J. F. McConnell

Prognostic Value of Early Magnetic Resonance Imaging in Dogs after Traumatic Brain Injury: 50 Cases

Background The prognostic value of early magnetic resonance imaging (MRI) in dogs after traumatic brain injury (TBI) remains unclear. Objectives Determine whether MRI findings are associated with prognosis after TBI in dogs. Animals Fifty client‐owned dogs. Methods Retrospective study of dogs with TBI that underwent 1.5T MRI within 14 days after head trauma. MRI evaluators were blinded to the clinical presentation, and all images were scored based on an MRI grading system (Grade I [normal brain parenchyma] to Grade VI [bilateral lesions affecting the brainstem with or without any lesions of lesser grade]). Skull fractures, percentage of intraparenchymal lesions, degree of midline shift, and type of brain herniation were evaluated. MGCS was assessed at presentation. The presence of seizures was recorded. Outcome was assessed at 48 h (alive or dead) and at 3, 6, 12, and 24 months after TBI. Results Sixty‐six percent of the dogs had abnormal MRI findings. MRI grade was negatively correlated (P < .001) with MGCS. A significant negative correlation of MRI grade, degree of midline shift, and percentage of intraparenchymal lesions with follow‐up scores was identified. The MGCS was lower in dogs with brain herniation (P = .0191). Follow‐up scores were significantly lower in dogs that had brain herniation or skull fractures. The possibility of having seizures was associated with higher percentage of intraparenchymal lesions (P = 0.0054) and 10% developed PTE. Conclusions and Clinical Importance Significant associations exist between MRI findings and prognosis in dogs with TBI. MRI can help to predict prognosis in dogs with TBI.

Effects of body position, imaging plane, and observer on computed tomographic measurements of the lumbosacral intervertebral foraminal area in dogs

OBJECTIVE To evaluate effects of imaging plane, flexion and extension, patient weight, and observer on computed tomographic (CT) image measurements of the area of the lumbosacral (L7-S1) intervertebral foramen (LSIF) in dogs. SAMPLE 12 dog cadavers (2 were excluded because of foraminal stenosis). PROCEDURES In each cadaver, sagittal, sagittal oblique, transverse oblique, and double oblique CT images were obtained at 3 zones (entrance, middle, and exit zones) of the region of the lateral lumbar spinal canal that comprises the LSIF while the lumbosacral junction (LSJ) was positioned in flexion or extension. Barium-impregnated polymethylmethacrylate was used to fill the intervertebral foramina to aid boundary detection. Measurements of interest were obtained. RESULTS Among the dog cadavers, there was large variability in LSIF cross-sectional areas (range, 0.12 to 0.44 cm2; SD, 0.1 cm2) and in foraminal angles required to obtain a double oblique plane in LSJ extension (SD, 8 ° to 9 °). For LSIF area measurements in standard sagittal CT images, interobserver variability was 23% to 44% and intraobserver variability was 4% to 5%. Sagittal oblique images obtained during LSJ extension yielded smaller mean LSIF areas (0.30 cm2), compared with findings in sagittal images (0.37 to 0.52 cm2). The exit and middle zone areas were smaller than the entrance zone area in sagittal images obtained during LSJ extension. CONCLUSIONS AND CLINICAL RELEVANCE Repeated measurements of the LSIF area in images obtained during LSJ extension may be unreliable as a result of interobserver variability and the effects of dog positioning and CT slice orientation.

Comparison between echocardiographic and non-ECG-gated CT measurements in dogs

The aim of this study was to compare echocardiographic measurements with non-ECG-gated contrast-enhanced cardiac CT measurements in dogs. Fifty-seven dogs were included in the study. The following echocardiographic parameters were measured: M-mode interventricular septum in diastole and systole, left ventricular internal diameter in diastole and systole, left ventricular free wall in diastole and systole, 2D left atrial maximal diameter, 2D left atrium to aorta ratio in diastole, 2D aortic annulus in systole and 2D pulmonary annulus in diastole and systole. CT measurements were obtained from multiplanar reconstruction images, replicating the imaging planes used for 2D measurements on echocardiography. It was not possible to discriminate between systole and diastole. The results showed moderate Lins concordance correlation coefficients between the left ventricular internal diameter in systole (0.77), the aortic annuli (0.84) and the pulmonary annuli in diastole (0.78) and systole (0.80). Low coefficients were obtained between the other parameters. Bland-Altman plots for the parameters with highest concordance correlation coefficients were calculated. They suggested equivalence between the measurements of the aortic annuli. Equivalence was not seen between the remaining echocardiographic and CT measurements. Therefore, non-ECG-gated CT is not a reliable way of quantitatively assessing cardiac size.

