Caudal cervical intervertebral disk disease in the small dog: role of distraction and stabilization in ventral slot decompression

The clinical outcomes in 112 dogs weighing less than 35 pounds that were presented with cervical intervertebral disk protrusions were retrospectively evaluated. Although the second to third cervical (C2 to C3) intervertebral space was the most common site (27%) of disk protrusion, 57% of disk protrusions presented were caudal to the fourth cervical (C4) vertebra. Dogs with cranial intervertebral disk protrusions, including the C2 to C3 and C3 to C4 intervertebral disk spaces, responded favorably to ventral slot decompression. By comparison, caudal intervertebral disk protrusions (within the C4 to the seventh cervical [C7] intervertebral disk spaces) responded less favorably to ventral slot decompression, demonstrating significantly more severe clinical effects in motor function, comfort, recovery, and long-term outcome following surgery. Significant improvement in clinical results was seen in caudal disk protrusions when additional surgical distraction and stabilization were provided following ventral slot decompression.     

Computed tomography myelographic findings in dogs with cervical spondylomyelopathy

Computed tomography (CT) myelography is used occasionally in the diagnosis of cervical spondylomyelopathy, but the type of lesion found in large- versus giant-breed dogs using this modality has not been characterized. Our purpose was to report the frequency of compressive lesions in large- and giant-breed dogs with cervical spondylomyelopathy and imaged using CT myelography. Fifty-eight dogs were retrospectively studied, 23 large-breed and 35 giant-breed dogs. Multiple sites of compression were found in 12 large-breed dogs (52.2%) compared to 30 (85.8%) giant-breed dogs. The main site of compression was at C5-6 and C6-7 in both large-breed (91.3%) and giant-breed (72.4%) dogs. The main cause and direction of compression was disc-associated and ventral in 19 (82.6%) of the large-breed dogs while osseous changes were the primary cause of compression in 27 (77.2%) of the giant-breed dogs, with most compressions being lateral (51.4%), followed by dorsolateral (14.2%). Osseous compression was observed at C7-T1 in eight giant-breed dogs (22.8%), and at T1-T2 or T2 only in five dogs (14.3%). Four of 23 large-breed dogs (17.4%), and seven (20%) of 35 giant-breed dogs had spinal cord atrophy. Therefore, giant-breed dogs often have multiple compressions, usually caused by osseous changes causing lateralized compressions. In large-breed dogs most compressions are disc-associated and located ventrally. Considering the number of giant-breed dogs with compressions at C7-T1, T1-2, and T2, it is important to include the cranial thoracic region when imaging dogs suspected of having cervical spondylomyelopathy.     

Comparison of the width of the intervertebral disk space and radiographic changes before and after intervertebral disk fenestration in dogs

Intervertebral disk space widths were measured on lateral radiographs of 73 anesthetized dogs. Weight was found to have a significant (P less than 0.01) effect on disk space width. Using weight-adjusted disk space width measurements for all subsequent studies, older (7- to 16-year-old) dogs and males had consistently, but not significantly, wider, disk spaces than did alternative groups. Cervical and lumbar intervertebral disk spaces tended to be wider than those in the caudal thoracic region. The widest cervical intervertebral disk spaces were C4-5 and C5-6 and the narrowest was C2-3. In the lumbar region, L2-3 was the widest disk space and L4-5 was the narrowest. Dachshunds generally had greater mean intervertebral disk space width than did other breeds of dogs. Cervical (n = 6 dogs) and thoracolumbar (n = 6 dogs) disk fenestration resulted in narrow intervertebral disk spaces, regardless of breed. When a ventral approach was used in thoracolumbar fenestration, the mean intervertebral disk space was narrower than that resulting from use of a dorsolateral approach. Spondylosis was found radiographically 1 to 4 years after intervertebral disk fenestration in 3 of 6 dogs that had cervical fenestrations and in 5 of 6 dogs that underwent thoracolumbar fenestration.     

