A study of the radiographic anatomy of the foramen magnum in dogs

The shape and size of the foramen magnum were investigated in a number of breeds. It was found that dorsal extension occurred in toy breeds, both with and without neurological symptoms. An increase in the size of the foramen magnum was not necessarily associated with a pathological process.     

Dorsal notch of foramen magnum due to incomplete ossification of supraoccipital bone in dogs

The shape of the foramen magnum and the variation in the ossification pattern of the supra-occipital bone were studied in 48 skulls, including 12 from neonatal and 33 from immature and mature beagles of known age. The shape varied markedly, and a dorsal notch, dorsomedial to the nuchal tubercles and present in over half of the beagles, developed as a result of incomplete ossification of the ventromedial part of the supra-occipital bone. In a pomeranian and a chihuahua a membrane of dure mater and connective tissue, which covered the prominent dorsal notch, prevented prolapse of the brain. The spinal cord passed through a smaller oval opening in the ventral half of the foramen magnum. As there was no apparent impairment of function or anomalies associated with the dorsal notch and since a prominent dorsal notch was common in small breeds with brachycephalic skulls, it was concluded that the dorsal notch is a variation in the normal morphological pattern.     

Resolution of life-threatening dysphagia caused by caudal occipital malformation syndrome following foramen magnum decompressive surgery

A Cavalier King Charles Spaniel was presented with acute onset, life-threatening dysphagia suspected to be secondary to medulla oblongata compression caused by caudal occipital malformation syndrome. The patient required urgent tracheostomy tube placement to remain stable and was subsequently cured of the presenting neurological deficits by foramen magnum decompressive surgery. Neurogenic dysphagia is a relatively common presenting sign in human Chiari malformation syndromes, but has not been described as a major clinical sign in veterinary patients. Caudal occipital malformation syndrome should be included in the differential diagnosis list for susceptible breeds presenting with dysphagia. Early recognition favours expeditious surgical intervention and a positive outcome in human patients, and this may also be the case in veterinary patients.     

Foramen magnum decompression for treatment of caudal occipital malformation syndrome in dogs

A method for foramen magnum decompression (FMD) in dogs with caudal occipital malformation syndrome (COMS) and results for 16 dogs are described. In brief, a dorsal approach to the caudal portion of the occiput and arch of the atlas was made, and a high-speed drill was used to remove a portion of the occiput in the region of the foramen magnum and the dorsal aspect of C1. The meninges that were exposed were removed or marsupialized to surrounding tissues. Foramen magnum decompression was performed in 16 dogs. No intraoperative complications occurred, and postoperative complications occurred in only 2 dogs after initial surgery and in 1 of these dogs after follow-up surgery. In both dogs, postoperative complications after the initial surgery resolved without additional treatment. One dog was nonambulatory tetraparetic after follow-up surgery and died of a suspected ruptured viscus 9 days after surgery. Four dogs developed evidence of scar formation at the surgery site and required additional surgery. Overall, 14 dogs survived, 1 died, and 1 was euthanatized. Clinical signs resolved in 7 of the 14 dogs that survived, improved in 6, and did not change in 1. Results suggest that FMD may be an effective treatment for dogs with COMS, especially if performed early in the course of the disease.     

Morphological features of the luminal surface of the magnum in the sexually immature ostrich (Struthio camelus)

Summary Observations were made, using scanning electron microscopy, of the surface features of the magnum in the immature ostrich during periods of ovarian inactivity, activity and regression. In birds with inactive ovaries the luminal surface of the magnum was lined with non-ciliated cells, which were densely covered by microvilli. In contrast, the magnum in birds with active ovaries was composed of ciliated and non-ciliated cells. The distribution of ciliated cells was not uniform, with clumps of cilia occurring next to non-ciliated areas. Samples collected from birds with regressing ovaries, during periods of decreasing daylength, revealed that the magnum was undergoing involution. The deciliation of ciliated cells and the presence of short microvilli on non-ciliated cells characterized magnal regression. These results suggest that ovarian activity and changes in daylength have a profound effect on the surface features of the magnum in the immature ostrich.     

