Traumatic Intervertebral Disc Herniation with Paraplegia in a Black-Tailed Prairie Dog (Cynomys ludovicianus)

A 2-year-old castrated male black-tailed prairie dog (Cynomys ludovicianus) was presented 48 hours after peracute onset of rear limb paraplegia secondary to a traumatic incident. The prairie dog was nonambulatory in the rear legs with absent deep pain; hematuria and pollakiuria were also observed. Diagnostic imaging revealed intervertebral disc herniation with compression of the spinal cord at the L1-L2 disc spaces. Hemilaminectomy at the L1-L2 disc space was performed. After 48 hours, the prairie dog regained anal tone, and a deep pain response was noted. Azotemia developed during the course of hospitalization likely secondary to neuromuscular damage causing an obstruction in the lower urinary tract but resolved with supportive care. The prairie dog recovered complete use of its hind legs and had normal excretory function at a 3-month recheck. Practitioners should consider intervertebral disc herniation secondary to trauma as a differential diagnosis for neurologic deficits affecting the rear limbs of prairie dogs. Surgical management of intervertebral disc herniation is a viable treatment option in appropriate cases.     

Influence of intervertebral disc fenestration at the herniation site in association with hemilaminectomy on recurrence in chondrodystrophic dogs with thoracolumbar disc disease: a prospective MRI study

Objective— To describe the influence of fenestration at the disc herniation site on recurrence in thoracolumbar disc disease of chondrodystrophoid dogs.
Study Design— Prospective clinical study.
Animals— Chondrodystrophic dogs (n=19).
Methods— Dogs were divided into 2 groups: group 1 (9 dogs) had thoracolumbar disc extrusion (Hansen type I) treated by hemilaminectomy and concomitant fenestration of the affected intervertebral disc and group 2 (10 dogs) had hemilaminectomy without fenestration. All dogs had 3 magnetic resonance imaging (MRI) examinations: preoperatively, immediately postoperatively to assess removal of herniated disc material, and again 6 weeks after surgery.
Results— There were 13 male and 6 female dogs; mean age, 7.1 years. Thoracolumbar disc herniation was confirmed with MRI. Immediate post surgical MRI revealed that the herniated disc removal was complete in all but 1 dog and that fenestration did not lead to complete removal of nucleus pulposus within the intervertebral disc space. On the 3rd MRI examination, none of the group 1 dogs had further disc material herniation at the fenestrated site. Six of the 10 group 2 dogs had a recurrence of herniation leading to clinical signs in 3 dogs (pain in 2 dogs, paresis in 1 dog).
Conclusion— In thoracolumbar disc herniation, fenestration of the affected intervertebral disc space prevents further extrusion of disc material.
Clinical Relevance— Fenestration reduces the risk of early recurrence of disc herniation and associated postoperative complications.     

INTRAVERTEBRAL DISC HERNIATION (SCHMORL'S NODE) IN FIVE DOGS

The herniation of intervertebral disc material into the vertebral body, known as Schmorl's nodes, is a well described disease process in man. Schmorl's nodes have not until now been described in the dog. This paper describes intravertebral disc herniation in the dog based on five patients taken from a retrospective study of dogs suspected of having cauda equina syndrome. The significance of intravertebral disc herniation in the dog at this time is that they indicate a disturbance in the vertebral endplate, they present definite radiographic signs, should be considered in patients with ostecohondrosis, and remain a possibls etiology for fibrocartilaginous emboli. Back pain is a common sign in people when Schmorl's nodes were the only pathologic findings. The common signs of palpatory pain in the lumbosacral region of the dogs in this report is noted but cannot be directly correlated at this time to the intravertebral disc herniation; however, it is suspected in two of the cases.     

COMPARISON BETWEEN CRANIAL THORACIC INTERVERTEBRAL DISC HERNIATIONS IN GERMAN SHEPHERD DOGS AND OTHER LARGE BREED DOGS

Cranial thoracic intervertebral disc herniations have been reported to be rare in dogs due to the presence of the intercapital ligament, however some studies have proposed they may not be uncommon in German Shepherd dogs. The purpose of this retrospective study was to compare cranial thoracic intervertebral disc herniations in German Shepherd dogs and other large breed dogs (control group). Medical records at the Ontario Veterinary College were searched for German Shepherd dogs and other large breed dogs that had magnetic resonance imaging studies including the T1‐T9 region. For each dog and each disc space from T1‐T9, three variables (compression, disc degeneration, and herniation) were recorded and graded based on review of sagittal T2‐weighted images. Twenty‐three German Shepherd dogs and 47 other large breed dogs met inclusion criteria. The German Shepherd dog group had higher scores than the control group for compression (P = 0.0099) and herniation (P < 0.001), but not disc degeneration (P = 0.97). In the German Shepherd dog group, intervertebral discs T2‐T3 and T4‐T5 had an increased risk for compression and T3‐T4 had an increased risk for compression and herniation. Findings from this study indicated that German Shepherd dogs may be more likely than other large breed dogs to have spinal cord compression due to cranial thoracic disc herniations. Imaging of the cranial thoracic spine, including T2‐T3, is recommended for German Shepherd dogs with T3‐L3 neurological signs.     

