Imaging findings and surgical treatment of hemivertebrae in three dogs

CASE DESCRIPTION

3 immature screw-tailed dogs were evaluated because of progressive pelvic limb paraparesis.

CLINICAL FINDINGS

Each dog had marked ataxia and paresis of the pelvic limbs and a palpable deformity of the midthoracic portion of the vertebral column. Pain perception in the pelvic limbs was considered normal, and there was no evidence of fecal or urinary incontinence in any of the 3 dogs. Radiography and magnetic resonance imaging revealed hemivertebrae with severe dorsoventral stenosis of the vertebral canal resulting in spinal cord compression in 2 dogs and lateral compression in the other.

TREATMENT AND OUTCOME

Each dog underwent decompressive surgery consisting of dorsal laminectomy or hemilaminectomy and vertebral stabilization by use of combinations of Kirschner wires or threaded external fixator pins plus polymethylmethacrylate bone cement. All dogs regained strong locomotor function with minimal residual pelvic limb ataxia.

CLINICAL RELEVANCE

Little detailed information regarding surgical treatment of hemivertebrae in dogs is available; results of treatment in these 3 dogs suggest that spinal cord decompression and stabilization of the vertebral column can achieve a satisfactory, functional outcome.

The assessment of the usefulness of hemilaminectomy without fenestration in the treatment of thoracolumbar disc disease in chondrodystrophic dogs

The aim of the publication is to assess the effectiveness of the treatment of type I disc extrusion according to Hansen by using the method of hemilaminectomy without fenestration. The evaluated clinical material comprised 36 chondrodystrophic dogs in which 38 surgical procedures were performed. All dogs were administered corticosteroid during the operation. Dachshunds made up to 79% of patients. In 34 cases grainy mass was extracted from the vertebral canal. In two cases it was plaster-like mass and in other two--granulo-chondral. Most often (12 cases) the prolapse of the nucleus pulposus was observed between the first and second lumbar vertebra. There was one case of the postoperative pyogenic infection of the wound. Recovery was observed in all dogs with 3rd grade clinical signs, 17 out of 18 dogs with 4th grade and 8 out of 13 dogs with 5th grade of dysfunction severity. The recovery time of the dog depended in the statistically significant way on the severity of symptoms and the grade of the present disease (p<0.00005). There did not appear to be any statistically significat relationship between the recovery time and the duration of symptoms pre operatively (p=0.42), the time of non-ambulatory status (p=0.27) and the breed of the dog (p=0.81).

The value of oblique versus ventrodorsal myelographic views for lesion lateralisation in canine thoracolumbar disc disease

OBJECTIVE

To determine the value of oblique versus ventrodorsal myelographic views for lesion lateralisation in canine thoracolumbar disc disease.

METHODS

The ventrodorsal and oblique views from 196 lumbar myelograms of dogs with single thoracolumbar disc extrusions or protrusions were blindly and independently reviewed by two of the authors for evidence of lesion lateralisation. Medical records were reviewed for details regarding hemilaminectomy surgery. The side (left versus right) of the surgery and whether or not the disc material was retrieved were noted.

RESULTS

Both reviewers lateralised significantly more disc lesions from the oblique views (93 and 95 per cent) than from the ventrodorsal views (59 and 70 per cent) (P<0.001). Using a combination of oblique and ventrodorsal views, 194 (99 per cent) and 195 (99.5 per cent) lesions were lateralised. Unilateral hemilaminectomy was performed in 193 dogs with myelographic lateralisation and in one dog without myelographic lateralisation. The side of spinal cord decompression corresponded with the myelographic findings in all dogs showing lateralisation on myelography. In the dog without myelographic lateralisation, a left (randomly chosen) hemilaminectomy revealed dorsal protrusion of the annulus fibrosus.

CLINICAL SIGNIFICANCE

Myelography, including oblique, ventrodorsal and lateral views, is an accurate method for determining lateralisation of extruded or protruded disc material in the vertebral canal before decompressive surgery. Combined oblique and ventrodorsal views are more useful than either view alone and should be routinely obtained in all lumbar myelographic studies when investigating thoracolumbar disc disease.

SUBFASCIAL SEROMA CAUSING COMPRESSIVE MYELOPATHY AFTER CERVICAL DORSAL LAMINECTOMY

Dorsal surgical approach to the cervical vertebral canal is indicated for a variety of spinal cord diseases. Compressive myelopathy due to subfascial seroma following dorsal laminectomy has not previously been documented in dogs. We describe neurologic findings, magnetic resonance (MR) imaging characteristics and clinical outcome in a young Rottweiler experiencing this complication after a successful dorsal decompression for treatment of cervical stenotic myelopathy. MR imaging allowed detection of pockets of high signal intensity material on T2-weighted images and low signal intensity in T1-weighted images. Prompt surgical revision and drainage allowed complete recovery.

Intervertebral disk prolapse in a ferret

This case report describes the diagnosis and resolution of an inter-vertebral disk prolapse in a 6-year-old ferret. No predisposing causes were found in the patient's history. A right hemilaminectomy, performed 1 week after presentation, was chosen to treat the patient surgically, and complete remission of clinical signs was achieved 2 months after presentation.

Intraoperative Use of Ultrasonography During Continuous Dorsal Laminectomy in Two Dogs with Caudal Cervical Vertebral Instability and Malformation ("Wobbler Syndrome")

OBJECTIVE

To describe an intraoperative ultrasound imaging technique during dorsal laminectomy in 2 dogs with caudal cervical vertebral instability and malformation (CCVIM, "Wobbler syndrome").

STUDY DESIGN

Clinical case report.

SAMPLE POPULATION

Two dogs with CCVIM.

RESULTS

On neurologic examination there was tetraparesis with upper motor neuron signs in the thoracic limbs and lower motor neuron signs in the pelvic limbs in dog 1, and hyperreflexia of the rear limbs, normoreflexia of the right front limb, and hyporeflexia of the left front limb of dog 2. Both dogs had signs of marked cervical pain and radiographic signs of cervical spinal cord compression. Intraoperative ultrasonography of the spinal cord revealed protruding intervertebral disc at C5-6 (dog 1) and C6-7 (dog 2), and the parallel borders of the spinal cord and central canal after decompression. Continuous dorsal laminectomy (CDL) resulted in improvement over 16 months (dog 1) and 20 months (dog 2).