Sensitivity and specificity of MRI for detecting facial nerve abnormalities in dogs with facial neuropathy

Idiopathic facial neuropathy in dogs is conventionally diagnosed by exclusion of structural and metabolic causes of a single cranial neuropathy. To investigate the reliability and validity of MRI for supporting a diagnosis of facial neuropathy in dogs, we examined MR images of the brainstem from 20 dogs with presumed idiopathic facial neuropathy, and 20 control dogs. Two different types of MRI sequence were compared: volumetric interpolated breath-hold examination MRI (VIBE-MRI), and conventional T1-weighted MRI. Three independent observers, blinded to the case details, were presented with VIBE-MR images in a random order, and were required to indicate the presence of hyperintensity of the facial nerve following intravenous contrast administration. The vestibulocochlear nerve was also assessed, and the whole process was repeated for conventional post-contrast T1-weighted images. Following contrast administration, the sensitivity of VIBE-MRI for detecting facial nerve abnormalities ranged from 86 per cent to 96 per cent, and the specificity from 87 per cent to 92 per cent; conventional T1-weighted images yielded a sensitivity of only 39 per cent – 65 per cent, and a specificity of 94 per cent – 96 per cent. MRI was not a sensitive detector of vestibulocochlear nerve abnormalities in 14 dogs with concurrent vestibular dysfunction. This study shows that VIBE-MRI is a robust technique for confirming presumed idiopathic facial neuropathy in dogs, and suggests an inflammatory component to this condition in a high proportion of dogs.

Trephination of the Frontal Sinuses and Instillation of Clotrimazole Cream: A Computed Tomographic Study in Canine Cadavers

OBJECTIVE To use computed tomography (CT) to assess the distribution of surgically administered clotrimazole cream and associated filling of the frontal sinuses and caudal aspect of the nasal cavities in canine cadavers. STUDY DESIGN Observational study. ANIMALS Small (n = 1) and medium-large (n = 11) breed canine cadavers. METHODS CT scans of 12 cadaveric canine heads were used to confirm absence of sinonasal disease. Then after creating an opening into the left and right frontal sinuses with a 3.2 mm Steinmann pin at standardized landmarks, clotrimazole cream (20 g) was instilled into each side. Postoperative CT scans of the heads was used to assess the distribution and degree of filling of the sinonasal cavities with clotrimazole cream, and to identify any damage to local structures. RESULTS Filling was excellent in 22 sinuses, very poor in 2, and excellent in all caudal nasal cavities. Two cadavers had damage: unilateral penetration of the cranium (2) and unilateral penetration of the lateral sinus wall (1). CONCLUSION Excellent filling of most of the frontal sinuses and caudal nasal cavity of cadavers with clotrimazole cream is achieved when administered by this technique. Damage to local structures may occur intraoperatively using this technique.

Corpus callosal abnormalities in dogs

Background Corpus callosal abnormalities (CCA) in dogs have been only sporadically reported and are poorly characterized. Hypothesis/Objectives To describe the clinical presentation and magnetic resonance imaging (MRI) characteristics of dogs with CCA. Animals Fifteen client‐owned dogs. Methods Retrospective study. Records of the contributing institutions were reviewed to identify dogs diagnosed with malformations affecting the corpus callosum (CC); cases in which the CCA was thought to be secondary were excluded. Results The most represented breeds were Staffordshire Bull Terriers (5/15) and Miniature Schnauzers (3/15; n = 3, 20%) and the mean age at time of presentation of 19 months (range 3–81 months). The clinical signs most commonly reported were adipsia/hypodipsia with associated hypernatremia (12/15), tremors (6/15), and seizures (6/15). Review of the MR images revealed that 10 dogs had absence of the rostral CC and hypoplasia of the caudal portion, 4 dogs had a diffusely hypoplastic and dysplastic CC, and 1 dog had a diffusely hypoplastic CC. In 14 cases, there was abnormal cortical development with fusion of the ventral frontal lobes and part of the diencephalon, indicating lobar holoprosencephaly. Conclusions and Clinical Importance Previous literature has mainly associated CCA with adipsia and only 12 of 15 dogs in the current series demonstrated this abnormality. There are different degrees of the malformation but in 10 dogs the rostral portion of the CC is most severely affected. Fourteen dogs have simultaneous fusion of the midline structures rostral to the CC; this region has several structures involved in thirst regulation and might explain this derangement.

