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Summary

Seventy-three horses with cervical stenotic myelopathy underwent cervical vertebral interbody fusion (n = 63) or dorsal laminectomy (n = 10). Neurologic function improved in 77% of horses, and 46% of horses achieved athletic function (racing, race training, or pleasure riding) after cervical vertebral interbody fusion for static and dynamic spinal cord compressive lesions. Neurologic status improved in 4 of 10 horses after dorsal decompression for static compressive spinal cord lesions. The duration of clinical signs prior to surgical intervention was shorter for horses that achieved athletic function or improved by at least 2 neurologic grades than for horses that did not improve in neurologic status or improved 1 neurologic grade after cervical vertebral interbody fusion. The number of cervical spinal cord compressive lesions and age of horses did not affect the long-term surgical outcome of cervical vertebral interbody fusion. Seroma formation, implant failure, right laryngeal hemiplegia, and colitis were nonfatal complications associated with cervical vertebral interbody fusion. Dorsal laminectomy and cervical vertebral interbody fusion of static compressive lesions of the caudal cervical vertebral column were associated with fatal postoperative complications, including vertebral body fracture, spinal cord edema, and implant failure.

Free access
in Journal of the American Veterinary Medical Association

Summary

Intravenous administration of quinidine gluconate converted atrial fibrillation (af) to sinus rhythm in 9 of 12 horses. Twelve horses that were diagnosed by ecg to have af were administered up to 11 mg of quinidine gluconate/kg of body weight in 1.0 -to 1.5-mg/kg bolus injections every 10 to 15 minutes. The total dose of quinidine administered iv ranged from 1.8 to 5.8 g. Increased ventricular rate, apprehension, and mild depression were observed during treatment. Other signs of toxicosis were not observed. One horse was successfully treated with iv administered quinidine gluconate on 3 occasions. Intravenous administration of quinidine is a safe and effective alternative for treatment of af in some horses.

Free access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine neurologic indications associated with abnormal results for computed tomography (CT) imaging of the head of horses affected by neurologic disorders.

Design—Retrospective case series.

Animals—57 horses.

Procedures—Signalment, history, clinical abnormalities, and clinicopathologic findings were obtained from medical records of horses examined because of neurologic disorders, and precontrast and postcontrast CT images of the head were reviewed. Data were analyzed by use of univariate and multivariate logistic regression.

Results—For a horse with abnormal mentation, odds of having abnormal results for CT imaging of the head was 30 times (95% confidence interval [CI], 2.36 to 374.63) the odds for a similar horse without abnormal mentation. For a horse with cranial nerve deficits, odds of having abnormal results for CT imaging of the head was 11 times (95% CI, 1.00 to 127.96) the odds for a similar horse without cranial nerve deficits. For a horse with seizure-like activity, odds of having abnormal results for CT imaging of the head was 0.05 times (95% CI, 0 to 0.90) the odds for a similar horse without seizures.

Conclusions and Clinical Relevance—These results suggested that alterations in consciousness and cranial nerve deficits were strong predictors of abnormal CT findings for the head of affected horses. Thus, CT can be a useful complementary diagnostic test in horses with these neurologic deficits. In contrast, alternative diagnostic tests (eg, electroencephalography and magnetic resonance imaging) should be considered in horses with seizure-like activity that do not have head trauma or cranial nerve deficits.

Full access
in Journal of the American Veterinary Medical Association

SUMMARY

We compared the frequency and severity of osteochondrosis lesions in young Thoroughbred horses with cervical stenotic myelopathy (csm) vs that in clinically normal Thoroughbreds of the same age. All lesions of the cervical vertebrae and appendicular skeleton were classified histologically as osteochondrosis or nonosteochondrosis and were measured for severity. Minimal sagittal diameter was significantly smaller in horses with csm from C2 through C6; no difference was detected at C7. Severity of cervical vertebral osteochondrosis was greater in the horses with csm, however frequency was not different. Frequency and severity of nonosteochondrosis lesions were not different in cervical vertebrae or appendicular skeleton. Frequency and severity of appendicular skeleton osteochondrosis lesions were both greater in horses with csm. Osteochondrosis and nonosteochondrosis lesions were more severe on facets at sites of compression than on facets at noncompressed sites in horses with csm. However, compression was also observed at sites with no articular facet lesions. The association of widespread osteochondrosis and spinal canal narrowing with csm suggests csm may represent a systemic failure in the development or maturation of cartilage and bone.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To determine the pharmacokinetics of voriconazole following IV and PO administration and assess the distribution of voriconazole into body fluids following repeated PO administration in horses.

