Evaluation of Fenestration for Treatment of Degenerative Disc Disease in the Caudal Cervical Region of Large Dogs

Seventeen large dogs (15 Doberman pinschers, one Labrador retriever, and one German short-haired pointer) with pain and gait abnormalities resulting from caudal cervical intervertebral disc degeneration were treated by disc fenestration. Four dogs recovered completely, two dogs appeared to have recovered but nerve root compression and pain returned 3 years later, five did not recover completely or did not improve, and six became progressively worse. In the dogs that recovered, preoperative myelograms showed that traction on or flexing the neck relieved the spinal cord compression. Such manipulation did not relieve slight persistent compression in the dogs that did not improve nor did it relieve severe compression by disc herniation or spinal canal stenosis in the dogs that became progressively worse. The return of nerve root compression after 3 years in two dogs was attributed to incomplete removal of dorsal anulus fibrosus. It was concluded that disc fenestration alone provided inadequate treatment of caudal cervical degenerative disc disease in large dogs.     

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.     

CERVICAL VERTEBRAL FUSION AND CONCURRENT INTERVERTEBRAL DISC EXTRUSION IN FOUR DOGS

Cervical vertebral fusion was noted radiographically in four dogs presented for signs of cervical spinal cord compression. Ventral extradural spinal cord compression was seen on myelography at intervertebral disc spaces adjacent to the fused vertebrae in two dogs and at a site removed in two dogs. At surgery, no intervertebral disc space was found in the area of fusion. No other instances of cervical vertebral fusion were identified in reviewing radiographs of 1225 other dogs with cervical intervertebral disc extrusion evaluated at our hospital. Clinical signs resolved in all dogs after surgical removal of extruded intervertebral disc material. Information from these four dogs suggest vertebral fusion may predispose adjacent discs to herniation.     

The surgical treatment of cervical disc protrusions in the dog: a review of 40 cases

The case histories of 40 dogs with cervical disc protrusions are described. In each case fenestration of the affected disc and prophylactic fenestration of the other cervical discs was carried out. The results of treatment are presented.     

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.     

Cervical vertebral malformation-malarticulation syndrome in the Bernese mountain dog: clinical and magnetic resonance imaging features

O bjectives : To describe the clinical and magnetic resonance imaging features of cervical vertebral malformation-malarticulation in Bernese mountain dogs.
M ethods : Seven Bernese mountain dogs (four males and three females) were diagnosed with cervical vertebral malformation-malarticulation by magnetic resonance imaging. The following data were evaluated retrospectively: (1) abnormalities of the cervical vertebral column and spinal cord, (2) spinal cord compression, (3) intervertebral disc degeneration and herniation, (4) severity of clinical signs pretreatment and after treatment, (5) type of treatment and (6) outcome.
R esults : Spin echo T1-weighted and T2-weighted images disclosed multi-level, extradural compressive spinal cord lesions (ventral, dorsolateral or both) spanning from intervertebral disc spaces C3-4 to C6-7. In all seven dogs, T2-weighted images disclosed one or more intramedullary hyperintensities associated with extradural spinal cord compression. Surgery was performed in five dogs. Two dogs were managed medically. The prognosis for surgical or conservative management in Bernese mountain dogs was similar to cervical vertebral malformation-malarticulation in other breeds.
C linical S ignificance : Cervical vertebral malformation-malarticulation is an important differential diagnosis for young to middle-aged Bernese mountain dogs with a C1-5 or C6-T2 neuroanatomic localisation. Dorsolateral spinal cord compression associated with articular process hypertrophy was the most common feature of cervical vertebral malformation-malarticulation in the seven Bernese mountain dogs evaluated.     

Intervertebral and intravertebral ratios in Doberman pinscher dogs with cervical spondylomyelopathy

No screening method is currently available to differentiate dogs with and without cervical spondylomyelopathy. Intravertebral and intervertebral ratios are used in horses and can predict cervical vertebral malformation. Intervertebral ratios could be a useful screening method for canine cervical spondylomyelopathy. Our purpose was to compare cervical intervertebral and intravertebral ratios in normal vs. affected Doberman pinschers. Forty dogs were studied, 27 affected and 13 normal. Cervical radiographs were obtained in all dogs. The minimum intra- and intervertebral sagittal diameter ratios were established for each cervical vertebrae and disc space from C(2) to C(7) . Comparisons were made between groups and specific vertebral body and disc levels. The effect of gender, age, and method of measurement (analog or digital radiographs) was also studied. There was no difference in either the intervertebral or intravertebral ratio between normal vs. affected dogs. The ratios decreased progressively along the cervical spine, being smallest at C(6) -C(7) and C(7) , respectively. Age, gender, and method of measurement had a significant influence on both inter- and intravertebral ratios, with smaller ratios seen as dogs aged and in male dogs. Based on our results, inter- or intravertebral ratios have no value to distinguish between clinically normal Doberman pinschers and Doberman pinschers with cervical spondylomyelopathy.     

