Hansen type I disk disease at T1-2 in a dachshund

A 7-year-old Dachshund was presented with chronic left thoracic limb lameness and acute neurological deficits to the hind limbs following trauma. A lesion was suspected between C7 and T2 on the basis of neurological examinations. Radiography and myelography identified a calcified intervertebral disk at C7-T1 and an extradural unilateral compressive lesion at T1-2. Computed tomography scans of the cranial thoracic spine revealed extrusion of disk material from the T1-2 intervertebral space resulting in marked spinal cord compression. Intervertebral disk disease is rarely reported at this location. The neurological condition deteriorated after a second myelogram, which was done to examine the thoracolumbar spine. A modified dorsal decompression of T1-2 was performed. The dog was euthanased due to further neurological deterioration 8 days after surgery.     

EVALUATION OF DIFFERENT COMPUTED TOMOGRAPHY TECHNIQUES AND MYELOGRAPHY FOR THE DIAGNOSIS OF ACUTE CANINE MYELOPATHY

Forty‐six dogs with either cervical (C1–C5 or C6–T2) or thoracolumbar (T3–L3) acute myelopathy underwent prospective conventional computed tomography (CT), angiographic CT, myelography, and CT myelography. Findings were confirmed at either surgery or necropsy. Seventy‐eight percent of lesions were extradural, 11% were extradural with an intramedullary abnormality, 7% were intramedullary, 2% were intradural–extramedullary, and 2% had nerve root compression without spinal cord compression. Intervertebral disc herniation was the most frequent abnormality regardless of signalment or neurolocalization. Twenty‐one of 23 Hansen type I disc extrusions but none of the Hansen type II disc protrusions were mineralized. Two chondrodystrophic dogs had acute myelopathy attributable to extradural hemorrhage and subarachnoid cyst. CT myelography had the highest interobserver agreement, was the most sensitive technique for identification of compression, demonstrating lesions in 8% of dogs interpreted as normal from myelography and enabling localization and lateralization in 8% of lesions incompletely localized on myelography due to concurrent spinal cord swelling. None of the imaging techniques evaluated permitted definitive diagnosis of spinal cord infarction or meningomyelitis but myelography and CT myelography did rule out a surgical lesion in those cases. While conventional CT was adequate for the diagnosis and localization of mineralized Hansen type I disc extrusions in chondrodystrophic breeds, if no lesion was identified, plegia was present due to concurrent extradural compression and spinal cord swelling, or the dog was nonchondrodystrophic, CT myelography was often necessary for correct diagnosis.     

Subarachnoid abscess as a complication of discospondylitis in a dog

A three-year-old German shepherd dog was presented with a history of acute neck pain. A diagnosis of acute discospondylitis involving two intervertebral disc spaces was made. The dog initially responded to conservative treatment over an eight-week period and then suddenly deteriorated. Spinal cord compression was evident on cervical myelography. At autopsy, a subarachnoid abscess was present at the intervertebral disc space between the sixth and seventh cervical vertebrae.     

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.     

Cervical vertebral canal endoscopy in a horse with cervical vertebral stenotic myelopathy

A 3-year-old Thoroughbred gelding presented with a history of neurological signs, including incoordination in his hindlimbs, of about 7 months' duration. On initial examination, the horse exhibited ataxia and paresis in all limbs with more severe deficits in the hindlimbs. Cervical radiographs displayed severe osteoarthritis of the articular processes between C5 and C6. On subsequent cervical myelography the dorsal contrast column was reduced by 90% at the level of the intervertebral space between C5 and C6. Cervical vertebral canal endoscopy, including epidural (epiduroscopy) and subarachnoid endoscopy (myeloscopy), was performed under general anaesthesia. A substantial narrowing of the subarachnoid space at the level between C6 and C7 was seen during myeloscopy, while no compression was apparent between C5 and C6. Epiduroscopy showed no abnormalities. After completion of the procedure, the horse was subjected to euthanasia and the cervical spinal cord submitted for histopathological examination. Severe myelin and axon degeneration of the white matter was diagnosed at the level of the intervertebral space between C6 and C7, with Wallerian degeneration cranially and caudally, indicating chronic spinal cord compression at this site. Myeloscopy was successfully used to identify the site of spinal cord compression in a horse with cervical vertebral stenotic myelopathy, while myelography results were misleading.     