Spontaneous intradural disc herniation with focal distension of the subarachnoid space in a dog

Myelo-computed tomography of a paraparetic 14-year-old dog revealed subarachnoid distension with an intradural filling defect above the T13–L1 disc space. T12–L1 hemilaminectomy followed by durotomy allowed removal of a large piece of degenerated disc material that compressed the spinal parenchyma. Full return to function was achieved 10 days post-surgery. The distension was likely secondary to the intradural herniation, and is a rare and distinct finding.     

犬腰椎间盘切除术入路探索

为了探索治疗犬腰椎间盘突出症的合理手术入路,选择2月龄～1岁龄临床健康的本地杂交犬5只,分别编为1号～5号犬,其中1号、2号、3号犬施行半侧椎板切除术,4号、5号犬施行全椎板切除术,手术2周后进行X线摄片并剖检其腰椎结构变化。结果显示,术后1号～3号犬精神状态良好,饮食欲及体温正常,术部切口正常愈合,椎间盘部分或全部髓核被顺利取出;4号、5号犬手术中大出血,经治疗4号犬痊愈,而5号犬因衰弱而死亡。结果表明,腰椎间盘切除术要求严格的无菌操作和有效控制的麻醉,术犬侧卧位保定行半侧椎板切除是良好的手术入路,能够充分显露椎间盘、打开纤维环通道和切除髓核,有利于提高手术的安全性和保持腰椎的完整性与稳定性。     

Ventral intraspinal cysts associated with the intervertebral disc: magnetic resonance imaging observations in seven dogs

Objective— To report clinical and diagnostic imaging features, and outcome after surgical treatment of ventral intraspinal cysts in dogs.
Study Design— Retrospective study.
Animals— Dogs (n=7) with ventral intraspinal cysts.
Methods— Clinical signs, magnetic resonance imaging (MRI) findings and surgical findings of 7 dogs and histologic findings (1 dog) with intraspinal cysts associated with the intervertebral disc were reviewed.
Results— Ventral intraspinal cyst is characterized by: (1) clinical signs indistinguishable from those of typical disc herniation; (2) an extradural, round to oval, mass lesion with low T1 and high T2 signal intensity on MRI, compatible with a liquid-containing cyst; (3) cyst is in close proximity to the intervertebral disc; and (4) MRI signs of disc degeneration. Although the exact cause is unknown, underlying minor disc injury may predispose to cyst formation.
Conclusion— Intraspinal cysts have clinical signs identical to those of disc herniation. Given the close proximity of the cyst to the corresponding disc and the similarity of MRI findings to discal cysts in humans, we propose the term "canine discal cyst" to describe this observation.
Clinical Relevance— Discal cysts should be considered in the differential choices for cystic extradural compressing lesions.     

7例犬椎间盘疝出疾病的磁共振影像诊断

为明确不同类型的椎间盘疝出疾病的磁共振影像(MRI)特点,本文对7例犬椎间盘疝出病例的诊治过程进行总结,通过一般检查、神经学检查和MRI扫描,诊断为椎间盘疝出。其中有3例为椎间盘突出,2例为椎间盘脱出,2例为椎间盘膨出。主要的MRI表现为椎间盘退变,T2加权像上的椎间盘信号降低,脊髓、硬膜囊不同程度的受压和变形。这些结果表明MRI扫描可对椎间盘组织是否发生退变以及椎间突出的程度进行准确判断,在犬椎间盘疝出的诊断与治疗中有极高的应用价值。     

THORACOLUMBAR INTRADURAL DISC HERNIATION IN EIGHT DOGS: CLINICAL,LOW‐FIELD MAGNETIC RESONANCE IMAGING,AND COMPUTED TOMOGRAPHIC MYELOGRAPHY FINDINGS

