Evaluation of decision criteria for detection of spinal cord compression based on cervical myelography in horses: 38 cases (1981-2001)

Evaluation of the diagnostic value of transcranial electrical stimulation (TES) to assess neuronal functional integrity in horses

Medical imaging allows for the visualization of spinal cord compression sites; however, it is impossible to assess the impact of visible stenotic sites on neuronal functioning, which is crucial information to formulate a correct prognosis and install targeted therapy. It is hypothesized that with the transcranial electrical stimulation (TES) technique, neurological impairment can be reliably diagnosed.

Objective

To evaluate the ability of the TES technique to assess neuronal functional integrity in ataxic horses by recording TES-induced muscular evoked potentials (MEPs) in three different muscles and to structurally involve multiple ancillary diagnostic techniques, such as clinical neurological examination, plain radiography (RX) with ratio assessment, contrast myelography, and post-mortem gross and histopathological examination.

Methods

Nine ataxic horses, showing combined fore and hindlimb ataxia (grades 2-4), were involved, together with 12 healthy horses. TES-induced MEPs were recorded bilaterally at the level of the trapezius (TR), the extensor carpi radialis (ECR), and tibialis cranialis (TC) muscles. Two Board-certified radiologists evaluated intra- and inter-sagittal diameter ratios on RX, reductions of dorsal contrast columns, and dural diameters (range skull-T1). Post-mortem gross pathological and segmental histopathological examination was also performed by a Board-certified pathologist.

Results

TES-MEP latencies were significantly prolonged in both ECR and TC in all ataxic horses as opposed to the healthy horses. The TR showed a mixed pattern of normal and prolonged latency times. TES-MEP amplitudes were the least discriminative between healthy and ataxic horses. Youden's cutoff latencies for ataxic horses were 24.6 ms for the ECR and 45.5 ms for the TC (sensitivity and specificity of 100%). For healthy horses, maximum latency values were 22 and 37 ms, respectively. RX revealed spinal cord compression in 8 out of 9 involved ataxic horses with positive predictive values of 0-100%. All ataxic horses showed multi-segmental Wallerian degeneration. All pathological changes recorded in the white matter of the spinal cord were widely dispersed across all cervical segments, whereas gray matter damage was more localized at the specific segmental level.

Conclusion

TES-MEP latencies are highly sensitive to detect impairment of spinal cord motor functions for mild-to-severe ataxia (grades 2-4).

Cerebrospinal fluid and serum proteomic profiles accurately distinguish neuroaxonal dystrophy from cervical vertebral compressive myelopathy in horses

BACKGROUND

Cervical vertebral compressive myelopathy (CVCM) and equine neuroaxonal dystrophy/degenerative myeloencephalopathy (eNAD/EDM) are leading causes of spinal ataxia in horses. The conditions can be difficult to differentiate, and there is currently no diagnostic modality that offers a definitive antemortem diagnosis.

OBJECTIVE

Evaluate novel proteomic techniques and machine learning algorithms to predict biomarkers that can aid in the antemortem diagnosis of noninfectious spinal ataxia in horses.

ANIMALS

Banked serum and cerebrospinal fluid (CSF) samples from necropsy-confirmed adult eNAD/EDM (n = 47) and CVCM (n = 25) horses and neurologically normal adult horses (n = 45).

METHODS

. A subset of serum and CSF samples from eNAD/EDM (n = 5) and normal (n = 5) horses was used to evaluate the proximity extension assay (PEA). All samples were assayed by PEA for 368 neurologically relevant proteins. Data were analyzed using machine learning algorithms to define potential diagnostic biomarkers.

RESULTS

Of the 368 proteins, 84 were detected in CSF and 146 in serum. Eighteen of 84 proteins in CSF and 30/146 in serum were differentially abundant among the 3 groups, after correction for multiple testing. Modeling indicated that a 2-protein test using CSF had the highest accuracy for discriminating among all 3 groups. Cerebrospinal fluid R-spondin 1 (RSPO1) and neurofilament-light (NEFL), in parallel, predicted normal horses with an accuracy of 87.18%, CVCM with 84.62%, and eNAD/EDM with 73.5%.

