The value of oblique versus ventrodorsal myelographic views for lesion lateralisation in canine thoracolumbar disc disease

OBJECTIVE: To determine the value of oblique versus ventrodorsal myelographic views for lesion lateralisation in canine thoracolumbar disc disease. METHODS: The ventrodorsal and oblique views from 196 lumbar myelograms of dogs with single thoracolumbar disc extrusions or protrusions were blindly and independently reviewed by two of the authors for evidence of lesion lateralisation. Medical records were reviewed for details regarding hemilaminectomy surgery. The side (left versus right) of the surgery and whether or not the disc material was retrieved were noted. RESULTS: Both reviewers lateralised significantly more disc lesions from the oblique views (93 and 95 per cent) than from the ventrodorsal views (59 and 70 per cent) (P<0.001). Using a combination of oblique and ventrodorsal views, 194 (99 per cent) and 195 (99.5 per cent) lesions were lateralised. Unilateral hemilaminectomy was performed in 193 dogs with myelographic lateralisation and in one dog without myelographic lateralisation. The side of spinal cord decompression corresponded with the myelographic findings in all dogs showing lateralisation on myelography. In the dog without myelographic lateralisation, a left (randomly chosen) hemilaminectomy revealed dorsal protrusion of the annulus fibrosus. CLINICAL SIGNIFICANCE: Myelography, including oblique, ventrodorsal and lateral views, is an accurate method for determining lateralisation of extruded or protruded disc material in the vertebral canal before decompressive surgery. Combined oblique and ventrodorsal views are more useful than either view alone and should be routinely obtained in all lumbar myelographic studies when investigating thoracolumbar disc disease.     

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.     

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.     

Association of spinal cord compression seen on magnetic resonance imaging with clinical outcome in 67 dogs with thoracolumbar intervertebral disc extrusion

OBJECTIVES: To determine whether there is an association between the degree of transverse spinal cord compression detected by magnetic resonance imaging following thoracolumbar Hansen type 1 intervertebral disc disease in dogs and their presenting and postsurgical neurological status. METHODS: Medical records of 67 dogs with surgically confirmed Hansen type 1 intervertebral disc disease (2000 to 2004) were reviewed to obtain the rate of onset of disease, duration of clinical signs and presurgical and postsurgical neurological grade. Percentage of spinal cord compression was determined on transverse T2-weighted magnetic resonance images. Linear regression was used to examine the association between spinal cord compression and each of the above variables. Chi-squared tests were used to examine associations among postsurgical outcome and presurgical variables. RESULTS: Eighty-five per cent (57 of 67) of dogs were chondrodystrophoid. Mean spinal cord compression was 53 per cent (sd=219.7, range 14.3 to 84.9 per cent). There was no association between the degree of spinal cord compression and the neurological grade at presentation, rate of onset of disease, duration of clinical signs or postsurgical outcome, with no difference between chondrodystrophoid and non-chondrodystrophoid dogs. CLINICAL SIGNIFICANCE: The degree of spinal cord compression documented with magnetic resonance imaging in dogs with thoracolumbar Hansen type 1 intervertebral disc disease was not associated with the severity of neurological signs and was not a prognostic indicator in this study.     

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.     

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.     

Detection of spinal cord compression in dogs with cervical intervertebral disc disease by magnetic resonance imaging

The medical records and magnetic resonance images of 33 dogs with surgically confirmed Hansen type I cervical intervertebral disc disease were reviewed. Fourteen of the dogs were chondrodystrophic and 19 were not chondrodystrophic. The most common clinical sign was neck pain, which affected 28 of the dogs, and 23 of the dogs were able to walk. Fifteen of the dogs had developed clinical signs acutely, within the previous 24 hours. On cross-sectional images the median area of spinal cord compression was 26 per cent (range 11 to 71 per cent) of the normal spinal cord area. The degree of spinal cord compression was significantly associated with the dogs' presurgical neurological status but not with their postsurgical neurological status. The dogs with an acute onset of clinical signs had more severe neurological dysfunction before surgery, but their condition improved more as a result of surgery.     

ACCURACY OF SURVEY RADIOGRAPHIC DIAGNOSIS OF INTERVERTEBRAL DISC PROTRUSION IN DOGS

To assess the diagnostic accuracy of survey radiography for canine thoracolumbar intervertebral disc protrusion, survey radiographs (lateral and ventrodorsal) of 64 dogs with surgically-confirmed thoracolumbar intervertebral disc protrusion, 51 dogs with negative myelograms and 29 dogs with various spinal conditions other than disc protrusion were reviewed by three independent observers who were unaware of any clinical information. There were marked differences in observer performance for diagnosis of intervertebral disc protrusion, although there were no significant differences in intraobserver diagnostic accuracy for small vs. large dogs. Accuracy of observers for determining sites of intervertebral disc protrusion using survey radiography was in the range 51-61%. All observers had low accuracy for identification of second sites of intervertebral disc protrusion. The most useful radiographic sign, narrowed intervertebral space, had only moderate sensitivity (range 64-69%) and moderate predictive value (range 63-71%) for intervertebral disc protrusion. Vacuum phenomenon was an infrequent but accurate sign of intervertebral disc protrusion. Recognition of multiple radiographic signs of intervertebral disc protrusion at one site was associated with increased accuracy of diagnosis. No observer was accurate enough to justify attempting targeted surgical treatment of intervertebral disc protrusion without myelography.     

