Parosteal osteosarcoma of the cervical vertebra in a dog

A 12-year-old Maltese terrier was evaluated for progressive tetraparesis and neck pain. On radiographs, there was a periosteal reaction involving the fourth cervical vertebra. Myelographically, there was extradural compression of the spinal cord associated with the lesion. The dog was euthanized and necropsied. Histopathologic diagnosis was parosteal osteosarcoma of the vertebra.

The pathophysiology of spinal cord injury and its clinical implications

The pathophysiology of spinal cord injury can be categorized as acute impact or compression. Acute impact injury is a concussion of the spinal cord. This type of injury initiates a cascade of events focused in the gray matter, and results in hemorrhagic necrosis. The initiating event is a hypoperfusion of the gray matter. Increases in intracellular calcium and reperfusion injury play key roles in cellular injury, and occur early after injury. The extent of necrosis is contingent on the amount of initial force of trauma, but also involves concomitant compression, perfusion pressures and blood flow, and administration of pharmacological agents. Preventing or quelling this cascade of events must involve mechanisms occurring in the initial stages. Spinal cord compression occurs when a mass impinges on the spinal cord causing increased parenchymal pressure. The tissue response is gliosis, demyelination, and axonal loss. This occurs in the white matter, whereas gray matter structures are preserved. Rapid or a critical degree of compression will result in collapse of the venous side of the microvasculature, resulting in vasogenic edema. Vasogenic edema exacerbates parenchymal pressure, and may lead to rapid progression of disfunction. Treatment of compression should focus on removal of the offending mass.

Intervertebral disk disease in dogs with signs of back pain alone: 25 cases (1986-1993)

OBJECTIVE

To evaluate the population characteristics, historical, clinical, and diagnostic findings; and treatment outcome of dogs with thoracolumbar intervertebral disk disease (IVDD) whose only clinical signs were those of back pain.

DESIGN

Retrospective case series.

ANIMALS

Dogs with IVDD and clinical signs of back pain only, without neurologic deficits, in which survey radiography of the vertebral column and diagnostic myelographic studies were performed.

PROCEDURE

Review of the medical record, evaluation of survey radiographs of the vertebral column, evaluation of myelograms and estimation of apparent extent of spinal cord compression, and follow-up information provided by telephone contact with owners.

RESULTS

Spinal cord compression was detected on myelography in 20 of 25 (80%) dogs. Treatment included decompressive surgery in 18 of 25 (72%) dogs and all dogs underwent intervertebral disk fenestration. The condition was improved in 24 of 25 (96%) dogs after surgery.

CLINICAL IMPLICATIONS

Dogs with thoracolumbar IVDD that have clinical signs of back pain alone, without neurologic deficits, may have substantial compression of the spinal cord.

Epidural lipomatosis in a six-year-old dachshund

A six-year-old female dachshund was examined because of intermittent lameness in its left pelvic limb and periodic back pain. Myelography, epidurography and computed tomography (CT) revealed a dorsal displacement of the dural sac in the lumbosacral region caused by a soft tissue mass which had the specific density of fat. The mass was removed via a dorsal laminectomy in the lumbosacral area and a histological examination confirmed that it was adipose tissue. The clinical signs resolved after the surgery and a follow-up CT five months later showed no evidence of compression of the dural sac. The diagnosis of epidural lipomatosis in this dog was based on the clinical findings, the results of diagnostic imaging, and the surgical and histological findings, all of which revealed many similarities with epidural lipomatosis in man.

Ubiquitin expression in degenerating axons of equine cervical compressive myelopathy

Neuropathologic examination revealed axonal swelling and breakdown leading to Wallerian degeneration of affected myelinated nerve fibers in the spinal cord white matter of four young horses with equine cervical compressive myelopathy. Immunohistochemical reactions for the cell stress protein ubiquitin revealed an enhanced presence in the swollen axons, which may reflect a role for ubiquitin in the neuronal catabolic process of axonal compression and degeneration in this myelopathy.