MAIN LIMITATIONS

Cross-species platform. Uneven sample size.

CONCLUSIONS AND CLINICAL IMPORTANCE

Proximity extension assay technology allows for rapid screening of equine biologic matrices for potential protein biomarkers. Machine learning analysis allows for unbiased selection of highly accurate biomarkers from high-dimensional data.

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.

Special Diagnostic Techniques in Equine Neurology (Radiography, Ultrasonography, Computed Tomography, and Magnetic Resonance Imaging)

Diagnostic imaging is often an important part of the diagnostic approach to neurologic disease. Advanced imaging techniques such as myelography, computed tomography (CT), and magnetic resonance imaging (MRI) provide more information than radiography and ultrasonography but are more limited in their availability. The clinician should be cognizant of the findings of the clinical examination when interpreting diagnostic imaging findings.

When radiography and ultrasonography are not enough: the use of computed tomography and magnetic resonance imaging for equine lameness cases

MRI and CT have enhanced our diagnostic abilities for equine lameness beyond what is available using radiography and ultrasonography. This has allowed veterinarians to better prognosticate and treat lameness conditions, improving patient outcomes. This article discusses the basic principles behind MRI and CT, their advantages and disadvantages, the different types of equipment available for clinical use in horses, the typical diagnostic workup prior to pursuing advanced imaging, and common regions where MRI and CT are used clinically. The companion Currents in One Health by Spriet, AJVR, July 2022, discusses even more advanced equine imaging in the form of positron emission tomography. Combined, these future directions of MRI, CT, and positron emission tomography may include improved ability to image standing horses or screen for injury prevention.

Characteristic computed tomographic myelography findings in 23 Thoroughbred horses

The purpose of this observational study was to determine the characteristic computed tomographic (CT) myelography findings of cervical vertebral stenotic myelopathy (CVSM) lesions in Thoroughbred horses. A total of 23 Thoroughbred horses (age range, 155–717 days on CT examination; mean, 410.9 days) were analyzed. All 23 Thoroughbred horses underwent unenhanced radiography, radiographic myelography, and CT myelography. Unenhanced radiographs were observed the presence of cervical vertebral malalignment and osseous lesions. Radiographic myelograms were observed for signs of cervical spinal cord compression; additionally, CT myelograms were used to detect cervical vertebral osseous lesions. Ventral compressions were frequently observed in the cranial cervical vertebrae (C2–C4), whereas dorsal compressions were frequently observed in the caudal cervical vertebrae (C5–C7). Furthermore, osseous lesions of the caudal articular process developed more frequently than those of the cranial articular process. CT myelography in Thoroughbred horses is a useful method for detecting CVSM changes.

An objective index for spinal cord compression on computed tomography in Thoroughbred horses

Background

Computed tomographic myelography can be a useful tool for evaluating vertebral canal stenosis. However, an index of spinal cord compression is yet to be established.

Objectives

This observational descriptive study aimed to establish an index for spinal cord compression using computed tomography (CT).

Methods

Twenty‐three Thoroughbred horses (age, 155–717 days; weight, 205–523 kg) with suspected cervical vertebral malformation were subjected to computed tomographic myelography in dorsal recumbency using large‐bore gantry CT to define the entire cervical vertebrae from C1 to C7. Subsequently, the height of the spinal cord was measured in the sagittal plane reformatted using curved multi‐planar reformation (MPR), thereby comparing it with stenotic ratio (i.e. dividing the area of spinal cord by that of the subarachnoid space) measured in the transverse plane. The measurement was performed at the level of each of six intervertebral spaces, for a total of 138 sites. Accordingly, the appropriate cut‐off value for spinal cord height was determined using the receiver‐operating characteristic curve, from which the area under the curve with 95% confidence interval was estimated.

