Assessment of the utility of using intra- and intervertebral minimum sagittal diameter ratios in the diagnosis of cervical vertebral malformation in horses.

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 < or = 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.     

Diagnosis,treatment and outcome of spinal lymphoma in a pony

This report describes the diagnostic approach to, and treatment of, a case of severe pelvic limb ataxia in a Miniature Shetland pony. Diagnosis of an intradural‐extramedullary lesion at the level of T11–12 was made using CT myelography. Dorsolateral hemilaminectomy allowed surgical debulking of an intradural mass, diagnosed histopathologically as T cell rich B cell lymphoma. Post operative treatment with prednisolone, cytarabine and cyclophosphamide was tolerated well and the degree of ataxia reduced markedly, allowing the pony to return to normal management.     

Lumbosacral spinal cord somatosensory evoked potentials for quantification of nociception in horses

Reasons for performing study: There is a need for objective evaluation and quantification of the efficacy of analgesic drugs and analgesic techniques in horses. Objectives: To determine whether lumbosacral spinal cord somatosensory evoked potentials (SSEP) can be a useful and reliable tool to assess nociception in equines. Methods: SSEPs and electromyograms (EMG) from the epaxial muscles were recorded simultaneously, following electrical stimulation applied to the distal hindlimb in lightly anaesthetised Shetland ponies (n = 7). In order to validate the model, the effect of increasing stimulus intensity was documented and the conduction velocities (CV) of the stimulated nerves were calculated. The effect of epidurally applied methadone (0.4 mg/kg bwt) in a randomised, crossover design was investigated. Results: Two distinct complexes (N1P1 and N2P2) were identified in the SSEP waveform. Based on their latency and conduction velocity and the depressant effect of epidurally applied methadone, the SSEP N2P2 was ascribed to nociceptive Aδ‐afferent stimulation. The SSEP N1P1 originated from non‐nociceptive Aβ‐afferent stimulation and was not influenced by epidurally applied methadone. Conclusions and potential relevance: The nociceptive Aδ component of the SSEP, the N2P2 complex, is presented as a valid and quantitative parameter of spinal nociceptive processing in the horse. Validation of the equine SSEP model enables the analgesic effects of new analgesics/analgesic techniques to be quantified and analgesia protocols for caudal epidural analgesia in equidae improved.     

Morphometric and volumetric analysis of the cervical spinal cord and vertebral canal using computed tomography images in normal Van cats

This study was performed on Van cats to determine the volumetric, morphometric and surface area measurement values of their cervical spinal cords (SC) and vertebral canals (CC) and the ratios between their dimensions using computed tomography (CT) images. The study also aims to reveal any biometric differences in these values between the two sexes. Spinal cord and vertebral canal CT images of 16 healthy adult Van cats (8 males and 8 females) were used in the study. First, three measurement points were selected for each vertebra on their cranial, medial and caudal sections along the sagittal axis. Next, the morphometric values were obtained using the transversal images of these measurement points. The surface areas for the SC and CC were calculated using the stereological planimetry method. The Cavalieri's principle was then used to calculate the relevant anatomic structure volumes. The obtained values were then statistically analysed. SC and CC were found to be larger in males in general, while ‘SC cranial/CC cranial’ and ‘SC medial/CC medial’ dimensions and volume ratios were found to be larger in female cats on average. Bodyweight and age values were found to have a negative correlation with SC and CC ratio, but the correlation was statistically insignificant. All SC and CC surface area and volume measurements were found to be higher in male cats (p < .05). We believe the results obtained by this study will provide valuable insight into veterinary clinicians in evaluating pathological lesions in the cervical spinal cord and vertebral canal CT scans.     

Computed tomographic evaluation of cervical vertebral canal and spinal cord morphometry in normal dogs

The height, width, and cross-sectional area of the vertebral canal and spinal cord along with the area ratio of spinal cord to vertebral canal in the cervical vertebra were evaluated in images obtained using computed tomography (CT). Measurements were taken at the cranial, middle, and caudal point of each cervical vertebra in eight clinically normal small breed dogs (two shih tzu, two miniature schnauzers, and four mixed breed), 10 beagles, and four German shepherds. CT myelography facilitated the delineation of the epidural space, subarachnoid space, and spinal cord except at the caudal portion of the 7th cervical vertebra. The spinal cord had a tendency to have a clear ventral border in the middle portion of the vertebral canal and lateral borders near both end plates. The height, width, and area of the vertebral canal and spinal cord in the cervical vertebra were increased as the size of dog increased. However, the ratio of the spinal cord area to vertebral canal area in the small dogs was higher than that of the larger dogs. Results of the present study could provide basic and quantitative information for CT evaluation of pathologic lesions in the cervical vertebra and spinal cord.     

