Association of magnetic resonance assessed disc degeneration and late clinical recurrence in dogs treated surgically for thoracolumbar intervertebral disc extrusions.

BACKGROUND: Radiographic signs of intervertebral disc mineralization are thought to indicate sites of future recurrence of disc extrusion (Hansen type I) but the relationship between evidence of disc degeneration on magnetic resonance imaging (MRI) and future disc extrusion with recurrence of clinical signs has not been examined. OBJECTIVES: To examine the relationship between MRI-assessed degeneration of thoracolumbar intervertebral discs and late recurrence of clinical signs in dogs presented with acute thoracolumbar intervertebral disc extrusion and treated by hemilaminectomy alone. ANIMALS: Ninety-two client-owned dogs presented to 2 referral hospitals between 2009 and 2014. METHODS: Retrospective analysis of association between clinical signs consistent with recurrent thoracolumbar intervertebral disc extrusion and MRI evidence of disc degeneration in dogs undergoing hemilaminectomy for acute thoracolumbar intervertebral disc extrusion. Univariable and multivariable Cox regression analyses were used to explore associations between recurrence of clinical signs and several characteristics of T10-L3 discs at initial diagnosis. RESULTS: Ninety-two cases were included, of which 42 (46%) were Dachshunds and median age was 5.3 years. Clinical signs recurred in 33/92 (36%) dogs. Finding a completely degenerate disc in the T10 to L3 region (in addition to the operated site) at the time of surgery was associated with a hazard ratio of 2.92 (95% confidence interval: 1.37-6.20) for recurrence of clinical signs. CONCLUSIONS AND CLINICAL IMPORTANCE: Our results suggest that in cases of thoracolumbar intervertebral disc extrusion in dogs, recurrence of signs is likely if at least 1 completely degenerate disc in addition to the currently symptomatic disc is visible on MRI.

Short-term clinical outcomes of 220 dogs with thoraco-lumbar disc disease treated by mini-hemilaminectomy.

Thoraco-lumbar intervertebral disc extrusion is a common condition seen in veterinary practice. Although there are different surgical techniques described for decompression, most of these techniques are based on the surgeon's preference or experience rather than clinical research. Our objective was to determine the clinical outcomes, using return to ambulation and micturition, as well as complication rates, in a large cohort of dogs by using a mini-hemilaminectomy for decompression of the thoraco-lumbar spinal cord with Hansen type I thoraco-lumbar intervertebral disc extrusions (IVDE). A retrospective study was performed on dogs presented for acute thoraco-lumbar IVDE undergoing surgical decompression. In total, 252 spinal decompression surgeries were performed. The recovery rates for patients graded with a modified Frankel score (MFS) of 5 to 0 were 100%, 99%, 100%, 96%, 86% and 64%, respectively. The mean days to micturition across all the MFS 5-0 were 1.5 (standard deviation [SD] ± 0.7), 1.8 (SD ± 1), 4.3 (SD ± 1.7), 6.4 (SD ± 2.2), 9.3 (SD 3) and 11.9 (SD ± 2.2), respectively. The mean days to ambulation across all the groups 5-0 were 2 (SD ± 0.7), 2.6 (SD ± 1), 7.6 (SD ± 4.4), 10.1 (SD ± 2.5), 16.1 (SD ± 2.9) and 19.3 (SD ± 2.6), respectively. Postoperative complications were seen in 32 of the surgeries, with a complication rate of 13%. Minor complications accounted for 38% of all complications, and major complications constituted 62% of all complications. In total, 15 dogs died or were euthanised as a direct result of thoraco-lumbar disc extrusion or the surgical procedure, with a mortality rate of 6% across all groups. A mini-hemilaminectomy provides similar clinical outcomes described in the literature for other methods of spinal cord decompressive surgery, and it also provides patients with similar short-term outcomes to other described decompressive surgical techniques in the dog, which have been described in the literature.

Effect of Duration and Onset of Clinical Signs on Short-Term Outcome of Dogs with Hansen Type I Thoracolumbar Intervertebral Disc Extrusion.