Results

The spinal cord compression cut‐off value was 7.06 mm, with an area under curve of 0.84. A weak relationship was observed between spinal cord height and stenotic ratio (R² = 0.08, p < 0.05).

Conclusions

Following curved MPR, a cut‐off value of 7.06 mm may serve as an index for spinal cord compression.

Computed tomographic myelography for assessment of the cervical spinal cord in ataxic warmblood horses: 26 cases (2015-2017)

OBJECTIVE

To quantify the degree of dural compression and assess the association between site and direction of compression and articular process (AP) size and degree of dural compression with CT myelography.

ANIMALS

26 client-oriented horses with ataxia.

PROCEDURES

Spinal cord-to-dura and AP-to-cross-sectional area of the C6 body ratios (APBRs) were calculated for each noncompressive site and site that had > 50% compression of the subarachnoid space. Site of maximum compression had the largest spinal cord-to-dura ratio. Fisher exact test and linear regression analyses were used to assess the association between site and direction of compression and mean or maximum APBR and spinal cord-todura ratio, respectively.

RESULTS

Mean ± SD spinal cord-to-dura ratio was 0.31 ± 0.044 (range, 0.20 to 0.41) for noncompressive sites and 0.44 ± 0.078 (0.29 to 0.60) for sites of maximum compression. Sites of maximum compression were intervertebral and extra-dural, most frequently at C6 through 7 (n = 10), followed by C3 through 4 (6). Thirteen horses had dorsolateral and lateral compression at the AP joints, secondary to AP (n = 7) or soft tissue proliferation (6). Site significantly affected direction of compression, and directions of compression from occiput through C4 were primarily ventral and lateral, whereas from C6 through T1 were primarily dorsal and dorsolateral. No linear relationship was identified between mean or maximum APBR and spinal cord-to-dura ratio.

CONCLUSIONS AND CLINICAL RELEVANCE

CT myelography may be useful for examination of horses with suspected cervical compressive myelopathy. Degree of compression can be assessed quantitatively, and site of compression significantly affected direction of compression.

Inflammatory cytokines in horses with cervical articular process joint osteoarthritis on standing cone beam computed tomography

BACKGROUND

Standing cone beam computed tomography (CT) provides cross-sectional imaging of the caudal cervical articular process joints (CAPJs) in the sedated horse, though the clinical implications of osteoarthritis (OA) identified on CT in this location are unknown. Increases in concentrations of intra-synovial cytokines could lend support to the clinical significance of CAPJ OA identified on this imaging modality.

OBJECTIVES

Investigate the presence and concentration of intra-synovial inflammatory cytokines in CAPJs with and without standing cone beam CT evidence of OA using an equine specific multiplex assay.

STUDY DESIGN

Prospective clinical study.

METHODS

Standing cone beam CT of C5-6 and C6-7 was performed on horses with CAPJ OA and control horses. Synovial fluid samples of the CAPJs of C5-6 and C6-7 were obtained bilaterally using ultrasound guidance and analysed for concentrations of IFN-γ, IL-1β, IL-6, IL-10, IL-17 and TNFα with the Milliplex® multi-analyte profiling kit. CT Images were retrospectively graded using a novel grading scheme. Significant differences between concentrations of inflammatory cytokines between joints with different categories of osteoarthritis severity were explored using a Wilcoxon rank-sum test or Kruskal-Wallis test.

RESULTS

Concentrations of intra-synovial cytokines were higher in joints with moderate to severe OA when compared to joints with no or mild OA, with differences in concentrations of IL-17 reaching statistical significance (P = .007).

MAIN LIMITATIONS

Limitations include discrepancy in number, age, and breed between control and OA populations, use of a novel grading scheme, and lack of a histologic gold-standard to confirm the presence and severity of CAPJ OA.