Animals—6 clinically normal adult horses.

Procedures—All horses received voriconazole (10 mg/kg) IV and PO (2-week interval between treatments). Plasma voriconazole concentrations were determined prior to and at intervals following administration. Subsequently, voriconazole was administered PO (3 mg/kg) twice daily for 10 days to all horses; plasma, synovial fluid, CSF, urine, and preocular tear film concentrations of voriconazole were then assessed.

Results—Mean ± SD volume of distribution at steady state was 1,604.9 ± 406.4 mL/kg. Systemic bioavailability of voriconazole following PO administration was 95 ± 19%; the highest plasma concentration of 6.1 ± 1.4 μg/mL was attained at 0.6 to 2.3 hours. Mean peak plasma concentration was 2.57 μg/mL, and mean trough plasma concentration was 1.32 μg/mL. Mean plasma, CSF, synovial fluid, urine, and preocular tear film concentrations of voriconazole after long-term PO administration were 5.163 ± 1.594 μg/mL, 2.508 ± 1.616 μg/mL, 3.073 ± 2.093 μg/mL, 4.422 ± 0.8095 μg/mL, and 3.376 ± 1.297 μg/mL, respectively.

Conclusions and Clinical Relevance—Results indicated that voriconazole distributed quickly and widely in the body; following a single IV dose, initial plasma concentrations were high with a steady and early decrease in plasma concentration. Absorption of voriconazole after PO administration was excellent, compared with absorption after IV administration. Voriconazole appears to be another option for the treatment of fungal infections in horses.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate use of kinetic gait analysis for detection, quantification, and differentiation of hind limb lameness and spinal ataxia in horses.

Design—Prospective clinical study.

Animals—36 horses.

Procedures—Kinetic gait analysis with a force plate was performed for 12 clinically normal horses, 12 horses with hind limb lameness, and 12 horses with spinal ataxia. Kinetic variables were compared among groups, correlated to subjective grading, and used to build predictive models to assess the accuracy of discrimination.

Results—Subsets of kinetic variables were characteristically altered in ataxic and lame gaits. Ataxic horses had significantly increased lateral force peak and variation in vertical force peaks in both hind limbs. Lame horses had significantly decreased vertical force peak and increased variation in vertical force peaks only in the lame hind limb. These variables were used to differentiate between spinal ataxia and hind limb lameness with excellent accuracy. There were significant correlations between a subset of kinetic variables and subjective lameness and neurologic grades.

Conclusions and Clinical Relevance—Kinetic gait variables, specifically lateral force peak and the variation in vertical force, can be used to support the differential diagnosis between spinal ataxia and hind limb lameness in horses. Kinetic gait analysis may also be applied for quantification of equine hind limb gait abnormalities as well as confirming lack of lameness and ataxia in soundness examinations.

Full access
in Journal of the American Veterinary Medical Association

Objective

To determine the seroprevalence of serum antibodies to Sarcocystis neurona in horses residing in Ohio.

Design

Prevalence survey.

Sample Population

Serum from samples from 1,056 horses. Serum was collected on every 36th sample submitted to the Ohio State Diagnostic Laboratory for testing for equine infectious anemia.

Procedure

Serum was frozen at −80 C and analyzed for antibodies to S neurona, using a western blot. Information regarding blood sample collection, age, breed, sex, and geographic location was recorded for each horse. Data were analyzed, using multivariable logistic regression.

