Usefulness of myelography with multiple views in diagnosis of circumferential location of disc material in dogs with thoracolumber intervertebral disc herniation

The usefulness of myelography with multiple views (lateral, ventrodorsal, left and right oblique view) in the diagnosis of the exact circumferential location of herniated disc material around the spinal cord in 80 dogs diagnosed with thoracolumbar intervertebral disc herniation at surgery was assessed by comparison of clinical and surgical findings. The circumferential location of the compressing mass was diagnosed in 94% of dogs on myelography. The oblique view was of more benefit than the ventrodorsal view in diagnosing the circumferential distribution of the compressing mass. Only the oblique view contributed to a diagnosis of lateralization of the compressing mass in 45% of dogs. Fourteen percent of dogs had clinical lateralization contralateral to myelographic lateralization. The myelographic localization agreed with the surgical localization in 97% of dogs with regard to the exact location of herniated disc material. The presence of clinical lateralization contralateral to myelographic lateralization and a high proportion of agreement of myelographic and surgical localization documents that myelography with multiple views is useful and essential to accurately determine the circumferential location of disc material around the spinal cord.     

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.     

A comparison of hemilaminectomy (with concomitant disc fenestration) and dorsal laminectomy for the treatment of thoracolumbar disc protrusion in dogs.

The techniques of hemilaminectomy (with concomitant disc fenestration) and dorsal laminectomy were compared statistically in two groups of 30 dogs with thoracolumbar disc disease. On presentation all the dogs were unable to walk and were graded 1 to 3 according to their degree of neurological dysfunction. Nineteen had a previous history of thoracolumbar pain or hindlimb paresis. Radiography showed a narrowed disc space or extruded calcified disc material in 52 of the dogs and lumbar myelography revealed an extradural mass in 57; 24 of the dogs had clinical or myelographic lateralisation of signs. Hemilaminectomy significantly improved the ability to retrieve protruded disc material compared with dorsal laminectomy, and the removal of protruded disc material significantly improved the degree of recovery. Fenestration significantly reduced the recurrence of thoracolumbar disc disease.     

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

OBJECTIVES: To describe the clinical features and outcome in dogs suffering from thoracolumbar disc extrusion associated with extensive epidural haemorrhage (DEEH) and treated with extensive hemilaminectomy (from three to seven vertebrae). METHODS: The records of 23 dogs with surgically confirmed DEEH were reviewed retrospectively. RESULTS: All cases were characterised by rapid progression to severe neurological dysfunction (grade III, V and VI). Myelography was performed in 21 cases and showed an absence (16 cases) or attenuation (five cases) of contrast medium column along three to seven vertebrae. In two dogs, magnetic resonance imaging was accurate in confirming extradural compression due to disc material and haemorrhage, determining the extent of compression and side of the lesion. All cases were treated surgically with extensive hemilaminectomy involving all the compressed spinal segments. Twenty-one dogs (91 per cent) recovered and regained ambulatory function. Two dogs, without deep pain perception before surgery, did not improve. A two-year follow-up history was available for 15 dogs. Disc extrusion recurred in two dogs (9 per cent), two and 20 months after surgery. CLINICAL SIGNIFICANCE: Extensive hemilaminectomy can adequately decompress the spinal cord after DEEH and may produce a recovery and recurrence rate similar to thoracolumbar disc extrusion not complicated by extensive epidural haemorrhage.     

Incidence of Spinal Compressive Lesions in Chondrodystrophic Dogs with Abnormal Recovery after Hemilaminectomy for Treatment of Thoracolumbar Disc Disease: A Prospective Magnetic Resonance Imaging Study

Objective— To investigate causes of the lack of clinical improvement after thoracolumbar disc surgery. Study Design— Case–control magnetic resonance imaging (MRI) study. Animals— Chondrodystrophic dogs with acute thoracolumbar disc disease treated by hemilaminectomy: 10 that had no short‐term clinical improvement and 12 with “normal” clinical improvement. Methods— Dogs that had surgery for treatment of intervertebral disc extrusion (2003–2008) where thoracolumbar disc disease was confirmed by MRI were evaluated to identify dogs that had lack of clinical improvement after surgery. Ten dogs with delayed recovery or clinical deterioration were reexamined with MRI and compared with 12 dogs with normal recovery and MRI reexamination after 6 weeks (control group). Results— Of 173 dogs, 10 (5.8%) had clinical deterioration within 1–10 days after surgery. In 8 dogs, residual spinal cord compression was identified on MRI. Bleeding was present in 1 dog. In 3 dogs, the cause was an incorrect approach and insufficient disc material removal. In 3 dogs, recurrence occurred at the surgical site. In 1 dog, the centrally located extruded material was shifted to the contralateral side during surgery. These 8 dogs had repeat surgery and recovery was uneventful. In 2 dogs, deterioration could not be associated with a compressive disc lesion. Hemorrhagic myelomalacia was confirmed by pathologic examination in 1 dog. The other dog recovered after 6 months of conservative management. Conclusion— Delayed postsurgical recovery or deterioration is commonly associated with newly developed and/or remaining compressive disc lesion. Clinical Relevance— We recommend early MRI reexamination to assess the postsurgical spinal canal and cord, and to plan further therapeutic measures in chondrodystrophic dogs with delayed recovery after decompressive hemilaminectomy for thoracolumbar disc disease.     