CONCLUSIONS

Differences in inflammatory cytokines between caudal CAPJs with and without evidence of moderate to severe osteoarthritis on standing cone beam CT exist. This finding lends support to the clinical relevance of a diagnosis of moderate to severe CAPJ OA in the caudal cervical vertebral column as identified with this imaging modality.

Computed tomographic cervical myelography in horses: Technique and findings in 51 clinical cases

Background

Three‐dimensional computed tomographic (CT) evaluation of the cervical vertebral column enables more accurate identification of osseous and soft tissue lesions than traditional latero‐lateral radiography. However, examination of the complete cervical vertebral column has been limited by horse size, preventing evaluation of the caudal cervical vertebrae.

Objectives

To describe a technique to enable CT myelography of the complete cervical spine and describe the findings in 51 horses.

Animals

Records of 51 horses presented for evaluation of cervical vertebral lesions.

Methods

A retrospective review of clinical records from all horses presented for CT myelography to further investigate possible cervical vertebral lesions was performed. A description of a novel approach to CT myelography in horses and retrospective review of the findings in clinical cases has been included.

Results

Degenerative joint disease was identified at 1 or more dorsal articular process joint in 50/51 horses, of which 44/51 had a site of grade 2 or greater. Spinal cord compression was observed on CT myelography in 31/51 horses, whereas attenuation of the dorsal contrast column was identified radiographically in 11/50 horses. Thirty‐three horses showed narrowing or obliteration of the intervertebral foramina at 1 or more site and osteochondral fragments were seen in 11/51 horses.

Conclusions and Clinical Importance

Computed tomography myelography is relatively safe and an easily performed technique with the correct equipment, enabling evaluation of the cervical vertebral structures of horses in all planes and volumetrically. It is possible that lesion extent might be underestimated with this diagnostic modality, hence interpretation should be complimented with flexed and extended views radiographically.

Accuracy of transcranial magnetic stimulation and a Bayesian latent class model for diagnosis of spinal cord dysfunction in horses

BACKGROUND

Spinal cord dysfunction/compression and ataxia are common in horses. Presumptive diagnosis is most commonly based on neurological examination and cervical radiography, but the interest into the diagnostic value of transcranial magnetic stimulation (TMS) with recording of magnetic motor evoked potentials has increased. The problem for the evaluation of diagnostic tests for spinal cord dysfunction is the absence of a gold standard in the living animal.

OBJECTIVES

To compare diagnostic accuracy of TMS, cervical radiography, and neurological examination.

ANIMALS

One hundred seventy-four horses admitted at the clinic for neurological examination.

METHODS

Retrospective comparison of neurological examination, cervical radiography, and different TMS criteria, using Bayesian latent class modeling to account for the absence of a gold standard.

RESULTS

The Bayesian estimate of the prevalence (95% CI) of spinal cord dysfunction was 58.1 (48.3%-68.3%). Sensitivity and specificity of neurological examination were 97.6 (91.4%-99.9%) and 74.7 (61.0%-96.3%), for radiography they were 43.0 (32.3%-54.6%) and 77.3 (67.1%-86.1%), respectively. Transcranial magnetic stimulation reached a sensitivity and specificity of 87.5 (68.2%-99.2%) and 97.4 (90.4%-99.9%). For TMS, the highest accuracy was obtained using the minimum latency time for the pelvic limbs (Youden's index = 0.85). In all evaluated models, cervical radiography performed poorest.

CLINICAL RELEVANCE

Transcranial magnetic stimulation-magnetic motor evoked potential (TMS-MMEP) was the best test to diagnose spinal cord disease, the neurological examination was the second best, but the accuracy of cervical radiography was low. Selecting animals based on neurological examination (highest sensitivity) and confirming disease by TMS-MMEP (highest specificity) would currently be the optimal diagnostic strategy.

Determination of magnetic motor evoked potential latency time cutoff values for detection of spinal cord dysfunction in horses

Background

Transcranial magnetic stimulation (TMS) and recording of magnetic motor evoked potentials (MMEP) can detect neurological dysfunction in horses but cutoff values based on confirmed spinal cord dysfunction are lacking.