CONCLUSIONS

Intraoperative ultrasonographic imaging of the cervical spinal cord after CDL was helpful in determining adequate decompression (postlaminectomy) of the spinal cord in relation to the ventral and lateral compressive component(s) and to image the protruding intervertebral disc.

CLINICAL RELEVANCE

Intraoperative ultrasonography can be used to provide valuable information on the spinal cord and surrounding soft tissues for the neurosurgeon.

Spinal epidural empyema in seven dogs

OBJECTIVE

To characterize the clinical signs, diagnostic and surgical findings, and outcome in dogs with spinal epidural empyema (SEE).

STUDY DESIGN

Retrospective study.

ANIMALS

Seven dogs.

METHODS

Dogs with SEE between 1992 and 2001 were identified from a computerized medical record system. Inclusion criteria were: neurologic examination, vertebral column radiographs, myelography, antimicrobial culture and susceptibility of material collected surgically from the vertebral canal, a definitive diagnosis of SEE confirmed by surgery, and microscopic examination of tissue from the vertebral canal.

RESULTS

Common signs were lethargy, fever, anorexia, apparent spinal pain, and paraparesis/plegia. Common laboratory abnormalities were peripheral neutrophilia, and neutrophilic pleocytosis in cerebrospinal fluid (CSF). Three dogs had concurrent discospondylitis and 1 of these had vertebral luxation. On myelography, extradural spinal cord compression was focal (2 dogs), multifocal (3), or diffuse (2). Bacteria were isolated not from CSF but from blood, surgical site, pleural fluid, or urine in 6 dogs. Dogs were administered antibiotics and had surgical decompression by hemilaminectomy. Five dogs improved neurologically and had a good long-term outcome. Two dogs were euthanatized, 1 because of worsening of neurologic signs and pneumonia, and the other because of herniation of a cervical intervertebral disc 1 month postoperatively, unrelated to the SEE.

CONCLUSION

Dogs with SEE may have a good outcome when treated by surgical decompression and antibiotic administration.

CLINICAL RELEVANCE

SEE should be included in a list of possible causes for dogs with fever, apparent spinal pain, and myelopathy.

Synovial cysts associated with cauda equina syndrome in two dogs

OBJECTIVE

To report synovial cysts associated with cauda equina syndrome in 2 dogs.

STUDY DESIGN

Clinical cases.

ANIMALS

Two German Shepherd dogs.

METHODS

After magnetic resonance imaging detection, cysts were surgically removed via dorsal laminectomy.

RESULTS

Six and 8 months after surgery, both dogs were free of clinical signs and no pain was elicited on lumbosacral joint manipulation.

CONCLUSION

Although described in dogs, cysts at the lumbosacral joint might cause compression of the cauda equina nerve roots. Radical excision of the cyst capsule can result in resolution of clinical signs.

CLINICAL RELEVANCE

Synovial cysts should be considered in the differential diagnosis of dogs with cauda equina compression syndrome when lumbosacral degenerative joint disease is present.

The effects of free fat graft or cellulose membrane implants on laminectomy membrane formation in dogs

The purpose of this study was to determine the effect of cellulose membrane or free fat grafts (FFG) on laminectomy membrane (LM) formation. Eighteen dogs were randomly divided into three groups of six dogs. All dogs underwent a modified dorsal laminectomy on T(13)-L(1). The laminectomy defect was left uncovered in the control group but either a FFG or a cellulose membrane implant was provided in the other two groups. The dogs were evaluated through neurological examination, myelography, macroscopic roundness index of spinal cord and histological evaluations of epidural fibrosis and spinal cord. The results showed a significant difference between the control and the FFG group, with the FFG causing neurological deficits and spinal cord compression as assessed by the roundness index of the spinal cord. Both FFG and cellulose membrane were partially effective in preventing LM formation. The use of FFG was associated with a high rate of significant neurological complications and spinal cord lesions.

Polyostotic Lymphoma With Vertebral Involvement and Spinal Extradural Compression in a Dog

A 10-year-old, male, mixed-breed dog that developed cervical pain and neurological deficits was diagnosed with primary lymphoma of the second cervical vertebra. The cervical lesion was not surgically resectable. A dorsal cervical hemilaminectomy was performed to provide temporary decompression. The dog had complete pain relief after surgery but was euthanized 6 weeks later with recurrent clinical signs and evidence of lymphoma in the right femur.

Thoracolumbar disc extrusion associated with extensive epidural haemorrhage: a retrospective study of 23 dogs

OBJECTIVES

To describe the clinical features and outcome in dogs suffering from thoracolumbar disc extrusion associated with extensive epidural haemorrhage (DEEH) and treated with extensive hemilaminectomy (from three to seven vertebrae).

METHODS

The records of 23 dogs with surgically confirmed DEEH were reviewed retrospectively.

RESULTS

All cases were characterised by rapid progression to severe neurological dysfunction (grade III, V and VI). Myelography was performed in 21 cases and showed an absence (16 cases) or attenuation (five cases) of contrast medium column along three to seven vertebrae. In two dogs, magnetic resonance imaging was accurate in confirming extradural compression due to disc material and haemorrhage, determining the extent of compression and side of the lesion. All cases were treated surgically with extensive hemilaminectomy involving all the compressed spinal segments. Twenty-one dogs (91 per cent) recovered and regained ambulatory function. Two dogs, without deep pain perception before surgery, did not improve. A two-year follow-up history was available for 15 dogs. Disc extrusion recurred in two dogs (9 per cent), two and 20 months after surgery.

CLINICAL SIGNIFICANCE

Extensive hemilaminectomy can adequately decompress the spinal cord after DEEH and may produce a recovery and recurrence rate similar to thoracolumbar disc extrusion not complicated by extensive epidural haemorrhage.