The Intraosseous Blood Supply of the Canine Radius: Implications for Healing of Distal Fractures in Small Dogs

The intraosseous vascular anatomy of the radius was studied in 12 pairs of canine cadaver limbs. Six pairs of specimens were obtained from small-breed dogs (less than 6 kg) and six pairs were obtained from large-breed dogs (18 to 30 kg). All specimens were studied after arterial injection with India ink. Samples were fixed, frozen, then sectioned and processed using a modified Spalteholz technique. In all specimens, the intraosseous blood supply arose from the nutrient artery with its associated branches and the metaphyseal arteries. In small-breed dogs, there was decreased vascular density at the distal diaphyseal-metaphyseal junction compared with large-breed dogs. The reduced vascularity corresponded to the region associated with a poor prognosis for fracture healing in small-breed dogs. This regional association suggests that a decreased vascular supply in the distal radius may contribute to a higher frequency of delayed union and nonunion in smaller dogs.     

Characteristics of dogs admitted for treatment of cervical intervertebral disk disease: 105 cases (1972-1982).

Case histories of 105 dogs that were treated for cervical intervertebral disk disease (IVDD) were studied retrospectively. To compare with previous data, dogs were grouped by age, gender, and breed. Dogs were also grouped by clinical signs of disease, and by presence and location of radiologic change. The age range of cases of cervical IVDD was 1 to 13 years (mean, 6.3 years). Fifty-nine percent of dogs treated for cervical IVDD were females, but the proportion of diseased females was similar to females in total hospital admissions. Twenty-eight breeds of dogs were treated for cervical IVDD. Dachshunds and Beagles were significantly over represented (P less than or equal to 0.001). However, gender-breed interaction was not observed. Prevalence of radiologic evidence of disk disease was detected at the following levels of the vertebral column: C2-3, 29%; C3-4, 24%; C4-5, 21%; C5-6, 15%; C6-7, 9%; and C7-T1, 2%. Significant difference was not observed in prevalence of cervical IVDD affecting the first 4 disk spaces. However, prevalence of cervical IVDD at C7-T1 was significantly less than that involving the first 4 disk spaces (P less than 0.02), and the space at C6-7 was significantly less affected than were the first 3 spaces (P less than 0.08). Significant association was not evident between clinical signs (pain and neurologic deficits) and radiologic signs of IVDD, although neurologic deficits were more likely to be observed in association with radiologic signs than with signs of pain.     

Zinc intoxication in dogs: 19 cases (1991-2003)

OBJECTIVE: To determine physical examination findings, clinicopathologic changes, and prognosis in dogs with zinc toxicosis. DESIGN: Retrospective case series. ANIMALS: 19 dogs with zinc toxicosis. PROCEDURES: Medical records from 1991 through 2003 were searched for animals with a diagnosis of zinc toxicosis. Information concerning signalment, body weight, historical findings, initial owner complaints, physical examination findings, clinicopathologic findings, blood zinc concentrations, source of zinc, treatments given, duration of hospital stay, and outcome was collected. RESULTS: Records of 19 dogs with zinc toxicosis were reviewed.The most common historical findings were vomiting (n = 14) and pigmenturia (12). The most common clinicopathologic findings were anemia (n = 19) and hyperbilirubinemia (12). Median age was 1.3 years, and median weight was 5.6 kg (12.3 lb). The prognosis was favorable, with 17 dogs surviving after a median hospital stay of 2 days. CONCLUSIONS AND CLINICAL RELEVANCE: Hemolytic anemia as a result of zinc toxicosis appeared to affect young small-breed dogs more frequently than older large-breed dogs. The prognosis with treatment is good, and most affected dogs had a short hospital stay.     