Objectives

To determine latency time cutoff for neurological dysfunction.

Animals

Five control horses and 17 horses with proprioceptive ataxia.

Methods

Case‐control study with receiver operating characteristic curve analysis, based on diagnostic imaging, TMS, and histopathological findings. Horses were included if all 3 examinations were performed.

Results

Diagnostic imaging and histopathology did not show abnormalities in the control group but confirmed spinal cord compression in 14 of 17 ataxic horses. In the remaining 3 horses, histopathological lesions were mild to severe, but diagnostic imaging did not confirm spinal cord compression. In control horses, latency time values of thoracic and pelvic limbs were significantly lower than in ataxic horses (20 ± 1 vs 34 ± 16 milliseconds, P = .05; and 39 ± 1 vs 78 ± 26 milliseconds, P = .004). Optimal cutoff values to detect spinal cord dysfunction were 22 milliseconds (sensitivity [95% CI interval], 88% [73%‐100%]; specificity, 100% [100%‐100%]) in thoracic and 40 milliseconds (sensitivity, 94% [83%‐100%]; specificity, 100% [100%‐100%]) in pelvic limbs. To detect spinal cord dysfunction caused by compression, the optimal cutoff for thoracic limbs remained 22 milliseconds, while it increased to 43 milliseconds in pelvic limbs (sensitivity, 100% [100%‐100%]; specificity, 100% [100%‐100%] for thoracic and pelvic limbs).

Conclusions and Clinical Importance

Magnetic motor evoked potential analysis using these cutoff values is a promising diagnostic tool for spinal cord dysfunction diagnosis in horses.

Comparison of the clinical and radiographic appearance of the cervical vertebrae with histological and anatomical findings in an eight-month old warmblood stallion suffering from cervical vertebral stenotic myelopathy (CVSM)

BACKGROUND

Cervical vertebral stenotic myelopathy (CVSM) remains one of the most important abnormalities of the cervical spine resulting in neurological deficits in horses. The aim of the following study was to compare the results of the clinical and neurological examination, the results of myelography and the post mortem anatomical and histological appearance of the spinal cord and cervical vertebrae in a horse with CVSM.

CASE PRESENTATION

The following study describes a clinical case of an eight-month-old stallion with ataxia. Plain cervical radiographs indicated narrowing of the spinal canal. Conservative therapy using NSAIDs did not result in any improvement in the gait of the horse. Due to economic constraints, surgical intervention was excluded. The owner chose to humanely euthanise the horse. Immediately after euthanasia, post mortem myelography was performed, and measurements of the myelographic dye column were taken. They revealed a 67% DMC reduction and a 64% DD reduction at the C3/C4 level. Afterwards, an anatomical dissection was performed. The cervical vertebrae and vertebral canal were macroscopically inspected and measured and indicated a 44% narrowing of the canal at the C3/C4 level. The spinal cord was removed and underwent histological evaluation after staining. Microscopic lesions were visible at the level of the compression and included axonal degeneration with partial or complete loss of myelin in the white matter of the lateral and dorsal funiculi as well as the formation of dysfunctional so-called "spongy structures". An increase in the number of microglial cells and collagen was also observed. The formation of glial scars was excluded. Immunohistochemical studies revealed a negative transmembrane glycoprotein CD68(-) - monocyte response and a negative tumor necrosis alpha TNFα (-) reaction.

CONCLUSIONS

CVSM may be difficult to diagnose, even for experienced veterinary surgeons. Currently, an ex vivo histopathologic examination of the spinal cord is thought to be the gold standard in the diagnosis of CVSM. Our histological examination revealed no CVSM-specific glial scar formation and a CD68(-) negative and TNF-α negative reaction, which have not been previously reported. Histological lesions in CVSM may vary depending show inter-individual variability and on the treatment, which further hinders ex-vivo diagnostics.