A Modified Lateral Approach to the Canine Cervical Spine: Procedural Description and Clinical Application in 16 Dogs with Lateralized Compressive Myelopathy or Radiculopathy

OBJECTIVE

To describe a modified lateral surgical approach to the cervical spine in dogs and evaluate clinical outcomes of dogs with neurologic disorders treated with this technique.

STUDY DESIGN

Retrospective study.

SAMPLE POPULATION

Sixteen dogs with lesions involving the cervical spine.

METHODS

Medical records (1998-2002) of dogs that had a modified lateral approach to the cervical spine were reviewed. To reduce procedural morbidity, the surgical approach was modified from original descriptions of the technique by minimizing disruption of epaxial and extrinsic thoracic limb musculature and limiting the size of the operative field to the affected vertebral segment. Signalment, neurologic status on admission; onset, progression, and duration of clinical signs; diagnostic testing, etiologic diagnosis, surgical site(s), intra- and postoperative complications, hospitalization, time to optimum recovery, neurologic status at discharge, final neurologic status, and outcome were recorded. Neurologic status (0-5) was scored preoperatively, 1 day postoperatively, at discharge, and at recheck examination (8 dogs). Telephone interviews were used to obtain additional follow-up information.

RESULTS

None of the dogs had postoperative deterioration in neurologic status. Outcomes were good or excellent in dogs with intervertebral disc disease, 3/4 dogs with caudal cervical spondylomyelopathy, 1/2 dogs with spinal neoplasia, and in 1 dog with the vascular anomaly; long-term outcomes were unknown in 2 dogs. Intraoperative complications occurred in 3 dogs and included controllable venous plexus hemorrhage (2) and incorrect lesion localization (1). One dog was euthanatized because of postoperative complications. Hospitalization, time to optimal recovery, and overall outcome were not different from previously reported results using other surgical approaches to treat analogous neurologic conditions.

CONCLUSIONS

A modified lateral approach to the cervical spine is viable for surgical treatment of cervical myelopathic or radiculopathic lesions when exposure to foraminal and lateralized lesions of the vertebral canal involving the C2-C7 vertebral articulations is desirable.

CLINICAL RELEVANCE

A modified lateral approach to the cervical spine can be successfully used in dogs of all sizes to treat caudal cervical spondylomyelopathy, other anomalous conditions of the cervical spine, intervertebral disc disease, and spinal neoplasms. Although long-term follow-up was not available for all patients, outcomes were generally favorable.

Hindbrain decompression in a dog with scoliosis associated with syringomyelia

A 6-month-old female Border Collie was examined because of a 1-month history of progressive curvature of the cervical portion of the vertebral column. Radiography revealed severe cervical and thoracic scoliosis. Cervical syringomyelia and hydrocephalus were observed by means of magnetic resonance imaging. Suboccipital craniotomy and laminectomy of the first cervical vertebra were performed, and substantial improvement in the scoliosis and syringomyelia was observed 3 months after surgery. No recurrences were seen during the first year after surgery.

Treatment of a prolapsed lumbar intervertebral disc in a ferret

A seven-month-old, male ferret had acute paraplegia and radiographs showed signs of disc prolapse between the second and third lumbar vertebrae (L2/3). Hemilaminectomy was performed to decompress the spinal cord. Histological examination revealed that the extradural material was consistent with annulus fibrosus and the L2/3 articular facets were enlarged as a result of bone remodelling. The ferret became ambulatory one month postoperatively. Five months postoperatively, the ferret had normal posture with mild proprioceptive deficits in the pelvic limbs, and fusion of the L2 and L3 vertebral bodies.

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.

Risk factors for recurrence of clinical signs associated with thoracolumbar intervertebral disk herniation in dogs: 229 cases (1994-2000)

OBJECTIVE

To assess risk factors for recurrence of clinical signs associated with thoracolumbar intervertebral disk disease (IVDD) in dogs that had decompressive laminectomy without attempted prophylactic treatment of other disk spaces.

DESIGN

Retrospective study.

ANIMALS

229 dogs.

PROCEDURE

Medical records of dogs that had decompressive laminectomy without prophylactic fenestration for a first episode of IVDD and were available for follow-up were reviewed. Information on 7 clinical and 8 radiographic potential risk factors were recorded.

RESULTS

Clinical signs associated with recurrence of IVDD developed in 44 (19.2%) dogs. Ninety-six percent of recurrences developed within 3 years after surgery. Recurrence developed in 25% of Dachshunds and 15% of dogs of other breeds combined. Number of opacified disks was a significant risk factor for recurrence. Risk increased with number of opacified disks in an almost linear manner; each opacified disk increased risk by 1.4 times. Dogs with 5 or 6 opacified disks at the time of first surgery had a recurrence rate of 50%.

CONCLUSIONS AND CLINICAL RELEVANCE

When all likely episodes of recurrence are considered and a long follow-up period is achieved, true rate of recurrence of IVDD appears to be higher than in many previous reports. Dogs with multiple opacified disks at the time of first surgery should be considered a high-risk subpopulation.

[Sacral osteochondrosis dissecans in a Bernese Mountain Dog: diagnosis and treatment]

A 18-month-old female Bernese Mountain Dog with chronic pain at jumping, extension of the right hind leg and paresis of the tail was referred to the Neurological Service of the Veterinary Hospital of the University of Zurich. Upon radiological examination a mineralised fragment at the dorsal aspect of the endplate of S1 was detected. The diagnosis of Osteochondrosis dissecans was confirmed by linear and computed tomography as well as histologic examination of the fragment, which was surgically removed. Preoperative imaging allowed a minimal surgical approach using a unilateral, modified dorsal laminectomy. Outcome was evaluated by neurological reevaluation and a CT scan performed 6 months after surgery.