Canine intervertebral disk disease: a retrospective study of clinical outcome in 238 dogs (2003-2004)

The aim of the study was the assessment of the prognosis of intervertebral disk diseases on the basis of a large case load with the help of currently available therapy modalities. Medical records of 238 dogs presented within 2 years (2003-2004) with neurological deficits resulting from intervertebral disk disease and surgical treatment at the Department of Small Animal Medicine and Surgery of the University of Veterinary Medicine Hannover were reviewed. 85% of the patients showed a good and 15% a poor long-term functional outcome. Both the presence of deep pain sensation and the weight of the dog were the only variables detected as having a significant impact on prognosis. The time needed to motor function improve depended on the degree of neurological deficits before surgery, and patients with a cervical lesion had a more rapid recovery than patients with a thoracolumbal disease. All other variables, including age, previous signs of intervertebral disk disease, preoperative steroid medication, a lower motor neuron involvement and durotomy did not significantly influence the outcome. Radiographic changes of the vertebral column such as spondylosis, spondylarthrosis, a narrowed disk space up to a fusion of the vertebral bodies mostly were found at the site of a removed intervertebral disk. In dogs with intervertebral disk disease evaluated in the current study a good result could be obtained after surgical decompression.     

Recurrence of thoracolumbar intervertebral disk extrusion in chondrodystrophic dogs after surgical decompression with or without prophylactic fenestration: 265 cases (1995-1999)

OBJECTIVES: To evaluate a population of chondrodystrophic dogs treated for Hansen type 1 intervertebral disk (IVD) disease by surgical decompression with or without prophylactic fenestration and determine the rate and location of surgically confirmed recurrence of intervertebral disk extrusion. ANIMALS: 265 dogs. STUDY DESIGN: Retrospective study. PROCEDURES: Medical records of dogs that underwent spinal decompression between 1995 and 1999 were reviewed. RESULTS: 3 (4.9%) dogs were euthanatized or died prior to discharge. Fenestration was performed in 252 dogs, including 37 (14.7%) at the site of decompression only, 48 (19%) at 3 to 4 disk spaces, and 167 (66%) at 5 to 7 disk spaces. There were 12 instances of recurrent disk extrusion confirmed by removal of disk at a second surgery 3.5 to 33 months after the first surgery. Recurrence was always at a new disk space, and rates did not significantly differ between dogs that underwent single or multiple fenestrations. Two recurrences were at a previously fenestrated disk space. Seven recurrences were at a site immediately adjacent to a fenestrated disk space, and 5 recurrences were at L4-5. CONCLUSIONS AND CLINICAL RELEVANCE: Prophylactic fenestration is generally successful in preventing future disk extrusions at fenestrated disk spaces. Prospective evaluation is still required to determine whether fenestration decreases the overall rate of recurrence. Prophylactic fenestration could promote disk extrusion at adjacent, nonfenestrated disk spaces. This could have a substantial clinical impact if recurrence develops at L4-5.     

Vertebral subluxation following ventral cervical decompression in the dog

Cervical intervertebral disk disease is commonly treated surgically by ventral decompression through a ventral slot. Nine dogs with documented vertebral subluxation following surgical creation of a ventral slot are reported. The location of the subluxation was at the fourth cervical (C4) to fifth cervical (C5) intervertebral space in two dogs, C5 to sixth cervical (C6) intervertebral space in four dogs, and C6 to seventh cervical (C7) intervertebral space in three dogs. The ventral slot width to vertebral body width ratio ranged from 0.39 to 0.80, with the ratio being 0.50 or greater in seven of eight cases evaluated radiographically. Surgical reduction and stabilization were performed in seven of nine dogs.     

Severe respiratory compromise secondary to cervical disk herniation in two dogs

Two dogs presented with acute tetraparesis, hypoventilation, and bradycardia with a second-degree atrioventricular heart block. Neurological examination localized both lesions to the cervical spine. Diagnostic imaging revealed a ventral extradural compression at the second to third cervical (C(2)-C(3)) region in one dog and at the third to fourth cervical (C(3)-C(4)) region in the other. Following surgical correction of the extruded disk, the hypoventilation and bradycardia resolved. Cervical disk extrusions are a common cause of acute tetraparesis in the dog. This report shows that respiratory and cardiac complications may occur concurrently. The authors recommend screening dogs with cervical myelopathies for respiratory and cardiac dysfunctions and treating appropriately. Prompt surgical intervention and supportive care can improve the prognosis.     

