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Abstract 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

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. [ABSTRACT FROM AUTHOR]

Background: Further development of surgical techniques for equine cervical stabilisation is necessary to make the procedure less technically demanding, reduce complications and improve outcomes. Objective: To describe clinical outcomes and owner reports in horses undergoing placement of an interbody fusion device and polyaxial pedicle screw and rod construct for cervical vertebral fusion in horses with cervical vertebral compressive myelopathy. Study design: Retrospective case series. Methods: Data were retrieved from medical records of 10 horses undergoing cervical vertebral fusion (2015‐2019). Records were evaluated for signalment, duration of clinical signs, number and location of compression sites, grade of ataxia, duration of hospitalisation and complications. Long‐term follow‐up was obtained through clinical re‐evaluation, postoperative radiographs and owner contact. Results: Breeds were mixed. Median age was 24 (range 12‐168) months. There were 2/10 mares, 4/10 geldings and 4/10 stallions. Preoperative grade of ataxia ranged from 1‐3/5. Fusion was performed at one (n = 3) or two (n = 7) sites. Two horses were euthanised within the first year. In 6 of 8 horses with ≥1‐year follow‐up, ataxia improved by 1‐3 grades, with an average improvement of 1.25 grades. In four horses, ataxia improved to grade 0‐1. In two horses the gait was unaffected, but neck comfort improved. Complications included seroma formation (n = 9), pain (n = 5), fever (n = 4), upper respiratory tract obstruction (n = 2), azotemia (n = 2), screw breakage (n = 2), progression of neurological signs (n = 1), Horner's Syndrome (n = 1), dysphagia (n = 1), hives (n = 1), implant infection (n = 1) and nondisplaced fracture (n = 1). Main limitations: Small case series, heterogeneous patient population. Conclusions: This technique resulted in ≥1 grade gait improvement in 6/10 cases operated and 6/8 cases for which ≥1‐year follow‐up was available, similar to other methods. Fatal complications related to implant placement did not occur. This technique may represent a safer alternative to current techniques of ventral interbody fusion with similar outcomes. [ABSTRACT FROM AUTHOR]

Abstract 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.

Abstract 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.

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Summary: A yearling Thoroughbred colt was presented for investigation of neck stiffness and episodes of intermittent neck pain without neurological signs. Osteochondrosis (OCD) of the cervical articular process joints (APJs) was diagnosed with the aid of radiography and computed tomography. An articular osteochondral fragment of the left fourth caudal cervical articular process was removed arthroscopically following a cut down approach to the joint capsule of the affected APJ. Surgical removal resulted in resolution of clinical signs at 4 weeks. However, subsequently the horse was markedly ataxic 6 weeks post surgery after being found cast in its stable. Cervical stenotic myelopathy was considered the most likely cause based on clinical and radiographic signs and the horse was subjected to euthanasia due to a poor prognosis for racing. Post‐mortem examination identified atypical cartilage within several cervical APJs with histological changes consistent with OCD. This case report supports OCD of the APJs as a cause of neck pain and confirms the clinical practicality and short‐term effectiveness of arthroscopic fragment removal. Surgical treatment for cervical OCD should be considered in horses without neurological signs, although case selection is important and the underlying pathology remains a risk factor for the development of subsequent neurological signs. [ABSTRACT FROM AUTHOR]

Skeletal lesions in the articular processes of cervical vertebrae C2 to C7 were compared between Thoroughbred horses with cervical stenotic myelopathy (17 males, 2 females; age, 6–50 months) and controls (6 males, 3 females; age, 9–67 months). Lesions identified by magnetic resonance imaging occurred with an increased frequency and severity in diseased horses and were not limited to sites of spinal cord compression. Lesions involved both the articular cartilage and trabecular bone and were further characterized using micro–computed tomography and histopathology. The most common histologic lesions included osteochondrosis, osseous cyst–like structures, fibrous tissue replacement of trabecular bone, retained cartilage matrix spicules, and osteosclerosis. Osseous cyst–like structures were interpreted to be true bone cysts given they were a closed cavity with a cellular lining that separated the cyst from surrounding bone. This is the first report of bone cysts in the cervical articular processes of horses with cervical stenotic myelopathy. The morphology and distribution of the lesions provide additional support for the previously proposed pathogenesis that developmental abnormalities with likely secondary biomechanical influences on the cervical spine contribute to equine cervical stenotic myelopathy. [ABSTRACT FROM AUTHOR]

Cervical vertebral malformation is one of the most common causes of ataxia in horses. The most important factor in the diagnosis of cervical vertebral malformation is the identification of cervical vertebral canal stenosis, but published data for minimum sagittal diameter ratios in adult horses are only available for C4–C7 intravertebral sites. Intra- and intervertebral sagittal diameter ratios at C2–C7 were evaluated in 26 ataxic horses, for which a complete clinical and neuropathological evaluation was undertaken. Eight of these horses were diagnosed with cervical vertebral malformation. In these horses the majority of compressive lesions were intervertebral. The mean sagittal diameter ratios of horses with cervical vertebral malformation were significantly smaller than those of horses without cervical vertebral malformation, and for an individual horse in our study, the site with the smallest intervertebral sagittal diameter ratio was always the site at which the spinal cord was compressed. Mean sagittal diameter ratio intravertebral site measurements of horses with cervical vertebral malformation were smaller than those of horses without cervical vertebral malformation; however, the site of compression could not be predicted from the data. For our dataset, horses with a sagittal diameter ratio of ≤0.485 at any inter- or intravertebral site could be correctly classified as having cervical vertebral malformation, and sagittal diameter ratio measurements were an effective tool to identify at least one site of compression in an individual case. [ABSTRACT FROM AUTHOR]