Myelography in calves: a comparative study between the contrast agents iopamidol and iohexol

ABSTRACT Due to the scarcity of myelogenous studies in cattle, the present study aimed to evaluate the efficacy and distribution of iopamidol and iohexol contrast agents in calves, in order to determine guidelines for obtaining diagnostic radiographs of spinal cord disorders in these animals. Ten healthy Holstein calves, seven days to two months of age, were divided into two groups, according to the contrast medium applied. Myelographic studies of the spine were performed with the calves in lateral recumbency, with radiographs repeated 20 times during a two-hour period. On the radiographs, the contrast medium was analyzed for opacity, detail of the image, distension of the medullary canal, and progression of the contrast line. After seven days, the myelographic studies were repeated, with the contrast media exchanged between the groups. There were no significant differences in the quality of the images and speed of the spinal column filling between the two contrast media. Furthermore, the best quality radiographic images were obtained six to eight minutes after injection of the contrast in the cervical spinal segment, 80 minutes in the thoracic, and 20 minutes in the lumbar, sacral, and cauda equina segments.

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.

Neurologic Conditions Affecting the Equine Athlete

EPM, CVSM, and EDM are currently recognized as the 3 most common neurologic diseases in US horses, with the latter 2 conditions being most prevalent in young animals. Moreover, horses competing at shows and performance events are at greater risk for exposure to highly contagious, neurologic EHV-1 outbreaks. A clinical diagnosis of any neurologic disease should be based on a careful history, complete neurologic examination, and appropriate diagnostic testing and interpretation. However, mild or early neurologic signs can often mimic or be mistaken for an orthopedic condition when horses present for performance-related concerns.

Magnetic motor evoked potentials of cervical muscles in horses

BACKGROUND

When surgical treatment of cervical vertebral malformation is considered, precise localization of compression sites is essential, but remains challenging. Magnetic motor evoked potentials (mMEP) from paravertebral muscles are useful in localizing spinal cord lesions, but no information about cervical muscle mMEP in horses is available yet. Therefore, the aim of this study was to determine the possibility, normal values, inter- and intra-observer agreement and factors that have an effect on cervical mMEP in healthy horses.

METHODS

Transcranial magnetic stimulation was performed on 50 normal horses and 4 (2 left, 2 right) muscle responses were recorded at the middle of each cervical vertebra (C1-C7) and additionally just caudal to C7 to evaluate cervical nerves (Cn) Cn1 to Cn8. Latency time and amplitude of the recorded mMEP were defined by both an experienced and an unexperienced operator.

RESULTS

Latency increased gradually from 14.2 ± 1.38 ms for Cn3 to 17.7 ± 1.36 ms for Cn8, was significantly influenced by cervical nerve (P < 0.01), gender (P = 0.02) and height (P = 0.03) and had a good intra-observer agreement. The smallest mean amplitude (4.35 ± 2.37 mV) was found at Cn2, the largest (5.99 ± 2.53 mV) at Cn3. Amplitude was only significantly influenced by cervical nerve (P < 0.01) and had a low intra-observer agreement. No significant effect of observer on latency (P = 0.88) or amplitude (P = 0.99) measurements was found.

CONCLUSION

mMEP of cervical muscles in normal horses are easy to collect and to evaluate with limited intra- and inter-observer variation concerning amplitude and should be investigated in future studies in ataxic horses to evaluate its clinical value.

Current dorsal myelographic column and dural diameter reduction rules do not apply at the cervicothoracic junction in horses