Retrospective analysis of axial skeleton osteosarcoma in 22 large-breed dogs

Medical-records of 22 large-breed dogs (>15 kg) with osteosarcoma (OSA) of the axial skeleton were reviewed to determine prevalence of metastasis and survival associated with this neoplasm. All dogs were treated with more than 1 mode of therapy including palliative radiation (n = 12), definitive radiation (n = 8), surgery (n = 7), chemotherapy (n = 12), or some combination of these therapies. Metastasis was documented in 10 of 22 dogs (46%), and the median survival for all dogs was 137 days. Primary cause of death was local tumor recurrence (54%). Breed (retriever versus purebred versus mixed-breed survival was 100, 182, and 264 days, respectively) and radiation therapy protocol (survival in dogs treated with palliative radiation therapy versus those treated with definitive radiation therapy was 79 and 265 days, respectively) were significantly related to survival (P < .05). Prevalence of metastasis and median survival for large-breed dogs with axial skeleton OSA seems to be similar to that reported for large-breed dogs with appendicular skeleton OSA. Definitive radiation therapy may have a role in the treatment of axial skeleton osteosarcoma.     

Effect of Disk Fenestration on Sagittal Kinematics of the Canine C5-C6 Intervertebral Space

OBJECTIVE: To determine the effect that ventral intervertebral disk fenestration has on the sagittal range of motion about the C5-C6 intervertebral space. STUDY DESIGN: A repeated measures in vitro mechanical study of spinal range of motion under controlled loading conditions before and after fenestration. SAMPLE POPULATION: A total of 10 canine cervical vertebral specimens (C4-C7) collected from clinically normal animals within 12 hours of euthanasia. METHODS: Specimens were loaded as cantilever beams fixed at C7. Weights (1 to 5 kg) were progressively applied to C4 to produce flexion or extension in the sagittal plane. Radiographs were taken at each load, 3 times before and 3 times after fenestration of the C5-C6 disk. The positions of radiodense markers embedded in the vertebrae were used to calculate flexion and extension angles and range of motion. RESULTS: Range of motion (difference between flexion and extension) and flexion and extension angles (individually) significantly increased after fenestration (P < .0001). CONCLUSION: Ventral fenestration produces sagittal instability of the C5-C6 disk space. CLINICAL RELEVANCE: In surgical fusion of caudal cervical intervertebral spaces in dogs, radiographically normal disks adjacent to the affected space are often fenestrated to facilitate distraction before surgical stabilization. This study shows that ventral fenestration produces instability of a caudal cervical intervertebral space in the model used. Such instability may contribute to the development of the secondary instability ("domino lesions") seen in some surgically treated dogs.     

Distracted cervical spinal fusion for management of caudal cervical spondylomyelopathy in large-breed dogs

Using an autogenous bone graft (obtained from the iliac crest), 4-mm cancellous bone screws, and polymethylmethacrylate, a distracted cervical spinal fusion technique was performed on 10 dogs with myelographic evidence of caudal cervical spondylomyelopathy. All dogs had evidence of dynamic soft tissue spinal cord compression, as indicated by flexion, extension, and traction myelographic views. Of the 10 dogs, 4 previously had undergone surgery by use of ventral slot or cervical disk fenestration techniques, and their neurologic status had deteriorated after the original surgery. Preoperative neurologic status of the 10 dogs included nonambulatory tetraparesis (n = 5), severe ataxia with conscious proprioceptive deficits (n = 2), and mild ambulatory ataxia with conscious proprioceptive deficits (n = 3). Five dogs had signs of various degrees of cervical pain. Clinical improvement was observed in 8 of 10 dogs--either improved neurologic status or elimination of cervical pain. Implant loosening developed in 3 dogs; 2 of them were euthanatized because of lack of neurologic improvement. Radiographic evidence of bony cervical fusion was observed during a 9- to 24-week period in 6 of the 8 surviving dogs. The distracted cervical fusion technique appears to be a valid surgical procedure to manage cervical spondylomyelopathy in those dogs in which the lesions are limited to one cervical intervertebral disk space.     