Magnetic resonance imaging in the diagnosis and surgical management of sacral osteochondrosis in a mastiff dog

The clinical, radiographic, magnetic resonance imaging (MRI), surgical and pathological findings related to an osteochondral lesion of the sacrum in a mastiff dog are described. The dog showed chronic signs of pain in its pelvic limbs. Radiography revealed a triangular mineralised opacity at the craniodorsal aspect of the sacrum consistent with sacral osteochondrosis. A T2-weighted spin-echo MRI revealed dorsal and lateral compression of the cauda equina. The osteochondral fragment was removed via a dorsal laminectomy, and the clinical signs resolved. Histological abnormalities in the fragment were consistent with a diagnosis of osteochondrosis.

Asymmetrical, Transitional, Lumbosacral Vertebral Segments in Six Dogs: A Characteristic Spinal Syndrome

Clinical findings in six dogs with asymmetrical, transitional, lumbosacral vertebral segments are reported. All dogs exhibited low back pain and varying degrees of asymmetrical cauda equina dysfunction. Results of myelography, epidurography, and magnetic resonance imaging (MRI) indicated a unilateral disk protrusion in all dogs. In the dogs with MRIs, focal degenerative alterations in the vertebral end plates and adjacent body of the vertebra were detected. All dogs were treated with a dorsal laminectomy or hemilaminectomy. Results following surgery were good or excellent in all six dogs.

[Cauda equina compression syndrome (CECS): retrospective study of surgical treatment with partial dorsal laminectomy in 86 dogs with lumbosacral stenosis]

We report our results of partial lumbosacral laminectomy for treatment of canine Cauda equina Compression Syndrome due to a lumbosacral stenosis. Opposite to conventional techniques of dorsal laminectomy, only widening of the Spatium interarcuale is performed. This is achieved by exstirpation of the Lig. flavum and partial dorsal laminectomy of the first sacral segment. The Proc. spinosi and integrity of facet joints are fully maintained by this technique. In 96.5% of 86 dogs treated with this method relief of dorsal pressure and permanent rapid regression of clinical symptoms was achieved. In two cases recurrence of clinical symptoms was observed during follow up and one case showed no improvement at all. In conclusion partial dorsal laminectomy is a minimal invasive technique for treatment of Cauda equina compression syndrome expressed by pain reaction accompanied by minor neurological deficits caused by lumbosacral stenosis. Maintained spinal stability allows short reconvalescence and the unrestricted use of dogs immediately post operation.

Suboccipital Craniectomy, Dorsal Laminectomy of C1, Durotomy and Dural Graft Placement as a Treatment for Syringohydromyelia with Cerebellar Tonsil Herniation in Cavalier King Charles Spaniels

OBJECTIVE

To evaluate retrospectively the efficacy of the suboccipital craniectomy and dorsal laminectomy of C1 with durotomy and placement of a dural graft for treatment of syringohydromyelia (SHM) because of cerebellar tonsil herniation in Cavalier King Charles spaniels (CKCS). This technique is used with great success in human medicine.

STUDY DESIGN

Four CKCS diagnosed by Magnetic resonance imaging (MRI) of SHM because of cerebellar tonsil herniation and not responsive to medical therapy underwent a suboccipital craniectomy and dorsal laminectomy of C1 (2 dogs) and of C1 and partial C2 (2 dogs) with durotomy and placement of a dural graft. Three dogs were evaluated neurologically 24 hours, 1 month, and 3 months postoperatively and evaluations were compared with preoperative neurological examination. Repeat MRI took place 3 months postoperatively.

RESULTS

Neurological examinations showed neither improvement nor progression of clinical signs 3 months postoperatively. MRI showed no regression of syrinx size 3 months postoperatively.

CONCLUSION

Improvement was not seen. Given the progressive nature of the disorder, evaluation over a longer period of time is necessary to detect if progression has stopped. Some modification to the surgical technique is needed to accomplish the same results as in human medicine. A study of a larger population is needed to attain more reliable information.

CLINICAL RELEVANCE

Suboccipital craniectomy and dorsal laminectomy of C1 with durotomy and placement of a dural graft is a feasible technique in CKCS, but needs some modification to accomplish the same results as in human medicine.

Endoscopic-Assisted Lumbosacral Foraminotomy in the Dog

OBJECTIVE

To determine if endoscopic-assisted foraminotomy significantly increased the area of the L7-S1 intervertebral foramen and if, over 12 weeks, stenosis would occur.

STUDY DESIGN

Prospective, experimental study.

ANIMAL POPULATION

Six clinically normal, 22-29 kg, adult dogs.

METHODS

Using endoscopic assistance, unilateral L7-S1 foraminotomy was performed. Computed tomography of L7-S1 was performed preoperatively, immediately postoperatively, and at 12 weeks. Parasagittal foramen area (PFA) measurements were obtained at the entry, middle, and exit zones of the treated and control foramen for each period. Objective and subjective data were compared among dogs by time period and treatment status.

RESULTS

Endoscopic-assisted foraminotomy resulted in a significant increase in the mean PFA of the entry and middle zones immediately postoperatively. The exit zone was not significantly larger at any time. The foramen remained significantly larger at 12 weeks only in the middle zone; however, some decrease in the surgically created foramen enlargement occurred at all 3 levels. The procedure was well tolerated but dogs did have transient, mild delay of functional return postoperatively.

CONCLUSIONS

Endoscopic-assisted foraminotomy in dogs can be performed for certain foraminal regions, allowing enhanced visibility of the spinal canal. The foramen can be surgically enlarged at the entry and middle zones using this technique; however, some reduction of the foraminal enlargement occurs by 12 weeks. The clinical implications of this reduction cannot be determined from this study.

CLINICAL RELEVANCE

Endoscopic-assisted foraminotomy could be used to improve intraoperative visualization in dogs with foraminal stenosis as a component of degenerative lumbosacral stenosis.

