Richard Lam

Computed tomographic findings in 15 dogs with eosinophilic bronchopneumopathy

Eosinophilic bronchopneumopathy is a disease characterized by the infiltration of the lung and bronchial mucosa by eosinophils. The aim of the present study was to describe the CT findings in a large series of dogs with confirmed diagnosis of eosinophilic bronchopneumopathy. Computed tomographic scans of 15 dogs with confirmed diagnosis of eosinophilic bronchopneumopathy were evaluated retrospectively by two boarded radiologists who reached a consensus. Abnormalities were identified in 14/15 (93%) dogs, including pulmonary parenchymal abnormalities in 14/15 (93%) dogs, bronchial wall thickening in 13 (87%) dogs, which was considered marked in eight (53%), plugging of the bronchial lumen by mucus/debris in 11 (73%) dogs, and bronchiectasis in nine (60%) dogs. Pulmonary nodules were identified in 5/15 (33%) dogs including one dog with a mass. All dogs with a nodular lung pattern had additional abnormalities. Lymphadenopathy was present in 10 dogs (67%). Lesions associated with eosinophilic bronchopneumopathy are variable and heterogeneous and encompass a wider variety of computed tomographic features than reported previously. Computed tomographic images were abnormal in the majority of affected dogs, hence CT is a useful modality to characterize the nature and distribution of thoracic lesions in dogs with eosinophilic bronchopneumopathy.

X‐RAY ATTENUATION OF THE LIVER AND KIDNEY IN CATS CONSIDERED AT VARYING RISK OF HEPATIC LIPIDOSIS

X-ray attenuation of the liver has been measured using computed tomography (CT) and reported to decrease in cats with experimentally induced hepatic lipidosis. To assess the clinical utility of this technique, medical records and noncontrast CT scans of a series of cats were retrospectively reviewed. A total of 112 cats met inclusion criteria and were stratified into three hepatic lipidosis risk groups. Group 1 cats were considered low-risk based on no history of inappetence or weight loss, and normal serum chemistry values; Group 2 cats were considered intermediate risk based on weight loss, serum hepatic enzymes above normal limits, or reasonably controlled diabetes mellitus; and Group 3 cats were considered high risk based on poorly controlled diabetes mellitus due to hypersomatotropism. Mean CT attenuation values (Hounsfield units, HU) were measured using regions of interest placed within the liver and cranial pole of the right kidney. Hepatic and renal attenuation were weakly positively correlated with each other (r = 0.2, P = 0.03) and weakly negatively correlated with body weight (r = -0.21, P = 0.05, and r = -0.34, P = 0.001, respectively). Mean (SD) hepatic and renal cortical attenuation values were 70.7 (8.7) HU and 49.6 (9.2) HU for Group 1 cats, 71.4 (7.9) HU and 48.6 (9.1) HU for Group 2, and 68.9 (7.6) HU and 47.6 (7.2) HU for Group 3. There were no significant differences in hepatic or renal attenuation among groups. Findings indicated that CT measures of X-ray attenuation in the liver and kidney may not be accurate predictors of naturally occurring hepatic lipidosis in cats.

Thoracic and Lumbar Vertebral Bone Mineral Density Changes in a Natural Occurring Dog Model of Diffuse Idiopathic Skeletal Hyperostosis

Ankylosing spinal disorders can be associated with alterations in vertebral bone mineral density (BMD). There is however controversy about vertebral BMD in patients wuse idiopathic skeletal hyperostosis (DISH). DISH in Boxer dogs has been considered a natural occurring disease model for DISH in people. The purpose of this study was to compare vertebral BMD between Boxers with and without DISH. Fifty-nine Boxers with (n=30) or without (n=29) DISH that underwent computed tomography were included. Vertebral BMD was calculated for each thoracic and lumbar vertebra by using an earlier reported and validated protocol. For each vertebral body, a region of interest was drawn on the axial computed tomographic images at three separate locations: immediately inferior to the superior end plate, in the middle of the vertebral body, and superior to the inferior end plate. Values from the three axial slices were averaged to give a mean Hounsfield Unit value for each vertebral body. Univariate statistical analysis was performed to identify factors to be included in a multivariate model. The multivariate model including all dogs demonstrated that vertebral DISH status (Coefficient 24.63; 95% CI 16.07 to 33.19; p <0.001), lumbar vertebrae (Coefficient -17.25; 95% CI -23.42 to -11.09; p < 0.01), and to a lesser extent higher age (Coefficient -0.56; 95% CI -1.07 to -0.05; p = 0.03) were significant predictors for vertebral BMD. When the multivariate model was repeated using only dogs with DISH, vertebral DISH status (Coefficient 20.67; 95% CI, 10.98 to 30.37; p < 0.001) and lumbar anatomical region (Coefficient -38.24; 95% CI, -47.75 to -28.73; p < 0.001) were again predictors for vertebral BMD but age was not. The results of this study indicate that DISH can be associated with decreased vertebral BMD. Further studies are necessary to evaluate the clinical importance and pathophysiology of this finding.