Effectiveness of cervical hemilaminectomy in canine Hansen Type I and Type II disc disease: a retrospective study

Medical records of 41 dogs, including 15 small breed dogs (<15 kg) and 26 large breed dogs (>15 kg), with cervical intervertebral disc disease (IVDD) that underwent a hemilaminectomy were reviewed. Dogs were diagnosed using myelography, computed tomography/myelography, or MRI, and dogs were classified as having either Hansen Type I disc extrusion or Hansen Type II disc protrusion located ventrally, ventrolaterally, or laterally within the cervical spinal canal. The most common clinical presentation was ambulatory tetraparesis and/or lameness (44%). The most affected sites for cervical IVDD were between the sixth and seventh cervical vertebrae (C6-C7; 78% of Hansen Type II discs) and C2-C3 (86% of Hansen Type I discs). Treatment was effective in 88% of dogs. Five large breed dogs (12%) did not improve. In dogs with a Hansen Type I disc extrusion, clinical signs improved in 96% of the cases. In dogs with a Hansen Type II disc protrusion, an excellent and good outcome was seen in 47% and 32% of cases, respectively. Outcome was significantly better for small breed dogs and dogs with Hansen Type I disc disease compared with large breed dogs and dogs with Hansen Type II disc disease.     

Prevalence of Pneumonyssoides caninum infection in dogs in Sweden.

A prospective study of 474 dogs, 145 cats, and 66 wild red foxes submitted for necropsy to the Departments of Pathology at the National Veterinary Institute and the Swedish University of Agricultural Sciences, Uppsala, Sweden, was conducted to examine for the presence of Pneumonyssoides caninum, the canine nasal mite. Pneumonyssoides caninum (P. caninum) was found in 95 (20%) of the dogs but in none of the cats or foxes. The median number of P. caninum mites per infected dog was 13 (range, 1 to 250). Dogs older than 3 years of age were more often infected with P. caninum than younger dogs, and large-breed dogs were more often infected than small-breed dogs. No sex predisposition was found.     

Perianesthetic morbidity and mortality in dogs undergoing cervical and thoracolumbar spinal surgery

ObjectiveTo evaluate and compare perioperative morbidity and mortality in dogs undergoing cervical and thoracolumbar spinal surgery.Study designProspective case series.Animals157 dogs undergoing cervical or thoracolumbar spinal surgery.MethodsData were collected sequentially on canine cases presented from the Neurology Section of the North Carolina State University Veterinary Teaching Hospital for anesthesia and surgery for cervical spinal cord disease. Simultaneously, data were collected on all thoracolumbar spinal surgery cases during the same time period. Data included signalment, drugs administered, surgical approach, disease process, cardiac arrhythmias during anesthesia, and outcome.ResultsData were collected from 164 surgical events in 157 dogs. There were 52 cervical approaches; four dorsal and 48 ventral. All thoracolumbar surgeries were approached dorsolaterally. Four dogs 4/52 (7.6%) undergoing a cervical approach did not survive to discharge. Two dogs (2/8; 25%) underwent atlanto-axial (AA) stabilization and suffered cardiovascular arrest and two dogs (2/38; 5.2%) undergoing cervical ventral slot procedures were euthanized following anesthesia and surgery due to signs of aspiration pneumonia. All dogs undergoing thoracolumbar surgery survived until discharge (112/112). Mortality in dogs undergoing cervical spinal surgery was greater compared with dogs undergoing thoracolumbar spinal surgery (p = 0.009), however, in dogs undergoing decompressive disc surgery, intraoperative death rates were not different between dogs undergoing a cervical compared with thoracolumbar approaches (p = 0.32) nor was there a significant difference in overall mortality (p = 0.07).Conclusion and clinical relevanceOverall, dogs undergoing cervical spinal surgery were less likely to survive until discharge compared with dogs undergoing thoracolumbar spinal surgery. Mortality in dogs undergoing cervical intervertebral disc decompression surgery was no different than for dogs undergoing thoracolumbar intervertebral disc decompression surgery. However, dogs undergoing cervical intervertebral disc decompression surgery should be considered at risk for aspiration pneumonia.     

