assessment of this novel procedure in horses clinically affected by CVSM.

Cervical Vertebral Stenotic Myelopathy

Cervical vertebral stenotic myelopathy is a common cause of ataxia in horses secondary to spinal cord compression. Early articles describing this problem indicate genetic predisposition as a known risk factor. Further studies have shown the problem is a developmental abnormality which might have genetic predisposition and environmental influences.

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

Ultrasound-guided injections can be used for a wide variety of conditions in the horse, including both diagnostic and therapeutic applications. Benefits of ultrasound guidance include more accurate deposition of injectate compared with blind approaches. Improved identification of vital structures, including nerves and blood vessels, allows their avoidance and thus reduces procedure-associated complications. Validation of such ultrasound-guided techniques has shown that they can be easily learnt by inexperienced veterinarians, assuming a proper knowledge of the sonographic anatomy. In many cases they can be employed in the field with a high level of accuracy, using widely available equipment, and with complete adherence to the sterility principles. Many ultrasound-guided injection techniques of the axial skeleton in the horse have been described in past years, enabling the equine veterinarian to perform more accurate treatments of specific anatomical areas. The goal of this review is to discuss diagnostic and therapeutic ultrasound-guided injection techniques of the skull and cervical spine in the horse, including those for the retrobulbar space, maxillary and inferior alveolar nerves, atlanto-occipital and atlanto-axial junctions, and cervical articular process joints, as well as the 1st cervical nerve, the C2 and C3 nerve plexus, and the 6th, 7th, and 8th cervical nerve roots.

Mesenchymal stem cell transplantation into the spinal cord of healthy adult horses undergoing cervical ventral interbody fusion

OBJECTIVE

To determine the feasibility of umbilical cord-derived mesenchymal stem cell (UC-MSC) transplantation into the cervical spinal cord of horses by using fluoroscopy with or without endoscopic guidance and to evaluate the neurological signs and tissue reaction after injection.

STUDY DESIGN

Experimental study.

ANIMALS

Eight healthy adult horses with no clinical signs of neurological disease.

METHODS

After cervical ventral interbody fusion (CVIF), ten million fluorescently labeled allogeneic UC-MSC were injected into the spinal cord under endoscopic and fluoroscopic guidance (n = 5) or fluoroscopic guidance only (n = 3). Postoperative neurological examinations were performed, and horses were humanely killed 48 hours (n = 4) or 14 days (n = 4) postoperatively. Spinal tissues were examined after gross dissection and with bright field and fluorescent microscopy.

RESULTS

Needle endoscopy of the cervical canal by ventral approach was associated with intraoperative spinal cord puncture (2/5) and postoperative ataxia (3/5). No intraoperative complications occurred, and one (1/3) horse developed ataxia with cell transplantation under fluoroscopy alone. Umbilical cord-derived MSC were associated with small vessels and detected up to 14 days in the spinal cord. Demyelination was observed in six of eight cases.

CONCLUSION

Fluoroscopically guided intramedullary UC-MSC transplantation during CVIF avoids spinal cord trauma and decreases risk of ataxia from endoscopy. Umbilical cord-derived MSC persist in the spinal cord for up to 14 days. Cell injection promotes angiogenesis and induces demyelination of the spinal tissue.

CLINICAL SIGNIFICANCE

Umbilical cord-derived MSC transplantation into the spinal cord during CVIF without endoscopy is recommended for future evaluation of cell therapy in horses affected by cervical vertebral compressive myelopathy.

Equine Cervical Pain and Dysfunction: Pathology, Diagnosis and Treatment

Simple Summary

Neck pain and dysfunction in the horse is becoming an increasingly important topic among riders, trainers and veterinarians. Some horses may present for a subtle performance decline, while others may show dramatic, dangerous behavior. It is important to recognize how to carefully evaluate the horse in an effort to understand the different types of pain that may be contributing to the different behaviors. The musculoskeletal and nervous systems may both play a role in the development of clinical signs. Recognizing that there are many diagnostic options as well as several treatments choices is important. This synopsis covers the disease processes that may contribute to the development of neck pain and dysfunction in the horse, as well as several possible diagnostic and treatment options.

Abstract

Interest in the cervical spine as a cause of pain or dysfunction is increasingly becoming the focus of many equine practitioners. Many affected horses are presented for poor performance, while others will present with dramatic, sometimes dangerous behavior. Understanding and distinguishing the different types of neck pain is a starting point to comprehending how the clinical presentations can vary so greatly. There are many steps needed to systematically evaluate the various tissues of the cervical spine to determine which components are contributing to cervical pain and dysfunction. Osseous structures, soft tissues and the central and the peripheral nervous system may all play a role in these various clinical presentations. After completing the clinical evaluation, several imaging modalities may be implemented to help determine the underlying pathologic processes. There are multiple treatment options available and each must be carefully chosen for an individual horse. Provided is a synopsis of the current knowledge as to different disease processes that can result in cervical pain and dysfunction, diagnostic approaches and treatment strategies. Improving the knowledge in these areas will ideally help to return horses to a state of well-being that can be maintained over time and through the rigors of their job or athletic endeavors.

