Computed tomography of temporal bone fractures and temporal region anatomy in horses.

BACKGROUND: In people, specific classifications of temporal bone fractures are associated with clinical signs and prognosis. In horses, similar classifications have not been evaluated and might be useful establishing prognosis or understanding pathogenesis of certain types of trauma. HYPOTHESIS/OBJECTIVES: We hypothesized associations between temporal bone fracture location and orientation in horses detected during computed tomography (CT) and frequency of facial nerve (CN7) deficit, vestibulocochlear nerve (CN8) deficit, or temporohyoid osteoarthropathy (THO). Complex temporal region anatomy may confound fracture identification, and consequently a description of normal anatomy was included. ANIMALS: All horses undergoing temporal region CT at our hospital between July 1998 and May 2008. METHODS: Data were collected retrospectively, examiners were blinded, and relationships were investigated among temporal bone fractures, ipsilateral THO, ipsilateral CN7, or ipsilateral CN8 deficits by Chi-square or Fischer's exact tests. Seventy-nine horses had CT examinations of the temporal region (158 temporal bones). RESULTS: Sixteen temporal bone fractures were detected in 14 horses. Cranial nerve deficits were seen with fractures in all parts of the temporal bone (petrosal, squamous, and temporal) and, temporal bone fractures were associated with CN7 and CN8 deficits and THO. No investigated fracture classification scheme, however, was associated with specific cranial nerve deficits. CONCLUSIONS AND CLINICAL IMPORTANCE: Without knowledge of the regional anatomy, normal structures may be mistaken for a temporal bone fracture or vice versa. Although no fracture classification scheme was associated with the assessed clinical signs, simple descriptive terminology (location and orientation) is recommended for reporting and facilitating future comparisons.

Use of 3D printer technology to facilitate surgical correction of a complex vascular anomaly with esophageal entrapment in a dog.

A 10 week old female intact Staffordshire terrier was presented with a total of five congenital cardio-thoracic vascular anomalies consisting of a patent ductus arteriosus (PDA) with an aneurysmic dilation, pulmonic stenosis, persistent right aortic arch, aberrant left subclavian artery and persistent left cranial vena cava. These abnormalities were identified with a combination of echocardiogram and computed tomography angiography (CTA). The abnormalities were associated with esophageal entrapment, regurgitation, and volume overload of the left heart with left atrial and ventricular enlargement. A 2 cm diameter aneurysmic dilation at the junction of the PDA, right aortic arch and aberrant left subclavian artery presented an unusual surgical challenge and precluded simple circumferential ligation and transection of the structure. A full scale three dimensional model of the heart and vasculature was constructed from the CTA and plasma sterilized. The model was used preoperatively to facilitate surgical planning and enhance intraoperative communication and coordination between the surgical and anesthesia teams. Intraoperatively the model facilitated spatial orientation, atraumatic vascular dissection, instrument sizing and positioning. A thoracoabdominal stapler was used to close the PDA aneurysm prior to transection. At the four-month postoperative follow-up the patient was doing well. This is the first reported application of new imaging and modeling technology to enhance surgical planning when approaching correction of complex cardiovascular anomalies in a dog.

Efficacy of Low-dose (2 millicurie) versus Standard-dose (4 millicurie) Radioiodine Treatment for Cats with Mild-to-Moderate Hyperthyroidism.