OBJECTIVE: The aim of this study was to determine if either the rate of onset of clinical signs or duration from initial clinical signs to surgical decompression affected the overall quality or duration of recovery in dogs with intervertebral disc extrusion. STUDY DESIGN: This was a retrospective case series of 131 client owned dogs. Medical records of dogs surgically treated with hemilaminectomy for intervertebral disc extrusion between January 2016 and December 2017 were reviewed for signalment, neurological grade at presentation, rate of onset and duration of clinical signs and surgical variables. These variables were analysed to determine their effect on return of pain sensation, urinary continence and ambulation. RESULTS: Duration of clinical signs prior to surgery and rate of onset of signs did not correlate with return of pain sensation, urinary continence or ambulation. Preoperative neurological grade was the main variable that was found to be associated with outcome. CONCLUSIONS: Delay from initial clinical signs of intervertebral disc extrusion to surgery is unlikely to affect the ultimate outcome or the length of time for a dog to regain pain sensation, urinary continence or ambulation. The rate of onset of signs likewise does not influence these outcomes.

Relationship of preoperative neurologic score with intervals to regaining micturition and ambulation following surgical treatment of thoracolumbar disk herniation in dogs.

OBJECTIVE To estimate the times required for dogs to regain micturition and ambulation following surgical treatment for thoracolumbar Hansen type I intervertebral disk extrusion (IVDE) and determine whether these variables were associated with preoperative modified Frankel score (MFS). DESIGN Retrospective case series with nested cohort study. ANIMALS 54 dogs weighing < 20 kg (44 lb) that were surgically treated for Hansen type I IVDE at a referral hospital between January and December 2015. PROCEDURES Medical records and CT and MRI data were reviewed. Information was collected regarding dog signalment, type and duration of clinical signs, preoperative MFS, degree of spinal cord compression, type of medical and surgical treatment provided, and intervals from surgery to regaining micturition and ambulation (outcomes). Collected data were evaluated for correlations with outcomes. RESULTS Mean ± SD interval from surgery to regaining micturition was 4.1 ± 4.4 days, and mean interval from surgery to regaining ambulation was 13.8 ± 25.1 days. These intervals differed significantly. Significant negative correlations with MFS were identified for interval to regaining micturition (r = -0.63) and interval to regaining ambulation (r = -0.64). No other correlations with outcome were identified. CONCLUSIONS AND CLINICAL RELEVANCE The amount of time required for dogs to regain micturition and ambulation following surgery for thoracolumbar IVDE was correlated with preoperative severity of clinical signs, as reflected by preoperative MFSs. This information should be useful for pre- and postoperative decision-making and setting of expectations for owners of and clinicians treating affected dogs.

Hemilaminectomy for thoracolumbar Hansen Type I intervertebral disk disease in ambulatory dogs with or without neurologic deficits: 39 cases (2008-2010).

OBJECTIVE: To describe prognostic factors, outcome, and time to recovery among ambulatory dogs having hemilaminectomy for Hansen Type I intervertebral disk disease. STUDY DESIGN: Retrospective case series. ANIMALS: Dogs (n = 38; 39 hemilaminectomies). METHODS: Medical records (January 2008-May 2010) on all dogs that had hemilaminectomy for Hansen Type I intervertebral disk disease were reviewed. Records for dogs that were ambulatory preoperatively were analyzed for signalment, duration and severity of signs, presence of neurologic deficits, and postoperative outcome. Dogs were categorized based on Frankel score and subcategorized by their level of conscious proprioceptive (CP) deficit. Postoperatively, time to ambulation and to regain normal CP responses was recorded. Results for each group were compared using a χ(2) test and considered significant when P < .05. Recovery times were analyzed using a Cox proportional hazards model. RESULTS: Seven dogs were categorized as modified Frankel grade I preoperatively and 32 dogs as grade II with varying levels of deficits (1 of these dogs had previously been operated as grade II and was reoperated again as grade II). Increasing degree of CP deficit preoperatively was significantly correlated with longer time to ambulation (P = .005) as well as longer time to CP normal (P = .01). Duration of signs was not significantly correlated with time to ambulation or neurologic recovery for either grade I or II dogs. CONCLUSIONS: Most dogs recovered well with surgical decompression. Increasing degree of deficits preoperatively is significantly correlated with longer recovery time.

Assessment of the usefulness of the fenestration method in cases of disc extrusion in the cervical and thoraco-lumbar spine in chondrodystrophic dogs.