Unilateral degenerative joint disease of a cervical articular process joint between the fourth and fifth cervical vertebrae causing asymmetrical ataxia in a young horse

A 5-year-old horse was examined for investigation of asymmetrical, quadrilateral ataxia and paresis. Clinical examination was unremarkable, and a thorough neurological examination localised the lesion to the cervical spine. Following this, magnetic motor evoked potentials were acquired to allow for latency times to be determined. Abnormal conduction times were found to the right thoracic and right pelvic limbs, confirming that the horse had an asymmetrical cervical spinal myelopathy. Radiographs were acquired to ensure that the horse had no significant pathology which would contraindicate general anaesthesia. There were no abnormalities noted on these, so the horse underwent contrast-enhanced computed tomography of its cervical spine which revealed enlargement of the right articular process joint between C4 and C5 with dorsolateral impingement of the spinal canal and cord. Due to the poor prognosis for future performance, the horse was subsequently euthanised. A post-mortem examination confirmed the findings of degenerative joint disease, with some unexpected changes seen on histology of the spinal cord. The unilateral right-sided compression had caused degenerative changes to ascending and descending tract bilaterally indicating a dynamic component to this lesion, which would be more commonly understood to be static.     

Estimation of sensitivity and specificity of pregnancy diagnosis using transrectal ultrasonography and ELISA for pregnancy-associated glycoprotein in dairy cows using a Bayesian latent class model

AIMS: To determine the sensitivity (Se) and specificity (Sp) of pregnancy diagnosis using transrectal ultrasonography and an ELISA for pregnancy-associated glycoprotein (PAG) in milk, in lactating dairy cows in seasonally calving herds approximately 85–100 days after the start of the herd’s breeding period.

METHODS: Paired results were used from pregnancy diagnosis using transrectal ultrasonography and ELISA for PAG in milk carried out approximately 85 and 100 days after the start of the breeding period, respectively, from 879 cows from four herds in Victoria, Australia. A Bayesian latent class model was used to estimate the proportion of cows pregnant, the Se and Sp of each test, and covariances between test results in pregnant and non-pregnant cows. Prior probability estimates were defined using beta distributions for the expected proportion of cows pregnant, Se and Sp for each test, and covariances between tests. Markov Chain Monte Carlo iterations identified posterior distributions for each of the unknown variables. Posterior distributions for each parameter were described using medians and 95% probability (i.e. credible) intervals (PrI). The posterior median estimates for Se and Sp for each test were used to estimate positive predictive and negative predictive values across a range of pregnancy proportions.

RESULTS: The estimate for proportion pregnant was 0.524 (95% PrI?=?0.485–0.562). For pregnancy diagnosis using transrectal ultrasonography, Se and Sp were 0.939 (95% PrI?=?0.890–0.974) and 0.943 (95% PrI?=?0.885–0.984), respectively; for ELISA, Se and Sp were 0.963 (95% PrI?=?0.919–0.990) and 0.870 (95% PrI?=?0.806–0.931), respectively. The estimated covariance between test results was 0.033 (95% PrI?=?0.008–0.046) and 0.035 (95% PrI?=?0.018–0.078) for pregnant and non-pregnant cows, respectively. Pregnancy diagnosis results using transrectal ultrasonography had a higher positive predictive value but lower negative predictive value than results from the ELISA across the range of pregnancy proportions assessed.

CONCLUSIONS AND CLINICAL RELEVANCE: Pregnancy diagnosis using transrectal ultrasonography and ELISA for PAG in milk had similar Se but differed in predictive values. Pregnancy diagnosis in seasonally calving herds around 85–100 days after the start of the breeding period using the ELISA is expected to result in a higher negative predictive value but lower positive predictive value than pregnancy diagnosis using transrectal ultrasonography. Thus, with the ELISA, a higher proportion of the cows with negative results will be non-pregnant, relative to results from transrectal ultrasonography, but a lower proportion of cows with positive results will be pregnant.     