BACKGROUND: Radioiodine (131 I) is effective treatment for hyperthyroidism in cats, but optimal dose to restore euthyroidism without inducing hypothyroidism is unclear. Treatment-induced hypothyroidism can lead to azotemia and reduced duration of survival. OBJECTIVE: To compare efficacy and short-term outcomes of low-dose 131 I versus higher, standard-dose 131 I as treatment for hyperthyroidism. ANIMALS: A total of 189 client-owned cats undergoing 131 I treatment for mild-to-moderate hyperthyroidism (serum T4 ≥ 4.0 µg/dL and <13.0 µg/dL). METHODS: Prospective, nonrandomized, cohort study comparing treatment with either low-dose (2 mCi, n = 150) or standard-dose (4 mCi, n = 39) 131 I. Serum T4 , thyroid-stimulating hormone (TSH), and creatinine concentrations were measured after 1, 3, and 6 months to determine persistent hyperthyroidism, overt hypothyroidism (low T4 , high TSH), subclinical hypothyroidism (normal T4 , high TSH), and azotemia. RESULTS: There was no significant difference in prevalence of cats with persistent hyperthyroidism between standard- and low-dose treatment groups at 3 (0% versus 5.3%; P = .34) and 6 (0% versus 3.3%; P = .51) months. Overt (18% versus 1%; P = .0005) or subclinical (46% versus 21%; P = .004) hypothyroidism was more common in cats at 6 months after standard-dose 131 I. No difference in incidence of azotemia existed between groups, but cats treated with standard-dose 131 I had higher creatinine concentrations (P < .05) and higher percent rises in creatinine (P < .0001). CONCLUSIONS AND CLINICAL IMPORTANCE: Low-dose 131 I is safe and effective for cats with mild-to-moderate hyperthyroidism, as evidenced by a cure rate of >95% with reduced frequency of iatrogenic hypothyroidism and azotemia.

Parelaphostrongylus tenuis Cerebrospinal Nematodiasis in a Horse with Cervical Scoliosis and Meningomyelitis.

There are reports of horses with acute onset acquired cervical scoliosis and cutaneous analgesia. The underlying dorsal gray column myelitis that produces these neurologic signs has been only presumptively attributed to migration of Parelaphostrongylus tenuis within the spinal cord. Despite previous confirmation brain by polymerase chain reaction testing, of P. tenuis within the brain of horses by polymerase chain reaction testing, genetic testing has failed to definitively identify the presence of this parasite in cases of equine myelitis. This case report provides molecular confirmation via polymerase chain reaction of P. tenuis within the cervical spinal cord of a horse with scoliosis and cutaneous analgesia.

Magnetic resonance imaging-based measures of atlas position: Relationship to canine atlantooccipital overlapping, syringomyelia and clinical signs.

Canine atlantooccipital overlapping (AOO) is characterized by a decreased distance between the dorsal arch of the atlas and the supraoccipital bone. Current diagnostic criteria for this condition are subjective and clinician-dependent; objective criteria are needed to allow a reliable and reproducible diagnosis in clinical and research settings and assess clinical significance. We propose four standardized MRI-based measurements to objectively assess the proximity of the atlas to the foramen magnum. Inclusion criteria for dogs in this study were bodyweight <15 kg, age >5 months, and availability of a complete MRI study performed with the craniocervical junction in extension. Exclusion criteria were space-occupying lesions and poor image quality (i.e. unclear bony margins). Measurements also included blinded determinations of skull type, presence of craniocervical junction anomalies and presence and severity of syringomyelia. Clinical status at the time of imaging was noted. Measurements were obtained in 271 dogs; these were reproducible and reliable. Findings varied by skull type: dolichocephalic dogs had smaller foramen magnum, whereas brachycephalic dogs had more cranially and dorsally positioned atlas bodies in comparison to the other skull types. Measurements also increased with increases in bodyweight. This study demonstrated a close association between AOO, syringomyelia and clinical signs. Toy and small breed dogs (including Cavalier King Charles spaniels) showed higher than previously reported prevalence of AOO; its occurrence was also associated with lower bodyweights within the study population of <15 kg toy/small breed dogs.

Three-dimensional conformal radiation therapy alone or in combination with surgery for treatment of canine intracranial meningiomas.

Treatment protocols, treatment planning methods and tumour types in studies evaluating radiotherapy for canine brain tumours have been varied. This case series retrospectively evaluated the outcome of definitive, three-dimensional conformal radiation therapy (3D-CRT) as either a sole modality or as an adjuvant to surgery in 31 dogs diagnosed with meningioma by histopathology (n = 10) or cross-sectional imaging of the head (n = 21, assessed independently by two board certified radiologists). Prescribed dose ranged from 45 to 54 Gy in 2.5 to 3 Gy fractions. Median overall survival was 577 days (interquartile range = 272-829 days; range = 30-1942 days) when all deaths were considered and 906 days (interquartile range = 336-912 days; range = 10 -1942 days) when only dogs dying due to meningioma were considered. No significant difference in survival time was detected for the defined clinical or imaging findings or between treatment with radiotherapy alone versus adjuvant radiotherapy, suggesting that 3D-CRT may be a viable alternative to surgery.