The aim of this paper was to assess the effectiveness of treatment of Type I (according to Hansen) intervertebral disc extrusion using the fenestration method. The evaluated clinical material included 37 chondrodystrophic dogs in which multiple fenestration (from 2 to 6 intervertebral spaces) was performed. Dachshunds comprised 86.5% of patients. All dogs were administered corticosteroids during the operation. A mass similar to a slightly jelly-like yogurt, cottage cheese or plaster-like consistency was extracted. In one case a post-surgical pyogenic infection of the wound occured. In two cases, a deterioration in the neurological state followed the fenestration procedure of the cervical spine. In one case of thoraco-lumbar spine fenestration, a deterioration of clinical state was found. Recovery was observed after disc extrusion from the cervical spine in 8 out of 11 dogs, from the thoraco-lumbar spine in 12 out of 14 dogs with the 2nd grade clinical signs and in 11 out of 12 dogs with the 3rd grade clinical sings. In 6 dogs, recurrence of first or second grade clinical signs occurred, but only half of them had to undergo treatment. The probability of dog recovery did not depend on the degree of symptom intensity in a statistically significant way (p=0.11) or on the duration of the disease before the surgical treatment (p=0.87).

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.

The assessment of the usefulness of hemilaminectomy without fenestration in the treatment of thoracolumbar disc disease in chondrodystrophic dogs.

The aim of the publication is to assess the effectiveness of the treatment of type I disc extrusion according to Hansen by using the method of hemilaminectomy without fenestration. The evaluated clinical material comprised 36 chondrodystrophic dogs in which 38 surgical procedures were performed. All dogs were administered corticosteroid during the operation. Dachshunds made up to 79% of patients. In 34 cases grainy mass was extracted from the vertebral canal. In two cases it was plaster-like mass and in other two--granulo-chondral. Most often (12 cases) the prolapse of the nucleus pulposus was observed between the first and second lumbar vertebra. There was one case of the postoperative pyogenic infection of the wound. Recovery was observed in all dogs with 3rd grade clinical signs, 17 out of 18 dogs with 4th grade and 8 out of 13 dogs with 5th grade of dysfunction severity. The recovery time of the dog depended in the statistically significant way on the severity of symptoms and the grade of the present disease (p<0.00005). There did not appear to be any statistically significat relationship between the recovery time and the duration of symptoms pre operatively (p=0.42), the time of non-ambulatory status (p=0.27) and the breed of the dog (p=0.81).

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.

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.

Outcome and prognostic factors in non-ambulatory Hansen Type I intervertebral disc extrusions: 308 cases.

Thoracolumbar intervertebral disc disease is the most common cause of caudal paresis in dogs. Whilst the pathogenesis of the extrusion has been widely studied, treatment protocols and prognostic factors relating to outcome remain controversial. Recent studies have examined a multitude of factors relating to time to regain ambulation after decompressive surgery. Most intervertebral disc herniations occur in the thoracolumbar region, causing upper motor neuron signs in the rear limbs, which are thought to have a more favourable prognosis compared to the lower motor neuron signs created by herniation of an intervertebral disc in the caudal lumbar region. Due to the potential disruption of the lumbar intumescence, lower motor neuron signs have been reported as having a less favourable prognosis. The purpose of this study was to evaluate the intervertebral disc space as a prognostic factor relating to ambulatory outcome and time to ambulation after decompressive surgery. Hansen Type I intervertebral disc extrusions were studied in 308 non-ambulatory dogs. Preoperative and postoperative neurological status, corticosteroid use, signalment, intervertebral disc space, postoperative physical rehabilitation, previous hemilaminectomy surgery, disc fenestration, return to ambulation, and time to ambulation were reviewed.

The role of extruded disk material in thoracolumbar intervertebral disk disease: a retrospective study in 40 dogs.

The objective of the study was to determine the effect of the dispersed or nondispersed form of the extruded disk material (EDM) on the neurological status and surgical outcomes in Hansen thoracolumbar intervertebral disk disease Type I (IVDD-I). Medical records of 40 dogs with IVDD-I were reviewed, including neurologic status on admission, findings on magnetic resonance imaging (MRI), intraoperative findings, and surgical outcomes. In MRI evaluations, EDM was on the right in 16, on the left in 18, and centrally in 6 cases; in all cases, findings were confirmed by surgery. Extruded disk material was localized and classified as dispersed disk (DD) or nondispersed disk (NDD) according to its dispersion in the epidural space on MRI. Twenty-five dogs had DD and 15 had NDD on both MRI and surgery. There was no significant difference between DD and NDD in preoperative neurological status and surgical outcomes (P > 0.05).

Aplastic articular facets in a dog with intervertebral disk rupture of the 12th to 13th thoracic vertebral space.

