Transpalpebral ultrasonographic measurement of the optic nerve sheath diameter in healthy dogs

Objective

To develop a reference range for ultrasonographically measured optic nerve sheath diameter (ONSD‐US) in dogs. We hypothesized that ONSD‐US can be measured reliably and is associated with weight but not age, sex, or body condition score (BCS), and that the relationship between weight and ONSD‐US in dogs is allometric due to canine size variations.

Design

Prospective, observational study.

Setting

University teaching hospital.

Animals

Seventy‐eight healthy adult dogs.

Interventions

The ONSD was measured by a standardized transpalpebral approach.

Measurements and Main Results

Regression analysis showed the relationship between weight and ONSD was better fit with a linear model (R² = 0.8510) than an allometric model (R² = 0.7917). Multiple regression analysis showed ONSD is associated with weight (P < 0.0001), age (P = 0.0021), and BCS (P = 0.0007), but not with sex. Dominance analysis showed 94.6% of the variance explained by the model was due to weight. Intraclass correlation coefficient (ICC) analysis showed excellent interobserver (ICC = 0.9338–0.9608) and intraobserver (ICC = 0.9893) reliability.

Conclusions

These results suggest that ONSD‐US may be reliably measured in dogs using our described transpalpebral approach, and we have calculated prediction intervals based on body weight. Future studies are needed to determine if ONSD‐US measurements are associated with intracranial hypertension as shown in human medicine.     

CORRELATIONS AMONG ULTRASONOGRAPHIC MEASUREMENTS OF OPTIC NERVE SHEATH DIAMETER,AGE, AND BODY WEIGHT IN CLINICALLY NORMAL HORSES

Early diagnosis of high intracranial pressure (ICP) is critical for minimizing progressive brain injury due to reduced cerebral perfusion. In people, detecting enlargement of the optic nerve sheath diameter (ONSD) by transpalpebral ultrasonography has been found to be an accurate test for high ICP. Aims of this prospective, observational, cross‐sectional study were to test hypotheses that (1) ultrasonographic measurement of ONSD would be repeatable in horses, (2) have acceptable interobserver agreement, and (3) would be correlated with age and body weight. The sample population included 48 horses without clinical signs of high ICP and with varying ages and body weights. Two observers independently performed ONSD measurements in both eyes. All measurements ranged from 2.6 to 6.5 mm. The mean difference of repeated measures within observers was ≤0.1 mm and the coefficients of variation ranged from 5.0% to 8.8%. The mean difference of measures between observers was ≤0.2 mm. After correcting for performing multiple tests, no significant rank correlation (all r < 0.4 [absolute value]) was detected between ONSD and age or body weight. However, we observed smaller ONSD in foals versus adults (all P ≤ 0.002). In the foals, all observed measures of rostrocaudal and dorsoventral ONSD were <5 mm. In the adults, all observed measures of rostrocaudal and dorsoventral ONSD were ≤6.5 mm. Findings indicated that ultrasonographic ONSD measurement is a feasible test for use in horses of varying ages and sizes. Further investigation of this ultrasonographic measure as a clinical test for horse with suspected high ICP is warranted.     

Clinical and imaging findings,treatments, and outcomes in 27 dogs with imaging diagnosed trigeminal nerve sheath tumors: A multi‐center study

The clinical behavior of canine trigeminal nerve sheath tumors and benefits of previously reported treatments are incompletely defined. Aims of this retrospective, multicenter, observational study were to describe clinical signs, tumor localization characteristics, treatments, and clinical outcomes in a group of dogs with this neoplasm. Databases at four hospitals were reviewed for dogs with a trigeminal nerve sheath tumor diagnosis, magnetic resonance imaging (MRI) studies, and presentation between 2004 and 2014. A single observer recorded medical record findings and two observers recorded MRI characteristics by consensus. A total of 27 dogs met inclusion criteria (15 treated with stereotactic radiation therapy and 12 unirradiated). Two unirradiated dogs were excluded from outcome analyses. The most common presenting signs were masticatory muscle atrophy (26 dogs), neurologic signs referable to intracranial disease (13), and ocular disease (12). Based on MRI findings, all dogs had disease extending centrally at the level of the brainstem. The most commonly affected trigeminal nerve branches were the mandibular (26 dogs), maxillary (22), and ophthalmic (10). Of 15 dogs treated with stereotactic radiation therapy, one had improved muscle atrophy, and six had poor ocular health after treatment. Neurologic signs improved in 4/5 dogs with intracranial signs. Overall median survival time for the 10 unirradiated dogs with available follow‐up was 12 days and 441 days for the 15 stereotactic radiation therapy dogs. Mean survival times between these groups were not significantly different (mean 95% CI for unirradiated dogs was 44–424 days and mean 95% CI for stereotactic radiation therapy dogs was 260–518 days).     