Cervical spondylomyelopathy (wobbler syndrome) in the Boerboel

The Boerboel is a South African large-breed dog resembling a Bullmastiff. The records of Onderstepoort Veterinary Academic Hospital were searched for dogs that had presented, between 1998 and 2003, with symptoms indicative of wobbler syndrome and had undergone survey radiographic and myelographic studies. Ten cases fitted the inclusion criteria. Dogs presented within the first 2 years of life, often with acute onset of symptoms. All presented with pelvic limb and 6 with concomitant thoracic limb ataxia or paresis. Treatment varied and included none (4), prednisolone (2), and dorsal laminectomy (2). Two dogs were euthanased at the time of diagnosis. The breed appears to be affected with a form of spondylomyelopathy that comprises bony malformation of cervical and/or thoracic vertebrae. In 8 dogs, malformations were evident on survey radiographs and were characterised by enlarged, irregular articular facets and associated medial deviation of the pedicles. These changes resulted in axial compression of the spinal cord best seen on ventrodorsal or dorsoventral myelographic studies. Multiple vertebrae were affected in some dogs and lesions were not confined to the caudal area of the cervical spine. Three dogs were alive and without symptoms at follow-up. Four were euthanased as a result of the disease and 1 died as a result of post-operative complications. Two additional dogs presenting with wobbler clinical signs are also described. One had medial deviation of the T5 and T6 caudal pedicles and 1 dog suffered from multiple cervical articular facet synovial cysts.

Reversal of neurologic deficit in an adult gorilla with severe symptomatic lumbar stenosis

STUDY DESIGN

A case report is presented.

OBJECTIVE

To describe a case of severe symptomatic lumbar stenosis in an adult gorilla successfully treated with decompressive surgery.

SUMMARY OF BACKGROUND DATA

Although spinal degenerative disease is thought to be less common in apes than in humans, gorillas and bonobos are known to have higher rates of disease than other African apes.

METHODS

A 42-year-old female gorilla presented with a history of progressive lower extremity weakness. She was unable to ambulate normally or climb, pulling herself around with her arms. Her keeper did not believe she was incontinent. Physical examination revealed that ankle plantarflexion and dorsiflexion were absent on the right and weak on the left. Radiographs revealed disc space narrowing with osteophytes at the last mobile segment. Myelogram and computed tomography revealed severe spinal stenosis at the last two mobile segments. Under general anesthesia, a standard laminectomy and bilateral lateral recess decompression were performed.

RESULTS

There were no anesthetic or wound complications. The gorilla was noted to have improved ankle strength bilaterally on postoperative day 1. On postoperative day 3, the animal began to walk and climb. At 20 months, the animal is back to her neurologic baseline.

CONCLUSIONS

Symptomatic lumbar degenerative disease with neurologic compromise may be treated surgically, with excellent outcome, in the adult gorilla. Though this is an unusual situation, knowledge that this is a potentially reversible condition may benefit other gorillas in captivity.

In vitro evaluation of biomechanical effects of multiple hemilaminectomies on the canine lumbar vertebral column

OBJECTIVE

To conduct an in vitro investigation of the biomechanical characteristics of the canine lumbar spinal column in flexion and extension and measure the destabilizing effects of multiple consecutive unilateral and bilateral hemilaminectomies.

SAMPLE POPULATION

30 isolated multisegmental spinal units (L1-L4) from nonhypochondroplastic dogs weighing 15 to 30 kg.

PROCEDURES

Physically normal and surgically altered spinal specimens were subjected to 4-point bending in flexion and extension to determine effects of multiple consecutive hemilaminectomies on the basis of analysis of test system load-displacement data. Six groups with 5 spinal columns in each were defined on the basis of the following procedures: hemilaminectomy at L2-L3, 2 adjacent hemilaminectomies at L1-L3, 3 adjacent hemilaminectomies at L1-L4, bilateral hemilaminectomies at L2-L3, 2 bilateral hemilaminectomies at L1-L3, and no hemilaminectomy (intact). Spinal stability before and after surgery was determined in all groups. Each group served as its own control for nondestructive testing. Spinal strength was evaluated through destructive testing to determine deformation at failure, strength to failure, and mode of catastrophic failure. The intact group served as the control for destructive testing.

RESULTS

Stability in extreme flexion and extreme extension did not change significantly following any hemilaminectomy procedure. Postoperative stability within the neutral zone was significantly decreased in all groups. Range of motion within the neutral zone was not significantly different from the intact condition in any group.

CONCLUSIONS AND CLINICAL RELEVANCE

Multiple hemilaminectomies did not decrease stiffness of the lumbar spinal column during flexion and extension. These results support clinical recommendations regarding multiple consecutive hemilaminectomies in dogs.

In vitro osteoblast proliferation as a predictor for spinal fusion mass

BACKGROUND CONTEXT

The biological factors determining a successful spinal fusion have not yet been fully determined.

PURPOSE

To determine the influence of graft cell vigor on fusion rate and fusion mass using in vitro osteoblast proliferation as a predictor.

STUDY DESIGN

Animal study randomizing to posterolateral fusion with autograft with or without pedicle-screw instrumentation.

PATIENT SAMPLE

Twenty adult Göttingen mini-pigs.

OUTCOME MEASURES

Fusion rate measured both with X-ray and computed tomography (CT) as well as amount of fusion mass determined with three-dimensional CT.

METHODS

Animals underwent posterolateral fusion with autograft either with or without pedicle-screw instrumentation. Additional graft was harvested for osteoblastlike cell culture. Cells were counted after 3 weeks, and their proliferative capacity was correlated to fusion rate and fusion amount.

RESULTS

Cell count was significantly higher in the fused animals (p<.011). Furthermore, a tendency toward a positive correlation to fusion mass amount was observed (p<.091).

CONCLUSIONS

The achievement of a solid spinal fusion using autograft is related to properties of the bone-forming cells in the graft and fusion bed. Most likely it is the number of cells and not their proliferative capacity that is the most important factor.

Long-term functional outcome of dogs with severe injuries of the thoracolumbar spinal cord: 87 cases (1996-2001)

OBJECTIVE

To determine long-term (> 6 months) outcome of dogs with paraplegia and loss of hind limb deep pain perception (DPP) resulting from intervertebral disk herniation or trauma.

DESIGN

Retrospective study.

ANIMALS

87 dogs.