CANINE CERVICAL DISCOGRAPHY

A technique was developed to perform cervical discography in dogs. The radiographic appearance of 70 normal canine cervical discograms was established. No clinical effects were detected when the contrast medium was injected into the discs. No abnormalities were found in subsequent pathologic examinations. In four dogs with cervical disc disease, dorsal and lateral ruptures of the annulus fibrosus were detected by discography. When combined with myelography, discography allowed differentiation between various causes of spinal compression at intervertebral spaces.     

Dynamic Compression of the Cervical Spinal Cord: A Myelographic and Pathologic Investigation in Great Dane Dogs

The authors report the radiographic and pathologic findings in 10 Great Dane dogs with the wobbler syndrome. In all 10 dogs it was possible to demonstrate myelographically that there was cervical spinal cord compression at 1 or 2 sites. The spinal cord compression was mainly dynamic in nature, as degree of compression increased in extension and decreased in flexion of the neck in 8 dogs. In 1 dog with deformed vertebral bodies (G6 and C7), compression increased slightly in flexion of the neck. In another dog, compression was lateral and could only be seen in the ventrodorsal view.The macroscopic findings substantiated the radiologic findings. The cause of the spinal cord compression was in 8 dogs a decrease in the dorsoventral diameter of the orifice of the vertebral canal of 1 or 2 vertebrae in combination with deformation and elongation of 1 or several vertebral arches. In extension of the neck, the cervical spinal cord was squeezed between the anterior tip of the elongated vertebral arch and the caudodorsal rim of the body of the adjacent cranial vertebra.Histologic examination was made of the spinal cord in 5 dogs and the compressive lesions that were found could explain the neurologic signs.In the discussion, the question is raised as to why pain is not a prominent sign in dogs with the wobbler syndrome in contrast to in dogs with cervical disc protrusion. It is believed that the inflammatory foreign body reaction, triggered by the protruded calcified nucleus pulposus is the main cause of pain in the disc protrusion syndrome. In the wobbler syndrome there is no obvious inflammatory reaction in the epidural space.Finally, the possible etiologic factors oC importance for the deformation oC the cervical vertebrae in wobblers are discussed. There are indications that both overnutrition and a genetic trait for rapid growth are of importance.     

Assessment of the usefulness of the fenestration method in cases of disc extrusion in the cervical and thoraco-lumbar spine in chondrodystrophic dogs

The aim of this paper was to assess the effectiveness of treatment of Type I (according to Hansen) intervertebral disc extrusion using the fenestration method. The evaluated clinical material included 37 chondrodystrophic dogs in which multiple fenestration (from 2 to 6 intervertebral spaces) was performed. Dachshunds comprised 86.5% of patients. All dogs were administered corticosteroids during the operation. A mass similar to a slightly jelly-like yogurt, cottage cheese or plaster-like consistency was extracted. In one case a post-surgical pyogenic infection of the wound occured. In two cases, a deterioration in the neurological state followed the fenestration procedure of the cervical spine. In one case of thoraco-lumbar spine fenestration, a deterioration of clinical state was found. Recovery was observed after disc extrusion from the cervical spine in 8 out of 11 dogs, from the thoraco-lumbar spine in 12 out of 14 dogs with the 2nd grade clinical signs and in 11 out of 12 dogs with the 3rd grade clinical sings. In 6 dogs, recurrence of first or second grade clinical signs occurred, but only half of them had to undergo treatment. The probability of dog recovery did not depend on the degree of symptom intensity in a statistically significant way (p=0.11) or on the duration of the disease before the surgical treatment (p=0.87).     