Incidence of contralateral versus ipsi-lateral neurological signs associated with lateralised Hansen type I disc extrusion

Asymmetrical neurological signs were noted in 50 dogs presenting with Hansen type I thoracolumbar disc extrusion. Thoracolumbar myelograms and surgical decompression were performed in all cases. Dogs were divided into two groups (acute and chronic) based on the duration of clinical signs prior to presentation to the University of Georgia. Lateralising extradural cord compressive lesions were noted on all myelograms. In the acute group, 35 per cent of the dogs had asymmetrical neurological signs contralateral to the myelographic and surgical lesion, while in the chronic group only 11 per cent had neurological signs contralateral to the lesion. There was found to be no significant difference in frequency of contralateral asymmetrical clinical signs between the two groups (Fischer's exact test; P = 0–095). The high frequency of contralateral signs documents the importance of thoracolumbar myelography for accurate localisation of the disc material before decompressive surgery.     

Comparison of hemilaminectomy and dorsal laminectomy for thoracolumbar intervertebral disc extrusion in dachshunds

Neurological improvement after decompressive surgery, without routine therapeutic or prophylactic disc fenestration, was evaluated retrospectively in a consecutive series of 93 dachshunds with thoracolumbar disc extrusion. In 24 per cent of procedures, deep pain sensation was not elicited in at least one hind paw before surgery. Median neurological status one to seven days after surgery, at the time of discharge, was significantly improved after hemilaminectomy compared with dorsal laminectomy (P < 0·05). After hemilaminectomy, deep pain sensation was not elicited in one or both hind paws of 8 per cent of dogs in which pain sensation was elicited before surgery, compared with 21 per cent after dorsal laminectomy (P > 0·05). Improvement in neurological grade at follow-up examination two to 12 weeks after hemilaminectomy was not significantly different compared with dorsal laminectomy (P > 0·05). Of dogs which were unable to walk before surgery, 83 per cent regained the ability to walk after hemilaminectomy, compared with 74 per cent after dorsal laminectomy (P > 0·05). In both groups, 50 per cent of dogs in which deep pain sensation was abnormal before surgery eventually regained the ability to walk after surgery (P = 1). One to two years after the first operation, a second laminectomy was performed in only 5 per cent of dogs because of extrusion of a different intervertebral disc which had not been fenestrated.     

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.     

Hemilaminectomy for the treatment of thoracolumbar disc disease in the dog: a follow-uo studv of 40 cases

A study was made of dogs with Hansen type I thoracolumbar disc extrusions that had been treated by hemilaminectomy and fenestration of the affected disc. Follow-up information was available for 40 dogs undergoing treatment over a five-year period. The follow-up period ranged from 12 to 72 months (mean 34 months). The case details and the results of treatment of these 40 dogs are presented. All dogs were graded according to the degree of neurological dysfunction at the time of initial presentation and at the conclusion of the study period. Twenty-seven dogs (68 per cent) had no detectable signs of neurological dysfunction or thoracolumbar pain at the final assessment and a further eight dogs (20 per cent) had mild ambulatory paraparesis but were regarded by their owners as functional pets. Recurrence of neurological signs consistent with thoracolumbar disc disease was seen in five dogs (13 per cent) and was successfully resolved completely in one of three dogs that were treated.     