CLINICAL AND MAGNETIC RESONANCE IMAGING FEATURES OF INFLAMMATORY VERSUS NEOPLASTIC MEDIAL RETROPHARYNGEAL LYMPH NODE MASS LESIONS IN DOGS AND CATS

Medial retropharyngeal lymph node (MRLN) mass lesions are a common cause of cranial cervical masses in dogs and cats, and are predominantly due to metastatic neoplasia, primary neoplasia, or inflammatory lymphadenitis. The purpose of this retrospective cross‐sectional study was to test the hypothesis that clinical and magnetic resonance imaging (MRI) characteristics for dogs and cats with MRLN mass lesions would differ for inflammatory vs. neoplastic etiologies. Dogs and cats with MRLN mass lesions that had undergone MRI and had a confirmed cytological or histopathological diagnosis were recruited from medical record archives. Clinical findings were recorded by one observer and MRI characteristics were recorded by two other observers who were unaware of clinical findings. A total of 31 patients were sampled, with 15 in the inflammatory lymphadenitis group and 16 in the neoplasia group. Patients with inflammatory lymphadenitis were more likely to be younger and present with lethargy (P = 0.001), pyrexia (P = 0.000), and neck pain (P = 0.006). Patients with inflammatory lymphadenitis were also more likely to have a leukocystosis (P = 0.02) and segmental neutrophilia (P = 0.001). Inflammatory masses were more likely to have moderate or marked MRI perinodal contrast enhancement (P = 0.021) and local muscle contrast enhancement (P = 0.03) whereas the neoplastic masses were more likely to have greater MRI width (P = 0.002) and height (P = 0.009). In conclusion, findings indicated that some clinical and MRI characteristics differed for dogs and cats with inflammatory vs. neoplastic medial retropharyngeal lymph node masses. Although histopathological or cytological diagnosis remains necessary for confirmation, these findings may help with the ranking of differential diagnoses of future cases.     

RETROSPECTIVE STUDY EVALUATING ASSOCIATIONS BETWEEN MIDLINE BRAIN SHIFT ON MAGNETIC RESONANCE IMAGING AND SURVIVAL IN DOGS DIAGNOSED WITH MENINGOENCEPHALITIS OF UNKNOWN ETIOLOGY

Difficulty has been encountered when trying to identify ante mortem prognostic indicators for dogs with meningoencephalitis of unknown etiology (MUE). Identifying MRI imaging parameters associated with prognosis may impact treatment decision‐making for clinician and owner. Our hypotheses for this retrospective cohort study are that dogs diagnosed with MUE that had midline shift on brain MRI would have a poorer survival compared to dogs without midline shift; and that younger age, lower weight, and low cerebrospinal fluid (CSF) cell count would be correlated with improved survival. Medical records were reviewed from two institutions. Inclusion criteria included: clinical signs referable to intracranial disease, brain MRI at presentation, abnormal CSF analysis, and negative infectious disease testing. Magnetic resonance imaging scans were evaluated for midline shift using the T2‐weighted transverse image at the interthalamic adhesion and at the site of maximal deviation. Fifty‐two dogs met the inclusion criteria. Median midline deviation was 0.12 cm. Median survival for dogs with no shift was 906 days and with shift was 84 days. Survival was not significantly different between groups (P = 0.11). This remained true when correcting for age (P = 0.22) and CSF TNCC (total nucleated cell count) (P = 0.12). Age at the time of diagnosis (P = 0.02) and CSF TNCC (P = 0.03) were significantly associated with survival. Cerebrospinal fluid protein value (P = 0.84) and weight (P = 0.82) were not significantly associated with survival. In this study of 52 dogs with MUE, MRI evidence of midline brain shift between 0.04 and 0.3 cm at the level of the interthalamic adhesion was not associated with shorter survival.     