The effect of prior thecal puncture on cerebrospinal fluid analytes in normal adult horses

Background

Serial cerebrospinal fluid (CSF) analysis might be required in clinical neurologic disease. The effect of lumbosacral (LS) or cervical (C1‐C2) centesis on subsequent CSF cytologic analyses has not been investigated in horses.

Objective

To evaluate the effect of thecal puncture on subsequent CSF analyses

Animals

Ten healthy adult horses.

Methods

Prospective study. Horses were randomly assigned to undergo CSF collection twice, 14 days apart, from either the C1‐C2 or LS space. After a 4‐month washout period, CSF collection was repeated from the alternate site. Continuous data were analyzed using linear mixed‐effects models and count data using mixed‐effects negative binomial regression. Statistical significance was set at P < .05.

Results

There was no significant effect of collection day (day 0 or day 14) for any CSF analytes, including protein concentration (C1‐C2: 45 [95% CI: 33‐57] mg/dL day 0 vs 49 [95% CI: 39‐62] mg/dL day 14, P = .12; LS: 64 [95% CI: 41‐100] mg/dL day 0 vs 83 [95% CI: 53‐129] mg/dL day 14, P = .37), or nucleated cell count (C1‐C2: 2 [95% CI: 1‐4] cells/μL day 0 vs 3 [95% CI: 1‐4] cells/μL day 14, P = .65; LS: 3 [95% CI: 2‐5] cells/μL day 0 vs 5 [95% CI: 3‐8] cells/μL day 14, P = .10). There was no significant difference in EPM titer or EPM serum : CSF ratio between days 0 and 14.

Conclusions and Clinical Importance

Repeat thecal puncture from the LS or C1‐C2 space 2 weeks apart does not appear to impact CSF analytes.

Cervical Epidural and Subarachnoid Catheter Placement in Standing Adult Horses

Horses underwent either cervical epidural space (CES) catheterization or subarachnoid space (SAS) catheterization while restrained in stocks, under deep sedation (detomidine and morphine) and local anesthesia (mepivacaine 2%) block. Catheters were placed under ultrasound guidance with visualization of the dura, SAS, and spinal cord between the first (C1) and second (C2) cervical vertebrae. Following sedation and sterile skin preparation, operator 1 placed under ultrasound guidance, a 6- or 8-inch Tuohy needle with the bevel oriented caudally. For CES, a 6-inch Touhy needle was used with the hanging drop technique to detect negative pressure, and operator 2 then passed the epidural catheter into the CES. For SAS, following puncture of the dura, cerebrospinal fluid (CSF) was aspirated prior to placement of the epidural catheter. Placement into either CES or SAS was confirmed with plain and contrast radiography. Catheters were wrapped for the duration of the study. CSF cytology was assessed up to every 24 h for the study period. Horses were assessed daily for signs of discomfort, neck pain, catheter insertion site swelling, or changes in behavior. A complete postmortem assessment of the spinal tissues was performed at the end of the study period (72 h). Two horses had CES catheters and five horses had SAS catheters placed successfully. All horses tolerated the catheter well for the duration of the study with no signs of discomfort. Ultrasound was essential to assist placement, and radiography confirmed the anatomical location of the catheters. CSF parameters did not change over the study period (P > 0.9). There was evidence of mild meningeal acute inflammation in one horse and hemorrhage in another consistent with mechanical trauma. Placement of an indwelling CES or SAS catheter appears to be safe, technically simple, and well tolerated in standing sedated normal horses.

Comparison of 2 collection methods for cerebrospinal fluid analysis from standing, sedate adult horses

Background

Cerebrospinal fluid (CSF) analysis is an important component of the evaluation of horses with neurologic disease. Lumbosacral (LS) centesis is routine, but CSF is also collected from the space between the first and second cervical vertebrae (C1‐C2).

Objectives

To compare collection times, CSF cytology results, and equine protozoal myelitis (EPM) titers of CSF collected from the C1‐C2 and LS sites.

Animals

Fifteen university‐owned adult horses with no evidence of neurologic disease, and 9 horses with signs of neurologic disease: 3 university‐owned and 6 client‐owned.

Methods

Prospective study. Cerebrospinal fluid collection from the LS space and C1‐C2 space of each horse was performed in randomized order. Continuous data were analyzed using mixed‐effects linear models and count data using mixed‐effects negative binomial regression. Statistical significance was set at P < .05.