Paresis secondary to an extradural hematoma in a Sumatran tiger (Panthera tigris sumatrae).

A 15-yr-old female Sumatran tiger (Panthera tigris sumatrae) was presented to the Boren Veterinary Medical Teaching Hospital at Oklahoma State University with a 3-wk history of progressive hind limb weakness. Neurologic evaluation was limited to review of videotape that demonstrated weakness and ataxia with conscious proprioceptive deficits of the tiger's pelvic limbs. Spinal radiography demonstrated disc space narrowing, and myelography demonstrated a large extradural compressive lesion at the level of L2-3. Computed tomography did not reveal bone involvement. Surgery was performed to decompress the spinal cord and obtain a definitive diagnosis. A right hemilaminectomy was performed after a dorsal approach to the lumbar spine. Histologic examination of the mass revealed a consolidated extradural spinal hematoma, presumed to be secondary to intervertebral disc herniation. Despite incomplete resection of the mass and plastic deformation of the spinal cord, the tiger returned to normal ambulation within 3 wk of surgical decompression.     

Compressive cervical myelopathy in young Texel and Beltex sheep

BACKGROUND: This investigation was prompted by the referral of increasing numbers of young Texel and Beltex rams with ataxia and weakness, or wobbler syndrome. HYPOTHESIS: The study aims were to describe the clinical and pathologic findings in affected sheep. ANIMALS: The animals evaluated in this study included 7 Texel sheep (6 male and 1 female) and 3 Beltex sheep (2 male and 1 female) referred from pedigree flocks. Typically, the sheep were 15-18 months of age at referral. METHODS: Diagnostic investigations included radiographic and computed tomographic (CT) myelography followed by gross postmortem and histopathologic examinations. RESULTS: Clinical findings typical of cervical spinal cord compression were present in all sheep but varied in severity. Myelography confirmed dorsal spinal cord compression in the region of C6-C7. No bony abnormalities were identified as described in cases of canine and equine wobbler syndrome. Postmortem examinations revealed discrete, smooth, nodular to polypoid projections of adipose tissue apparently prolapsing through the dorsolateral intervertebral space at C6-C7 and causing localized spinal cord compression. Histopathology of the nodules confirmed that they were composed of well-differentiated adipocytes typical of fatty tissue. Spinal cord lesions were similar in all sheep with marked Wallerian degeneration at the site of compression and mild Wallerian degeneration present cranial and caudal to the lesion. CONCLUSIONS AND CLINICAL IMPORTANCE: The findings of this study suggest a novel cervical myelopathy in these sheep breeds caused by the presence of fatty nodules encroaching into the dorsal vertebral canal at C6-C7. Additional investigations are required to establish the etiology and possible hereditary risk factors for this unique clinicopathologic syndrome.     

USE OF COMPUTED TOMOGRAPHY AND COMPUTED TOMOGRAPHIC MYELOGRAPHY FOR ASSESSMENT OF SPINAL TUMORAL CALCINOSIS IN A DOG

Spinal tumoral calcinosis is reported in a Berner sennenhund puppy. The condition was manifested clinically as a non-ambulatory tetraparesis associated with neck pain. On survey radiographs there was a focal calcified mass at the atlantoaxial articulation. Computed tomography and computed tomographic myelography gave additional information on the extent of the mass and on the degree of spinal cord compression. The mass was removed surgically and the dog made a complete recovery.     

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.     

Paraparesis as initial manifestation of a Prototheca zopfii infection in a dog

A case of protothecosis causing non‐ambulatory paraparesis in a dog without clinical evidence of disseminated infection is described. A five‐year‐old female Labrador retriever was referred with a 10‐day history of progressive non‐ambulatory paraparesis and lumbar pain as the only physical and neurological abnormalities. Lumbar myelography revealed severe extradural spinal cord compression extending from L4 to L7 vertebrae, and a right hemilaminectomy was performed. Surgical findings included an adherent whitish hard ill‐defined mass. Cytology and biopsy results disclosed the presence of algae enclosed in a matrix of chronic inflammatory infiltrate. Culture confirmed the presence of Prototheca species. Neurological improvement occurred within a month, and the dog received antifungal treatment without evidence of clinical disseminated disease for 6 months, but died after a generalised tonic–clonic seizure. Post‐mortem examination revealed multiple foci of inflammatory granulomatous infiltrate and algae‐like structures in the brain, lumbar intumescence and cauda equina. Prototheca zopfii was identified using molecular biology methods.     