Correlation between severity of clinical signs and motor evoked potentials after transcranial magnetic stimulation in large-breed dogs with cervical spinal cord disease

OBJECTIVE: To evaluate use of transcranial magnetic motor evoked potentials for assessment of the functional integrity of the cervical spinal cord in large-breed dogs with cervical spinal cord disease. DESIGN: Randomized, controlled, masked study. ANIMALS: 10 healthy large-breed control dogs and 25 large-breed dogs with cervical spinal cord diseases. PROCEDURE: Affected dogs were allocated to 3 groups on the basis of neurologic status: signs of neck pain alone, ambulatory with ataxia in all limbs, or nonambulatory. Transcranial magnetic stimulation was performed on each dog with the same standard technique. Motor evoked potentials (MEP) were recorded from electrodes inserted in the tibialis cranialis muscle. Following the procedure, each dog was anesthetized and cervical radiography, CSF analysis, and cervical myelography were performed. The MEP latencies and amplitudes were correlated with neurologic status of the dogs after correction for neuronal path length. RESULTS: Mean MEP latencies and amplitudes were significantly different between control dogs and dogs in each of the 3 neurologic categories, but were not significantly different among dogs in the 3 neurologic categories. A linear association was evident between MEP latencies and amplitudes and severity of neurologic deficits; the more severe the neurologic deficits, the more prolonged the latencies and the more decreased the amplitudes. CONCLUSIONS AND CLINICAL RELEVANCE: Transcranial magnetic MEP are useful to assess severity of cervical spinal cord disease in large-breed dogs. Impairment of the functional integrity of the cervical spinal cord was found even in dogs with neck pain alone.     

Surgical cytoreduction for the treatment of non-lymphoid vertebral and spinal cord neoplasms in cats: retrospective evaluation of 26 cases (1990–2005)

Medical records of 26 cats with non‐lymphoid vertebral and spinal cord neoplasms treated surgically were reviewed to determine outcome and prognostic factors for survival. Of the factors examined, only tumour phenotype was significantly associated with survival. Osteosarcoma (3/26 cats) and meningioma (16/26 cats) were the most common malignant and benign tumours, respectively. The median survival time for cats with malignant neoplasms was 110.5 days, compared with 518 days for cats with benign tumours. Cytoreductive surgery resulted in clinical improvement in 25/26 cats, but local treatment failure occurred in 10/26 cats. Overall, 19/26 cats died of confirmed (12/19) or suspected (7/19) tumour‐related causes, including all eight cats with malignant neoplasms. Results suggest that contemporary neurosurgical techniques commonly result in incomplete excision of feline non‐lymphoid vertebral and spinal cord tumours but are efficacious at palliation of clinical signs of spinal cord dysfunction.     

Accuracy of an indirect fluorescent-antibody test and of a complement-fixation test for the diagnosis of Babesia caballi in field samples from horses

We evaluated the indirect fluorescent-antibody (IFA) test and complement-fixation (CF) test for diagnosis of equine piroplasmosis in the absence of a gold standard. Using Evan's blue, we estimated the specificity of the IFA test on a parasite-free, field horse population to be 98% (95% confidence interval=97, 99). We observed an excellent test agreement (kappa=0.83) between two collaborating laboratories when the IFA test was performed on identical samples from an endemic area. Using Bayesian analysis with informative prior probability distributions, we estimated the sensitivity of the IFA test to be 92% (95% probability interval, PI=81, 98), and specificity to be 95% (95% PI=88, 99). The CF test sensitivity and specificity estimates were 28% (95% PI=15, 47) and 99% (95% PI=96, 100), respectively. We found the IFA to be superior to the CF test, and the inclusion of Evan's blue in test protocol improved the performance of the IFA test. We conclude that the IFA test for Babesia caballi is a sensitive and specific test for the diagnosis of equine piroplasmosis.     

Application of a semi-dependent latent model in the Bayesian estimation of the sensitivity and specificity of two faecal culture methods for diagnosis of paratuberculosis in sub-clinically infected Greek dairy sheep and goats

In this study, we compared the frequency of isolation of Mycobacterium avium subsp. paratuberculosis (MAP) from faecal samples grown on Herrold's egg-yolk medium (HEYM) or on Lowenstein-Jensen (LJ) medium and estimated the sensitivity (Se) and specificity (Sp) of the methods separately in sub-clinically infected Greek dairy sheep and goats, using latent-class models and Bayesian estimation procedures. Faecal and blood samples were collected from 400 animals > or =1 year old in April-May 2002. The HEYM supported growth of MAP better than the LJ method and their agreement was very poor (weighted kappa=0.062 (95% CI: -0.098, 0.222)). There was no evidence of dependence between the Ses whereas the Sps were positively correlated. Thus, a semi-dependent model that assumed independence of Ses and accounted for the dependence of Sps was adopted. Under this model, the parallel interpretation of the results of the two methods gave median estimates and 95% credible intervals (CrIs) for Se(par), Sp(par) of 15% (CrIs: 3, 45%), 96% (92, 98%) in sheep and 16% (6, 36%) and 97% (94, 99%) in goats.     