Convergence‐Retraction Nystagmus Associated with Dorsal Midbrain Lesions in Three Dogs

Convergence-retraction nystagmus is an irregular, jerky nystagmus in which both eyeballs rhythmically converge and retract into the orbit, particularly on attempting an upward gaze. In humans it is seen as part of Parinaud’s syndrome, also known as dorsal midbrain syndrome, in which a lesion of dorsally located midbrain structures (the ventral pretectum, the periaqueductal area, and the medial longitudinal fasciculus in the dorsal tegmentum) prevents upward or downward movement of the eyes. It has been hypothesized that convergence-retraction nystagmus is caused by damage (ischemia, neoplasia, compression, or demyelination) to supranuclear fibers that have an inhibitory effect on the convergence neurons or divergence neurons in the midbrain, resulting in a sustained discharge of medial rectus and other extraocular muscle neurons. The rostral interstitial nuclei of the medial longitudinal fasciculus (RINMLF) of the midbrain, located dorsal to the oculomotor nuclei, contain the final relays producing all vertical saccades, and hence it has been suggested that Parinaud’s syndrome may result from damage to their neuronal cell bodies, as well as their afferent and efferent pathways. Convergence-retraction nystagmus is a highly localizing clinical sign that to the best of our knowledge has not yet been described in the dog. Here, we report 3 large breed dogs that were presented with convergenceretraction nystagmus and in which magnetic resonance imaging (MRI) identified focal lesions within the dorsal midbrain. Case 1: An 11-year, 5-month-old male neutered Staffordshire Bull Terrier was presented with a 14-day history of acute onset, nonprogressive vestibular ataxia with lethargy and disorientation. General physical examination was normal. On neurological examination, the dog was found to be mildly obtunded with a mild right-sided head tilt and circling to the right. Convergence-retraction nystagmus was noted (Video S1), with decreased vestibulo-ocular reflex bilaterally. The remainder of the neurological examination was normal and the findings were considered consistent with a right brainstem neurolocalization. The CBC results were within reference intervals (RIs). Serum biochemistry results included a mildly increased alkaline phosphatase (ALKP) activity (313 U/ L; RI, 19–285 U/L), alanine transferase (ALT) activity (171 U/L; RI, 13–88 U/L), and calcium concentration (2.73 mmol/L; RI, 2.13–2.7 mmol/L). Serum thyroxine and thyroid-stimulating hormone (TSH) concentrations were within normal limits. Prothrombin time and activated partial thromboplastin time were within normal limits. Noninvasive blood pressure assessment identified a pressure of 170–175 mmHg. Urine-specific gravity was 1.043, and urine chemistry dipstrip analysis and sediment examination were normal. A Baermann test for Angiostrongylus was negative. The dog underwent general anesthesia. A combination of acepromazine maleate (0.01 mg/kg IV) and methadone (0.1–0.2 mg/kg IV) was used for premedication, followed by induction with propofol (4–6 mg/kg IV) and maintenance of anesthesia with isoflurane in oxygen. A MRI examination was performed and included T2weighted (T2W) (repetition time, [TR] [ms], echo time [TE], [ms] 3333/110) sagittal and transverse images, T2W fluid attenuated inversion recovery (FLAIR) (TR/TE, 3612/80, inversion time [TI] [ms] 2000) transverse images, and T2*W fast field echo (FFE) transverse images. Sagittal and transverse, T1-weighted (T1W) (TR/TE, 515/15) images were acquired before and after IV administration of gadolinium contrast (0.1 mmol/kg, gadobutrol). Slice From the Clinical Science and Services, Royal Veterinary College, University of London, Hatfield, Herts UK (Crawford, Beltran, Lam, Kenny). The work was conducted at the Royal Veterinary College. Corresponding author: A.H. Crawford, Clinical Science and Services, Royal Veterinary College, University of London, Hawkshead Lane, North Mymms, Hatfield, Herts AL9 7TA, UK; e-mail: ahcrawford@rvc.ac.uk. Submitted February 3, 2016; Revised April 10, 2016; Accepted April 21, 2016. Copyright