Transcranial Doppler Ultrasound Examination in Dogs with Suspected Intracranial Hypertension Caused by Neurologic Diseases

Background

Transcranial Doppler ultrasound examination (TCD) is a rapid, noninvasive technique used to evaluate cerebral blood flow and is useful for the detection of intracranial hypertension in humans. However, the clinical usefulness of TCD in diagnosing intracranial hypertension has not been demonstrated for intracranial diseases in dogs.

Objectives

To determine the association between the TCD variables and intracranial hypertension in dogs with intracranial diseases.

Animals

Fifty client‐owned dogs with neurologic signs.

Methods

Cross‐sectional study. All dogs underwent TCD of the basilar artery under isoflurane anesthesia after magnetic resonance imaging (MRI). Dogs were classified into 3 groups based on MRI findings: no structural diseases (group I), structural disease without MRI evidence of intracranial hypertension (group II), and structural disease with MRI evidence of intracranial hypertension (group III). The TCD vascular resistance variables (resistive index [RI], pulsatility index [PI], and the ratio of systolic to diastolic mean velocity [Sm/Dm]) were measured.

Results

Fifteen, 22, and 13 dogs were classified into groups I, II, and III, respectively. Dogs in group III had significantly higher Sm/Dm (median, 1.78; range, 1.44–2.58) than those in group I (median, 1.63; range, 1.43–1.75) and group II (median, 1.62; range, 1.27–2.10). No significant differences in RI and PI were identified among groups.

Conclusions and Clinical Importance

Our findings suggest that increased Sm/Dm is associated with MRI findings of suspected intracranial hypertension in dogs with intracranial diseases and that TCD could be a useful tool to help to diagnose intracranial hypertension.     

Comparison of a computed tomographic pulmonary trunk to aorta diameter ratio with echocardiographic indices of pulmonary hypertension in dogs

There are limited criteria for the detection of pulmonary hypertension in dogs undergoing computed tomography (CT) for pulmonary disease. This retrospective analytical exploratory study compared a CT pulmonary trunk to aorta ratio with echocardiographic estimates of pulmonary hypertension. Dogs having both a contrast thoracic CT and echocardiogram were selected and maximal pulmonary trunk and descending aorta diameters were measured by two observers on a single transverse CT image. Computed tomographic diameter ratios were compared with the echocardiographic parameters of tricuspid regurgitation gradient, right ventricular acceleration time‐to‐ejection time ratio, pulmonary insufficiency gradient, and pulmonary artery to aorta diameter. A total of 78 dogs were sampled, with 44 dogs having one or more finding suggestive of pulmonary hypertension. A moderate positive correlation was shown between tricuspid regurgitation gradient and CT pulmonary trunk to aorta ratio (r = 0.61, P‐value < 0.0001). Mean CT pulmonary trunk to aorta ratio of dogs with moderate (P = 0.0132) and severe (P < 0.0003) pulmonary hypertension were significantly higher than normal dogs. There was no significant difference in mean CT pulmonary trunk to aorta ratio between normal and mild pulmonary hypertension dogs (P = 0.4244). The intraclass correlation coefficient (0.72) showed good reproducibility of the ratio. Findings indicated that CT pulmonary trunk to aorta ratio is a reproducible and potentially useful method to predict moderate and severe pulmonary hypertension in dogs, but not mild pulmonary hypertension. In dogs undergoing thoracic CT for pulmonary disease, an increased ratio should prompt follow up echocardiography.     