Lumbosacral intervertebral disk disease in six cats

Medical records of six cats diagnosed with lumbosacral intervertebral disk disease were reviewed. Clinical signs included reluctance to jump, low tail carriage, elimination outside the litter box, reluctance to ambulate, pelvic-limb paresis, urinary incontinence, and constipation. All cats had lumbosacral hyperpathia on palpation. Computed tomography in four cats revealed evidence of extradural spinal cord compression at the seventh lumbar (L(7)) to first sacral (S(1)) vertebral interspace. Compression was confirmed via myelography in three of these four cats, with confirmation in the fourth cat at the time of decompressive laminectomy. Each of the six cats underwent dorsal decompressive laminectomy at the L(7) to S(1) interspace. Postoperative clinical follow-up lasted 3 to 35 months, with most cats having excellent outcomes.     

EVALUATION OF TRADITIONAL AND NOVEL RADIOGRAPHIC VERTEBRAL RATIOS IN GREAT DANES WITH VERSUS WITHOUT CERVICAL SPONDYLOMYELOPATHY

Great Danes are predisposed to osseous‐associated cervical spondylomyelopathy (Wobbler syndrome). The first aim of this prospective study was to compare values measured using previously published intravertebral and intervertebral ratio methods and a novel ventrodorsal ratio method in radiographs of clinically normal and affected Great Danes. The second aim was to determine whether these ratios could be used as predictors of sites of spinal cord compression based on magnetic resonance imaging (MRI). Thirty dogs (15 normal, 15 affected) were prospectively enrolled. Lateral and ventrodorsal radiographs were obtained and six measurements were recorded from C3‐T1. For each vertebral location, intravertebral ratios and intervertebral ratios were calculated from lateral views, and the ratio of the distance between the articular process joints vs. vertebral body width (novel ventrodorsal ratio) was calculated from ventrodorsal views. Values for these three ratios were compared, by vertebral location and dog group. Intravertebral and intervertebral ratios did not differ between dog groups. The ventrodorsal ratio was significantly smaller in affected Great Danes at C5–6 (P = 0.005) and C6–7 (P < 0.001). The ventrodorsal ratio was significantly associated with MRI presence of spinal cord compression. For each 0.1 unit increase in this ratio value, there was a 65% decrease in the odds of spinal cord compression being present at that site, independent of vertebral location (P = 0.002). Findings from this study supported use of the novel ventrodorsal ratio as an initial radiographic screening method for Great Danes with suspected cervical spondylomyelopathy.     

Intervertebral disc protrusion in a cat

A case of prolapsed intervertebral disc at C_5–6 is described in an adult cat with a history of quadriparesis and two episodes of quadriplegia in a two year period. Plain radiographs showed no abnormality, there was no narrowing of the intervertebral space, but the protrusion was detected by myelography. Severe degeneration was found in the spinal cord.     

Atlanto-axial approach for cervical myelography in a Thoroughbred horse with complete fusion of the atlanto-occipital bones

A 2-year-old Thoroughbred gelding with clinical signs localized to the first 6 spinal cord segments (C1 to C6) had complete fusion of the atlanto-occipital bones which precluded performing a routine myelogram. An ultrasound-assisted myelogram at the intervertebral space between the atlas and axis was successfully done and identified a marked extradural compressive myelopathy at the level of the atlas and axis, and axis and third cervical vertebrae.     

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.     

Cervical intervertebral disc protrusion in two horses

Two horses with ataxia of all four limbs were found to have cervical intervertebral disc protrusion. Severe pelvic limb ataxia, proprioceptive deficits and spasticity were present in both horses with similar but less severe signs in the thoracic limbs. Cerebrospinal fluid analysis was within normal limits. Metrizamide myelography allowed definitive diagnosis in one case when a compression of the spinal cord was demonstrated at the level of the second intervertebral space. In the second case, an intervertebral disc protrusion between cervical vertebrae 6 and 7 was found at necropsy. Fiber degeneration with poor myelin staining characterized the spinal cords histologically.     