Results

Horses of 37 breeds from 81 of Ohio's 88 counties were included in the study population. There were 481 females, 133 males, and 442 geldings ranging in age from 3 months to 27 years; > 48% were < 5.6 years old. More than 53% of samples were seropositive for antibodies to S neurona. A gender or breed effect on seroprevalence was not identified. There was a significant effect of age (P ≤ 0.0001; with older horses more likely to be affected), and of location (statistical and extension districts; P = 0.02 and P = 0.03, respectively) on seroprevalence. Location effects appeared to be correlated to the number of days with temperatures below freezing (P < 0.05).

Clinical Implications

The high seroprevalence of antibodies to S neurona found in the sample population emphasizes the importance of examining CSF for S neurona-specific antibodies when establishing a diagnosis of equine protozoal myeloencephalitis. (J Am Vet Med Assoc 1997;210:519–524)

Free access
in Journal of the American Veterinary Medical Association

Summary

Magnification of cervical radiographs prevents accurate interpretation of vertebral canal absolute minimum sagittal diameter (msd) values and application of the established msd values for diagnosis of cervical stenotic myelopathy (csm). Variability in msd determination in human beings, owing to radiographic magnification, is minimized by assessing a ratio of the vertebral canal diameter to the sagittal width of the vertebral body. This relative measurement technique improves the accuracy of diagnosis of cervical spinal stenosis in human beings. The msd of the vertebral canal was determined in 50 horses with csm and 50 control horses, using a radiopaque marker method for correction of magnification. In addition, a ratio of the absolute msd to the sagittal width of the vertebral body and a ratio of the absolute msd to the length of the vertebral body were determined in 100 csm-affected and 100 control horses. Response operating characteristic curve analysis of each method determined that the sagittal ratio method of canal diameter assessment provided the most accurate interpretation of cervical radiographs for diagnosis of csm, with sensitivity and specificity of ≥ 89% at each vertebral site. The accuracy of the ratio method, without consideration of bony malformation, supports the importance, and perhaps prerequisite, of generalized vertebral canal stenosis in the pathogenesis of csm. Subjective evaluation of bony malformations from cervical radiographs of 100 csm-affected horses and 100 control horses indicated that csm-affected horses have more severe bony malformation than do control horses. However, moderate to marked degenerative joint disease of the articular processes was frequently observed in control horses. Subjective evaluation of bony malformation does not distinguish between csm-affected and unaffected horses.

Free access
in American Journal of Veterinary Research

Summary

Six untrained mares were subjected to incremental treadmill exercise to examine exercise-induced changes in plasma renin activity (pra) and plasma aldosterone (aldo) and plasma arginine vasopressin (avp) concentrations. Plasma renin activity, aldo and avp concentrations, and heart rate (hr) were measured at each step of an incremental maximal exercise test. Mares ran up a 6° slope on a treadmill set at an initial speed of 4 m/s. Speed was increased 1 m/s each minute until hr reached a plateau. Plasma obtained was stored at − 80 C and later was thawed, extracted, and assayed for pra and aldo and avp values by use of radioimmunoassay. Exercise caused significant increase in hr from 40 ± 2 beats/min (mean ± sem) at rest to 206 ± 4 beats/min (hr max) at speed of 9 m/s. Plasma renin activity increased from 1.9 ± 1.0 ng/ml/h at rest to a peak of 5.2 ± 1.0 ng/ml/h at 9 m/s, paralleling changes in hr. Up to treadmill speed of 9 m/s, strong linear correlations were obtained between exercise intensity (and duration) and hr (r = 0.87, P < 0.05) and pra (r = 0.93, P < 0.05). Heart rate and pra reached a plateau and did not increase when speed was increased from 9 to 10 m/s. Plasma aldo concentration increased from 48 ± 16 pg/ml at rest to 191 ± 72 pg/ml at speed of 10 m/s. Linear relation was found between exercise intensity (and duration) and aldo concentration (r = 0.97, P < 0.05). Plasma avp concentration increased from 4.0 ± 3.0 pg/ml at rest to 95 ± 5.0 pg/ml at speed of 10 m/s. The relation between avp concentration and exercise intensity (and duration) appeared to be curvilinear, and was described by an exponential function (r = 0.92, P < 0.05). These data indicate that pra and aldo and avp concentrations increase in horses during progressive treadmill exercise.

Free access
in American Journal of Veterinary Research