Acute postretinal blindness: ophthalmologic,neurologic, and magnetic resonance imaging findings in dogs and cats (seven cases)

Objective To describe the ophthalmologic, neurologic, and magnetic resonance imaging (MRI) findings of seven animals with acute postretinal blindness as sole neurologic deficit. Methods Medical records were reviewed to identify dogs and cats with postretinal blindness of acute presentation, that had a cranial MRI performed as part of the diagnostic workup. Only animals lacking other neurologic signs at presentation were included. Complete physical, ophthalmic, and neurologic examinations, routine laboratory evaluations, thoracic radiographs, abdominal ultrasound, electroretinography, and brain MRI were performed in all animals. Cerebrospinal fluid analysis and postmortem histopathologic results were recorded when available. Results Four dogs and three cats met the inclusion criteria. Lesions affecting the visual pathways were observed on magnetic resonance (MR) images in six cases. Location, extension, and MRI features were described. Neuroanatomic localization included: olfactory region with involvement of the optic chiasm (n = 4), pituitary fossa with involvement of the optic chiasm and optic tracts (n = 1), and optic nerves (n = 1). Of all lesions detected, five were consistent with intracranial tumors (two meningiomas, one pituitary tumor, two nasal tumors with intracranial extension), and one with bilateral optic neuritis that was confirmed by cerebrospinal fluid analysis. Histologic diagnosis was obtained in four cases and included one meningioma, one pituitary carcinoma, one nasal osteosarcoma, and one nasal carcinoma. Conclusions Central nervous system (CNS) disease should be considered in dogs and cats with acute blindness, even when other neurologic deficits are absent. This study emphasizes the relevance of MRI as a diagnostic tool for detection and characterization of CNS lesions affecting the visual pathways.     

COMPARISON OF CLOSURE TIMES FOR CRANIAL BASE SYNCHONDROSES IN MESATICEPHALIC,BRACHYCEPHALIC, AND CAVALIER KING CHARLES SPANIEL DOGS

Premature closure of cranial base synchondroses has been proposed as the mechanism for brachycephaly in dogs and caudal occipital malformation syndrome (COMS) in Cavalier King Charles Spaniels. The purpose of this retrospective study was to compare times of closure for cranial base synchondroses in mesaticephalic, brachycephalic, and Cavalier King Charles Spaniel dogs. Cranial magnetic resonance imaging studies were retrieved for client‐owned dogs less than 18 months of age. Breed, age, skull conformation, and the open or closed state of cranial base synchondroses were independently recorded by two observers. For dogs with a unanimous observer agreement, regression analysis was used to test effects of age and gender on the open or closed status of synchondroses and differences between groups. A total of 174 dogs were included in MRI interpretations and 165 dogs were included in the regression analysis. Statistically significant differences in closure time of the spheno‐occipital synchondrosis were identified between brachycephalic and mesaticephalic dogs (P = 0.016), Cavalier King Charles Spaniels and mesaticephalic dogs (P < 0.0001), and Cavalier King Charles Spaniels and brachycephalic dogs (P = 0.014). Findings from the current study supported the theory that morphological changes leading to the skull phenotype of the Cavalier King Charles Spaniels could be due to an earlier closure of the spheno‐occipital synchondrosis.     

COMPARISON BETWEEN NONCONTRAST COMPUTED TOMOGRAPHY AND MAGNETIC RESONANCE IMAGING FOR DETECTION AND CHARACTERIZATION OF THORACOLUMBAR MYELOPATHY CAUSED BY INTERVERTEBRAL DISK HERNIATION IN DOGS