Adverse reactions in horses that underwent general anesthesia and cervical myelography.

BACKGROUND: The study was prompted by a perceived high prevalence of myelographic complications varying in severity and type, and attributed to the contrast material or the procedure. HYPOTHESES: 1. Any adverse reaction (AAR) is associated with a change in CSF volume induced either by removal of CSF or addition of contrast material. 2. AAR occurs more frequently in horses with higher premyelography neurologic grade. 3. Nonspecific hyperthermia is attenuated by anti-inflammatory and osmotic agents. ANIMALS: Horses (n = 278) that underwent myelography between 2000 and 2012 at 5 institutions: A (87), B (68), C (65), D (46), and E (12). METHODS: Multi-institutional, retrospective, observational cross-sectional study. RESULTS: AAR were observed in 95/278 (34%) horses, were associated with longer general anesthesia time (P = .04) and higher contrast-medium volume (P = .04); euthanasia because of AAR was performed in 5/278 (2%) horses. Adverse neurologic reactions were the most common type of complication observed occurring in 15/278 (5%) and 42/235 (18%) of horses in the intra- and postmyelography periods. A relationship between AAR and premyelography neurologic grade was not identified (P = .31). Nonspecific hyperthermia was observed in 25/235 (11%) horses; no relationship was observed with administration of anti-inflammatory drugs and osmotic agents (P = .30). CONCLUSIONS AND CLINICAL IMPORTANCE: The category of AAR occurred in one-third of the horses generally was mild and self-limiting. These reactions were associated with increased contrast-medium volume and longer anesthesia time; but, no specific procedural recommendations could be made because of small odds ratios (OR) of <2 for each 1 mL increase in contrast material and for each 1 minute of additional anesthesia time.

Evaluation of decision criteria for detection of spinal cord compression based on cervical myelography in horses: 38 cases (1981-2001).

REASONS FOR PERFORMING STUDY: Different criteria have been described based on height reduction of the total myelographic contrast column and components of it as tests for compression of the spinal cord due to cervical stenotic myelopathy (CSM). Fifty percent height reduction of the dorsal myelographic column (DMC), <2 mm empiric height of the DMC and a 40% reduction of the ratio of stenosis calculated based on the height reduction of the entire dural diameter (DD) have been described as decision criteria for considering the test result positive. The reasons for selecting these decision criteria or their accuracies have rarely been reported. OBJECTIVES: To evaluate the accuracy of diagnostic criteria based on reduced height of the total myelographic column and components of it for diagnosing extradural spinal cord compression using different decision criteria, and make recommendations for consistent myelographic interpretation in horses suspected of having CSM. METHODS: Four measurements were obtained by 2 readers in a retrospective sample population of 38 horses in which both cervical myelography and histopathological examination of the cervical spinal cord were performed. The prevalence of CSM in the sample was 50%. At intervertebral sites, the minimum heights of the DD and DMC were measured. At intravertebral sites, the maximum heights of the entire DD and DMC were obtained. Percent height reductions of the DMC and DD were determined as the ratio of minimum intervertebral height to maximum intravertebral height within the next cranial vertebra. Histological examination was used as the gold standard for determining the actual site of spinal cord compression. Sensitivity and specificity for the diagnostic criteria were estimated at each site in neutral and flexed neck positions using several different decision criteria. CONCLUSIONS: At C6-C7, in neutral or flexed neck position and using 20% reduction of DD, the test was highly sensitive and specific for CSM. At other sites, reduced height of the myelographic column generally was not accurate for diagnosing extradural spinal cord compression. Using 20% reduction of DD in neutral position at the mid-cervical sites, the test had only low sensitivity and high specificity. Flexion of the neck appeared to increase detection of spinal cord compression in the mid-cervical region, but also substantially increased the frequency of false-positive diagnoses. POTENTIAL RELEVANCE: By using the reported sensitivity and specificity estimates, readers may decide on a decision criterion for diagnosis of extradural spinal cord compression due to CSM. However, in planning a surgical correction, it is difficult to define a decision criterion that combines acceptable sensitivity and specificity, especially at the mid-cervical sites.