Clinical application of multidetector computed tomography and magnetic resonance imaging for evaluation of cranial nerves in horses in comparison with high resolution imaging standards

Although horses are affected by cranial nerve disease, our understanding of these structures' imaging anatomy is limited, and the optimal modality for imaging of each of these nerves is unclear. The aim of this study was to describe the imaging appearance of the equine cranial nerves on high‐resolution 1.5T magnetic resonance imaging (MRI) and computed tomography (CT) scans of a cadaver head, and with these as standards, examine the utility of MRI and CT performed in clinical cases. High‐resolution MRI and CT images were prospectively acquired of the head of a normal Thoroughbred gelding following euthanasia. Ten clinical cases undergoing high‐field MRI under general anaesthesia and 10 clinical cases undergoing CT in the standing horse under sedation were retrospectively evaluated by three reviewers to assess cranial nerve visibility. On high‐resolution, thin‐slice, MRI scans of the normal cadaver head, each of the 12 cranial nerves and their topographic location could be appreciated. On high‐resolution cadaver CT, cranial nerves II, V and VII were clearly visible, but others were less easily identified; osseous structures were clearly visualised. Clinical MRI and CT allowed for variable visualisation of the cranial nerves, dependent on the sequence and the orientation of scan planes. High‐field MRI allowed excellent visualisation of equine cranial nerves, whereas CT allowed for more detailed visualisation of the osseous canals and foramina. In live horses, the ability to identify all 12 nerves is challenging with either MRI or CT; however, high‐field MRI enables better visualisation of the nerve bundles than CT.     

Diaphragmatic dysfunction in dogs with cervical spinal disorders before and after surgery using fluoroscopy,motion‐mode ultrasound and radiography was not different than a group of control dogs

Cervical spinal disorders can lead to life‐threatening respiratory complications. Diaphragmatic dysfunction is attributed to spinal cord morbidity secondary to cervical myelopathy or decompressive surgical intervention. The purpose of this observational case‐control study was to determine the frequency of diaphragmatic dysfunction in dogs with cervical spinal disorders and a control group, the strength of association between cervical myelopathies and decompressive surgery with diaphragm paresis, and the agreement between and clinical usefulness of fluoroscopy, motion‐mode ultrasonography, and radiography for diagnosing diaphragmatic dysfunction. Thirty‐five client‐owned dogs were recruited with 14 control dogs and 21 test dogs. Dogs were evaluated for the presence of diaphragmatic dysfunction using radiography, M‐mode ultrasonography, and fluoroscopy before and after an anesthetic or surgical event. Diaphragmatic dysfunction was observed more frequently in dogs with cervical spinal disease prior to surgery (8/21; 38.1%) compared to control dogs (3/14; 21.4%) but was not statistically significant (P = .30). The occurrence of diaphragmatic dysfunction did not significantly increase following surgical decompression in either group. There was no to slight agreement between all imaging modalities. Most dogs with diaphragmatic dysfunction were asymptomatic. Diaphragmatic dysfunction was not statistically associated with cervical myelopathy or decompressive surgery. Ultrasonography and radiography were not useful diagnostic tests for determining diaphragmatic dysfunction in asymptomatic dogs when compared to fluoroscopy.     

Cerebrospinal fluid analysis and magnetic resonance imaging in the diagnosis of neurologic disease in dogs: a retrospective study

BACKGROUND: Diagnosis of central nervous system (CNS) abnormalities in dogs can be challenging antemortem. Historically, cerebrospinal fluid (CSF) analysis has been used for routine diagnostic evaluation of animals with suspected neurologic disease; however, with increasing availability of magnetic resonance (MR) imaging, the need for concurrent CSF analysis may be questioned. OBJECTIVE: The purpose of this study was to retrospectively assess and compare the diagnostic information contributed from MR imaging and CSF analysis in a population of dogs presenting with neurologic disease. METHODS: Results of concurrent MR imaging and CSF analysis were evaluated in dogs presented for neurologic diseases. Based on clinical diagnosis, the sensitivity of CSF analysis and MR imaging for detecting a nervous system abnormality was calculated. Dogs with diagnoses confirmed by other diagnostic modalities were also evaluated separately. RESULTS: A total of 256 dogs were included in the study. For clinical diagnoses in which abnormalities were expected, MR imaging abnormalities were found in 89% and CSF abnormalities in 75% of dogs; CSF abnormalities were more common than MR imaging abnormalities only in inflammatory CNS disease. The majority of CSF abnormalities were nonspecific; an etiologic diagnosis was determined in only 2% of CSF samples. MR imaging excelled in detecting structural disorders, revealing 98% of vertebral abnormalities. In confirmed cases (n = 55), 76% of MR images and 9% of CSF samples were diagnostic. When intervertebral disk disease (IVDD) and vertebral malformation were excluded from analysis (n = 16 remaining), 25% of MR images and 6% of CSF cytology results were highly indicative of the confirmed diagnoses; CSF titer results provided the diagnosis in 25% of these cases. CONCLUSION: CSF analysis may not be necessary when MR findings of IVDD or vertebral malformation/instability are obvious; however, when the cause of neurologic disorder is uncertain, concurrent MR imaging and CSF analysis provides the greatest assistance in establishing a clinical diagnosis.     