Magnetic resonance imaging (MRI) and computed tomography (CT) are commonly used to evaluate dogs with thoracolumbar myelopathy; however, relative diagnostic sensitivities for these two modalities have not been previously reported. The purpose of this prospective study was to compare diagnostic sensitivity and observer agreement for MRI and CT in a group of dogs with thoracolumbar myelopathy due to surgically confirmed intervertebral disk herniation (IVDH). All included dogs had magnetic resonance (MR) imaging followed by noncontrast CT using standardized protocols. Three experienced observers interpreted each imaging study independently without knowledge of clinical or surgical findings. The operating surgeon was aware of MR findings but not CT findings at the time surgical findings were recorded. Forty‐four dogs met the inclusion criteria. The sensitivity of CT was 88.6% (79.5%–94.2%) and of MR was 98.5% (95% confidence interval, 94.1%–99.7%) for diagnosis of intervertebral disk herniation. Specificity was not calculated, as all dogs had IVDH at surgery. Magnetic resonance imaging was more accurate than CT for identifying the site of intervertebral disk herniation‐associated spinal cord compression and differentiating disk extrusion vs. protrusion. Computed tomography was less accurate for lesion localization in per acute cases, as well as for chondrodystrophic, female, older and smaller (<7 kg) dogs. Inter‐rater agreement was good for lesion lateralization for both MR and CT (κ = 0.687, 95% CI = 0.552, 0.822, P = 0.002, and κ = 0.692, 95% CI = 0.542, 0.842, P = 0.003). Findings from the current study indicated that MR imaging was more sensitive and accurate than noncontrast CT for diagnosis and characterization of thoracolumbar myelopathy due to IVDH in dogs.     

DOES CHANGING THE ORIENTATION OF A THORACIC RADIOGRAPH AID DIAGNOSIS OF RIB FRACTURES?

To test the hypothesis that changing the orientation of a thoracic radiograph aids diagnosis of rib fractures, a case–control study was carried out using 120 radiographs of small animal patients with recent thoracic trauma. Six independent observers representing three levels of experience viewed the radiographs in randomized order in conventional and unconventional orientations at 15‐s intervals in a PowerPoint^® presentation. Sensitivity for rib fractures was 53–69% and specificity was 74–97%, depending on the observer. Radiologists had higher specificity than less experienced observers (P=0.0001), but comparable sensitivity for rib fractures. Radiologists had significantly higher accuracy than residents (P=0.03), and residents had higher accuracy than interns (P=0.02). Accuracy of diagnosis was reduced significantly when based on lateral radiographs compared with dorsoventral (DV)/ventrodorsal (VD) views (P=0.02) mainly because of low sensitivity of lateral radiographs of dogs with rib fractures. Rotating radiographs 90° clockwise was associated with increased specificity of one intern (from 74 to 90%, P=0.03), but had no effect on accuracy of diagnosis by other observers (P>0.16). Turning DV/VD views upside down had no effect on accuracy of diagnosis of any observers (P>0.40). Changing the orientation of a thoracic radiograph may make it easier for some novices to examine the ribs; hence it could be considered a training aid rather than a technique that will benefit an experienced radiologist.     

COMPARATIVE MAGNETIC RESONANCE IMAGING FINDINGS BETWEEN GLIOMAS AND PRESUMED CEREBROVASCULAR ACCIDENTS IN DOGS

Cerebrovascular accidents, or strokes, and gliomas are common intraaxial brain lesions in dogs. An accurate differentiation of these two lesions is necessary for prognosis and treatment decisions. The magnetic resonance (MR) imaging characteristics of 21 dogs with a presumed cerebrovascular accident and 17 with a glioma were compared. MR imaging findings were reviewed retrospectively by three observers unaware of the final diagnosis. Statistically significant differences between the appearance of gliomas and cerebrovascular accidents were identified based on lesion location, size, mass effect, perilesional edema, and appearance of the apparent diffusion coefficient map. Gliomas were predominantly located in the cerebrum (76%) compared with presumed cerebrovascular accidents that were located mainly in the cerebellum, thalamus, caudate nucleus, midbrain, and brainstem (76%). Gliomas were significantly larger compared with presumed cerebrovascular accidents and more commonly associated with mass effect and perilesional edema. Wedge‐shaped lesions were seen only in 19% of presumed cerebrovascular accidents. Between the three observers, 10–47% of the presumed cerebrovascular accidents were misdiagnosed as gliomas, and 0–12% of the gliomas were misdiagnosed as cerebrovascular accidents. Diffusion weighted imaging increased the accuracy of the diagnosis for both lesions. Agreement between observers was moderate (κ=0.48, P<0.01).     