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.

Modified distraction-stabilization technique using an interbody polymethyl methacrylate plug in dogs with caudal cervical spondylomyelopathy

A modified technique for distraction-stabilization that used an interbody polymethyl methacrylate plug was performed in 22 dogs with confirmed caudal cervical spondylomyelopathy. Myelographically, all compressive lesions were dynamic and predominantly located ventral to the spinal cord. Nineteen of 21 (90%) dogs for which success/failure could be determined had a successful outcome, and 11 of 22 (50%) dogs attained normal neurologic status. The 2 cases that were considered failures involved dogs that were nonambulatory tetraparetic prior to surgery and failed to improve to a functional status. Complications were self-limiting and included ventral displacement of the cement without loss of distraction in 1 dog and diskosponsylitis at an adjacent disk space in another dog. Evidence of fusion of the affected vertebrae, in the distracted position, was radiographically evident in all dogs. Use of the interbody polymethyl methacrylate plug appears to be a viable surgical treatment of caudal cervical spondylomyelopathy in dogs.

Compression of spinal cord caused by spinal deformation in a cat

An 8-month-old cat with bilateral hindlimb paresis was admitted. Radiography revealed a curvature of the thoracic spine and a partial deformation of thoracolumbar vertebrae (dorsal extrusion of the cranial and caudal edges). Compression of the spinal cord (T9-L1 and L6-7) was found by myelography. Medicinal treatment did not yield the desired result. Hemilaminectomy and laminectomy were done to relieve pressure on the spinal cord leading to improved gait. It is, however, not clear whether this syndrome was primarily caused by metabolic or genetic factors.

Studies on the factors affecting the recording of somatosensory evoked potentials induced by tibial nerve stimulation in dogs

Since spinal cord abnormalities are often associated with lesion in the thoracic or lumber vertebrae, examination of Somatosensory evoked potential (SEP) induced by hind limb nerve stimulation will be useful. In the experiment, scalp recorded SEP in dogs by tibial nerve stimulation was studied on the distribution, the change of latency by body size and the influence of experimental compression to the spinal cord. Greatest response was got at Fz, and shorter latencies for SEP recorded on the ipsilateral stimulation side than from the contralateral side. The equation describing the regression line of the latency with the distance to the recording site from stimulating site was Y = 0.072X+13.23 and the regression was statistically significant. In the experimental study of compression to spinal cord, dorsal compression tended to be sensitive compared to the ventral compression. This study suggested that not only increase of latency but also reduction of amplitude could occur as a result of spinal cord disorders.

Myositis, lameness, and paraparesis associated with use of an oil-adjuvant bacterin in beef cows

Right hind limb lameness, progressing to bilateral paraparesis, was observed in 56 of 610 (9%) beef cows. Lameness began 6 days to 4 weeks after vaccination in the right longissimus lumborum (loin) muscle with an Escherichia coli/Campylobacter bacterin in an oil adjuvant. Postmortem examination of 5 affected cows revealed a large inflammatory mass at the site of vaccination. In each cow, the mass spread through adjacent intervertebral foramina into the vertebral canal and compressed the lumbar portion of the spinal cord. Microbiologic procedures did not reveal a microbial agent in affected tissues or in an unopened bottle of bacterin from the same lot used in the herd. Histologic examination revealed pyogranulomatous inflammation of the vaccination site and adjacent epidural tissue, with inflammatory nodules centered around large clear spaces that probably represented remnant emulsion from the oil adjuvant in the bacterin. As evident in these cows, IM injection of irritating products may cause severe myositis. Vaccination into paravertebral muscles is risky because of possible extension of inflammation through intervertebral foramina.