Effects of acepromazine and butorphanol on positive-contrast upper gastrointestinal tract examination in dogs.

OBJECTIVE: To determine whether acepromazine (ACE) and butorphanol (BUT) combination can be used for restraint of dogs during positive-contrast upper gastrointestinal tract (UGIT) examination. ANIMALS: 6 healthy dogs. PROCEDURE: In a randomized crossover design study, weekly UGIT examinations were performed on each dog for 5 weeks after administration of normal saline solution (0.5 ml), xylazine (1.0 mg/kg of body weight), or a combination of ACE (0.1 mg/kg) and 1 of 3 doses of BUT (0.05, 0.2, 1.0 mg/kg). Gastrointestinal tract emptying time, GI motility, pulse, respiratory rate, and quality of restraint were assessed. RESULTS: Total gastric emptying time was significantly prolonged by use of an ACE and BUT (0.05 mg/kg) combination. Xylazine and higher dosages of BUT significantly prolonged gastric and intestinal emptying times. All anesthetic protocols significantly decreased motility and facilitated nonmanual restraint. Xylazine and BUT (1.0 mg/kg) significantly decreased pulse and respiratory rate. CONCLUSION: The ACE and BUT combination prolonged GI tract emptying times, decreased GI motility, and facilitated nonmanual restraint for duration of the examination. Although GI motility was decreased and total gastric emptying time was prolonged, administration of ACE (0.1 mg/kg) plus BUT (0.05 mg/kg) allowed morphologic examination of the GI tract within 5 hours. Xylazine prolonged GI tract emptying, decreased GI motility, and provided good to excellent initial restraint. Clinical Relevance-The ACE and BUT combination prohibits functional examination of the GI tract; however, morphologic examination is possible when low dosages of BUT (0.05 mg/kg) are used.

Results of double-contrast cystography in cats with idiopathic cystitis: 45 cases (1993-1995).

OBJECTIVE: To determine results of double-contrast cystography in cats with idiopathic cystitis. DESIGN: Retrospective study. ANIMALS: 45 cats with clinical signs of nonobstructive lower urinary tract disease for which an underlying cause could not be determined. PROCEDURE: Medical records and double-contrast cystograms performed initially and during 6- and 12-month reevaluations were reviewed. RESULTS: 105 cystograms were reviewed. Fifteen (33%) cats had abnormalities evident on cystograms obtained at the time of initial examination. Of these, only 1 had abnormalities 6 and 12 months later. Thirty cats did not have abnormalities evident on cystograms obtained at the time of initial examination. Of these, 1 had abnormalities on a cystogram performed 6 months later and another had abnormalities on a cystogram performed 12 months later. Abnormalities evident on cystograms included focal thickening of the bladder wall (n = 11), diffuse thickening of the bladder wall (6), irregularities of the bladder mucosa (10), decreased opacity of the bladder wall (3), increased opacity of the bladder mucosa (3), filling defects (4), contrast medium in unexpected locations (3), and altered ureteral opacity (15). CLINICAL IMPLICATIONS: Results suggested that a large percentage of cats with idiopathic cystitis do not have cystographic abnormalities when initially examined but that abnormalities may be apparent during follow-up evaluations. In addition, a smaller percentage of cats with idiopathic cystitis may have nonspecific cystographic signs of cystitis or hemorrhage. Leakage of contrast medium into the peritoneal space during cystography does not necessarily require surgical management.

Results of retrograde urethrography in cats with idiopathic, nonobstructive lower urinary tract disease and their association with pathogenesis: 53 cases (1993-1995).