The role of extruded disk material in thoracolumbar intervertebral disk disease: a retrospective study in 40 dogs

The objective of the study was to determine the effect of the dispersed or nondispersed form of the extruded disk material (EDM) on the neurological status and surgical outcomes in Hansen thoracolumbar intervertebral disk disease Type I (IVDD-I). Medical records of 40 dogs with IVDD-I were reviewed, including neurologic status on admission, findings on magnetic resonance imaging (MRI), intraoperative findings, and surgical outcomes. In MRI evaluations, EDM was on the right in 16, on the left in 18, and centrally in 6 cases; in all cases, findings were confirmed by surgery. Extruded disk material was localized and classified as dispersed disk (DD) or nondispersed disk (NDD) according to its dispersion in the epidural space on MRI. Twenty-five dogs had DD and 15 had NDD on both MRI and surgery. There was no significant difference between DD and NDD in preoperative neurological status and surgical outcomes (P > 0.05).     

Functional outcome following hemilaminectomy without methylprednisolone sodium succinate for acute thoracolumbar disk disease in 51 non-ambulatory dogs

Objective: To report the functional outcome of hemilaminectomy in dogs with acute thoracolumbar intervertebral disk disease (IVDD) without the administration of a methylprednisolone sodium succinate (MPSS) protocol. Design: Prospective study. Setting: Private practice specialty hospital. Animals: Fifty‐one, client owned, non‐ambulatory dogs weighing less than 15 kg that had not been treated with MPSS. Interventions: Myelography and hemilaminectomy Measurements and main results: Fifty‐one dogs met the inclusion criteria. Before surgery, all dogs were non‐ambulatory (26 paraplegic, 25 paraparetic), and 98% were painful. Preoperative incontinence was not assessed or unknown in most cases. Ten days following surgery, 90% were ambulatory, 98% were pain free, and 82% were fully continent. By 6 weeks, 100% were ambulatory, 94% were pain free, and 86% were fully continent. By 16 weeks, 96% were pain free, and 88% were fully continent. Conclusion: Hemilaminectomy is highly successful in returning non‐ambulatory, small breed dogs to full function and in these dogs MPSS may not be a necessary adjunct to surgery.     

Functional outcome in dogs after surgical treatment of caudal lumbar intervertebral disk herniation.

Caudal lumbar disk herniations (i.e., third lumbar [L3] to seventh lumbar [L7] intervertebral spaces) represent approximately 15% of surgically treated thoracolumbar disk herniations in dogs. A retrospective case-control study was conducted to determine the postoperative outcome of this subset of dogs in the authors' neurosurgical practice. Medical records (1985 through 1996) were reviewed for dogs with caudal lumbar disk herniation confirmed at surgery. Thirty-six cases were identified. For each case, two dogs that underwent surgical treatment for upper motor neuron thoracolumbar disk herniation (tenth thoracic [T10] to L3 intervertebral spaces) were selected as controls. Probabilities of functional recovery for cases and controls were 81% and 85%, respectively (p value of 0.49). In dogs with caudal lumbar disk herniation, complete sensorimotor loss was the only significant predictor of functional recovery (p value of 0.005). Disk herniations that occur at the thoracolumbar junction and those that occur in the caudal lumbar region should not be considered to be different in terms of surgical treatment and postoperative outcome. The lower motor neuron signs that often accompany caudal lumbar disk herniation reflect the site of spinal cord injury and do not necessarily predict a poor prognosis.     

Owner complaints of canine behavior in Iran–A preliminary survey

The current survey assessed 17 common behavioral complaints reported by 234 dog owners attending the Small Animal Hospital, University of Tehran using a questionnaire. According to the results, nearly 95% of dog owners reported at least 1 undesirable behavior in their dogs. Aggression toward other dogs and people, jumping up, and excessive barking were the most common behavioral complaints. Owners of large-breed dogs were more likely to complain about their dogs’ aggressive behaviors toward people/dogs and excessive barking compared with owners of small-breed dogs. Dogs without access to a yard were more likely to show phobia-associated behaviors, fearfulness, and separation-related behaviors, whereas those having access to a yard were more likely to show aggressive behaviors toward people/dogs and excessive barking. Interaction of dogs with people and type of reaction used by owners in response to the behavior were also related with some other behavioral characteristics of the animals.