PROCEDURE

Outcome was determined as successful or unsuccessful. The association of neuroanatomic localization, breed, age, weight, sex, and (for dogs with intervertebral disk herniation) speed of onset of signs and duration of paraplegia prior to surgery with outcome was evaluated. Owners were contacted by telephone to identify long-term health problems.

RESULTS

Nine of 17 dogs with traumatic injuries were treated, and 2 regained the ability to walk; none of the 17 dogs regained DPP. Sixty-four of 70 dogs with intervertebral disk herniation underwent surgery; 9 (14%) were euthanatized within 3 weeks after surgery (7 because of ascending myelomalacia), 37 (58%) regained DPP and the ability to walk, 7 (11%) regained the ability to walk without regaining DPP, and 11 (17%) remained paraplegic without DPP. Outcome was not associated with any of the factors evaluated, but speed of recovery of ambulation was significantly associated with body weight and age. Fifteen (41%) and 12 (32%) dogs that regained DPP had intermittent fecal and urinary incontinence, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that the prognosis for paraplegic dogs without DPP because of trauma was guarded, while dogs with disk herniation had a better chance of recovering motor function. A third of the dogs that recovered motor function had intermittent incontinence. Persistent loss of DPP did not preclude recovery of motor function, but such dogs remained incontinent.

Lumbosacral stenosis in 29 military working dogs: epidemiologic findings and outcome after surgical intervention (1990-1999)

OBJECTIVE

To study the outcome of military working dogs (MWDs) diagnosed with degenerative lumbosacral stenosis (DLS) after surgical intervention and to determine what prognostic indicators affected outcome.

STUDY DESIGN

Retrospective study.

ANIMALS

Twenty-nine MWDs with DLS.

METHODS

The medical records of dogs diagnosed and surgically treated for DLS at the Department of Defense Military Working Dog Veterinary Service Hospital were reviewed. Retrieved data were signalment, clinical signs, survey radiograph results, and surgical findings.

RESULTS

Breed and sex were not found to have prognostic significance. Increasing age at surgery correlated with a poor surgical outcome. Twelve dogs (41%) returned to normal function, 11 (38%) improved, and 6 (20%) never returned to active duty. The average age at surgery was 74 months, 93 months, and 112 months for normal, improved, and dogs not returning to duty, respectively. Significant clinical findings associated with a poor prognosis were related to increasing neurologic severity. The only significant radiographic finding indicating a poor prognosis was foraminal narrowing. Surgical findings with negative prognostic significance were hypertrophic articular facets and interarcuate ligament. Recurrence rates were 16.7% and 54.5% for normal and improved dogs, respectively.

CONCLUSIONS

MWDs with DLS have a good prognosis with surgical decompression if they are young dogs with mild clinical signs at the time of diagnosis. As age and severity of clinical signs increase, the prognosis for successful outcome decreases. Recurrence may be seen in some dogs.

CLINICAL RELEVANCE

Information provided by this study should help military veterinarians determine the prognosis for working dogs with DLS after surgical treatment.

Fracture of L7 vertebral articular facets and pedicles following dorsal laminectomy in a dog

A 6.5-year-old German Shepherd Dog underwent decompressive surgery for cauda equina syndrome. On the basis of intraoperative findings, the dorsal laminectomy was extended from L6 to S2. Partial dorsal annulectomies were also performed on the L6-7 and L7-S1 intervertebral disks. Two weeks following discharge, the dog had an acute onset of signs of pain and worsening of the neurologic status. Radiography and surgical exploration revealed bilateral fractures of the vertebral pedicles and caudal articular facets of L7. Vertebral stabilization was achieved with intramedullary pins and methylmethacrylate. The dog fully recovered. Although the destabilizing effect of various procedures on the vertebral column has been documented in vitro, vertebral fractures associated with instability have not been reported. Our description of a vertebral fracture following a cauda equina decompressive procedure in a dog emphasizes the need for caution when performing multi-level dorsal laminectomy and diskectomy.

Spinal compression due to atlantal vertebral malformation in two African lions (Panthera leo)

Two young (14-mo-old and 6-mo-old), unrelated, male African lions (Panthera leo) were presented to the Veterinary Teaching Hospitals of Oklahoma State University and Kansas State University with progressive ambulatory difficulty. In both cases, limited neurologic evaluation demonstrated pelvic limb paresis and ataxia with conscious proprioceptive deficits. Spinal imaging showed nearly identical lesions in both cases. Radiography and myelography demonstrated cervical stenosis secondary to atlantal (C1) malformation producing a dorsoventral deformity of the laminar arch with atlantoaxial spinal cord compression between the ventrally displaced laminar arch of the atlas and the underlying odontoid process of C2. Computed tomography of the atlanto-axial junction confirmed cervical stenosis and cord compression, showing flattening of the spinal cord between the laminar arch of C1 and the dens of C2. Decompressive surgery consisting of dorsal laminectomy of C1 was performed. Each lion demonstrated progressive improvement of neurologic status to recovery of normal ambulation after surgical intervention. Neurologic disease in large captive felids is rare; atlanto-axial spondylomyelopathy has not been reported previously.

Dorsal laminectomy for caudal cervical spondylomyelopathy: postoperative recovery and long-term follow-up in 20 dogs

OBJECTIVE

To evaluate the postoperative morbidity and long-term outcome of dogs after dorsal laminectomy for caudal cervical spondylomyelopathy (CCSM).

STUDY DESIGN

Retrospective study.

SAMPLE POPULATION

Twenty dogs with CCSM.

METHODS

Medical records of dogs treated by dorsal laminectomy for CCSM at North Carolina State University and Colorado State University between 1989 and 1999 were reviewed. Information on signalment, onset, progression and duration of clinical signs, diagnostic testing, sites of dorsal laminectomy, postoperative complications, length of hospitalization, and the ambulatory status on discharge was recorded. A minimum follow-up of 7 months was required for inclusion in the study. Neurologic status was graded (0 to 5) preoperatively, 2 days after surgery, and at the time of the study (final score). Improvement or worsening of the neurologic status was assessed by comparison of different scores for each dog. Additional follow-up information was obtained by means of a detailed telephone questionnaire directed at both the owner and referring veterinarian.