OBJECTIVE: To describe results of retrograde urethrography in cats with idiopathic, nonobstructive lower urinary tract disease (LUTD), to review the normal anatomy of the feline urethra, and to relate anatomy observed radiographically to the pathogenesis and diagnosis of LUTD in cats. DESIGN: Retrospective case series and anatomic study. ANIMALS: 53 cats with signs of nonobstructive LUTD for which an underlying cause could not be determined. Results for these cats were compared with those for 6 healthy female cats undergoing urethrocystoscopy for another study and 6 male cats without a history of LUTD undergoing necropsy examination. PROCEDURE: Medical records, results of positive-contrast retrograde urethrography (cats with idiopathic, nonobstructive LUTD) and urethrocystoscopy (healthy female cats), and necropsy findings (healthy male cats) were reviewed. RESULTS: Abnormalities were not detected during urethrocystoscopy, dissection, or urethrography. Previously, the urethra in male cats has been described simply as a long tube that tapers caudally, and the only structures consistently differentiated by radiography have been pelvic and penile parts. In this study, the seminal colliculus, isthmus of the urethra, preprostatic part of the urethra, and urethral crest were consistently observed in male cats in addition to pelvic and penile parts. The urethral crest also was observed in the comparatively simple female urethra. CLINICAL IMPLICATIONS: During retrograde urethrography in cats, prior distention of the bladder with positive-contrast medium may obscure radiographic signs associated with normal anatomic structures. Knowledge of urethral anatomy and radiographic signs associated with idiopathic, nonobstructive LUTD in cats should improve understanding of the pathogenesis and diagnosis of this disease.

Influence of patient positioning on sensitivity of mesenteric portography for detecting an anomalous portosystemic blood vessel in dogs: 34 cases (1997-2000).

OBJECTIVE: To determine whether sensitivity of detecting an anomalous portosystemic blood vessel during operative mesenteric portography varied with patient positioning. DESIGN: Retrospective study. ANIMALS: 34 dogs with a portosystemic shunt diagnosed via scintigraphy or surgery. PROCEDURE: Portograms were evaluated for a portosystemic blood vessel. Sensitivity was calculated from results obtained with dogs in left lateral, right lateral, and dorsal recumbency and from results obtained with dogs in 2 or 3 positions. Differences in sensitivity among positions and between 2 examiners were evaluated. RESULTS: Sensitivity was 85, 91, and 100% in dorsal, right lateral, and left lateral recumbency, respectively. Sensitivity was lower in dorsal recumbency than in left lateral recumbency, although differences were not significant. There was no significant difference between sensitivity of results obtained in dorsal and right lateral recumbency or right lateral and left lateral recumbency. Sensitivity for combined right lateral and dorsal positions was 97%, which was better than that in dorsal recumbency alone, although the difference was not significant. Because sensitivity in left lateral recumbency was 100%, there was no need to evaluate the improvement obtained by combining the result of this position with the results of other positions. CONCLUSION AND CLINICAL RELEVANCE: Results of mesenteric portography varied with patient positioning. The optimal position varied among patients but left lateral recumbency may be better and dorsal recumbency worse. Sensitivity may be improved by performing the test with the patient in orthogonal recumbent positions.

Clinical evaluation of cats with nonobstructive urinary tract diseases.

OBJECTIVE: To identify the underlying cause of clinical signs in cats with nonobstructive diseases of the bladder and urethra. DESIGN: Prospective case series. SAMPLE POPULATION: 109 cats examined by the urology service of The Ohio State University's veterinary teaching hospital because of stranguria, hematuria, pollakiuria, or urination in inappropriate locations. PROCEDURE: History was obtained and a CBC, serum biochemical analyses, serologic tests for FeLV and feline immunodeficiency virus, urinalysis, bacterial culture of urine, and contrast radiography or urethrocystoscopy (females only) were performed. RESULTS: 16 cats had cystic calculi: 8 had struvite uroliths, 7 had calcium oxalate uroliths, and 1 had a urolith of unknown composition in conjunction with an anatomic defect. Anatomic defects, including diverticulae, urethral strictures, and a malpositioned urethra, were identified in 12 cats. A urinary tract infection was identified in 1 cat, and neoplasia was diagnosed in 2. One of the cats with neoplasia also had a struvite urolith. The remaining 80 cats did not have an anatomic defect, urolith, or tumor. Ten of these cats also did not have radiographic or cystoscopic abnormalities and were presumed to have a behavioral disorder. The remaining 70 cats had radiographic or cystoscopic abnormalities, and idiopathic cystitis was diagnosed. In 14 of the cats with idiopathic cystitis, results of a urinalysis were normal. Cats with idiopathic cystitis were significantly more likely to eat dry food exclusively (59%) than were cats in the general population (19%). CLINICAL IMPLICATIONS: Results suggest that idiopathic cystitis occurs commonly in cats with stranguria, hematuria, pollakiuria, or inappropriate elimination and is associated with consumption of dry foods. Contrast radiography or cystoscopy is necessary for differentiating idiopathic cystitis from behavioral disorders in some cats.

