MAGNETIC RESONANCE IMAGING OF THE NORMAL AND DISEASED FELINE MIDDLE EAR

The magnetic resonance imaging appearance of the feline middle ear is described in three healthy cats and in five cats with middle ear disease. Owing to the good spatial resolution, multiplanar slice orientation as well as display high contrast resolution of soft tissue, in particular fluids, MR imaging was helpful prior to surgery. It is superior to radiography which failed to allow identification of the abnormality in two of our five cats. MR imaging for middle ear disease should include dorsal and transverse plane images using T1- and T2-weighted sequences. In the presence of a mass within the bulla or the external ear canal application of contrast medium is helpful.     

Implantation of an Uncemented Total Hip Prosthesis Technique and Initial Results of 100 Arthroplasties

A porous-coated modular total hip system was developed for uncemented implantation in dogs. The operative technique was developed in cadaver bones and live animals. One hundred uncemented total hip arthroplasties were performed in 92 dogs. Results were successful in 98% of the joints during follow-ups of 3 months or more. Complications included three luxations of the prosthetic joint, two fissure fractures of the femoral cortex, and one complete displacement of the acetabular component from its bony bed. Four complications were resolved successfully.     

VOLUMETRIC IMAGE PROCESSING FOR THREE-DIMENSIONAL DISPLAY OF THE SKELETAL ANATOMY OF THE SEA OTTER

Volumetrically correct, three-dimensional color images of the sea otter, ( Enhydra lutris ), were generated from computed tomographic (CT) data using a Sun 3/160 workstation and a Pixar Imaging Computer. These images could be displayed as static images (1024×768) or rotated about any axis in real-time by displaying sequential rotation sequences generated by the Pixar Imaging Computer. The images provided realistic depth of field through overshadowing and differential opacification. This was obtained through an opacification algorithm which traced rays from a selected viewing plane through colored gel volumes, and calculated absorbance percentages as a function of the transparency of the gels penetrated. Reconstructions of this type serve as alternative anatomy tutorials for species otherwise unavailable for routine dissection. They also permit topographical studies without interfering with populations of endangered animals.     

Myasthenia Gravis in the Cat

Myasthenia gravis (MG) was diagnosed in four cats--one had an apparently congenital form and three had the acquired autoimmune form. All four cats were examined because of episodes of weakness including gait abnormalities, voice change, neck ventroflexion, and regurgitation. Palpebral reflexes were absent in all cats. Administration of edrophonium chloride resulted in transient resolution of clinical signs in all four cats. Three cats were tested for the presence of serum autoantibodies against acetylcholine receptor (AChR) by radioimmunoassay. Two cats with acquired MG had anti-AChR antibody titers of 10.5 and 96.8 nmol/l (normal, less than or equal to 0.03 nmol/l). Antibodies were not detected in the cat with presumptive congenital MG. All four cats were treated with pyridostigmine bromide. Two cats with acquired MG were euthanatized because of clinical deterioration. The third cat with acquired MG has been asymptomatic since 2 months after diagnosis. The cat with presumed congenital MG is alive 3 years after diagnosis.     

Tumor-Associated Erythrocytosis in a Dog With Nasal Fibrosarcoma

Erythrocytosis (hematocrit, 79%) was diagnosed in an 8-year-old, neutered female, mixed-breed dog with an intranasal fibrosarcoma. Both serum and tumor erythropoietin (Ep) activities were elevated, as determined by the polycythemic exhypoxic mouse model, and the Ep activity was neutralized in that model by rabbit anti-Ep antibodies. Tumor resection normalized the hematocrit.     

MAGNETIC RESONANCE IMAGING OF THE EQUINE FOOT

The purpose of this study was to assess the ability of magnetic resonance imaging to depict abnormalities of the equine foot. MRI was performed on isolated limbs which had lesions of the foot. These images were made in 3 perpendicular planes (sagittal, transverse and frontal) using a T1 weighted sequence and were 5mm thick. Images accurately depicted normal and pathologic structures in the foot and proved to be very precise for documenting degenerative joint disease, navicular disease and laminitis lesions. This preliminary study demonstrates the considerable potential of MRI in the diagnosis of locomotor problems in the horse.     

Bluetongue and Douglas virus activity in New South Wales in 1989: further evidence for long-distance dispersal of the biting midge Culicoides brevitarsis

SUMMARY: Infection of cattle with bluetongue and Douglas viruses was detected on the central and southern coast of New South Wales from January to April 1989. Bluetongue virus infection was found well south of areas of expected occurrence. Evidence is presented to support wind-borne dispersal of infected vectors, Culicoides brevitarsis , southwards from the Hunter Valley.     

Complete Heart Block in a Dog Seropositive for Borrelia burgdorferi: Similarity to Human Lyme Carditis

Lyme disease has been recognized in humans since 1975 when it was associated with an outbreak of oligoarthritis in children in Lyme, Connecticut. Erythema chronicum migrans (ECM) is a clinical marker for the human disease, which usually appears within 3 to 32 days after an infected tick bite. Lyme disease is caused by spirochete, Borrelia burgdorferi, which is vectored by the hard ticks Ixodes dammini or Ixodes pacificus in the United States. In humans, Lyme disease has been found to cause a variety of clinical syndromes including cardiopathy, neuropathy, dermatopathy, and arthropathy. Human Lyme carditis is characterized by varying degrees of atrioventricular (AV) heart block that usually resolve regardless of therapy. Lyme disease has been reported in the dog as an arthropathy. This article reports a case of complete heart block and myocarditis in a dog with a positive titer for B burgdorferi, in which clinical and pathologic findings were similar to those seen in human Lyme myocarditis.     

CEREBRAL VENTRICULAR SIZE IN DEVELOPING NORMAL KITTENS MEASURED BY ULTRASONOGRAPHY

To evaluate the age of fontanelle closure of normal kittens and the size of their lateral ventricles, 50 ultrasonographic examinations using the bregmatic fontanelle as an acoustic window were made. Seven kittens, laboratory animals, were included in the study. To verify the location of the lateral ventricle, two of the kittens were sacrificed as neonates. In one of them ink was injected prior to autopsy into one lateral ventricle under sonographic guidance. In a longitudinal study of five of the kittens, the skull depth and the depth of the central part of the lateral ventricle reproduced in a longitudinal view could be measured up to the age of about 5 months. During that period, the skull depth increased from a median value of 1.95 cm (1.92-1.98) in a seven-day-old cat to 2.58 cm (2.52-2.59) in a 154-day-old cat, while the afore-mentioned ventricle values increased from 0.3 mm to 1.1 mm.