Previously published myelographic studies do not report findings at the junction between the seventh cervical (C7) and first thoracic vertebrae (T1). Modern digital radiographic equipment allows improved visualization of C7-T1. Based on clinical experience, we hypothesized that 50% reduction of the dorsal myelographic column or 20% reduction of the dural diameter, criteria commonly used as a supportive finding for spinal cord compression in the cervical vertebral column, do not apply at C7-T1. A myelographic study was performed on 12 healthy, neurologically normal horses. Our hypothesis was confirmed; using established criteria eight of 12 horses would have been classified as having evidence of spinal cord compression at C7-T1. The dorsal myelographic column reduction at C7-T1 was 48 ± 12%, while the C6-C7 dorsal myelographic column reduction was 33 ± 17% (mean ± standard deviation) (P = 0.010). The dural diameter reduction at C7-T1 (22.0 ± 6.7%) was significantly greater than the dural diameter reduction at C6-C7 (13.2 ± 9.5%) (P = 0.0007). Further measurements and comparisons suggested that the apparent greater reduction of dorsal myelographic column and dural diameter at C7-T1 was due to larger intravertebral measurements at C7 rather than smaller intervertebral values at C7-T1. Based on these findings, alternative criteria should be used at C7-T1 when assessing clinical cases for cervical stenotic myelopathy. Reduction of the dorsal myelographic column by 60% or of the dural diameter by 30% would avoid high numbers of false positive myelographic cases at C7-T1.

A importância dos exames neurológico e radiográfico no diagnóstico de lesões cervicais em equino: relato de caso

RESUMO As lesões vertebrais cervicais são relativamente comuns nos equinos. No entanto, são poucas as descrições a respeito desse tema na literatura. Acredita-se que esse fato se deva, em parte, às limitações relacionadas ao diagnóstico. Em virtude de um traumatismo cervical, o animal pode apresentar sinais clínicos de paresia e paraplegia até tetraparesia ou tetraplegia, que podem culminar em estado comatoso e, eventualmente, em morte. Esses sinais clínicos podem ser detectados no exame físico, porém, quando associado à imaginologia (avaliação radiográfica), permite a obtenção de diagnóstico mais preciso da lesão. Consequentemente, um prognóstico mais adequado pode ser estabelecido para o paciente. Em face do exposto, apresenta-se o caso de uma égua Mangalarga, de quatro anos de idade, com sinais de tetraplegia pós-trauma, aumento de tônus muscular e paralisia espástica, com hiperreflexia, nos quatros membros. Por meio dos exames neurológicos realizados na paciente, em associação com as imagens radiográficas convencionais e contrastadas, foi possível estabelecer o diagnóstico do quadro. O animal apresentava lesões envolvendo as duas primeiras vértebras cervicais, atlas (C1) e áxis (C2), e a quinta e a sexta vértebra (C5-C6), destacando fratura de C1, deslocamento do dente de C2 e subluxação entre C5 e C6, com compressão ventrodorsal da medula espinhal. Confirmadas as suspeitas neurológicas e mediante prognóstico desfavorável, o animal foi submetido à eutanásia, com consentimento do proprietário. As lesões observadas nas imagens radiográficas foram confrontadas e confirmadas na necropsia.

Rater agreement on gait assessment during neurologic examination of horses

Background

Reproducible and accurate recognition of presence and severity of ataxia in horses with neurologic disease is important when establishing a diagnosis, assessing response to treatment, and making recommendations that might influence rider safety or a decision for euthanasia.

Objectives

To determine the reproducibility and validity of the gait assessment component in the neurologic examination of horses.

Animals

Twenty‐five horses referred to the Royal Veterinary College Equine Referral Hospital for neurological assessment (n = 15), purchased (without a history of gait abnormalities) for an unrelated study (n = 5), or donated because of perceived ataxia (n = 5).

Methods

Utilizing a prospective study design; a group of board‐certified medicine (n = 2) and surgery (n = 2) clinicians and residents (n = 2) assessed components of the equine neurologic examination (live and video recorded) and assigned individual and overall neurologic gait deficit grades (0–4). Inter‐rater agreement and assessment‐reassessment reliability were quantified using intraclass correlation coefficients (ICC).

Results

The ICCs of the selected components of the neurologic examination ranged from 0 to 0.69. “Backing up” and “recognition of mistakes over obstacle” were the only components with an ICC > 0.6. Assessment‐reassessment agreement was poor to fair. The agreement on gait grading was good overall (ICC = 0.74), but poor for grades ≤ 1 (ICC = 0.08) and fair for ataxia grades ≥ 2 (ICC = 0.43). Clinicians with prior knowledge of a possible gait abnormality were more likely to assign a grade higher than the median grade.