Percutaneous ultrasound‐guided cholecystocentesis: complications and association of ultrasonographic findings with bile culture results

OBJECTIVES To retrospectively evaluate cases presented for percutaneous ultrasound-guided cholecystocentesis for associated complications, identify risk factors associated with complications and to assess ultrasonographic findings and relate these to bacterial culture results. METHODS Data on 300 patients presented for percutaneous ultrasound-guided cholecystocentesis were retrospectively collected and ultrasonographic images were assessed for defined structural changes. The incidence of major complications was determined. Multi-variable multi-level logistic regression was used to investigate the association of ultrasonographic findings with positive bile culture. RESULTS Three hundred percutaneous ultrasound-guided cholecystocentesis procedures performed in 201 dogs and 51 cats were included; 35 patients had the procedure performed more than once. The overall incidence of major complications was 8 of 300 procedures (2·7%). Bile peritonitis occurred in 2 of 300 procedures (0·7%). An ultrasonographically abnormal gall bladder was found in 52% of cases and had a sensitivity, specificity and accuracy of 82, 55·7 and 61·5% respectively, to predict a positive bile culture. CLINICAL SIGNIFICANCE Percutaneous ultrasound-guided cholecystocentesis is overall a safe technique when carried out in selected patients. Abnormal ultrasonographic findings are only a fair predictor of a positive bile culture.

UNIQUE TOPOGRAPHIC DISTRIBUTION OF GREYHOUND NONSUPPURATIVE MENINGOENCEPHALITIS

Greyhound nonsuppurative meningoencephalitis is an idiopathic breed-associated fatal meningoencephalitis with lesions usually occurring within the rostral cerebrum. This disorder can only be confirmed by postmortem examination, with a diagnosis based upon the unique topography of inflammatory lesions. Our purpose was to describe the magnetic resonance (MR) imaging features of this disease. Four Greyhounds with confirmed Greyhound nonsuppurative meningoencephalitis were evaluated by MR imaging. Lesions predominantly affected the olfactory lobes and bulbs, frontal, and frontotemporal cortical gray matter, and caudate nuclei bilaterally. Fluid attenuation inversion recovery (FLAIR) and T2 weighted spin-echo (T2W) sequences were most useful to assess the nature, severity, extension, and topographic pattern of lesions. Lesions were predominantly T2-hyperintense and T1-isointense with minimal or absent contrast enhancement.

Agreement between transverse T2-weighted and three-dimensional constructive interference in steady state sequences in the evaluation of spinal cord disease in dogs

The constructive interference in steady state (CISS) sequence has been widely used in human neuroimaging. It has been shown to be advantageous in the evaluation of intra-axial and extra-axial cystic abnormalities, arteriovenous and dysraphic malformations and disturbances of cerebrospinal fluid circulation. To assess the utility of this technique in small animals, interpretations based on this sequence were compared with those based on T2-weighted (T2W) sequences in 145 dogs that underwent MRI of the spine for suspected spinal cord disease. Two sets of images (T2W and CISS) were reviewed separately by three observers in random order and intraobserver and interobserver agreements between both sequences were evaluated for several categorical variables. The overall agreement between T2W and CISS sequences was good. The highest agreement was observed for lesion diagnosis (0.739<k<0.928), treatment recommendation (0.715<k<0.833) and degree of spinal cord compression (0.772<k<0.952). The agreement for intramedullary intensity change (0.192<k<0.332) was lower compared with the other variables. Lesions that were predominantly characterised by focal hyperintense parenchymal changes on T2W were in some instances undetected on the CISS sequence while lesions consistent with spinal arachnoid diverticula on CISS sequences were occasionally missed on T2W. CISS enabled demonstration that lesions were directly affecting associated spinal nerves in some cases where T2W sequence was equivocal. Although CISS does not replace standard spin echo sequences, the results support inclusion of this sequence in small animal spinal MRI studies when subarachnoid diverticula or spinal nerve compression is suspected.

Late-onset recurrence of neurological deficits after surgery for spinal arachnoid diverticula

Spinal cord dysfunction secondary to spinal arachnoid diverticula (SAD) has been widely reported in the veterinary literature and there is some suggestion that surgical treatment may provide better outcomes than medical treatment. Despite this, previous reports have mentioned cases with recurrence of clinical signs following surgical treatment but the cause for this has not been further investigated. The medical records of seven dogs and one cat which presented for investigation of recurrence of neurological deficits at least six months after surgery for SAD were retrospectively reviewed. Median time to relapse of the neurological deficits was 20.5 months after surgery. On repeated imaging, 3/8 cases showed clear regrowth of diverticulum, 2/8 cases showed dorsal compression at the previous laminectomy site (presumed to be the laminectomy membrane), and 3/8 cases showed herniation of the spinal cord through the laminectomy defect associated with a stellate appearance to the spinal cord with small multiloculated areas of dilation of the subarachnoid space. Repeat surgical intervention was most successful in the cases where SAD recurrence was identified while medical treatment resulted in either subtle improvement or stabilisation on the clinical signs, sometimes followed by slow deterioration.