Comparison of vedaprofen and meloxicam in dogs with musculoskeletal pain and inflammation

In this randomised, multicentre clinical study, dogs with musculoskeletal pain and inflammation were treated with either vedaprofen or meloxicam administered orally at the recommended dose rates. Clinical examinations were carried out regularly and clinical severity scores assigned. In total, 214 cases (73 acute, 141 chronic) were evaluated. Treatment with vedaprofen and meloxicam was continued for 14 and 17 days, respectively, in the acute cases, and 38 and 39 days in the chronic cases. NSAID treatment resulted in a significant improvement in clinical scores. The overall response to treatment ('responders') at the final clinical examination was 89 per cent and 87 per cent in the acute cases and 72 per cent and 65 per cent in the chronic cases in the vedaprofen and meloxicam groups, respectively. Mild transient gastrointestinal signs were observed in both groups (11 per cent vedaprofen, 12 per cent meloxicam). Adverse effects related to NSAIDs resulted in treatment cessation in 5 per cent of the dogs in each group. Vedaprofen and meloxicam were efficacious in, and well tolerated by, most of the dogs in the study.     

Degenerative lumbosacral stenosis in 18 dogs

Eighteen dogs with degenerative lumbosacral stenosis were presented to the University of Queensland Small Animal Clinic (UQSAC) over a three-year period. Presenting clinical signs included lumbosacral pain (89 per cent), hindlimb paresis and proprioceptive deficits (56 per cent), lameness (49 per cent), flaccid tails (22 per cent), and urinary dysfunction (16 per cent). All 18 dogs were treated by decompressive laminectomy. Two dogs were also treated by a pin fixation-fusion technique. The major compressive lesion was a type II disc protrusion (72 per cent). Seventeen dogs (94 per cent) showed improvement postoperatively with minimal complications. Confirmation of diagnosis is difficult in that many aged dogs without clinical signs show radiographic signs compatible with stenosis.     

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.     

Modified lateral spinal decompression in 61 dogs with thoracolurnbar disc protrusion

A modified lateral spinal decompression technique was performed in 61 dogs with thoracolumbar disc protrusion. Myelography combined with plain radiography and neurological examination determined the side of greatest compression in 93 per cent of the dogs. Disc material was retrieved in 98 per cent of the cases. Of the 35 non-ambulatory dogs, 95 per cent regained the ability to walk. The recovery time was three weeks.     

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.     

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.     

Laminectomy for 34 dogs with thoracolumbar intervertebral disc disease and loss of deep pain perception

The case details and the results of treatment of 34 dogs with thoracolumbar intervertebral disc disease, without deep pain perception, that had been treated by laminectomy and fenestration, are presented. The association of a number of potential prognostic factors with the neurological outcome is examined. Twenty-one dogs (62 per cent) recovered neurological function, seven (21 per cent) failed to recover neurological function and three (9 per cent) developed progressive myelomalacia postoperatively, while three dogs (9 per cent) were euthanized intraoperatively because of diffuse myelomalacia. Twenty of the dogs that recovered neurological function showed a return of deep pain perception within two weeks of decompressive surgery. Statistical analysis showed significant differences in the outcome between dogs that took less than one hour to lose the ability to ambulate and dogs with a longer duration of onset of inability to ambulate. The extent of spinal cord swelling determined by myelography was not found to be a useful prognostic indicator.     

Lumbosacral osteochondrosis: radiological features and surgical management in 34 dogs

Lumbosacral osteochondrosis has been diagnosed with increasing frequency over the past few years. Nevertheless, poor recognition of the condition continues to lead to frequent misdiagnosis. A study was therefore undertaken over a 12-year period (1986 to 1998) to describe the use of a variety of radiological studies to define the syndrome and the use of different surgical techniques for optimal treatment of the condition. Dogs with clinical signs of cauda equina neuropathy and radiological signs of lumbosacral osteochondrosis were older than 14 months (mean age 6.3 years). German shepherd dogs, boxers and rottweilers were heavily represented. Of the 34 dogs with osteochondrosis in this study, the lesion appeared to be related to the sacrum in 31 dogs (91 per cent) and the seventh lumbar vertebra in the remaining three dogs (9 per cent). Twenty-seven male and seven female dogs were affected (4:1). Out of the 34 dogs, six (18 per cent) were treated conservatively and the remaining 28 (82 per cent) were treated surgically. The outcome of surgical treatment was considered to be satisfactory in 24 (86 per cent) of these latter dogs.     

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.     

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.     

Analgesic effects of acupuncture in thoracolumbar disc disease in dogs

The analgesic effects of acupuncture were studied in 38 dogs affected by acute thoracolumbar disc disease, type I to IV. Steel acupuncture needles were inserted into selected acupuncture points. Stimulation time was 20 minutes. Electrical stimulation of needles, ear-acupuncture, vitamins B and C and antibiotics were occasionally used in some dogs of types I and II and in the majority of types III and IV. Pain relief was observed in 62.5 per cent of dogs of type I (back-pain), in 70.5 per cent of dogs of type II (hindlimb paresis, backpain) and in 39 per cent of dogs of types III and IV (hindlimb paralysis, backpain) after the first acupuncture treatment. Dogs of type I and II responded significantly better (P<0.01) than dogs of type III and IV at the fourth treatment (100 per cent and 61.5 per cent, respectively).     

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.