Use of the ventrodorsal myelographic view to predict lateralization of extruded disk material in small-breed dogs with thoracolumbar intervertebral disk extrusion: 104 cases (2004-2005)

OBJECTIVE: To determine whether the ventrodorsal myelographic view can be used to accurately predict the circumferential location of extruded disk material in dogs with thoracolumbar intervertebral disk extrusion (IVDE) and to describe paradoxical contrast obstruction (PCO). DESIGN: Retrospective case series. ANIMALS:104 dogs with Hansen type I IVDE. Procedures-Ventrodorsal myelographic views were reviewed, and contrast patterns were categorized according to 8 predetermined patterns. Agreement among observers was compared, and the predicted location of extruded disk material was compared with surgical findings. RESULTS: Agreement regarding myelographic pattern and location of extruded disk material was moderate (kappa = 0.74 and 0.80, respectively) among the 4 observers. Ninety-three (89%) dogs had myelographic evidence of lateralized extrusion, and in 83 of the 93 (89%), predicted location of extruded disk material matched the surgically confirmed location. In 33 of the 40 (83%) dogs with bilateral contrast column gaps of unequal length, disk material was found to be located on the side with the shorter, rather than the longer, contrast gap, a phenomenon described as PCO. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that the ventrodorsal myelographic view could be used to predict the circumferential location of extruded disk material in dogs with thoracolumbar IVDE more often than previously reported. The PCO phenomenon may be useful in determining the side of lateralization when contrast material does not outline the extruded disk material.     

Hemilaminectomy and vertebral stabilisation for the treatment of thoracolumbar disc protrusion in 28 dogs

Objectives : To evaluate the results of hemilaminectomy and vertebral stabilisation (+/? annulectomy) for the treatment of thoracolumbar disc protrusion. Methods : The medical records of dogs with thoracolumbar annular protrusions treated by hemilaminectomy and vertebral stabilisation were reviewed. Neurological function was assessed 24 hours following surgery. Long‐term follow‐up was by clinical examination or telephone questionnaire. Results : Twenty‐eight dogs fulfilled the criteria. Age ranged from 4 to 12·5 years (median 8 years, mean 7·7 years), bodyweight from 5·1 to 51·5 kg (median 28 kg, mean 27·1 kg), and duration of neurological signs before presentation from 48 hours to 104 weeks (median 5 weeks, mean 9·3 weeks). At presentation 22 dogs were ambulatory and six were non‐ambulatory. Myelography and/or magnetic resonance imaging (MRI) identified 31 thoracolumbar protrusions causing spinal cord compression. Unilateral hemilaminectomy was performed in 27 dogs and bilateral hemilaminectomy in one dog. Partial annulectomy was performed in 24 of 31 protrusions. Stabilisation was performed using vertebral body bone plates in 26 dogs and vertebral body screws and bone cement in two dogs. Internal vertebral venous plexus haemorrhage was recorded in nine dogs. A screw was inadvertently placed into an intervertebral disc in two dogs. Neurological examination 24 hours postoperatively revealed deterioration in pelvic limb motor function in 17 dogs. One dog was euthanatised at the owner’s request 6 days after surgery. Long‐term evaluation of 24 cases was performed 3 to 52 months following surgery (median 21 months, mean 23·9 months). Six dogs had improved from their preoperative status and one had deteriorated as assessed by the authors. Fifteen dogs had improved from their preoperative status and two were unchanged as assessed by owners. Clinical Significance : Hemilaminectomy and vertebral stabilisation are an effective treatment for chronic spinal cord compression due to thoracolumbar annular protrusion in dogs. A temporary deterioration in neurological function is not uncommon following surgery. Internal vertebral plexus haemorrhage and inappropriate vertebral body screw placement are potential complications.     

Canine intervertebral disc disease: Changes in the cerebrospinal fluid

Data was obtained from 118 cerebrospinal fluid (CSF) samples from dogs with intervertebral disc disease. The effect of lesion location and the severity and duration of clinical signs was studied. Ninety-seven samples were obtained from the cerebellomedullary cistern and 21 from the lumbar cistern. Changes in CSF were identified in 84.7 per cent of the lumbar samples, compared with only 37.1 per cent of the cerebellomedullary samples. More pronounced pleocytosis and protein level increases were seen in dogs with acute and clinically severe lesions. The protein concentration was more commonly elevated than the total white blood cell count. These results indicate that marked protein and white blood cell count elevations can occur in association with intervertebral disc extrusion. Such findings, therefore, should not necessarily preclude myelographic examination in dogs presented for paralysis.     