Development and validation of the Canine Atopic Dermatitis Lesion Index,a scale for the rapid scoring of lesion severity in canine atopic dermatitis

Background – The third iteration of the Canine Atopic Dermatitis Extent and Severity Index (CADESI‐03) is the only tool rigorously validated for canine atopic dermatitis (CAD) lesion scoring. The CADESI‐03 requires 248 evaluations, limiting its widespread use. Hypothesis/Objectives – The goal of the study was to develop and validate a practical method of grading CAD lesions that requires scoring only the frequently affected body regions. Animals – Fifty‐seven privately owned atopic dogs were used in the study. Methods – The Canine Atopic Dermatitis Lesion Index (CADLI) was evaluated in an open, multicentre reliability study. Validity was assessed with expert opinion (content validity) and comparison of CADLI with existing disease severity measures (construct and criterion validity). Reliability was evaluated by analysing repeated observations of each dog. Convenience was assessed in terms of the time required to complete the scale. Results – The CADLI scores correlated with overall assessment scores (r = 0.60, P < 0.001, linear mixed model) and pruritus severity scores (r = 0.53, P < 0.001, linear mixed model), establishing construct validity. The CADLI was strongly correlated with CADESI‐03 (r = 0.84, P < 0.001, linear mixed model), establishing criterion validity. The CADLI values obtained by two observers correlated very strongly (r = 0.91, P < 0.001), as did the repeat values for the same observer (r = 0.98, P < 0.001). The mean time to complete the CADLI was less than that required for CADESI‐03 (1.9 and 12.6 min, respectively), a highly significant difference (P < 0.001). Conclusion and clinical importance – The CADLI was found to be an effective measure of CAD lesion severity, strongly correlating with CADESI‐03. The convenience of CADLI makes it suitable for use in both clinical research and practice.     

Concurrent medical conditions and long-term outcome in dogs with nontraumatic intracranial hemorrhage

Nontraumatic intracranial hemorrhage is bleeding originating from the brain or surrounding structures. It results from blood vessel rupture and may be primary or secondary in origin. The magnetic resonance imaging (MRI) characteristics of 75 dogs with nontraumatic intracranial hemorrhage were reviewed to determine signalment; intracranial compartment involved, size and number of lesions; type and prevalence of concurrent medical conditions; and long‐term outcome. Hemorrhagic lesions were intraparenchymal (n = 72), subdural (n = 2) or intraventricular (n = 1). Thirty‐three of 75 dogs had a concurrent medical condition. A concurrent condition was detected in 13 of 43 dogs with a single lesion ≥5 mm and included Angiostrongylus vasorum infection, intracranial lymphoma and meningioma. Of the 20 dogs with multiple lesions ≥5 mm, 7 had A. vasorum infection, 2 had hemangiosarcoma metastasis, 5 had suspected brain metastasis, and 1 was septicemic. Of the 12 dogs with multiple lesions, 2 had hyperadrenocorticism, 2 had chronic kidney disease, and 1 had hypothyroidism. Of these five dogs, all were hypertensive and four died within 12 months. No dog had a single lesion <5 mm. Long‐term outcome was favorable in 26 of 43 dogs with single lesions ≥5 mm, 6 of 20 dogs with multiple lesions ≥5 mm, and 8 of 12 dogs with multiple lesions <5 mm. A. vasorum infection was the most common concurrent condition in dogs with nontraumatic intracranial hemorrhage (16/75), with an excellent outcome in 14 of 16 dogs. Prognosis in nontraumatic intracranial hemorrhage is reported in terms of concurrent medical conditions and the number and size of lesions. © 2012 Crown copyright. This article was written by M. Lowrie, F. Llabrés‐Diaz and L. Garosi of Davies Veterinary Specialists and L. De Risio and R. Dennis of the Animal Health Trust. It is published with the permission of the Controller of HMSO and the Queen's Printer for Scotland     

EFFECTS OF INTRAVENOUS DEXMEDETOMIDINE ON CARDIAC CHARACTERISTICS MEASURED USING RADIOGRAPHY AND ECHOCARDIOGRAPHY IN SIX HEALTHY DOGS