Multifocal polyostotic aneurysmal bone cysts in a llama.

A 3.3-year-old 125-kg castrated male llama was evaluated because of acute non-weight-bearing lameness on the left hind limb. Physical examination revealed crepitus in the midportion of the femur. On radiographs, a comminuted middiaphyseal fracture was seen. There was also a region of bone lysis with cortical thinning and expansion in the distal metaphysis and epiphysis of the left femur. Multiple small circular lesions were observed in the proximal metaphysis of the left femur, and the proximal portion of the left tibia appeared irregular. The owner elected to pursue treatment, and the fracture was repaired with 2 compression plates. Multiple bone biopsy specimens were obtained and submitted for bacterial culture and histologic examination. Cultures yielded neither bacteria nor fungi. Histologic examination revealed fibrous connective tissue, normal appearing cortical bone, and an absence of medullary structures. The llama was maintained in a hind-limb sling for 14 days after surgery, at which time follow-up radiography revealed a comminuted fracture of the proximal portion of the femur. The llama was euthanatized, and multifocal polyostotic aneurysmal bone cysts were found in the proximal and distal metaphyses of the left femur and tibia. Cysts were lined by fibroblasts or endothelial-like cells.

Myelographic artifacts.

During myelography, injection of contrast outside the subarachnoid space can lead to false-negative or false-positive studies by not contrasting lesions or creating spurious signs. The production of high-quality myelograms and successful interpretation depend on knowledge of meningeal anatomy and the appearance of contrast material when injected between different meningeal layers. Opacification of the subdural space is a recently described technical complication in veterinary medicine, and increasingly is being recognized as a common problem during myelography. The purpose of this article is to describe the appearance of the different columns of contrast material that can be produced during myelography and to correlate these findings to the relevant anatomy, especially the subdural space.

Gallbladder perforation associated with cholelithiasis and cholecystitis in a dog.

A four-year-old female Japanese akita was admitted with icterus, ascites and chronically elevated serum bilirubin and liver enzymes. Abdominal ultrasonography revealed a diffusely thickened, hyperechoic gallbladder wall with a focal defect, hepatic lymphadenopathy and a large volume of anechoic fluid within the peritoneal space. Diagnosis of biliary tract rupture with bile peritonitis was based on the findings of bile and suppurative exudate in peritoneal aspirates. A perforated gallbladder and cholelithiasis were found on exploratory celiotomy, while histopathology revealed chronic suppurative cholecystitis. The dog recovered uneventfully after cholecystectomy. Although rare, the triad of cholelithiasis, cholecystitis and gallbladder perforation should be considered after detection of one of these conditions.

Maximal and submaximal mouth opening with mouth gags in cats: implications for maxillary artery blood flow.