Iatrogenic compressive lumbar myelopathy and radiculopathy in adult cattle following injection of an adjuvanted bacterin into loin muscle: histopathology and ultrastructure

Compressive lumbar myelopathy is a recognized iatrogenic complication of injecting water-in-oil vaccines into paravertebral sites of laboratory animals and chickens. Herein, we report the histologic and ultrastructural features of a similar complication in a herd of cattle. Iatrogenic posterior paresis developed over 34 days in 56 of 610 cows (9.2%) following injection of a commercial bacterin 11-34 days earlier into M. longissimus lumborum. The bacterin was composed of inactivated Escherichia coli and Campylobacter fetus ssp. venerealis in a proprietary adjuvant. Tissues were collected for histopathology from 9 affected cattle that died or were euthanized after clinical signs lasting 6-38 days. A range of tissues, including the injection site lesion and lumbar spinal nerve roots, was obtained for ultrastructural examination from a cow with paresis of 31 days duration. There was locally extensive pyogranulomatous myositis with fibrosis and necrosis in right M. longissimus lumborum. Extension of the lesion into the vertebral canal via spinal nerve foramina resulted in focal pyogranulomatous inflammation in epidural fat and in adjacent dura mater. There was axonal degeneration in dorsal, lateral, and ventral columns and chromatolysis of spinal motor neurons in lumbar spinal cord, secondary to compression. A distinctive histologic and ultrastructural feature of pyogranulomata was the presence of osmiophilic material at the center of inflammatory foci, surrounded by macrophages and giant cells that contained intracytoplasmic lipid droplets. Ultrastructural examination of entrapped spinal nerves revealed axonal degeneration and loss of myelinated and unmyelinated fibers, segmental demyelination with remyelination, axonal spheroid formation, and early axonal regeneration.(ABSTRACT TRUNCATED AT 250 WORDS)

Observation of a secondary compressive lesion after treatment of caudal cervical spondylomyelopathy in a dog

In a 7-year-old Doberman Pinscher with an atactic gait, neurologic examination revealed tetraparesis, conscious proprioceptive deficits, and rigid ventral flexion of the neck. Radiography and myelography revealed a ventral, extradural, dynamic compressive lesion between C6 and C7. Distraction decompression was performed, using cancellous bone screws and methylmethacrylate. After initial improvement, clinical signs recurred 2 weeks after surgery and progressed until the dog was euthanatized 6 weeks after surgery. Postmortem myelography revealed an extradural compressive lesion adjacent to the implant, between C5 and C6. Secondary compressive lesions induced by surgical or biomechanical alterations of the cervical portion of the spine may be complications of treatment of caudal cervical spondylomyelopathy.

[Osteochondrosis syndrome and arthropathia deformans as the cause of habitual and stationary luxatio incompleta of the sixth thoracic vertebra in laying hens with paralysis]

151 laying hens were kept in two experiments until the age of 610 or 786 days in floor pens, large cages with flat wire floor or small cages having inclined wire floor bottoms of 8 or 15 degrees. Paralysis was observed in 24 of the 151 hens. There was no relationship between the incidence of paralysis and the different housing systems. Fractures of the vertebral column or decreased stability of the skeleton were not observed. But in all of the 24 hens the paralysis was the result of the compressed spinal cord. The cause of the compression was the luxatio incompleta of the 6th thoracic vertebra. Different degrees of arthropathia deformans were observed in the diarthrotic vertebral joints of all the hens of the two experiments. The arthrotic lesions were accompanied by deformed articular surfaces. The destroyed and deformed articular surfaces were the cause of the instability of the 6th thoracic vertebra with spondylolisthesis or luxatio incompleta. The hypothesis, that the arthrotic lesions developed during the growing period of the hens, was supported by histological findings of disturbed growth of the epiphyseal cartilage. Overstressing of the epiphyseal cartilage was the causative agent of the arthrotic lesions in the vertebral joints. In this way the lesions are very similar to the osteochondrosis syndrome in broiler chickens and fast growing mammals.