Appearance of the canine meninges in subtraction magnetic resonance images

The canine meninges are not visible as discrete structures in noncontrast magnetic resonance (MR) images, and are incompletely visualized in T1-weighted, postgadolinium images, reportedly appearing as short, thin curvilinear segments with minimal enhancement. Subtraction imaging facilitates detection of enhancement of tissues, hence may increase the conspicuity of meninges. The aim of the present study was to describe qualitatively the appearance of canine meninges in subtraction MR images obtained using a dynamic technique. Images were reviewed of 10 consecutive dogs that had dynamic pre- and postgadolinium T1W imaging of the brain that was interpreted as normal, and had normal cerebrospinal fluid. Image-anatomic correlation was facilitated by dissection and histologic examination of two canine cadavers. Meningeal enhancement was relatively inconspicuous in postgadolinium T1-weighted images, but was clearly visible in subtraction images of all dogs. Enhancement was visible as faint, small-rounded foci compatible with vessels seen end on within the sulci, a series of larger rounded foci compatible with vessels of variable caliber on the dorsal aspect of the cerebral cortex, and a continuous thin zone of moderate enhancement around the brain. Superimposition of color-encoded subtraction images on pregadolinium T1- and T2-weighted images facilitated localization of the origin of enhancement, which appeared to be predominantly dural, with relatively few leptomeningeal structures visible. Dynamic subtraction MR imaging should be considered for inclusion in clinical brain MR protocols because of the possibility that its use may increase sensitivity for lesions affecting the meninges.

Computed tomographic morphometry of tympanic bulla shape and position in brachycephalic and mesaticephalic dog breeds

Anatomic variations in skull morphology have been previously described for brachycephalic dogs; however there is little published information on interbreed variations in tympanic bulla morphology. This retrospective observational study aimed to (1) provide detailed descriptions of the computed tomographic (CT) morphology of tympanic bullae in a sample of dogs representing four brachycephalic breeds (Pugs, French Bulldogs, English Bulldog, and Cavalier King Charles Spaniels) versus two mesaticephalic breeds (Labrador retrievers and Jack Russell Terriers); and (2) test associations between tympanic bulla morphology and presence of middle ear effusion. Archived head CT scans for the above dog breeds were retrieved and a single observer measured tympanic bulla shape (width:height ratio), wall thickness, position relative to the temporomandibular joint, and relative volume (volume:body weight ratio). A total of 127 dogs were sampled. Cavalier King Charles Spaniels had significantly flatter tympanic bullae (greater width:height ratios) versus Pugs, English Bulldogs, Labrador retrievers, and Jack Russell terriers. French Bulldogs and Pugs had significantly more overlap between tympanic bullae and temporomandibular joints versus other breeds. All brachycephalic breeds had significantly lower tympanic bulla volume:weight ratios versus Labrador retrievers. Soft tissue attenuating material (middle ear effusion) was present in the middle ear of 48/100 (48%) of brachycephalic breeds, but no significant association was found between tympanic bulla CT measurements and presence of this material. Findings indicated that there are significant interbreed variations in tympanic bulla morphology, however no significant relationship between tympanic bulla morphology and presence of middle ear effusion could be identified.

