Contrast-enhanced computed tomography and myelography in six horses with cervical stenotic myelopathy.

The cervical spines of 6 horses with cervical stenotic myelopathy (CSM) were examined using myelography and contrast-enhanced computed tomography (CECT). Histopathology of the spinal cord of these horses identified 10 neurologically significant compressive lesions. Myelography and CECT were both able to demonstrate all 10 spinal cord compressive lesions, but myelography falsely identified 2 sites and CECT falsely identified 1 site as compressive lesions of the spinal cord which were not supported by histopathology. Additional qualitative information was obtained by CECT regarding the source, severity and location of spinal cord compression. Computed tomography identified stenosis of the vertebral canal with circumferential loss of contrast agent and documented lateral compressive lesions of the spinal cord due to malformed articular facets. Compression of the peripheral nerve roots by malformed articular facets encroaching on the intervertebral foramen was easily identified by CECT in the axial plane. No compressive lesions were identified in 3 unaffected horses by either method. Minimum sagittal diameter (MSD) values obtained from CECT images were strongly correlated with necropsy measurements, validating CECT as an accurate method of obtaining MSD values. The MSD values in the CSM-affected horses were significantly narrowed (P less than 0.05) from C3C6 regardless of the site of spinal cord compression, when compared with the unaffected controls. This finding supports previous reports suggesting that generalised stenosis of the vertebral canal is an important feature in the pathogenesis of cervical stenotic myelopathy.     

Dysplasia of the caudal vertebral articular facets in four dogs: results of radiographic, myelographic and magnetic resonance imaging investigations

Congenital anomalies of the vertebral column associated with aberrations of one of the primary vertebral ossification centres have been frequently described in the veterinary literature, but clinically significant abnormalities of secondary vertebral ossification centres, particularly involving the caudal articular processes, are much less frequently reported. This paper describes three dogs with aplasia and one dog with hypoplasia of the caudal vertebral articular processes. Thoracolumbar spinal cord compression and ataxia was evident in the three dogs with aplasia but no clinical signs were evident in the dog with hypoplasia. The radiographic appearance was similar in all four cases, with aplasia or hypoplasia of the caudal articular facets at one or more intervertebral joints in the thoracolumbar region. Bone proliferation was evident secondary to an associated degenerative joint disease. Compensatory hyperplasia of the adjacent cranial articular facets and ligamentum flavum protruded into the vertebral canal, resulting in a compressive myelopathy observed by myelography and magnetic resonance imaging.     

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.     

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.     

Cervical Myelopathy Associated with Extradural Synovial Cysts in 4 Dogs

Three Mastiffs and 1 Great Dane were presented to the University of Wisconsin Veterinary Medical Teaching Hospital for cervical myelopathy based on history and neurologic examination. All dogs were males and had progressive ataxia and tetraparesis. Degenerative arthritis of the articular facet joints was noted on survey spinal radiographs. Myelography disclosed lateral axial compression of the cervical spinal cord medial to the articular facets. Extradural compressive cystic structures adjacent to articular facets were identified on magnetic resonance imaging (1 dog). High protein concentration was the most important finding on cerebrospinal fluid analysis. Dorsal laminectomies were performed in all dogs for spinal cord decompression and cyst removal. Findings on cytologic examination of the cystic fluid were consistent with synovial fluid, and histopathologic results supported the diagnosis of synovial cysts. All dogs are ambulatory and 3 are asymptomatic after surgery with a follow-up time ranging from 1 to 8 months. This is the 1st report of extradural synovial cysts in dogs, and synovial cysts should be a differential diagnosis for young giant breed dogs with cervical myelopathy.     

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     

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.     

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.     

Development of a functional scoring system in dogs with acute spinal cord injuries

OBJECTIVES: To develop and compare the reliability of 2 methods of scoring pelvic limb gait in dogs recovering from thoracolumbar spinal cord injuries and to use this scoring system to determine the rate and level of functional recovery of dogs with acute thoracolumbar intervertebral disk herniations. ANIMALS: 46 dogs with spinal cord injuries resulting from intervertebral disk herniations. PROCEDURE: Dogs' gaits were videotaped at different time intervals after injury. In phase 1 of the study, the stages of recovery of pelvic limb function were identified, and a numeric scoring system was devised to reflect that recovery. In phase 2, pelvic limb gait was scored by different observers, using a numeric and a visual analog scale. Intra- and interobserver coefficients of variability of both methods were compared. In phase 3, pelvic limb function was scored, using the numeric scale at various intervals after acute thoracolumbar disk herniations. RESULTS: The numeric scale was significantly more reliable than the visual analog scale when both intra- and interobserver coefficients of variability were evaluated. Dogs that were paraplegic with no deep pain sensation recovered at different rates during the first 3 months, whereas dogs that were paraplegic with deep pain sensation typically recovered within 1 month of injury. CONCLUSIONS: Pelvic limb gait of dogs recovering from thoracolumbar spinal cord injuries can be reliably quantified, using a numeric scale. This scale will facilitate the performance of clinical trials aimed at improving the outcome of acute spinal cord injuries.     