Occipital condylar dysplasia in two Jacob sheep

Two young Jacob sheep which presented with severe ataxia and torticollis had abnormally formed atlanto-occipital joints. Postmortem examination revealed marked dissimilarity in size between the left and right occipital condyles, with reduction in size of the foramen magnum. The atlantoaxial joint and dens were normally formed, and were not abnormally positioned in radiographs taken of one lamb. Histological evaluation of the cervicomedullary junction demonstrated extensive loss of axons and myelin, gliosis, and mild hydromyelia in one lamb.

Somatosensory potentials in dogs with naturally acquired thoracolumbar spinal cord disease

Somatosensory evoked potentials (SEP) were recorded at the scalp and at various levels along the lumbar and caudal thoracic parts of the spine in response to tibial nerve stimulations. The SEP were observed in 24 diseased dogs, 2 with a vertebral fracture, 1 with a spinal cord tumor, 1 with a vertebral tumor, and 20 with disk herniation. Cord compression location was confirmed by myelography, laminectomy, or both. The clinical state had significant (P < 0.0001) influence on SEP characteristics. The scalp-recorded SEP latency changed only in association with the most severe lesions; spine-recorded SEP conduction velocity was lower in association with mild lesions; scalp-recorded SEP amplitude changed with lesions of intermediary severity. Because these 3 electrophysiologic variables were influenced differently by cord damage, it was possible to discriminate the various clinical grades by use of these techniques. However, dogs with signs of pain only could not be differentiated from clinically normal dogs. The evoked injury potential was observed in all but 4 diseased dogs, and its maximal amplitude corresponded, in all cases, with cord damage location. Increased duration (P < 0.05) of the spine-recorded SEP was associated with long-standing problems, but not necessarily with clinically detectable malfunction. Use of SEP and evoked injury potential for identifying lateralized cord damage may be of value.

Diagnosis and prediction of cervical vertebral malformation in thoroughbred foals based on semi-quantitative radiographic indicators

Over a period of 5 years on a central Kentucky Thoroughbred stud farm 132 foals were evaluated for the presence of cervical vertebral malformation (CVM). Lateral cervical vertebral radiographs were obtained on 70 standing foals. These radiographs were evaluated semi-quantitatively and scored numerically for the presence of stenosis of the vertebral canal, enlarged physeal growth plates, caudal extension of the dorsal border of the orifice of the vertebral canal, angular fixation, delayed ossification of bone and degenerative joint disease. From these scores a total CVM score was given for each set of radiographs. All foals were repeatedly examined for clinical signs of neurological disease. Foals with no clinical signs of CVM had maximal total CVM scores (mean +/- sd) of 5.7 +/- 2.8 and foals affected with CVM had maximal total CVM scores of 17.0 +/- 2.8. Determination of the total CVM score was non-invasive, inexpensive and a very accurate procedure for predicting and diagnosing the presence of CVM in Thoroughbred foals up to 1 year of age.

Examination of frozen cross sections of cervical spinal intersegments in nine horses with cervical vertebral malformation: lesions associated with spinal cord compression

Nine horses with clinical and radiographic findings of cervical vertebral malformation that were necropsied and examined using frozen cervical spinal cord cross sections were reviewed. Only cases with actual distortion of the spinal cord due to compression were selected. The goal of the study was to determine the morphologic features responsible for narrowing of the spinal canal and compression of the spinal cord. In individual cases, bony changes are associated with osteochondrosis and osteomyelitis of the dorsal articular facets and osteosclerosis of the dorsal cervical lamina. Soft tissue pathology associated with spinal cord compression included ligamentum flavum hypertrophy, joint capsule swelling and hypertrophy, and synovial cysts. In most cases, a combination of abnormalities was found in horses with spinal cord compression.