Foramen magnum decompression with cranioplasty for treatment of caudal occipital malformation syndrome in dogs

Objectives— To describe a cranioplasty procedure used in conjunction with foramen magnum decompression (FMD) for the treatment of canine caudal occipital malformation syndrome (COMS), and to evaluate the clinical outcome. Study Design— Prospective clinical study. Animals— Dogs (n=21) with COMS diagnosed by magnetic resonance imaging (MRI). Methods— After FMD, titanium screws were placed around the perimeter of the foramen magnum defect and a skull plate fashioned from titanium mesh and polymethylmethacrylate was attached to the back of the skull, using the titanium screws as anchor posts. Follow‐up was obtained by direct examination by the authors, telephone interviews with owners and referring veterinarians, and a questionnaire sent to owners of surviving dogs designed to assign objective measures of response to surgical intervention. Surgical success was defined as improvement in ≥1 aspects of clinical dysfunction (e.g. scratching, pain) postoperatively. Owner‐assigned pre‐ and postoperative quality‐of‐life (QOL) scores (1–5) for surviving dogs were compared using a Wilcoxon's signed rank test for paired data (P≤.05). Results— No intraoperative complications occurred and postoperative complications were limited to transient worsening of a pre‐existing head tilt and ataxia in 1 dog, and the need for oral pain medication for 1–4 weeks in 3 dogs. Seventeen dogs (81%) had clinical improvement after surgery. Although clinical signs resolved in 1 dog, it died after being hit by a car, 5 months after surgery. One dog had no change in clinical signs; this patient's clinical signs were not severe and the owners had opted for surgery primarily to prevent progression of disease. Two dogs were euthanatized; 1 because of no improvement of severe clinical signs, and 1 because of sustained recurrence of apparent head and neck pain 7 months later. One dog required a dorsal laminectomy at a second site (C1/C2 vertebral level), 2 months later. Four dogs has transient “flare‐ups” of apparent head/neck pain 2–13 months later; all resolved with transient re‐institution of oral analgesic therapy. Further surgery at the FMD was not needed. Based on the returned questionnaires, there was an overall significant improvement in QOL scores. Conclusions— FMD with cranioplasty was well tolerated, with no intraoperative complications, and minor postoperative complications. Most dogs improved clinically, and none required further surgery at the original FMD site. Clinical Relevance— FMD with cranioplasty may be an effective surgical method of treating dogs with COMS and is well tolerated. Based on prior reports of FMD for this disorder, it appears that cranioplasty may reduce the rate of surgical failure caused by formation of compressive scar tissue at the FMD site in the short term. Results of this preliminary study support further evaluation of the cranioplasty procedure in a larger group of dogs over a more extended follow‐up period.     

Phenotypic analysis of hepatic lymphocytes from healthy dogs

Phenotypes of lymphocytes from laparoscopically biopsied liver tissues of eleven healthy beagle dogs were analyzed. The proportion of CD3(+) lymphocytes (T cells), CD3 (-)CD21(+) lymphocytes (B cells) and CD3 (-)CD21(-) lymphocytes (non-T non-B lymphocytes), and the CD4(+)/CD8(+) ratio in the canine hepatic lymphocytes were 54.8 +/- 11.9%, 4.7 +/- 3.1%, 40.7 +/- 13.2%, and 0.33 +/- 0.12, respectively, while those in peripheral blood lymphocytes were 85.4 +/- 6.5%, 9.3 +/- 6.1%, 5.3 +/- 1.8%, and 1.64 +/- 0.36, respectively. These results indicated that the constitution of hepatic lymphocytes quite differed from that of peripheral blood lymphocytes in dogs, and suggested that the regional immunity in canine liver might be specific.     

Morphological and immunohistochemical characterisation of seminomas in Norwegian dogs

Background

Seminomas in the dog have traditionally been assumed to resemble human spermatocytic seminomas, based on their low malignancy and high occurrence in old individuals. However, recently published studies indicate that canine seminomas can be classified as classical and spermatocytic seminomas in a similar way as in man, and that classical seminomas comprise a substantial proportion of seminomas in the dog. These two factors both contribute to increasing the potential of canine seminoma as a relevant model for human testicular cancer. The aim of the present study was to characterise seminoma in Norwegian dogs using morphology and immunohistochemistry, and determine whether these tumours are comparable with human classical seminoma.

Methods

By applying diagnostic criteria from human pathology, 45 seminomas from the Norwegian Canine Cancer Register were examined histologically with hematoxylin and eosin (HE) and periodic acid-Schiff (PAS) stains. All sections were stained immunohistochemically with antibodies against human placental alkaline phosphatase (PLAP) and the transmembrane receptor c-KIT.

Results

Although two of the seminomas showed immunohistochemical staining characteristics indicative of classical seminoma (PLAP+/c-KIT+), all 45 examined seminomas were morphologically consistent with spermatocytic seminoma.