Intradural disc herniation is a rarely reported cause of neurologic deficits in dogs and few published studies have described comparative imaging characteristics. The purpose of this retrospective cross sectional study was to describe clinical and imaging findings in a group of dogs with confirmed thoracolumbar intradural disc herniation. Included dogs were referred to one of four clinics, had acute mono/paraparesis or paraplegia, had low field magnetic resonance imaging (MRI) and/or computed tomographic myelography, and were diagnosed with thoracolumbar intradural disc herniation during surgery. Eight dogs met inclusion criteria. The prevalence of thoracolumbar intradural disc herniation amongst the total population of dogs that developed a thoracolumbar intervertebral disc herniation and that were treated with a surgical procedure was 0.5%. Five dogs were examined using low‐field MRI. Lesions that were suspected to be intervertebral disc herniations were observed; however, there were no specific findings indicating that the nucleus pulposus had penetrated into the subarachnoid space or into the spinal cord parenchyma. Thus, the dogs were misdiagnosed as having a conventional intervertebral disc herniation. An intradural extramedullary disc herniation (three cases) or intramedullary disc herniation (two cases) was confirmed during surgery. By using computed tomographic myelography (CTM) for the remaining three dogs, an intradural extramedullary mass surrounded by an accumulation of contrast medium was observed and confirmed during surgery. Findings from this small sample of eight dogs indicated that CTM may be more sensitive for diagnosing canine thoracolumbar intradural disc herniation than low‐field MRI.     

IMAGING FINDINGS IN DOGS WITH CAUDAL INTERVERTEBRAL DISC HERNIATION

The radiographic and magnetic resonance imaging (MRI) findings for four dogs with herniation of the Cd1–Cd2 intervertebral disc are described. All dogs were 7 years of age at the time of presentation, with one neutered male and three neutered females. Breeds included one Beagle, one Bassett hound, and two large, mixed breed dogs. All dogs had tail pain on manipulation, two had pain during defecation, and two maintained an abnormal tail position. Three dogs had radiographs in which mineralization within the disc space was apparent. Two of these dogs also had mineralization within the vertebral canal. Three dogs underwent MRI, which was characterized by varying degrees of disc herniation and nerve root compression at Cd1–Cd2. Mobility may be a factor predisposing to disc herniation in the cranial aspect of the caudal spine. We documented that caudal disc herniation does occur occasionally in dogs and that radiography and MRI may be used to identify this disease. Caudal intervertebral disc herniation should be considered as a differential for dogs with caudal vertebral pain, pain with tail manipulation, pain during defecation, or abnormal tail carriage.     

Cranial thoracic disc protrusions in three German Shepherd dogs

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

Intervertebral disc degeneration in the dog. Part 1: Anatomy and physiology of the intervertebral disc and characteristics of intervertebral disc degeneration

Intervertebral disc (IVD) degeneration is common in dogs and can give rise to a number of diseases, such as IVD herniation, cervical spondylomyelopathy, and degenerative lumbosacral stenosis. Although there have been many reports and reviews on the clinical aspects of canine IVD disease, few reports have discussed and reviewed the process of IVD degeneration. In this first part of a two-part review, the anatomy, physiology, histopathology, and biochemical and biomechanical characteristics of the healthy and degenerated IVD are described. In Part 2, the aspects of IVD degeneration in chondrodystrophic and non-chondrodystrophic dog breeds are discussed in depth.     

Subdural accumulation of fluid in a dog after the insertion of a ventriculoperitoneal shunt

A dog with hydrocephalus as a result of aqueduct stenosis and cerebellar herniation underwent ventriculoperitoneal shunting. Magnetic resonance images and computed tomography scans taken after the surgery revealed subdural accumulations of haemorrhagic fluid and cereberocortical collapse caused by overshunting and leakage of cerebrospinal fluid from the site of insertion of the shunt. However, the degree of cerebellar herniation was reduced after the shunt was inserted, and the dog did not develop any neurological signs and made good progress.     

Hypertrophic scar in a dog: histological and clinical features

An adult male bullmastiff dog was treated for paraparesis and ataxia due to discospondylitis and disc herniation. At this time, the dog had a nonhealing ulcer between the pads of the left hindfoot. At re-evaluation, the dog had developed a large exophitic mass in the previously ulcerated area. Cytological examination revealed occasional spindle cells with mild atypia, and a soft tissue tumour was suspected. The mass was excised and submitted for histology. The lesion was characterized by superficial ulceration, an intermediate layer of granulation tissue and a deep portion containing vertically orientated capillaries and perpendicularly arranged fibroblasts and collagen. The histological features led to a diagnosis of hypertrophic scar. Eight weeks after surgery, the lesion recurred and was treated with an intralesional injection of methylprednisolone acetate. The lesion regressed in 10 days, but recurred after 3 months following severe self-trauma. Hypertrophic scars and keloids are two types of exuberant scarring reported in human beings, the pathogenesis of which is still unclear but seems to involve several cytokines, growth factors and inflammatory cells. The histological features identified in this case paralleled those reported in hypertrophic scars in humans. In this case, intralesional corticosteroid therapy was useful in the management of the lesion, but the severe self-trauma could have influenced the recurrence. Even if uncommon, hypertrophic scar should be included among the differential diagnoses of spindle cell tumours in dogs.     

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.     