Surgical treatment of cervical stenotic myelopathy in horses: 73 cases (1983-1992)

Seventy-three horses with cervical stenotic myelopathy underwent cervical vertebral interbody fusion (n = 63) or dorsal laminectomy (n = 10). Neurologic function improved in 77% of horses, and 46% of horses achieved athletic function (racing, race training, or pleasure riding) after cervical vertebral interbody fusion for static and dynamic spinal cord compressive lesions. Neurologic status improved in 4 of 10 horses after dorsal decompression for static compressive spinal cord lesions. The duration of clinical signs prior to surgical intervention was shorter for horses that achieved athletic function or improved by at least 2 neurologic grades than for horses that did not improve in neurologic status or improved 1 neurologic grade after cervical vertebral interbody fusion. The number of cervical spinal cord compressive lesions and age of horses did not affect the long-term surgical outcome of cervical vertebral interbody fusion. Seroma formation, implant failure, right laryngeal hemiplegia, and colitis were nonfatal complications associated with cervical vertebral interbody fusion. Dorsal laminectomy and cervical vertebral interbody fusion of static compressive lesions of the caudal cervical vertebral column were associated with fatal postoperative complications, including vertebral body fracture, spinal cord edema, and implant failure.

Osteochondroma causing progressive posterior paresis in a lakeland terrier puppy

A lakeland terrier puppy had progressive hindlimb ataxia associated with pain in the thoracic spine. Plain radiographs revealed a lesion affecting the dorsal neural arch of the fourth thoracic vertebra and myelography revealed compression of the spinal cord associated with the lesion. Surgical excision of the mass cured the dog's clinical signs. A histopathological examination of the excised tissue supported a diagnosis of osteochondromatosis.

Systemic aspergillosis in a dog

Systemic aspergillosis was diagnosed in a two-and-a-half-year-old spayed German shepherd dog which had suffered an acute attack of paralysis of the pelvic limbs. The neurological deficits were attributed to the destruction of the seventh vertebral body and the intervertebral disc, with protrusion of necrotic material into the vertebral canal and compression of the spinal cord at this level. Microscopically, fungal invasion and destruction of the body of T-7 was observed and Aspergillus species were identified. Fungal granulomas were also found in the liver, lung, spleen and mesenteric lymph nodes.

Use of ventral cervical stabilization for treatment of a suspected articular facet fracture in a horse

A 3-year-old Thoroughbred filly examined because of poor performance after a fall was found to be ataxic. Radiography revealed a linear defect in the right dorsal cranial articular facet of the fifth cervical vertebra. The defect was thought to be a fracture or a developmental defect. Arthrodesis and stabilization were achieved by ventral implantation of a Bagby basket in the articulation between the fourth and fifth cervical vertebrae. The ataxia resolved within 4 months, and the filly was able to resume full race training.

Cervical fibrotic stenosis in a young Rottweiler

An 18-month-old neutered male Rottweiler was examined because of slowly progressive spastic tetraparesis and ataxia. Signalment and clinical signs were suggestive of 2 neuronal degenerative diseases presumed to be inherited in young Rottweilers: leukoencephalomyelopathy and neuroaxonal dystrophy. Myelography revealed an extradural compression at the articulation of the second and third cervical vertebrae. At surgery, focal hypertrophy of the yellow ligament was observed to compress the spinal cord ventrally at that site.

[Cytology of the cerebrospinal fluid in dogs with brain tumors and spinal cord compression. Part 4]

The results of cerebrospinal fluid (CSF) cytology of 9 dogs with brain tumors and 50 dogs with spinal cord compression are discussed. Of the 50 dogs with spinal cord compression, disc protrusion was diagnosed in 31, myelomalacia in 7, discospondylitis in 3 and spinal cord tumors in 9 dogs. In 4 of 9 dogs with brain tumors, tumor cells could be found by the sedimentation apparatus of Kölmel. Pleocytosis existed in 6 patients. In about 70% (29 of 41) of cases with disc protrusion, more than 200 cells could be evaluated in the CSF sediment, consisting mostly of transformed lymphocytes and activated monocytes. As the neurologic deficits increased, the amount of cells and especially cell complexes increased. This was especially evident in cases with myelomalacia of the spinal cord. Only in cases with discospondylitis or spinal cord neoplasia was the CSF cytology unchanged.