TRUNCATION ARTIFACT IN MAGNETIC RESONANCE IMAGES OF THE CANINE SPINAL CORD

The truncation artifact in magnetic resonance (MR) images is a line of abnormal signal intensity that occurs parallel to an interface between tissues of markedly different signal intensity. In order to demonstrate the truncation artifact in sagittal images of the canine spinal cord and the effect of changing spatial resolution, we conducted an experimental in vitro study. A section of fixed canine spinal cord was imaged using a 1.5T magnet. Spatial resolution was increased by increasing the acquisition matrix and reconstruction matrix, producing series of T2-weighted (T2w) images with the following pixel sizes: A, 1.6 (vertical) × 2.2 mm2 (horizontal); B, 1.2 × 1.7 mm2 ; C, 0.8 × 1.1 mm2 ; D, 0.4 × 0. 6 mm2 . Plots of mean pixel value across the cord showed variations in signal intensity compatible with truncation artifact, which appeared as a single, wide central hyperintense zone in low-resolution images and as multiple narrower zones in high spatial resolution images. Even in images obtained using the highest spatial resolution available for the MR system, the edge of the spinal cord was not accurately defined and the central canal was not visible. The experiment was repeated using an unfixed spinal cord specimen with focal compression applied to mimic a pathologic lesion. Slight hyperintensity was observed within the spinal cord at the site of compression although the cord was normal histologically. Results of this study suggest that caution should be applied when interpreting hyperintensity affecting the spinal cord in T2w sagittal images of clinical patients because of the possibility that the abnormal signal could represent a truncation artifact.

Exophthalmia due to intracranial abscess from grass seed foreign material in a dog

This is a unique report of a patient diagnosed antemortem with mild to moderate signs of retrobulbar cellulitis, secondary brain abscessation and absent neurological signs. Ocular ultrasound yielded a negative result whereas MRI supported the diagnosis and confirmed the need for immediate surgery. The cause was confirmed to have been the migrating grass seed foreign bodies that were surgically retrieved from the abscess inside the calvarium before medical treatment and resolution of clinical signs.

Variations in magnetic resonance venographic anatomy of the dorsal dural venous sinus system in 51 dogs.

Variations in intracranial dural venous sinus anatomy have been widely reported in humans, but there have been no studies reporting this in dogs. The purpose of this retrospective study was to describe variations in magnetic resonance (MR) venographic anatomy of the dorsal dural venous sinus system in a sample population of dogs with structurally normal brains. Medical records were searched for dogs with complete phase contrast, intracranial MR venograms and a diagnosis of idiopathic epilepsy. Magnetic resonance venograms were retrieved for each dog and characteristics of the dorsal dural sinuses, symmetry of the transverse sinuses and other anatomic variations were recorded. A total of 51 dogs were included. Transverse sinus asymmetry was present in 58.8% of the dogs, with transverse sinus hypoplasia seen in 39.2%, and aplasia in 23.5% of dogs. For 70.6% of dogs, at least one anatomic variation in the dorsal sagittal sinus was observed, including deviation from the midline (33.3%) and collateral branches from either the dorsal sagittal sinus or dorsal cerebral veins (54.9%). In 5 dogs (9.8%) a vessel was also identified running from the proximal transverse sinus to the distal sigmoid sinus, in a similar location to the occipital sinus previously reported in children. Findings from this study indicated that, as in humans, anatomic variations are common in the intracranial dural venous sinus system of dogs. These anatomic variations should be taken into consideration for surgical planning or diagnosis of cerebrovascular disease.

A case of scapular avulsion with concomitant scapular fracture in a cat

An 11-year-old cat was referred following vehicular trauma for evaluation and treatment of right thoracic limb lameness which was non-responsive to conservative management. Gait assessment revealed a severe weight-bearing right thoracic limb lameness, soft tissue swelling over the dorsal border of the scapula, crepitus upon direct palpation over the scapula and lateralisation of the scapula upon adduction of the distal limb allowing a diagnosis of scapular avulsion to be made. Computed tomography (CT) demonstrated a comminuted fracture of the right scapula and a tear of the serratus ventralis muscle. The scapular fractures involved the caudal scapular angle and therefore a circumcostal suture was not placed. Stabilisation was achieved through reattachment of the scapula to the serratus ventralis muscle with sutures placed through small holes in the dorsal and cranial borders of the scapula. Follow-up revealed resolution of lameness at 14 weeks postoperatively but non-union of the scapular fractures as evidenced by repeat CT. This case report details the medium-term outcome following this very unusual injury and contributes to the sparse literature regarding the progression of conservatively managed scapular fractures. It demonstrates that full return to function can occur following this injury even when radiographic union of the fracture is not achieved. To our knowledge this is the first report of this specific combination of injuries detailed with medium-term and advanced imaging follow-up.