THE RADIOLOGICAL DIAGNOSIS OF THORACOLUMBAR DISC DISEASE IN THE DACHSHUND

The accuracy of survey radiographs in the diagnosis of acute thoracolumbar disc disease in 36 Dachshunds was determined by comparison with lumbar myelographic findings using iohexol. The value of making radiographs immediately after injection of contrast medium and the effectiveness of oblique radiographs in determining the exact circumferential distribution of extruding or protruding disc material were assessed. The presence of a double contrast medium column, resistance to injection and the presence of cerebrospinal fluid flow during needle placement was also evaluated. The location of the affected disc was accurately determined on survey radiographs in only 26 dogs. The myelographic technique used in this study resulted in the correct intervertebral space being identified, together with the exact circumferential distribution of disc material, in 35 dogs. Survey radiographs alone are inadequate for localization of protruding or extruding disc material.     

Vertebral stabilisation and selective decompression for the management of triple thoracolumbar disc protrusions

Triple adjacent thoracolumbar disc protrusions causing moderate to severe spinal cord compression were diagnosed by magnetic resonance imaging in two German shepherd dogs with marked paraparesis and pelvic limb ataxia. Both cases were managed by selective hemilaminectomy, partial annulectomy and bilateral quadruple vertebral body stabilisation using novel canine locking fixation plates (SOP). The stabilisation of multiple vertebrae in the thoracolumbar spine was possible because the plates could be contoured with six degrees of freedom. Spinal pain resolved and neurological function improved in both dogs. Screw breakage was evident in one dog five months following surgery.     

Correlation of Clinical, Radiographic, and Surgical Localization of Intervertebral Disc Extrusion in Small-Breed Dogs: A Prospective Study of 50 Cases

Objective —To compare prospectively clinical, radiographic, and surgical findings of intervertebral disc extrusion (IDE) localization in small-breed dogs and to determine the best means of lesion localization for the purpose of hemilaminectomy. Study Design —Clinical, radiographic, and surgical findings of small-breed dogs with thoracolumbar IDE were prospectively compared for agreement on lesion localization. Sample Population—50 small-breed dogs with IDE treated at the three participating veterinary hospitals were included in the study if no other confounding diseases were identified and if the owner gave permission for diagnostic tests and surgery. Methods —Clinical and surgical findings were recorded by the surgeon assigned to the case. Radiographic studies were evaluated independently by two radiologists blinded as to the clinical and surgical findings. values and 95% confidence intervals were calculated for agreement on lesion localization by clinical, radiographic, and surgical means and for agreement between radiologists. Results —K values for agreement of lesion localization were as follows: clinical versus surgical, 0.595; radiologist A versus radiologist B, 0.81; radiologist A versus surgical findings, 0.60; radiologist B versus surgical findings, 0.71. Both radiologists' interpretation of IDE localization agreed with surgical localization in 60% of cases. Conclusions —Clinical lateralization of IDE was found to be the least reliable factor of those studied for determining on which side the hemilaminectomy should be performed. Results of this study differ from those of previous studies examining the reliability of myelography to localize the site of IDE accurately. The results of this study further suggest that surgery may not be an absolute standard for determination of the localization of IDE in small-breed dogs. Clinical Relevance —Intervertebral disc extrusion in small-breed dogs frequently results in bilateral distribution of extruded material. Computed tomography or magnetic resonance imaging may be necessary to delineate completely the distribution of extruded disc material in IDE.     

Unilateral arytenoid lateralisation: An assessment of technique and long term results in 62 dogs with laryngeal paralysis

Sixty-two dogs with laryngeal paralysis were presented over a three year period. Presenting clinical signs included inspiratory stridor (100 per cent), exercise intolerance or syncopal episodes (81 per cent), loss or alteration in phonation (48 per cent) and coughing or gagging when eating (29 per cent). Causes of the paralysis were determined as traumatic (two dogs), neoplastic (two dogs), iatrogenic (two dogs), congenital (one dog) and idiopathic (55 dogs). Unilateral arytenoid lateralisation was performed in all dogs. The perioperative complication rate was approximately 10 per cent, while the success rate as judged by owners one year postoperatively was greater than 90 per cent. The technique avoided many of the recorded complications of intralaryngeal surgery. Operative times were short and the requirement for postoperative monitoring was minimal. Increasing familiarity with the technique favourably influenced the incidence of complications and the success rate.     