RESULTS

Mean duration of clinical signs before surgery was 4.9 months. At admission, 15 dogs were ambulatory and 5 were nonambulatory. Neurologic status worsened in 70% of dogs 2 days after surgery but improved in all but 1 dog over the long term. Mean time to optimal recovery was 3.6 months. Long-term follow-up ranged from 7 months to 9 years (mean +/- SD, 3.2 +/- 2.4 years). Four dogs had confirmed recurrence; 2 other dogs may have had recurrence.

CONCLUSIONS

Dorsal cervical laminectomy is an effective treatment for CCSM in those dogs with dorsal compression or multiple sites of involvement.

CLINICAL RELEVANCE

Although most dogs' neurologic status transiently worsened after surgery, long-term outcome and recurrence rates were comparable to those seen with other surgical techniques for CCSM.

Management of spinal trauma in 69 cats

This study sought to evaluate a series of clinical and radiological findings on spinal trauma in cats and the outcome that emerged from conservative or surgical treatment using 2 types of spinal stapling: stabilization using a Steinmann pin and coated polypropylene. Case records were reviewed for their diagnostic approaches on the basis of physical and neurological conditions, and concurrent disorders in addition to spinal trauma. Radiological examinations of the vertebral column were carried out using survey radiography, myelography and epidurography. All cases were classified according to etiopathogenesis of the disease. Surgical treatment consisted of decompression (laminectomy, hemilaminectomy and durotomy), or decompression with stabilization which was performed by one of two methods. The first one was the employment of translaminar stapling at the base of a spinous process and the other involved spinal stapling at the spinous process. The spinal lesions were identified as cervical (n = 2), thoracic (n = 35), lumbar (n = 22), sacral and caudal (n = 10). While 19 out of 30 conservatively managed cases recovered, the rest had persistent residual paresis and ataxia. Complete recovery was seen in 4 cats that underwent hemilaminectomy and 3 subjected to laminectomy. Partial recovery was observed in 5 cases involving laminectomy; however, there was no improvement observed in another 2 cases. Each animal was followed for at least a 3-month period to evaluate the clinical assessment of the results following treatment. The results of conservative and operative management of spinal trauma indicated that the type and degree of spinal cord degradation strongly influenced any prognosis. The results emerging from decompressive procedures seemed satisfactory for those cases where instability was not an issue. Both stabilization techniques were not ideal in terms of their methodological versatility or regarding weaknesses of bone structure observed in intra- and postoperative periods. However, translaminar stapling at the base of a spinous process was deemed to be the superior technique.

Magnetic resonance imaging features of extradural hematomas associated with intervertebral disc herniation in a dog

Myelography and magnetic resonance imaging (MRI) were performed on a 4-year-old neutered female Rottweiler with bilateral pelvic limb paresis. On the myelogram, there was extradural spinal cord compression at the level of the T11-12 intervertebral disc. Inadvertent placement of epidural contrast medium also allowed identification of a 1-cm circular filling defect in the epidural space dorsal to the compressed spinal cord. MRI showed partial loss of the nucleus pulposus signal of the T11-12 disc, a focal signal void within the vertebral canal at T11 compatible with a free disc fragment, and extradural masses compressing the spinal cord at T10-11 and T11-12. Hemorrhage within the masses was confirmed on T2*-weighted images. A mixture of hematoma and mineralized disc material was found at surgery, and there was no histopathologic evidence of neoplasia. In this article, the appearance on MRI of hemorrhage associated with intervertebral disc herniation is discussed.

Thoracolumbar disc disease in 71 paraplegic dogs: influence of rate of onset and duration of clinical signs on treatment results

Seventy-one paraplegic dogs with confirmed intervertebral thoracolumbar disc disease and intact deep pain sensation were treated by hemilaminectomy and fenestration of at least two adjacent discs. The success rate of treatment in the overall population was 86 per cent (61/71 cases), with a mean length of time to regaining the ability to walk of 10.8 days and a mean follow-up time of 29 months. The rate of onset of clinical signs significantly influenced the clinical outcome (P=0.01) but not the length of recovery time (P=0.45). Conversely, the duration of clinical signs did not seem to significantly affect the outcome (P=0.27), but did affect the length of recovery time (P=0.001). Animals which had shown clinical signs for more than six days took significantly longer to regain the ability to walk (ie, an additional 6.9 days, P=0.04 and 4.5 days, P=0.01), when compared with those which had shown clinical signs for less than two days, or more than two but less than six days, respectively.

Extradural spinal synovial cysts in nine dogs

Nine dogs presenting for investigation of cervical or thoracolumbar myelopathies were diagnosed with extradural spinal synovial cysts. Degenerative disease affecting the articular facets or intervertebral discs was present on plain spinal radiographs in all cases. Myelography was consistent with dorsolateral, extradural spinal cord compression. Two groups of dogs were identified: (1) young, giant breed dogs with multiple cysts involving one or more levels of the cervical spinal cord; and (2) older, large breed dogs with solitary cysts involving the thoracolumbar spinal cord. The synovial cysts constituted the major compressive lesions in four of the dogs. Analysis of lumbar cerebrospinal fluid demonstrated albuminocytological dissociation, consistent with chronic compressive myelopathy, in six dogs. All dogs underwent decompressive surgery and the diagnosis of synovial cysts was confirmed histologically. The mean follow-up period was 17 months (range four to 36 months). At the time of follow-up, all dogs were fully ambulatory with improved neurological function compared with that at initial presentation.

Predictors of outcome after dorsal decompressive laminectomy for degenerative lumbosacral stenosis in dogs: 69 cases (1987-1997)

OBJECTIVE

To identify predictive factors of long-term outcome after dorsal decompressive laminectomy for the treatment of degenerative lumbosacral stenosis (DLSS) in dogs.

DESIGN

Retrospective study.

SAMPLE POPULATION

69 client-owned dogs.