Results

Cerebrospinal fluid collected from the C1‐C2 site had a significantly lower mean protein concentration (49 [95% CI: 43‐55.8] mg/dL C1‐C2 versus 52.1 [95% CI: 45.7‐59.3] mg/dL LS; P = .03) and red blood cell count (6 [95% CI: 2‐16] cells/μL versus 33 [95% CI: 13‐81] cells/μL; P = .02). Collection time, total nucleated cell count, EPM titers, and serum:CSF EPM titer ratios were not significantly different between collection sites.

Conclusions and Clinical Importance

Cerebrospinal fluid from the C1‐C2 space provides an acceptable alternative to LS CSF collection with decreased likelihood of clinically important blood contamination of samples.

Equine cervical intervertebral disc degeneration is associated with location and MRI features

Morphology of the equine cervical intervertebral disc is different from that in humans and small companion animals and published imaging data are scarcely available. The objectives of this exploratory, methods comparison study were (a) to describe MRI features of macroscopically nondegenerated and degenerated intervertebral discs (b) to test associations between spinal location and macroscopic degeneration or MRI‐detected annular protrusion and between MRI‐detected annular protrusion and macroscopic degeneration, and (c) to define MRI sequences for characterizing equine cervical intervertebral disc degeneration. Ex vivo MRI of intervertebral discs was performed in 11 horses with clinical signs related to the cervical region prior to macroscopic assessment. Mixed‐effect logistic regression modeling included spinal location, MRI‐detected annular protrusion, and presence of macroscopic degeneration with “horse” as random effect. Odds ratio and 95% confidence interval were determined. Reduced signal intensity in proton density turbo SE represented intervertebral disc degeneration. Signal voids due to presence of gas and/or hemorrhage were seen in gradient echo sequences. Presence of macroscopic intervertebral disc degeneration was significantly associated with spinal location with odds being higher in the caudal (C5 to T1) versus cranial (C2 to C5) part of the cervical vertebral column. Intervertebral discs with MRI‐detected annular protrusion grades 2‐4 did have higher odds than with grade 1 to have macroscopic degeneration. It was concluded that MRI findings corresponded well with gross macroscopic data. Magnetic resonance imaging of the equine cervical intervertebral disc seems to be a promising technique, but its potential clinical value for live horses needs to be explored further in a larger and more diverse population of horses.

Update on Surgical Treatment of Wobblers

Cervical vertebral compressive myelopathy (CVCM) represents the most significant disease of the spinal cord in horses for which surgical treatment is described. Current surgical methods used include ventral interbody fusion with kerf cut cylinders and dorsal laminectomy. Polyaxial pedicle screw and rod constructs and ventral locking compression plating have been introduced in the treatment of equine CVCM and present promising alternative approaches to achieve ventral interbody fusion. Advancements in diagnostic imaging and endoscopy of the cervical vertebral canal may improve reliable preoperative identification of the exact locations of spinal cord compression in horses with CVCM to improve postoperative outcomes.

Development of two surgical approaches to the pituitary gland in the Horse

BACKGROUND

Current treatment of equine pituitary pars intermedia dysfunction (PPID) requires daily oral medication. Minimally invasive surgical palliation of this condition is appealing as a single treatment to alleviate the clinical signs of disease, dramatically improving the welfare of the horse.

OBJECTIVE

To develop a surgical approach to the equine pituitary gland, for subsequent treatment of PPID.

STUDY DESIGN

A cadaver study to develop methodology and a terminal procedure under anaesthesia in the most promising techniques.

ANIMALS AND METHODS

Four surgical approaches to the pituitary gland were investigated in cadaver animals. A ventral trans-basispheniodal osteotomy and a minimally invasive intravenous approach via the ventral cavernous sinus progressed to live horse trials.

RESULTS

Technical complications prevented the myeloscopic and trans-sphenopalatine sinus techniques from being successful. The ventral basisphenoidal osteotomy was repeatable and has potential if an intra-operative imaging guidance system could be employed. The minimally invasive approach was repeatable, atraumatic and relatively inexpensive.

CONCLUSIONS

A minimally invasive surgical approach to the equine pituitary gland is possible and allows for needle placement within the target tissue. More work is necessary to determine what that treatment might be, but repeatable access to the gland has been obtained, which is a promising step.

Arthroscopic approach and intra-articular anatomy of the equine atlanto-occipital joint

OBJECTIVE

To develop arthroscopic approaches to the atlanto-occipital (A-O) and describe associated arthroscopic anatomy.

STUDY DESIGN

Experimental ex vivo study and clinical case report.

ANIMALS

Ten equine cadaver joints and 1 clinical case.