Dexmedetomidine is a highly specific and selective α2‐adrenergic receptor agonist widely used in dogs for sedation or analgesia. We hypothesized that dexmedetomidine may cause significant changes in radiographic and echocardiographic measurements. The objective of this prospective cross‐sectional study was to test this hypothesis in a sample of six healthy dogs. Staff‐owned dogs were recruited and received a single dose of dexmedetomidine 250 μg/m² intravenously. Thoracic radiography and echocardiography were performed 1 h before treatment, and repeated 10 and 30 min after treatment, respectively. One observer recorded cardiac measurements from radiographs and another observer recorded echocardiographic measurements. Vertebral heart score and cardiac size to thorax ratio on the ventrodorsal projection increased from 9.8 ± 0.6 v to 10.3 ± 0.7 v (P = 0.0007) and 0.61 ± 0.04 to 0.68 ± 0.03 (P = 0.0109), respectively. E point‐to‐septal separation and left ventricle internal diameter in diastole and systole increased from 2.4 ± 1.1 to 6.6 ± 1.9 mm, 32.3 ± 8.1 to 35.5 ± 8.8 mm, and 19.4 ± 6 to 27.0 ± 7.2 mm, respectively (P < 0.05). Fractional shortening and sphericity index decreased from 40.7 ± 5.8 to 24.4 ± 2.9%, and 1.81 ± 0.07 to 1.58 ± 0.04, respectively (P < 0.05). Moderate‐to‐severe mitral regurgitation and mild pulmonic regurgitation occurred in all dogs after dexmedetomidine administration. Findings indicated that dexmedetomidine could cause false‐positive diagnoses of valvular regurgitation and cardiomegaly in dogs undergoing thoracic radiography and echocardiography.     

EFFECTS OF STIFLE FLEXION ANGLE AND SCAN PLANE ON VISIBILITY OF THE NORMAL CANINE CRANIAL CRUCIATE LIGAMENT USING LOW‐FIELD MAGNETIC RESONANCE IMAGING

Low‐field magnetic resonance imaging (MRI) is commonly used to evaluate dogs with suspected cranial cruciate ligament injury; however, effects of stifle positioning and scan plane on visualization of the ligament are incompletely understood. Six stifle joints (one pilot, five test) were collected from dogs that were scheduled for euthanasia due to reasons unrelated to the stifle joint. Each stifle joint was scanned in three angles of flexion (90°, 135°, 145°) and eight scan planes (three dorsal, three axial, two sagittal), using the same low‐field MRI scanner and T2‐weighted fast spin echo scan protocol. Two experienced observers who were unaware of scan technique independently scored visualization of the cranial cruciate ligament in each scan using a scale of 0–3. Visualization score rank sums were higher when the stifle was flexed at 90° compared to 145°, regardless of the scan plane. Visualization scores for the cranial cruciate ligament in the dorsal (H (2) = 19.620, P = 0.000), axial (H (2) = 14.633, P = 0.001), and sagittal (H (2) = 8.143, P = 0.017) planes were significantly affected by the angle of stifle flexion. Post hoc analysis showed that the ligament was best visualized at 90° compared to 145° in the dorsal (Z = ?3.906, P = 0.000), axial (Z = ?3.398, P = 0.001), and sagittal (Z = ?2.530, P = 0.011) planes. Findings supported the use of a 90° flexed stifle position for maximizing visualization of the cranial cruciate ligament using low‐field MRI in dogs.     

Efficacy of stereotactic radiation therapy for the treatment of confirmed or presumed canine glioma