Usefulness of hemilaminectomy for cervical intervertebral disk disease in small dogs

Hemilaminectomy was performed to treat cervical disc disease in 18 small dogs. Cervical spinal cord compression was characterized by ventral and/or lateral compression on myelograms. The duration of follow-up examinations ranged from 2 to 72 months. The optimal response time after surgery ranged from 2 days to 3 months. The outcome was determined to be excellent if clinical signs resolved and the dog had completely improved. The outcome was determined to be good if the dog improved, but was not clinically normal or if the degree of the owner's satisfaction was insufficient. Fourteen dogs achieved complete neurologic recovery without complications. One dog was initially neurologically worse after surgery, but ultimately improved to normal neurologic status. These outcomes were judged to be excellent. In the remaining 3 dogs, 2 dogs had relapse of neck pain and one dog remained mildly ataxic. These outcomes were judged to be good. These results suggest that hemilaminectomy is an effective option for surgical treatment of spinal cord compression secondary to cervical disc disease in small dogs.     

Vertebral stabilisation for cervical spondylopathy using a screw and washer technique

A transvertebral screw and interbody washer technique was used to stabilise the vertebrae and maintain the intervertebral space in 34 adult dobermann pinschers with cervical spondylopathy. The long term success of the procedure was 50 per cent. Pre-operatively three dogs were considered mildly ataxic, 16 moderately ataxic, 13 severely ataxic and two non-ambulatory. Thirty dogs had radiographic changes of calcified disc, vertebral malalignment or narrow intervertebral disc space and all dogs had myelographic abnormalities in the caudal cervical spine. Vertebral malalignment and narrow intervertebral space correlated closely with myelographic cord compression. However, compressive lesions were not identified in 11 cases on plain films. Follow-up was available on 30 dogs of which 25 showed neurological improvement. This was temporary in 10 cases which were destroyed two weeks to three years following surgery.     

MAGNETIC RESONANCE IMAGING OF THE CERVICAL SPINE IN 27 DOGS

The cervical spine of 27 dogs with cervical pain or cervical myelopathy was evaluated using magnetic resonance imaging (MRI). Spin echo T1, T2, and post-contrast T1 weighted imaging sequences were obtained with a 0.5 Tesla magnet in 5 dogs and a 1.5 Tesla magnet in the remaining 22 dogs. MRI provided for visualization of the entire cervical spine including the vertebral bodies, intervertebral discs, vertebral canal, and spinal cord. Disorders noted included intervertebral disc degeneration and/or protrusion (12 dogs), intradural extramedullary mass lesions (3 dogs), intradural and extradural nerve root tumors (3 dogs), hydromyelia/syringomyelia (1 dog), intramedullary ring enhancing lesions (1 dog), extradural synovial cysts (1 dog), and extradural compressive lesions (3 dogs). The MRI findings were consistent with surgical findings in 18 dogs that underwent surgery. Magnetic resonance imaging provided a safe, useful non-invasive method of evaluating the cervical spinal cord.     

Comparison of recovery times and complication rates between a modified slanted slot and the standard ventral slot for the treatment of cervical disc disease in 20 dogs

OBJECTIVES: To compare the recovery times and complication rates between the standard ventral slot and the modified slanted ventral slot for the treatment of cervical disc disease in dogs with the same neurological grade. METHODS: A retrospective analysis of an equal number of cervical disc cases for each procedure was carried out specifically to determine the recovery times and complication rates. To allow for meaningful comparison only dogs that had the same neurological grade were selected. Outcomes were determined by time to recover and the resolution of symptoms and complications were graded in terms of severity. RESULTS: The standard ventral slot cases had a higher complication rate than the modified slanted slot cases with one case dying in the postoperative period. However, the modified slanted slot cases on average had a marginally slower recovery time than standard ventral slot cases. CLINICAL SIGNIFICANCE: Ventral decompression using the modified slanted slot instead of the standard ventral slot will allow for spinal decompression with potentially less destabilisation, and incur a similar incidence of complications and rate of recovery.     

CANINE CHEMONUCLEOLYSIS

Lumbar and cervical chemonucleolysis was evaluated on 16 clinically normal adult Beagle dogs in two age groups, using chymopapain at dose rates of 200 and 500 units (U). Lumbar discs injections in four discs were made transcutaneously under fluoroscopic guidance, and cervical disc injections in four discs were made after surgical exposure. Postinjection radiographs revealed a progressive narrowing of the disc spaces, first noted 24 hours after injection. Gross examination of the discs at 1-, 2-, 4-, and 8-day intervals showed a time-dependent change, with no detectable difference between the two doses and age groups. The overall rate of successful chemonucleolysis was 82.4% in the cervical discs and 78% in the lumbar discs. Clinically, the dogs showed minimal evidence of pain and no detectable postural abnormality following chemonucleolysis.     