Reoperative neurosurgery in dogs with thoracolumbar disc disease

OBJECTIVE: To characterize the subset of dogs in our neurosurgical practice that underwent spinal surgery for thoracolumbar (TL) disc herniation and subsequently underwent additional decompressive TL surgery. STUDY DESIGN: A retrospective case series. SAMPLE POPULATION: Thirty dogs that underwent reoperation for TL disc herniation. A comparison group of Dachshunds that underwent only one decompressive TL disc surgery was also studied. METHODS: Dogs that underwent reoperation were divided into two groups based on the interval between their first and second surgery. The early reoperation group included those dogs having a second surgery less than 4 weeks after the initial operation. The late reoperation group included those dogs having a second surgery more than 4 weeks after the initial operation. For each Dachshund in the late reoperation group, two Dachshunds that underwent only one decompressive TL disc surgery were selected and formed the comparison group. Dogs in the comparison group were matched with reoperated cases based on the severity of preoperative neurologic deficit and site of disc herniation. These two groups were compared to determine: (1) if age and body weight were risk factors for reoperation, and (2) if dogs had a poorer functional outcome after their second decompressive surgery than did those in the comparison group after their first (and only) decompressive surgery. RESULTS: A total of 30 of 467 (6.4%) dogs that underwent decompressive TL disc surgery were reoperated. In the early reoperative cases (n = 5 dogs), the inciting cause in all cases was residual compression from disc material at the site of the initial surgery. In the late reoperation group, 22 of 25 (88%) cases had a second disc herniation at a site distinct from the initial lesion. Dachshunds had a significantly higher risk for late reoperation (odds ratio and 95% CI = 3.67, 1.46 to 10.03); other small and medium-sized breeds (<20 kg) were underrepresented. Age and body weight were not significant predictors for reoperation. A total of 21 of 23 (91%) dogs had functional recovery after late reoperation. Complete sensorimotor loss was a significant negative predictor of functional recovery in the late reoperative cases (P = .01). Likelihood of functional recovery in dogs after their second decompressive surgery was identical to the functional recovery of dogs in the comparison group. CONCLUSIONS AND CLINICAL RELEVANCE: Our results show that a second disc herniation occurring at a site distinct from the initial lesion is the most common cause for reoperation and that Dachshunds have a significantly greater risk than other breeds.     

Correlation of plain radiographic and lumbar myelographic findings with surgical findings in thoracolumbar disc disease

The results of a prospective study to compare the plain radiographic and lumbar myelographic findings with the surgical findings in 70 cases of suspected thoracolumbar disc protrusion in the dog are reported. The aim was to assess the relative accuracy of disc lesion localisation using plain and contrast radiography. From the plain radiographs, the affected disc space was correctly identified in 40 cases (57.1 per cent), and incor- rectly identified in seven. More than one site was identified in 11; in eight of these dogs, the affect- ed disc space was strongly suspected. It was not possible to identify an affected disc in 12 cases. The site of disc protrusion was accurately identified by myelography in 60 dogs (85.7 per cent). In four dogs, myelography was helpful in identifying an adjacent disc and, in a further two, cord swelling was found at surgery. In one dog, neither disc material nor cord swelling was identified. Three myelograms were non-diagnostic.     

Hiatal herniation as a complication of chronic diaphragmatic herniation

Three of four cases of chronic diaphragmatic herniation seen over a period of 12 months developed hiatal herniation within five to eight days of corrective surgery for the diaphragmatic herniation. None of the dogs had shown any prior signs referrable to hiatal herniation. The features that developed subsequent to diaphragmatic herniorrhaphy in all cases were dyspnoea, increased intra-abdominal pressure due to decreased abdominal domain and laxity of the oesophageal hiatus as judged subjectively at the time of surgery for hiatal herniation correction. These conditions may be significant underlying factors for the development of hiatal herniation not preceded by diaphragmatic herniation in the dog. Those associated factors accepted as important in humans, including reduced lower oesophageal sphincter tone and gastroesophageal reflux, may not be of similar importance in small animals.     

Colonic perforation after corticosteroid and surgical treatment of intervertebral disk disease in a dog

Colonic perforation after corticosteroid and surgical treatment of intervertebral disk disease in a dog Perforation of the distal segment of the descending colon, after corticosteroid and neurosurgical treatment for an intervertebral disk herniation, resulted in the death of a 3-year-old, male, Lhasa Apso. Initially, the dog was paraparetic in the hindlimbs, but became paraplegic after 4 days of conservative treatment. Corticosteroids were administered before referral and during decompressive hemilaminectomy. Six days after surgery, the dog had improved neurologically, but was depressed, anorectic, and vomiting. Abdominocentesis revealed septic peritonitis. The dog died shortly after a perforation in the descending colon was surgically corrected.     

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.