Conclusions

The value of canine seminoma as a model for SE in man remains unclear. Among the 45 investigated tumours from Norwegian dogs, none were classified as classical seminoma based on morphological criteria consistent with human seminomas. Regional or breed differences in the occurrence of classical seminoma in the dog, as well as the lack of uniform diagnostic criteria, might explain the discrepancy between the findings in the current study and the results presented by other authors.     

Genetic analysis of canine parvovirus from dogs in Australia

OBJECTIVE: To determine the genetic variants of canine parvovirus-2 (CPV) present in domestic dogs in Australia and to investigate 26 cases of apparent vaccine failure. DESIGN: Thirty-three samples of faeces or intestinal tissues and 16 cell culture virus isolates collected over a period from 1980 to 2005 from five Australian states were analysed. Procedure DNA was extracted from the samples and a 1975 bp fragment of the VP1/2 gene of CPV was amplified by polymerase chain reaction (PCR) and sequenced. Sequences were compared to published strains of CPV-2, CPV-2a, CPV-2b and CPV-2c. RESULTS: Forty-one of 43 PCR-positive samples contained CPV-2a viruses. One sample collected in 2002 from a pup in northern NSW contained a CPV-2b virus. One sample that had been included in the study as a CPV-antigen negative control sample contained a CPV-2 virus. CONCLUSION: CPV-2a remains the predominant genetic variant of CPV in dogs in Australia and has not been replaced by CPV-2b or CPV-2c as in many other countries. The vaccine failures investigated in the study were likely caused not by genetic variation of field viruses but by maternal antibody interference in the response of pups to vaccination.     

Computer-assisted image analysis of neovascularization in thyroid neoplasms from dogs

OBJECTIVE: To develop a computer-assisted image analysis procedure for quantitation of neovascularization in formalin-fixed paraffin-embedded specimens of thyroid gland tissue from dogs with and without thyroid gland neoplasia. SAMPLE POPULATION: 47 thyroid gland carcinomas, 8 thyroid gland adenomas, and 8 specimens of thyroid tissue from dogs without thyroid gland abnormalities (normal). PROCEDURE: Serial tissue sections were prepared and stained with antibodies against human CD31 or factor VIII-related antigen (factor VIII-rag). The areas of highest vascularity were identified in CD31-stained sections, and corresponding areas were then identified in factor VIII-rag-stained sections. Image analysis was used to calculate the total vascular density in each section, and neovascularization, expressed as a percentage, was determined as the absolute value of the total vascular density derived from factor VIII-rag-stained sections minus the vascular density derived from CD31-stained sections. RESULTS: Mean vascular density of thyroid gland carcinomas derived from CD31-stained sections was significantly greater than density derived from factor VII I-rag-stained sections. This incremental difference was presumed to represent degree of neovascularization. However, significant differences were not detected between vascular densities derived from CD31 and factor VIII-rag-stained sections for either normal thyroid gland tissue or thyroid gland adenomas. No significant correlations were found between vascular density in thyroid gland carcinomas and survival time following surgery. CONCLUSION AND CLINICAL RELEVANCE: A computer-assisted image analysis method was developed for quantifying neovascularization in thyroid gland tumors of dogs. This method may allow identification of dogs with tumors that are most likely to respond to treatment with novel antiangiogenesis agents.     

Genetic analysis of the RNA polymerase gene of caliciviruses from dogs and cats.

Caliciviruses that infect animals including humans cause a specific disease syndrome in their respective hosts. Feline calicivirus (FCV) is a major pathogen of respiratory disease of cats, and human caliciviru is a causative agent of diarrhea. It has been suggested, furthermore, that FCV and newly recognized canine calicivirus (CaCV) may also be possible causes of diarrhea in these animal species. In this study nucleotide sequence of the RNA polymerase gene of two caliciviruses of canine origin, namely CaCV strain No. 48 and FCV-like strain Sapporo/283, and a number of FCV strains of respiratory and enteric origins was examined. The length of sequenced region, from the 5'LKDEL motif through the 3'YGDD motif of the gene, was 555 bp for CaCV No. 48 strain and 552 bp for the other FCV strains including Sapporo/283 strain. In phylogenetic analysis, CaCV No. 48 strain grouped as a distinct branch sharing ancestral roots with San Miguel sea lion virus, and FCVs formed one compact group in which Sapporo/283 strain was included.