METHODS

CT arthrograms of 8 A-O joints were performed to determine the placement of an arthroscopic portal. Arthroscopy was performed via dorsal and/or ventral approaches (dorsal or ventral to the longissimus capitis tendon) in 10 cadaveric A-O joints and the A-O joint of a 2-week-old foal with septic arthritis. Accessible cartilage was debrided in 3 cadaver joints. Accessibility and risks were assessed by review of arthroscopic images, postoperative necropsy, and computed tomography (CT).

RESULTS

Dorsal and ventral outpouchings of the A-O joint were identified with CT. Arthroscopy of the dorsal pouch provided access to 50% of the dorsocranial occipital condyle and 15% of the dorsocranial atlas articular surfaces. Joint distension caused displacement of the dura. Dura perforation occurred with a blind dorsal approach in 2 of 5 joints. Dura perforation did not occur after ultrasonography-guided approaches. Arthroscopic debridement of septic arthritis and osteomyelitis was successful in 1 clinical case.

CONCLUSION

Approaches to the A-O joint were determined from CT examinations. The cranial aspect of the dorsal pouch of the A-O joint was accessed via arthroscopic triangulation in all horses of this study. Ultrasound-guided joint access prevented perforation of vital structures, including the spinal canal.

CLINICAL SIGNIFICANCE

Advanced imaging improves the diagnosis of A-O joint pathology. Descriptions of arthroscopic anatomy and accessibility provide important information for surgical intervention.

Evaluation of epiduroscopy for detection of vertebral canal and spinal cord lesions in dogs

OBJECTIVE To evaluate the potential usefulness of epiduroscopy for clinical diagnosis and treatment of vertebral canal and spinal cord lesions in dogs. SAMPLE Cadavers of 6 mixed-breed dogs. PROCEDURES Dogs were positioned in sternal recumbency, and an endoscope was introduced into the lumbosacral epidural space. A fiberscope (diameter, 0.9 mm; length, 30 cm) was used for 3 dogs, and a videoscope (diameter, 2.8 mm; length, 70 cm) was used for the other 3 dogs. Visibility and identities of anatomic structures were recorded, and maneuverability of the endoscopes was assessed. Extent of macroscopic tissue damage was evaluated by manual dissection of the vertebral canal at the end of the procedure. RESULTS Intermittent saline (0.9% NaCl) solution infusion, CO2 insufflation, and endoscope navigation improved visualization by separating the epidural fat from the anatomic structures of interest. Images obtained with the fiberscope were small and of poor quality, making identification of specific structures difficult. Maneuverability of the fiberscope was difficult, and target structures could not be reliably reached or identified. Maneuverability and image quality of the videoscope were superior, and spinal nerve roots, spinal dura mater, epidural fat, and blood vessels could be identified. Subsequent manual dissection of the vertebral canal revealed no gross damage in the spinal cord, nerve roots, or blood vessels. CONCLUSIONS AND CLINICAL RELEVANCE A 2.8-mm videoscope was successfully used to perform epiduroscopy through the lumbosacral space in canine cadavers. Additional refinement and evaluation of the technique in live dogs is necessary before its use can be recommended for clinical situations.

Anatomical variation of the spinous and transverse processes in the caudal cervical vertebrae and the first thoracic vertebra in horses

REASONS FOR PERFORMING STUDY

There are scant data on the incidence of different anatomical variants of the equine caudal cervical spine, despite interest in cervical pathology.

OBJECTIVES

To identify morphological radiographic variation in the 6th and 7th cervical vertebrae and the first thoracic vertebra in horses of different breeds and to determine whether there are breed- and sex-related differences.

STUDY DESIGN

Retrospective descriptive study.

METHODS

Radiographs of the cervical spine of 270 horses were assessed retrospectively. The Chi-square test, or Fisher's exact test when appropriate, was used to test for associations between radiographic findings and sex or breed, and residual analysis was performed to localise differences. Chi-square tests and calculation of phi coefficient (φ) were used to test for associations between different types of radiological variation.

RESULTS

Three variants were identified in the spinous process of the 7th cervical vertebra, and 2 variants were identified in the spinous process of the first thoracic vertebra. The presence of the spinous process of the 7th cervical vertebra was associated with breed, and transposition of the ventral process of the 6th cervical vertebra onto the ventral aspect of the 7th cervical vertebra was associated with sex. The shape of the spinous process of first thoracic vertebra was associated with the shape of the spinous process of the 7th cervical vertebra and with the presence of transposition of the ventral process of the 6th cervical vertebra onto the ventral aspect of the 7th.

CONCLUSIONS

A large number of anatomical variants can be detected radiographically in the caudal cervical area; some of these have a higher frequency, depending on sex and breed. Knowledge of the different shapes is very important in avoiding misdiagnosis of periarticular new bone formation. The spinous process of the first thoracic vertebra has 2 morphological variants.