PROCEDURE

Medical records of dogs that had undergone dorsal laminectomy at North Carolina State University and the University of Tennessee between 1987 and 1997 were reviewed. Dogs with diskospondylitis, traumatic lesions, or neoplasia of the lumbosacral region were excluded. All dogs had evidence of cauda equina compression on myelography, epidurography, computed tomography, or magnetic resonance imaging, along with subsequent confirmation of the lesion at surgery. Follow-up was performed by telephone inquiries to the referring veterinarian, the owner, or both, using a detailed questionnaire.

RESULTS

The outcome was excellent or good in 54 of 69 (78%) dogs over a mean follow-up period of 38+/-22 months. Five of these 54 dogs had been incontinent for a median of 2 weeks prior to surgery. Six of the 15 dogs with a poor outcome had been incontinent for a median of 8 weeks before surgery. A significant correlation was detected between the presence of urinary and fecal incontinence prior to surgery and outcome. When duration of signs was considered, urinary incontinence was the only variable that significantly affected outcome.

CONCLUSIONS AND CLINICAL RELEVANCE

Decompressive laminectomy is an effective treatment for DLSS, although dogs with urinary or fecal incontinence have a worse prognosis than dogs that are continent before surgery. Chronic urinary incontinence is a predictor of poor outcome for dogs with DLSS.

Design and use of a protective jacket to prevent self-inflicted injury following cervical laminoplasty in the goat (Capra hircus)

A group of dairy goats underwent cervical laminoplasty procedures as part of a biomechanics project. Although most animals had minimal incisional complications, several developed excoriations exacerbated by scratching at the incision site 6 to 8 weeks after the surgery. Local and systemic treatment was instituted as indicated. Bandages were inadequate to protect the neck from self-trauma, and the potential existed for serious injury to or infection of the old surgical site. We designed and made custom padded jackets for these animals. Treatment continued. While allowing the animals to exercise their scratching behavior, the jackets protected the traumatized area until healing was complete and the pruritus resolved. This jacket or modifications of it may be useful in other goat, sheep, or calf projects in which protection of the neck, shoulders, and thorax is needed.

Magnetic resonance imaging features of cervical stenotic myelopathy in 21 dogs

The cervical spine of 21 dogs with clinical signs of cervical stenotic myelopathy was evaluated using magnetic resonance (MR) imaging. Spin echo T1, T2 and gradient echo T2 weighted images were obtained with a 1.5 Tesla magnet in 12 dogs and a 1.0 Tesla magnet in 9 dogs. Sagittal or parasagittal T1W and T2W images were helpful in determining the presence of spinal cord compression or degenerative disease of the articular processes. Transverse T1W and T2W images were the most useful for the identification of dorsolateral spinal cord compression secondary to soft tissue and ligament hypertrophy, as well as synovial cysts, associated with the articular processes. The MR imaging findings were consistent with the surgical findings in all 14 dogs that underwent surgery. Magnetic resonance imaging provided a safe, non-invasive method of evaluating the cervical spine in dogs suspected of having cervical stenotic myelopathy. Veterinary

Intraspinal synovial cyst in a dog

An eight-year-old, male Siberian husky cross was referred with a history of an acute onset of pelvic-limb ataxia and paraparesis. Radiography and subsequent myelography of the spine revealed an extradural compression of the spinal cord at the level of the 13th thoracic (T13) to first lumbar (L1) vertebrae. Hemilaminectomy resulted in the successful removal of an extradural cystic lesion. The morphological diagnosis based on histopathology was a synovial cyst with chondromatosis. There were no postoperative complications, and the dog's condition improved markedly. At two years postoperatively, the animal remains normal on both physical and neurological examination. To the authors' knowledge, this article is the first report of an intraspinal synovial cyst in a dog.

Cervical spinal arachnoid cyst in a dog

An 18-month-old, intact male Akita presented with a 12-month history of progressive ataxia, hypermetria, and loss of conscious proprioception of the thoracic and pelvic limbs. Neurological examination and myelography localized a lesion at cervical vertebrae 1 and 2 consistent with an arachnoid cyst. Hemilaminectomy and cyst fenestration led to virtually full recovery.

Dermoid sinus at the lumbosacral junction in an English springer spaniel

A dermoid sinus was identified in a springer spaniel that presented with hindlimb neurological deficits. The sinus was continuous with the dura mater at the level of the lumbosacral junction. The presence of hair and debris adjacent to neural tissue had elicited a myelitis. A dorsal laminectomy was required to allow complete surgical resection of the sinus. The dog's neurological status improved after treatment and this improvement was maintained over a five-month follow-up period.

Vertebrectomy, bone allograft fusion, and antitumor vaccination for the treatment of vertebral fibrosarcoma in a dog

OBJECTIVE

To describe the surgical technique of vertebrectomy with bone allograft fusion and the use of antitumor vaccine for the treatment of a primary vertebral neoplasm in a dog.

STUDY DESIGN

Case Report.

ANIMALS OR SAMPLE POPULATION

A 3 year old 32 kg female spayed mixed breed dog with progressive paraplegia.

METHODS

Myelography was performed to identify an L5 lytic lesion with spinal cord compression. A dorsal laminectomy was performed to decompress the spinal cord and obtain biopsies. Pathologic fracture of the vertebral body two days later was treated with L5 vertebrectomy, cortical allograft implantation, and bilateral plating from L4 to L6. Tumor samples were used to create an autologous cytokine-gene-engineered tumor cell vaccine. Recheck radiographs and neurologic examinations were obtained 1, 2, 7, and 13 months after surgery.

RESULTS

The histopathologic diagnosis was fibrosarcoma. Although slight osteopenia of the allograft was noted thirteen months after surgery, the allograft and plate fixation remained stable. The patient tolerated the antitumor vaccination protocol well. Two years after the procedures the dog was able to ambulate normally but remained urinary and fecal incontinent.

CONCLUSIONS AND CLINICAL RELEVANCE

Vertebrectomy and cortical allograft implantation with plating permitted this patient to return to a functional lifestyle with its owners.