Conclusion and Clinical Importance

Clinicians should be aware of poor agreement even between skilled observers of equine gait abnormalities, especially when the clinical signs are subtle.

Movement associated reduction of spatial capacity of the equine cervical vertebral canal

Laterolateral radiographs of equine necks are reported to be inaccurate in determining the site of spinal cord lesions even when a myelogram is carried out. The goal of this study was to assess constrictions present in the cervical vertebral canal at any time point throughout the extremes of movement. Sixteen equine cervical vertebral columns without history of cervical disease were used. After removal of the spinal cord, the dura mater was filled with polyurethane foam and during its plastic phase the cervical vertebral column was passively moved in flexion-extension, lateral bending and 30° rotated flexion and extension. Resulting moulded foam structures were scanned with a 3D laser scanner. Functional narrowing of the vertebral canal was located in the dorsolateral or ventrolateral regions, explaining its under-representation on laterolateral radiographs.

A preliminary modelling study on the equine cervical spine with inverse kinematics at walk

REASON FOR PERFORMING STUDY

The motion of the atlanto-occipital, cervical vertebral and cervicothoracic joints play an important role in equestrian sports and they are also common sites for lesions limiting performance in horses.

OBJECTIVES

To calculate inverse kinematics based on cervical vertebral motion and to develop a model close to the measured neck movements.

MATERIALS AND METHODS

Measurements were recorded in 6 horses without neck pain. Reflective markers were placed on both cristae facialis, both sides of cervical vertebra 1, 3 and 6 on the withers and hooves. The neck model was reconstructed from CT scans of the osseus structures and was developed in SIMM (Software for Interactive Musculoskeletal Modelling). Inverse kinematics calculation was done in OpenSim. Three degrees of freedom: Flexion-extension (FE), axial rotation (AR) and lateral bending (LB) were considered. The simulated motion was generated from the recorded motion of the skin markers. The differences in angular range of motion (ROM) of the joints were analysed using paired sample t tests.

RESULTS

From the model, the smallest FE ROM was in the C5-C6 joint (2° ± 1°) and the largest was in the C3-C4 joint (11° ± 5°). The smallest AR ROM was in the C5-C6 joint (2° ± 1°) and largest AR ROM was in the atlantoaxial joint (7° ± 2°). The smallest LB ROM was in the C5-C6 joint (2° ± 1°) and the largest LB ROM was in the cervicothoracic joint (18° ± 5°). There were significant differences between the ROM of joints in 51 of 168 comparisons (P < 0.05).

CONCLUSIONS

The result of the motion of each joint gives an insight into the biomechanics of the equine neck. The small FE ROM at C5-C6 illustrates the pathogenetical relevance of the model for the development of osteoarthritis. The calculated data also provides a source for inverse dynamics.

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

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.

An evidence-based approach to clinical questions in the practice of equine neurology

The practice of equine neurology has special challenges posed by the size of the animal being examined. Many diagnostic procedures routinely used in small animal practice are unsafe when applied to the equine patient or unavailable to the equine practitioner. Therefore, astute observation is the mainstay of making a neuroanatomic diagnosis, and detailed evidence on the deficits present may be difficult to obtain. Because clinical observation can sometimes be ambiguous and somewhat subjective, it is even more important to approach equine neurology from an evidence-based point of view. Here, such an approach is outlined for the diagnosis of cervical vertebral compressive myelopathy (CVCM), one of the most common noninfectious causes of equine neurologic disease. This article is an attempt to summarize all aspects of making a diagnosis of CVCM on the basis of signalment, clinical examination, ancillary diagnostic tests, and pathologic examination. Each of these considerations has inherent limitations regarding diagnostic accuracy, which are discussed.