Intracranial gliomas are the second most common brain tumour in dogs. Radiation therapy provides a minimally invasive treatment option for this tumour type. Earlier publications reporting on the use of non-modulated radiation therapy suggested a poor prognosis for dogs with glioma, with median survival times ranging between 4 and 6 months; more recent literature utilizing stereotactic radiation therapy (SRT) demonstrates that the prognosis for canine gliomas may be more promising, with survival times closer to 12 months. A single institution retrospective study was performed between 2010 and 2020 investigating the outcomes of dogs with biopsy-confirmed glioma or a presumptive diagnosis of intra-cranial glioma based on MRI characteristics that were treated with SRT. Twenty-three client-owned dogs were included. Brachycephalic breeds were overrepresented, totalling 13 dogs (57%). SRT protocols included 16 Gy single fraction (n = 1, 4%), 18 Gy single fraction (n = 1, 4%), 24 Gy in 3 daily fractions (n = 20, 91%), or 27 Gy in four daily fractions (n = 1, 4%). Twenty-one dogs (91%) had improvement of their presenting clinical signs following SRT. Median overall survival time (MST) was 349 days (95% CI, 162–584). Median disease specific survival time was 413 days (95% CI, 217–717). When SRT is incorporated into the management plan for dogs with confirmed or presumed intracranial glioma, a median survival time of approximately 12 months may be achievable.     

Relationships among neuroscore,magnetic resonance imaging features,and intracranial pressure in sheep affected by slow‐growing brain lesions

Diagnosing high intracranial pressure by clinical and diagnostic imaging is particularly challenging for chronic or slow‐growing lesions. The aim of this prospective case‐control study is to determine whether the neuroscore and brain magnetic resonance imaging (MRI) are related to the direct measurement of intracranial pressure in sheep affected by intracranial slow‐growing lesions due to chronic cerebral coenurosis (Coenurus cerebralis). Seventeen affected and 10 control sheep were included. All animals underwent a neurological examination, MRI of the brain, and direct measurement of intracranial pressure. The severity of clinical signs and MRI findings were scored. Data were statistically analyzed. The invasive intracranial pressure value was higher in affected animals. A severely altered neuroscore is related to an increased intracranial pressure beyond the normal threshold (P < 0.05). The volume of the calvarium was larger in affected animals than in control animals (P = 0.0001) and was positively influenced by the presence and volume of the parasitic cyst (r = 0.7881, P < 0.01). Several degrees of deviation and deformation of both the ventricular system and brain parenchyma were detected by MRI. Subjective MRI findings were not associated with intracranial hypertension. In conclusion, this study shows that in sheep affected by slow‐growing lesions, severe alterations in the neuroscore and the results of objective MRI are related to an increased intracranial pressure beyond the normal threshold.     

Echocardiographic and tissue Doppler imaging alterations associated with spontaneous canine systemic hypertension

Background: Feline systemic arterial hypertension (SHT) is associated with a wide spectrum of left ventricular (LV) geometric patterns as well as diastolic, and to a lesser extent, systolic myocardial dysfunction. However, little is known about SHT‐related cardiac changes in dogs. Hypothesis: SHT in dogs is responsible for morphological and functional cardiac alterations. Animals: Thirty dogs with spontaneous untreated SHT and 28 age‐ and body weight‐matched healthy dogs as controls. Methods: Prospective observational study. Conventional echocardiography and 2‐dimensional color tissue Doppler imaging were performed in SHT dogs by trained observers and compared with controls. Results: Forty‐seven percent of SHT dogs (14/30) had diffuse concentric hypertrophy. None had left atrial dilatation and 10/30 (33%) had aortic insufficiency (AoI) associated with proximal aortic dilatation. Longitudinal diastolic left ventricular free wall (LVFW) motion was altered in all SHT dogs at the base (early to late diastolic wave ratio, E/A = 0.5 ± 0.1 versus 1.3 ± 0.3 for controls, P < .0001) and the apex (E/A = 1.6 ± 1.7 versus 3.9 ± 3.1, P < .05). Longitudinal motion of the interventricular septum at the base (E/A = 0.7 ± 0.4 versus 1.1 ± 0.1, P < .01) and radial LVFW motion in the subendocardium (E/A = 0.9 ± 0.5 versus 1.6 ± 0.3, P < .01) were also altered in dogs with SHT. Longitudinal LVFW systolic velocities and gradients were also significantly decreased (P < .05) in SHT dogs. Conclusion and Clinical Importance: As in SHT in cats, SHT in dogs is associated with myocardial dysfunction independently of the presence of myocardial hypertrophy. However, unlike feline SHT, it results in a homogeneous LV geometric pattern with a relatively high prevalence of AoI.