The use of spring-loaded mouth gags in cats can be associated with the development of central neurological deficits, including blindness. In this species, the maxillary arteries are the main source of blood supply to the retinae and brain. Spring-loaded gags generate constant force after placement that could contribute to bulging of the soft tissues between the mandible and the tympanic bulla. Under these circumstances, the maxillary arteries can become compressed as they course between these osseous structures. Smaller gags that might apply less force to the mouth were investigated to determine if they preserved maxillary artery blood flow. Six healthy adult cats were anesthetized. Electroretinography (ERG) and magnetic resonance angiography (MRA) were performed without the use of a mouth gag and during submaximal (plastic mouth gags of 20, 30 and 42 mm in length between canine teeth) and maximal mouth opening. Maximal mouth opening produced alterations in ERG waveforms consistent with circulatory compromise in 1/6 cats and reductions in signal intensity during MRA in 4/6 cats. Placement of a 42 mm plastic gag produced a reduction in MRA signal in 1/6 cats. No changes were observed with smaller gags. The force applied against the mouth was significantly higher with the spring-loaded gag than with any other gags. The use of a smaller mouth gags was associated with fewer alterations of indicators of maxillary artery blood flow. Nevertheless, a 42 mm plastic gag, equivalent to the size of a needle cap, resulted in an abnormal MRA in one cat.

Evaluation of maxillary arterial blood flow in anesthetized cats with the mouth closed and open.

The mouth-gag is a common tool used in veterinary medicine during oral and transoral procedures in cats but its use has recently been associated with the development of blindness. The goal of this study was to investigate whether maximal opening of the mouth affects maxillary artery blood flow in six anesthetized cats. To assess blood flow, the electroretinogram (ERG), brainstem auditory evoked response (BAER) and magnetic resonance angiography (MRA) were evaluated qualitatively with the mouth closed and open. During dynamic computer tomography (CT) examinations, detection of contrast medium in the maxillary artery was quantified by measuring the Hounsfield units (HUs). The peak HU, time to peak and mean HU were determined. Changes ⩾10% of these parameters were considered indicative of altered blood flow. ERG and BAER were normal with the mouth closed in all cats, but was abnormal with the mouth opened maximally in two cats and one cat, respectively. During MRA, blood flow was undetected in either maxillary artery in one cat and reduced in the right maxillary artery in two cats, when the mouth was open. During CT, the peak HU decreased ⩾10% in three cats, the time to peak was ⩾10% longer in two cats, and the mean HU was ⩾10% lower in one cat when the mouth was open. No cat developed apparent blindness or deafness. Maximal opening of the mouth caused alterations in several indicators of blood flow in some individual cats.

Observer agreement study of cervical-vertebral ratios in horses.

REASON FOR PERFORMING STUDY: Different examiners or the same examiner were observed at different times producing slightly different results when obtaining cervical-vertebral ratios. If the difference is substantial, then measurement variability would have an important impact of radiographic interpretation. OBJECTIVE: To quantify agreement and repeatability of these measurements. METHODS: An observer agreement study was performed using 75 horses. Measurements were made at C3-4 and C6-7 by a board-certified radiologist and an imaging resident. Intra- and interobserver agreement was quantified using Bland-Altman plots. Repeatability was assessed as the percentage of differences between duplicate measurements by the radiologist that were within ± 2 s.d. of the differences. RESULTS: At C3-4, the limits of agreement for the intra-vertebral ratio were between -5 and 4% for the intra- and -5 and 6% for interobserver comparison. For the intervertebral ratio, they were between -9 and 8% for the intra- and -10 and 10% for interobserver comparison. At C6-7, the limits of agreement for the intra-vertebral ratio were between -6 and 5% for the intra- and -6 and 8% for interobserver comparison. For the intervertebral ratio, they were between -7 and 7% for the intra- and -6 and 13% for interobserver comparison. At C3-4, all measurements were 95% repeatable (differences typically ≤ 4% and always ≤ 8%) for the intra-vertebral ratio and 96% repeatable (differences typically ≤ 8% and always ≤ 11%) for the intervertebral ratio. At C6-7, all measurements were 98% repeatable (differences typically ≤ 6% and always ≤ 7%) for the intravertebral ratio and 92% repeatable (differences typically ≤ 6% and always ≤ 10%) for the intervertebral ratio. CONCLUSIONS: Cervical-vertebral ratios typically varied by 5-10% within and between examiners. POTENTIAL RELEVANCE: When using cervical-vertebral ratios in practice, the impact of measurement agreement should be factored into the interpretation of the test result because measurement variability may lead to misdiagnosis and limit the clinical usefulness of these tests.