Evaluation of osseous‐associated cervical spondylomyelopathy in dogs using kinematic magnetic resonance imaging

Osseous‐associated cervical spondylomyelopathy in dogs is characterized by both static and dynamic spinal cord compression; however, standard MRI methods only assess static compression. In humans with cervical spondylotic myelopathy, kinematic MRI is commonly used to diagnose dynamic spinal cord compressions. The purpose of this prospective, analytical study was to evaluate kinematic MRI as a method for characterizing the dynamic component of osseous‐associated cervical spondylomyelopathy in dogs. We hypothesized that kinematic MRI would allow visualization of spinal cord compressions that were not identified with standard imaging. Twelve client‐owned dogs with osseous‐associated cervical spondylomyelopathy were enrolled. After standard MRI confirmed a diagnosis of osseous‐associated cervical spondylomyelopathy, a positioning device was used to perform additional MRI sequences with the cervical vertebral column flexed and extended. Morphologic and morphometric (spinal cord height, intervertebral disc width, spinal cord width, vertebral canal height, and spinal cord area) assessments were recorded for images acquired with neutral, flexion, and extension imaging. A total of 25 compressions were seen with neutral positioning, while extension identified 32 compressions. There was a significant association between extension positioning and presence of a compressive lesion at C4‐C5 (p = 0.02). Extension was also associated with a change in the most severe site of compression in four out of 12 (33%) dogs. None of the patients deteriorated neurologically after kinematic imaging. We concluded that kinematic MRI is a feasible method for evaluating dogs with osseous‐associated cervical spondylomyelopathy, and can reveal new compressions not seen with neutral positioning.     

MRI features of cervical articular process degenerative joint disease in Great Dane dogs with cervical spondylomyelopathy

Cervical spondylomyelopathy or Wobbler syndrome commonly affects the cervical vertebral column of Great Dane dogs. Degenerative changes affecting the articular process joints are a frequent finding in these patients; however, the correlation between these changes and other features of cervical spondylomyelopathy are uncertain. We described and graded the degenerative changes evident in the cervical articular process joints from 13 Great Danes dogs with cervical spondylomyelopathy using MR imaging, and evaluated the relationship between individual features of cervical articular process joint degeneration and the presence of spinal cord compression, vertebral foraminal stenosis, intramedullary spinal cord changes, and intervertebral disc degenerative changes. Degenerative changes affecting the articular process joints were common, with only 13 of 94 (14%) having no degenerative changes. The most severe changes were evident between C4-C5 and C7-T1 intervertebral spaces. Reduction or loss of the hyperintense synovial fluid signal on T2-weighted MR images was the most frequent feature associated with articular process joint degenerative changes. Degenerative changes of the articular process joints affecting the synovial fluid or articular surface, or causing lateral hypertrophic tissue, were positively correlated with lateral spinal cord compression and vertebral foraminal stenosis. Dorsal hypertrophic tissue was positively correlated with dorsal spinal cord compression. Disc-associated spinal cord compression was recognized less frequently.     

Intramedullary epidermoid cyst in the thoracic spine of a dog

A 5 yr old female spayed mastiff was evaluated for a 3-4 mo history of paraparesis and 3 days of acutely worse paraparesis and incontinence. On magnetic resonance imaging, a spinal cord lesion was present at the ninth thoracic vertebra. The lesion was hyperintense on T2-weighted images (T2-W), and a hyperintense rim was present on T1-weighted postcontrast images. Histologic examination showed a cystic mass lined by squamous epithelial cells. Histopathologic diagnosis was an intramedullary epidermoid spinal cyst. Epidermoid cyst should be a differential diagnosis in young dogs with a myelopathy and an intramedullary spinal cord lesion on magnetic resonance imaging examination.     

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.     