Cervical vertebral malformation/malarticulation syndrome in large dogs

To anticipate improvement of a chronically affected animal may be expecting too much because reserve or functional spinal cord tissue may be minimal. An accurate prognosis is sometimes impossible to formulate because the extent of spinal cord damage is not known. Treatment may result only in halting progression of the disease, and even with total relief of spinal cord compression, recovery may be minimal. Animals with minimal neurologic deficits treated early in the course of the disease with adequate decompression and stabilization are more likely to return to function. The goals of treatment for cervical spinal cord compression are decompression and stabilization of the affected area. Adequate stabilization may result in atrophy of the soft tissues and further decompression once stabilization is achieved (see Fig. 3). If stabilization is not provided, adequate decompression of the spinal cord and the nerve roots is essential.

Decompressive procedures. Indications and techniques

Hemilaminectomy and dorsal laminectomy are the surgical techniques most suited for decompression of the thoracic, thoracolumbar, lumbar, and lumbosacral spine. Hemilaminectomy is preferred for decompressing the spinal cord before applying fixation devices for fractures/luxations. Dorsal laminectomy is the method of choice for exploration of the spinal canal and for decompression of the lumbosacral region. Either method is applicable to removal of herniated intervertebral disc material and fenestration of other disc spaces.

Thoracic spinal calcinosis circumscripta causing cord compression in two German shepherd dog littermates

Two young German shepherd dog littermates had progressive, painless, hindlimb ataxia. In both dogs plain radiography of the vertebral column revealed a solitary mineralised lesion on the dorsal laminae between the dorsal spines of the second and third thoracic vertebrae, and myelography with iopamidol demonstrated cord compression at the level of the lesions. The first dog died 18 hours after the myelography. A dorsal laminectomy performed in the second dog resulted in neurological improvement. A histopathological examination confirmed that both lesions were calcinosis circumscripta. The cause of the death of the first dog was meningitis.

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.

Multicentric osseous lymphoma with spinal extradural involvement in a dog

Multicentric osseous lymphoma involving the ribs and multiple vertebrae was observed in a 7-year-old Siberian Husky. Extradural spinal cord compression was treated by surgical decompressive hemilaminectomy of L1-2 without noticeable improvement of signs neurologic dysfunction. However, palliation of signs of pain was noticed after irradiation in conjunction with chemotherapy and surgical decompression.

Thoracolumbar vertebral osteochondroma in a young dog

Osteosarcoma was diagnosed in a 7-month-old female German Shepherd Dog with hind limb paresis. Radiography revealed a circumscribed calcified mass in the dorsal vertebral lamina at T13-L1 resulting in extradural compression of the spinal cord. Surgical excision of the mass resulted in gradual return to normal neurologic function. Four weeks after surgery, the dog became severely atactic after rolling onto its back. A chip fracture of T13 was identified, and the dog was euthanatized at the owners' request.

Chronic cervical compressive myelopathy in horses: clinical correlations with spinal cord alterations

Histological examination was performed on the cervical spinal cord from 13 horses with chronic cervical compressive myelopathy of 4 to 29 months duration. Structural alterations were correlated with clinical features. At the level of compression, the spinal cord was grossly deformed. Histological alterations included nerve fibre swelling and degeneration, occasional spheroids, astrocytic gliosis, increased macrophage activity and increased perivascular collagen. Myelin degeneration or loss at the level of the compressive lesion was greatest in the ventral and lateral funiculi and less consistently present in the dorsal funiculi. Asymmetry of lesions in the dorsal funiculi was associated with asymmetry of clinical signs in 5 horses. Histological alterations in areas of Wallerian degeneration were similar to that at the level of spinal cord compression, except that perivascular collagen was not increased. Wallerian degeneration was present cranial to the compressed site in the superficial portions of the lateral funiculi and in the middle of the dorsal funiculi. Caudal to the compressed site it was present in the ventral funiculi adjacent to the ventral median fissure and in the middle of the lateral funiculi. Deformation of the spinal cord did not correlate with the severity or duration of clinical signs but was positively correlated with the amount of perivascular collagen increase. The amount of nerve fibre swelling was not correlated with the severity of clinical signs but was negatively correlated with their duration. A rapid loss of nerve fibres apparently occurred early in the course of compression, since there was a marked decrease in the amount of nerve fibre swelling and Marchi stained degenerating myelin with increasing clinical duration.(ABSTRACT TRUNCATED AT 250 WORDS)