Evaluation of magnetic resonance imaging for the differentiation of inflammatory,neoplastic, and vascular intradural spinal cord diseases in the dog

Magnetic resonance imaging (MRI) is a common test for dogs with suspected intradural spinal cord lesions, however studies on diagnostic performance for this test are lacking. Objectives of this multi‐institutional, retrospective, case‐control study were to estimate sensitivity and specificity of MRI for (1) distinguishing between histopathologically confirmed intradural spinal cord disease versus degenerative myelopathy in dogs, (2) categorizing intradural spinal cord diseases as neoplastic, inflammatory, or vascular; and (3) determining tumor type within the etiologic category of neoplasia. Additional aims were to (1) determine whether knowledge of clinical data affects sensitivity and specificity of MRI diagnoses; and (2) report interrater agreement for MRI classification of intradural spinal lesions. Cases were recruited from participating hospital databases over a 7‐year period. Three reviewers independently evaluated each MRI study prior to and after provision of clinical information. A total of 87 cases were sampled (17 degenerative myelopathy, 53 neoplasia, nine inflammatory, and eight vascular). Magnetic resonance imaging had excellent (>97.6%) sensitivity for diagnosis of intradural spinal cord lesions but specificity varied before and after provision of clinical data (68.6% vs. 82.4%, P = 0.023). Magnetic resonance imaging had good sensitivity (86.8%) and moderate specificity (64.7–72.5%) for diagnosing neoplasia. Sensitivity was lower for classifying inflammatory lesions but improved with provision of clinical data (48.1% vs. 81.5%, P = 0.015). Magnetic resonance imaging was insensitive for diagnosing vascular lesions (25.0%). Interrater agreement was very good for correctly diagnosing dogs with intradural lesions (? = 0.882–0.833), and good (? = 0.726–0.671) for diagnosing dogs with neoplasia.     

Evaluation of basal plasma α‐melanocyte‐stimulating hormone and adrenocorticotrophic hormone concentrations for the diagnosis of pituitary pars intermedia dysfunction from a population of aged horses

Reasons for performing study: The sensitivity and specificity of basal plasma α‐melanocyte‐stimulating hormone (α‐MSH) and adrenocorticotrophic hormone (ACTH) for the diagnosis of pituitary pars intermedia dysfunction (PPID) has not been evaluated in a population‐based study. Objectives: To evaluate basal plasma α‐MSH and ACTH concentrations for the diagnosis of PPID in a population of horses aged ≥15 years. Methods: Owner‐reported data were obtained using a postal questionnaire distributed to an equestrian group. A subgroup of surveyed owners was visited and veterinary examination performed on horses aged ≥15 years. Blood samples were analysed for plasma α‐MSH and ACTH concentrations. Seasonally adjusted cut‐off values for α‐MSH and ACTH concentrations for the diagnosis of PPID were obtained using Youden index values against a clinical gold standard diagnosis (hirsutism plus 3 or more clinical signs of PPID). Results: α‐melanocyte‐stimulating hormone and ACTH were highly correlated with each other and with clinical and historical indicators of PPID. The increase in both α‐MSH and ACTH with increasing numbers of clinical signs in affected horses supports a spectrum of disease. Both variables were affected by season, with derived cut‐off values being higher in autumn compared with other seasons. Sensitivity and specificity were moderate and good in nonautumn seasons (59 and 93%, respectively) for α‐MSH using a cut‐off of 52.0 pmol/l. Sensitivity and specificity were good in nonautumn seasons (80 and 83%, respectively) for ACTH using a cut‐off of 29.7 pg/ml. For both α‐MSH and ACTH, sensitivity and specificity were close to 100% for samples obtained during the autumn period. Conclusions and potential relevance: Basal plasma α‐MSH and ACTH had moderate‐to‐good sensitivity and specificity for the diagnosis of PPID, which improved substantially during the autumn period, suggesting this may be the ideal time to test. Further studies to develop seasonally adjusted reference intervals for different geographical locations are warranted.