Evaluation of a proposed therapeutic protocol in 12 dogs with tentative degenerative myelopathy

The objective of this work was to evaluate the long-term efficacy of a proposed therapeutic protocol in 12 dogs with a tentative diagnosis of degenerative myelopathy, followed-up for a 6-month period. Twelve dogs fulfilling the antemortem inclusion criteria (breed, age, adequate vaccination, history of progressive posterior ataxia and/or paraparesis, no radiographic and myelographic abnormalities in the spinal cord and vertebral column) were allocated. All these dogs presented signs of thoracolumbar syndrome (T3-L3), scored as grade I (mild to moderate ataxia and paraparesis) in 10 and grade II (severe ataxia and ambulatory paraparesis) in 2 cases. Treatment included the use of epsilon-aminocaproic acid and N-acetylcysteine, supplemented with vitamins B, C and E. Prednisolone was given for the first two weeks and upon worsening of neurological signs. Daily exercise, performed as walking or swimming, was strongly recommended. Clinicopathological evaluation was normal in all 12 dogs, and survey radiographs and myelograms did not show spinal cord compression. Magnetic resonance imaging (MRI), performed only in 4 dogs, did not disclose compressive disorders or intramedullary lesions. Neurological signs were progressively worsening in all 12 animals, eventually resulting in severe paraparesis (grade III) or paraplegia (grade IV). The applied medications do not appear to be an attractive alternative to conservative management (physiotherapy) or euthanasia in canine degenerative myelopathy, irrespective of its chronicity.     

Magnetic resonance imaging features of spinal epidural empyema in five dogs.

Spinal epidural empyema is defined an accumulation of purulent material in the epidural space of the vertebral canal. Spinal epidural empyema should be considered as a differential diagnosis in dogs with pyrexia, spinal pain, and rapidly progressing myelopathy. Magnetic resonance (MR) imaging is the imaging test of choice in humans. Here, we describe the MR imaging features of five dogs with confirmed spinal epidural empyema. The epidural lesions appeared as high or mixed signal masses in T2-weighted (T2W) images. Increased signal within the spinal cord gray matter at the site of the lesion was detected in T2W images in all dogs. Two patterns of enhancement were detected on postcontrast T1-weighted (T1W) images. Mild to moderate peripheral enhancement was seen in three dogs and a diffuse pattern of enhancement was seen in one. Discospondylitis was identified in three dogs on T1W postcontrast images. Decompressive spinal surgery was performed in all dogs. Bacteria isolated from the abnormal epidural tissue were Enterobacter cloacae, coagulase-positive Staphylococci, Pasteurella multocida, and Escherichia coli. In one dog bacteria were not isolated. These MR imaging features, along with appropriate clinical signs, can allow prompt diagnosis and appropriate treatment planning.     

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.     

Epidural Idiopathic Sterile Pyogranulomatous Inflammation Causing Spinal Cord Compressive Injury in Five Miniature Dachshunds

Objective— To characterize the clinical signs, diagnostic and surgical findings, and outcome of dogs with idiopathic sterile pyogranulomatous inflammation (ISP) of epidural fat causing spinal cord compression.
Study Design— Retrospective study.
Animals— Dogs (n=5).
Methods— Dogs with epidural ISP (2002–2006) were identified retrospectively. Inclusion criteria were neurologic examination, myelography, and definitive diagnosis of ISP confirmed by surgery and histopathologic examination of epidural spinal cord compressive tissue.
Results— The most common clinical sign was paraparesis/paraplegia. No abnormalities were detected by laboratory testing or survey spine radiographs. On myelography, extradural spinal cord compressions were focal (dogs 1, 3, and 5) or multifocal (dogs 2 and 4). Surgical decompression of the spinal cord was completed by hemilaminectomy. Epidural fat collected surgically had pyogranulomatous inflammation of unknown cause and was histologically similar to subcutaneous ISP. All dogs had good long-term neurologic outcome (10–45 months follow-up). Some dogs had episodes of ISP at other sites before or after surgical treatment of epidural ISP, suggesting there may be a systemic form of ISP.
Conclusion— Epidural ISP may cause a spinal cord compressive lesion in Miniature Dachshunds, which can be treated by surgical decompression of the spinal cord with or without administration of adjunctive steroids.
Clinical Relevance— Epidural ISP should be considered as a possible cause of thoracolumbar myelopathy for Miniature Dachshunds.     

Spinal nephroblastoma in an Irish wolfhound

A 1-year-old Irish wolfhound was presented with a history of slowly progressive left pelvic limb paresis. A neurological examination demonstrated bilateral deficits referable to the thoracolumbar spinal cord. Lumbar cerebrospinal fluid contained neoplastic cells. An intradural, extramedullary mass was demonstrated by myelography at the caudal aspect of T13. Surgical excision was abandoned owing to severe macroscopic damage to, and apparent infiltration of, the cord, and the dog was euthanased. The tumour was diagnosed histologically as an extrarenal nephroblastoma. Nephroblastoma should be suspected in young, large-breed dogs with intradural extramedullary masses over spinal segments T10-L2. The prognosis for complete recovery after surgical excision is guarded to poor.