Chronic cervical compressive myelopathy in horses: patterns of astrocytosis in the spinal cord

The distribution and morphology of fibrous astrocytes in the cervical spinal cord of normal horses and horses with chronic compressive myelopathy were demonstrated using immunohistochemical staining for glial fibrillary acidic protein. In the spinal cord from normal horses, astrocytes with stellate cell bodies and short processes were irregularly distributed in grey matter. In the white matter, their cell bodies were small and angular in areas adjacent to grey matter and larger and more stellate-shaped in the subpial area. Astrocyte processes were fine, and evenly distributed in a predominantly radial pattern in transverse sections of cord. Gliosis was marked in the spinal cords of horses with cervical compressive myelopathy. In the grey matter at the level of compression astrocytes were often enlarged and rounded, with short, blunt processes, but the gliosis was generally mild. In the white matter, gliosis was obvious in areas of nerve fibre swelling and degeneration at the level of compression and in areas of ascending and descending Wallerian degeneration. The fine radial pattern of astrocyte fibres was replaced by a dense, irregular arrangement. Gliosis persisted in the cords of chronically affected horses after active nerve fibre degeneration had subsided. The areas of gliosis coincided with the areas of Marchi staining for degenerating myelin and with areas of myelin loss in osmium tetroxide post-fixed tissue. Histological observations were consistent with astrocytes replacing areas of extracellular space that remained after nerve fibre degeneration. it is concluded that astrocytic gliosis is a prominent and persistent alteration of the spinal cord of horses with chronic cervical compressive myelopathy.

Frequency and severity of osteochondrosis in horses with cervical stenotic myelopathy

We compared the frequency and severity of osteochondrosis lesions in young Thoroughbred horses with cervical stenotic myelopathy (CSM) vs that in clinically normal Thoroughbreds of the same age. All lesions of the cervical vertebrae and appendicular skeleton were classified histologically as osteochondrosis or nonosteochondrosis and were measured for severity. Minimal sagittal diameter was significantly smaller in horses with CSM from C2 through C6; no difference was detected at C7. Severity of cervical vertebral osteochondrosis was greater in the horses with CSM, however frequency was not different. Frequency and severity of nonosteochondrosis lesions were not different in cervical vertebrae or appendicular skeleton. Frequency and severity of appendicular skeleton osteochondrosis lesions were both greater in horses with CSM. Osteochondrosis and nonosteochondrosis lesions were more severe on facets at sites of compression than on facets at noncompressed sites in horses with CSM. However, compression was also observed at sites with no articular facet lesions. The association of widespread osteochondrosis and spinal canal narrowing with CSM suggests CSM may represent a systemic failure in the development or maturation of cartilage and bone.

Ataxia in Swedish warmblood and standardbred horses. A radiologic and pathology study

Lesions in the cervical spine of 28 young horses (Standardbred Trotters and Swedish Warmbloods), killed because of longstanding or severe ataxia, are described. The material consists of all horses with ataxia available for necropsy and presented to the large animal clinic of the School of Veterinary Medicine, Uppsala and the Animal Hospital in Helsingborg during 1981 through 1983. After a clinical and radiographic examination, including myelography in all but 2 cases, the horses were killed and necropsy was performed. The cases were divided into three categories based on the radiographic and pathological findings. 1. Static Cervical Compressive Myelopathy (SCM): There were three causes of the stenosis, locked, flexed position of cervical vertebrae, arthropathy of the intervertebral joints, and epidural cyst in the cervical spinal canal. 2. Dynamic Cervical Compressive Myelopathy (DCM) was diagnosed when the myelogram showed stenosis when the horse's neck was in a flexed position. No stenosis was observed in neutral position, or when the neck was extended. 3. Cervical Myelopathy (CM): In this category neither static nor dynamic stenosis was observed, but histologic evidence of spinal cord degeneration was seen. The fact that all the horses were young, suggests that a disturbance of normal growth of the cervical vertebrae is involved in the aetiology.