Spondylosis deformans and diffuse idiopathic skeletal hyperostosis (dish) resulting in adjacent segment disease

Spondylosis deformans and diffuse idiopathic skeletal hyperostosis (DISH) are usually incidental findings and in most dogs are either asymptomatic or associated with mild clinical signs. Severe spondylosis deformans and DISH can result in complete bony fusion of consecutive vertebral segments. One of the recognised complications following vertebral fusion in human patients is the development of adjacent segment disease, which is defined as degenerative changes, most commonly degenerative intervertebral disc disease, in the mobile vertebral segment neighboring a region of complete vertebral fusion. A similar syndrome following cervical fusion in dogs has been termed the domino effect. The purpose of this retrospective study was to investigate the hypothesis that vertebral fusion occurring secondary to spondylosis deformans or DISH in dogs would protect fused intervertebral disc spaces from undergoing degeneration, but result in adjacent segment disease at neighbouring unfused intervertebral disc spaces. Eight dogs with clinical signs of thoracolumbar myelopathy, magnetic resonance imaging of the thoracolumbar vertebral column, and spondylosis deformans or DISH producing fusion of > or = 2 consecutive intervertebral disc spaces were evaluated. Vertebral fusion of > or = 2 consecutive intervertebral disc spaces was correlated (P = 0.0017) with adjacent segment disease at the neighbouring unfused intervertebral disc space. Vertebral fusion appeared to protect fused intervertebral disc spaces from undergoing degeneration (P < 0.0001). Adjacent segment disease should be considered in dogs with severe spondylosis deformans or DISH occurring in conjunction with a thoracolumbar myelopathy.     

Cranial thoracic disc protrusions in three German Shepherd dogs

Although intervertebral disc degeneration can occur at any level of the spine, cervical and thoraco-lumbar discs are more commonly affected. The presence of the inter-capital ligament between the rib heads results in an extremely low incidence of cranial thoracic intervertebral disc herniation. In this case series, the clinical, radiological, and surgical findings, as well as the post-operative outcome, in three German Shepherd dogs with T2–T3 disc protrusions is reported. These dogs had chronic progressive paraparesis and lumbar myelography and post-myelographic computerised tomography revealed ventrolateral, extra-dural spinal cord compressions over the T2–T3 intervertebral disc. All animals exhibited transient deterioration in their clinical signs and one developed unilateral Horner’s syndrome following T2–T3 hemi-dorsal laminectomy. Subsequently two of the dogs improved progressively and neurological dysfunction had completely resolved by 2 months. To the authors’ knowledge, this is the first case series describing T2–T3 disc protrusions in the dog.     

Clinical and magnetic resonance imaging features of canine compressive cervical myelopathy with suspected hydrated nucleus pulposus extrusion

Objective : To describe clinical and magnetic resonance imaging features in dogs with compressive cervical myelopathy due to acute suspected hydrated nucleus pulposus extrusion. Design : Retrospective case series. Animals : Ten dogs with compressive cervical myelopathy caused by acute suspected hydrated nucleus pulposus extrusion. Materials and Methods : Medical records and magnetic resonance images of dogs evaluated from 2005 through 2010 were reviewed. The inclusion criteria were clinical signs compatible with cervical myelopathy, magnetic resonance imaging of the spine performed within 48 hours after onset, magnetic resonance imaging findings consistent with compressive suspected hydrated nucleus pulposus extrusion, complete medical records and follow‐up information. Results : Six dogs were presented with acute onset tetraplegia and four dogs with acute onset of nonambulatory tetraparesis. Compromised respiratory function was present in three dogs. Compressive suspected hydrated nucleus pulposus extrusion was found on magnetic resonance imaging at the C4‐C5 (n=6), C3‐C4 (n=3) and C5‐C6 (n=1) intervertebral disc spaces. Seven dogs underwent surgical treatment and three dogs were treated conservatively. All dogs except one regained ambulatory status within two weeks after the onset, and had a favourable outcome. Clinical Significance : Compressive myelopathy caused by acute suspected hydrated nucleus pulposus extrusion has not been reported previously and, even though neurological deficits can be severe on presentation, outcome is favourable.