Evaluation of decision criteria for detection of spinal cord compression based on cervical myelography in horses: 38 cases (1981-2001)

REASONS FOR PERFORMING STUDY: Different criteria have been described based on height reduction of the total myelographic contrast column and components of it as tests for compression of the spinal cord due to cervical stenotic myelopathy (CSM). Fifty percent height reduction of the dorsal myelographic column (DMC), <2 mm empiric height of the DMC and a 40% reduction of the ratio of stenosis calculated based on the height reduction of the entire dural diameter (DD) have been described as decision criteria for considering the test result positive. The reasons for selecting these decision criteria or their accuracies have rarely been reported. OBJECTIVES: To evaluate the accuracy of diagnostic criteria based on reduced height of the total myelographic column and components of it for diagnosing extradural spinal cord compression using different decision criteria, and make recommendations for consistent myelographic interpretation in horses suspected of having CSM. METHODS: Four measurements were obtained by 2 readers in a retrospective sample population of 38 horses in which both cervical myelography and histopathological examination of the cervical spinal cord were performed. The prevalence of CSM in the sample was 50%. At intervertebral sites, the minimum heights of the DD and DMC were measured. At intravertebral sites, the maximum heights of the entire DD and DMC were obtained. Percent height reductions of the DMC and DD were determined as the ratio of minimum intervertebral height to maximum intravertebral height within the next cranial vertebra. Histological examination was used as the gold standard for determining the actual site of spinal cord compression. Sensitivity and specificity for the diagnostic criteria were estimated at each site in neutral and flexed neck positions using several different decision criteria. CONCLUSIONS: At C6-C7, in neutral or flexed neck position and using 20% reduction of DD, the test was highly sensitive and specific for CSM. At other sites, reduced height of the myelographic column generally was not accurate for diagnosing extradural spinal cord compression. Using 20% reduction of DD in neutral position at the mid-cervical sites, the test had only low sensitivity and high specificity. Flexion of the neck appeared to increase detection of spinal cord compression in the mid-cervical region, but also substantially increased the frequency of false-positive diagnoses. POTENTIAL RELEVANCE: By using the reported sensitivity and specificity estimates, readers may decide on a decision criterion for diagnosis of extradural spinal cord compression due to CSM. However, in planning a surgical correction, it is difficult to define a decision criterion that combines acceptable sensitivity and specificity, especially at the mid-cervical sites.     

CLINICAL AND MAGNETIC RESONANCE IMAGING CHARACTERISTICS OF THORACOLUMBAR INTERVERTEBRAL DISK EXTRUSIONS AND PROTRUSIONS IN LARGE BREED DOGS

Treatment recommendations differ for dogs with intervertebral disk extrusion vs. intervertebral disk protrusion. The aim of this retrospective, cross‐sectional study was to determine whether clinical and magnetic resonance imaging (MRI) variables could be used to predict a diagnosis of thoracolumbar intervertebral disk extrusion or protrusion in dogs. Dogs were included if they were large breed dogs, had an MRI study of the thoracolumbar or lumbar vertebral column, had undergone spinal surgery, and had the type of intervertebral disk herniation (intervertebral disk extrusion or protrusion) clearly stated in surgical reports. A veterinary neurologist unaware of surgical findings reviewed MRI studies and recorded number, location, degree of degeneration and morphology of intervertebral disks, presence of nuclear clefts, disk space narrowing, extent, localization and lateralization of herniated disk material, degree of spinal cord compression, intraparenchymal intensity changes, spondylosis deformans, spinal cord swelling, spinal cord atrophy, vertebral endplate changes, and presence of extradural hemorrhage. Ninety‐five dogs were included in the sample. Multivariable statistical models indicated that longer duration of clinical signs (P = 0.01), midline instead of lateralized disk herniation (P = 0.007), and partial instead of complete disk degeneration (P = 0.01) were associated with a diagnosis of intervertebral disk protrusion. The presence of a single intervertebral herniation (P = 0.023) and dispersed intervertebral disk material not confined to the disk space (P = 0.06) made a diagnosis of intervertebral disk extrusion more likely. Findings from this study identified one clinical and four MRI variables that could potentially facilitate differentiating intervertebral disk extrusions from protrusions in dogs.     

Osteochondromatosis of the cervical spine causing compressive myelopathy in a dog

A 10-month-old Alaskan malamute presented with cervical pain and hindlimb proprioceptive deficits. Plain and myelographic radiographic studies of the cervical spine demonstrated extradural compression of the spinal cord at the level of C7 and C5. Computed tomography assisted presurgical characterisation of the lesions as osteochondromatosis. Laminectomy permitted successful removal of the lesions.