Duration and severity of clinical signs as prognostic indicators in 30 dogs with thoracolumbar disk disease after surgical decompression

The objective of this study was to evaluate the duration and severity of neurological dysfunction as prognostic indicators for the final outcome in 30 dogs with thoracolumbar intervertebral disk disease, treated surgically with hemilaminectomy without concurrent prophylactic fenestration. The lesion localization was assessed comparing plain radiographic, myelographic and surgical findings and success rates were evaluated during case follow-up. Evidence of a single disk extrusion existed in 17 dogs on survey spinal radiographs, while myelography revealed definite spinal cord compression in 28 cases and was inconclusive in the remaining two cases. Case follow-up continued for a period ranging from 3 months to 2 years post-operatively, depending on the degree of neurological dysfunction on presentation and owner compliance. The severity of clinical signs and the interval elapsing prior to decompressive surgery did not correlate with the case outcome, with 12 of 20 dogs (60%) that exhibited the most pronounced neurological dysfunction (paraplegia with or without analgesia) regaining voluntary motor function during the follow-up period. Recurrences proven to be disk-related did not occur in any dog throughout the post-surgical observation period. It was concluded that the time elapsing from loss of motor function and the severity of clinical signs is not an objective method to predict the case outcome.     

Partial percutaneous discectomy for treatment of thoracolumbar disc protrusion: retrospective study of 331 dogs

OBJECTIVES: To determine retrospectively the prognosis and outcome for dogs diagnosed with thoracolumbar intervertebral disc disease treated with partial percutaneous discectomy (PPD). METHODS: Three hundred and thirty-one dogs presenting with symptoms of thoracolumbar intervertebral disc disease from 1998 to 2003 were treated with PPD. Diagnosis and location of intervertebral disc disease was confirmed by clinical examination, radiography, myelography and magnetic resonance imaging. PPD was performed via fluoroscopy-guided removal of a 5 mm bore cylinder out of the central intervertebral space. RESULTS: Clinical success after surgery was achieved in 159 (88.8 per cent) grade II to IV patients and 58 (38.2 per cent) grade V patients. The mean (sd) time from percutaneous discectomy to first improvement was 8.3 (13.2) days. CLINICAL SIGNIFICANCE: The PPD approach to the thoracolumbar spine involves minor trauma (yielding rapid recovery) and less pain, and produces results comparable with open fenestration. Consequently, this simple minimal invasive technique can be recommended as an alternative to the technique of fenestration and can be easily performed in addition to open surgical decompression techniques or prophylactically. However, it is not a replacement for surgical treatment in dogs with thoracolumbar disc disease that require removal of disc fragments causing spinal cord or nerve root compression.     

Effect of multi-planar CT image reformatting on surgeon diagnostic performance for localizing thoracolumbar disc extrusions in dogs

Accurate pre-operative localization and removal of disc material are important for minimizing morbidity in dogs with thoracolumbar disc extrusions. Computed tomography (CT) is an established technique for localizing disc extrusions in dogs, however the effect of multi-planar reformatting (MPR) on surgeon diagnostic performance has not been previously described. The purpose of this study was to test the effect of MPR CT on surgeon diagnostic accuracy, certainty and agreement for localizing thoracolumbar disc extrusions in dogs. Two veterinary surgeons and one veterinary neurologist who were unaware of surgical findings independently reviewed randomized sets of two-dimensional (2D) and MPR CT images from 111 dogs with confirmed thoracolumbar disc extrusions. For each set of images, readers recorded their localizations for extruded disc material and their diagnostic certainty. For MPR images, readers also recorded views they considered most helpful. Diagnostic accuracy estimates, mean diagnostic certainty scores and inter-observer agreement were compared using surgery as the gold standard. Frequencies were compared for MPR views rated most helpful. Diagnostic accuracy estimates were significantly greater for MPR vs. 2D CT images in one reader. Mean diagnostic certainty scores were significantly greater for MPR images in two readers. The change in agreement between 2D and MPR images differed from zero for all analyses (site, side, number affected) among all three readers. Multi-planar views rated most helpful with the highest frequency were oblique transverse and curved dorsal planar MPR views. Findings from this study indicate that multi-planar CT can improve surgeon diagnostic performance for localizing canine thoracolumbar disc extrusions.     

Clinical evaluation of metrizamide as a myelographic agent in the dog.

Metrizamide, a new, water-soluble contrast agent, was clinically evaluated as a myelographic agent in 17 dogs. Nine dogs were given lumbar subarachnoid injections and six were given cisternal injections. Two dogs were given cisternal and lumbar injections; in one dog, both injections were given on the same day. The dosage ranged from 0.3 to 0.57 ml/kg of body weight, using an isotonic solution of metrizamide. Of eight dogs given cisternal injections, two experienced convulsive activity requiring diazepam treatment during the anesthetic recovery period. The lumbar injections did not cause convulsions. Satisfactory radiographic density persisted up to 45 minutes after injection, allowing time for several views to be obtained. In general, metrizamide appeared to be an adequate myelographic agent in the dog.