Melanoma as a cause of spinal cord compression in two horses

Spinal cord compression by melanomas at C7-T1 is described in 2 horses. Despite similar location of the lesions, the onset of neurologic signs and clinical progression varied. Both horses were gray, but few cutaneous melanomas were found. Internal dissemination, however, was extensive in both horses. Antemortem diagnosis was made in one horse, and surgical decompression of the spinal cord was performed. Neoplasms of the vertebral canal and spinal cord are uncommon in horses. Melanoma in the spinal canal should be included in the differential diagnosis of neurologic disease, especially in mature gray horses.

Iohexol myelography in the horse

Iohexol, a water soluble non-ionic contrast agent, was evaluated for myelography in the horse. Both 300 and 350 mg iodine/ml iohexol gave diagnostic cervical myelograms. Pathological changes were limited to extradural oedema and an increase in the number of white blood cells and specific gravity in the cerebrospinal fluid two days after myelography. This increase in white blood cells in the cerebrospinal fluid was, however, much less than that recorded by other authors using metrizamide and iopamidol contrast media. These findings indicate that iohexol is a less irritant myelographic contrast agent than those previously evaluated in the horse.

Problems and complications associated with the nonsurgical management of intervertebral disc disease

Intervertebral disc disease (IVDD) is a common problem encountered in veterinary practice. The primary goal in treating animals with IVDD should be to relieve nerve root and spinal cord compression, thereby retaining or regaining normal neurologic function. Methods of nonsurgical management include corticosteroid medication, nonsteroidal anti-inflammatory drugs, acupuncture therapy, and chemonucleolysis. Each one of these modalities have their own inherent advantages and disadvantages that should be considered before instituting therapy.

Clinical evaluation of three surgical methods for treatment of caudal cervical spondylomyelopathy of dogs

Sixty-four dogs with caudal cervical spondylomyelopathy (CCSM) caused by chronic degenerative disc disease were treated with ventral decompression (n = 20), linear traction and interbody screw stabilization (n = 7), or linear traction and plastic plate stabilization (n = 37). Interbody screw stabilization was ineffective in treating CCSM because of an unacceptably high rate of implant failures. Ventral decompression or linear traction and plastic plate stabilization were effective in the treatment of most patients with mild to moderate neurologic deficits (neck pain, paraparesis, or ambulatory tetraparesis). Although these techniques were also used successfully in some patients with severe neurologic deficits (weakly ambulatory tetraparesis or nonambulatory tetraparesis), variable success rates and prolonged postoperative recovery periods were noted.

Occipitoatlantoaxial malformation with duplication of the atlas and axis in a half Arabian foal

An unusual occipitoatlantoaxial malformation is described in a 2-week-old male part Arabian foal that was unable to stand at birth and showed signs of spastic tetraparesis due to a cervical spinal cord compression. There were 2 atlases present. One was fused to the occipital bones. The other articulated with the first atlas and an axis which had a long dens that projected into the vertebral canal. Examination of the ossification centers of the axis indicated partial duplication of that bone.

Paraparesis caused by epidural granuloma in a cat

Caudal paraparesis in a cat was determined to be caused by an epidural mass. Surgical decompression was performed, and the mass was determined to be a granuloma. Fusobacterium and Bacteroides spp were isolated from the granuloma. Epidural granulomas are seldom reported in dogs and cats. Decompression and administration of antibiotics led to recovery of this cat even though in human beings an unfavorable prognosis is given if neurologic deficits have developed.