A 6-year-old, female spayed Pomeranian was presented with acute hind-limb paraplegia with the presence of deep pain perception and urinary incontinence. Myelography showed a Hansen type I herniation of the12th to 13th thoracic intervertebral space (T(12-13)). Articular facets of the T(12-13) and T(13) to first lumbar vertebra (L(1)) were absent. The spinal cord was decompressed using a bilateral T(12-13) modified lateral hemilaminectomy (pediculectomy). The aplastic sites were associated with minimal instability of the vertebral column, and stabilization of the vertebral column was not required. Familiarity with this condition is important, because articular facet aplasia may cause vertebral instability and may require an adjusted surgical approach or vertebral reduction and fusion following decompression.

Recurrence of thoracolumbar intervertebral disk extrusion in chondrodystrophic dogs after surgical decompression with or without prophylactic fenestration: 265 cases (1995-1999).

OBJECTIVES: To evaluate a population of chondrodystrophic dogs treated for Hansen type 1 intervertebral disk (IVD) disease by surgical decompression with or without prophylactic fenestration and determine the rate and location of surgically confirmed recurrence of intervertebral disk extrusion. ANIMALS: 265 dogs. STUDY DESIGN: Retrospective study. PROCEDURES: Medical records of dogs that underwent spinal decompression between 1995 and 1999 were reviewed. RESULTS: 3 (4.9%) dogs were euthanatized or died prior to discharge. Fenestration was performed in 252 dogs, including 37 (14.7%) at the site of decompression only, 48 (19%) at 3 to 4 disk spaces, and 167 (66%) at 5 to 7 disk spaces. There were 12 instances of recurrent disk extrusion confirmed by removal of disk at a second surgery 3.5 to 33 months after the first surgery. Recurrence was always at a new disk space, and rates did not significantly differ between dogs that underwent single or multiple fenestrations. Two recurrences were at a previously fenestrated disk space. Seven recurrences were at a site immediately adjacent to a fenestrated disk space, and 5 recurrences were at L4-5. CONCLUSIONS AND CLINICAL RELEVANCE: Prophylactic fenestration is generally successful in preventing future disk extrusions at fenestrated disk spaces. Prospective evaluation is still required to determine whether fenestration decreases the overall rate of recurrence. Prophylactic fenestration could promote disk extrusion at adjacent, nonfenestrated disk spaces. This could have a substantial clinical impact if recurrence develops at L4-5.

Prognostic indicators for time to ambulation after surgical decompression in nonambulatory dogs with acute thoracolumbar disk extrusions: 112 cases.

OBJECTIVES: To determine prognostic indicators for time to ambulation after surgical decompression in nonambulatory dogs with intact pain sensation and acute Hansen type-1 disk extrusions. STUDY DESIGN: Retrospective clinical study. ANIMALS: One-hundred twelve dogs with Hansen type-I disk extrusions that had decompressive hemilaminectomy or dorsal laminectomy. METHODS: All dogs had thoracolumbar disk extrusion and were nonambulatory with intact pain sensation at admission. Variables considered included age, weight, voluntary motor function at time of anesthetic induction, glucocorticoid use, times from onset of nonambulatory status to admission and surgical decompression, time in hospital to surgical decompression, anesthetic time, surgical time, number of contrast injections required to perform a diagnostic myelogram, postoperative pain sensation, and postoperative voluntary motor function. Time to ambulation was defined as the number of days from surgical decompression until the dog was able to stand and take a series of steps without assistance. RESULTS: One-hundred seven dogs (96%) were able to ambulate within 3 months. The mean time to ambulation was 12.9 days and was significantly shorter if dogs had postoperative voluntary motor function (7.9 days v 16.4 days, P <.0001). No other variable had a significant association with time to ambulation. CONCLUSIONS: Few perioperative variables have prognostic value for return to ambulation. Nonambulatory dogs with intact pain sensation and Hansen type-1 disk extrusions in the thoracolumbar spine that are treated with surgical decompression have a favorable prognosis. CLINICAL RELEVANCE: The presence of postoperative voluntary motor function is a favorable prognostic indicator for early return to ambulation.

The role of acute decompression and restoration of spinal alignment in the prevention of post-traumatic syringomyelia: case report and review of recent literature.

STUDY DESIGN: Case report. INTRODUCTION: Acute post-traumatic syringomyelia formation after spinal cord injury has been considered a rare complication. At this writing, most recent reports have surfaced in neurosurgical journals. As an entity, post-traumatic syringomyelia has not been widely appreciated. It has been confused with conditions such as Hansen's disease or ulnar nerve compression at the cubital tunnel. One study also demonstrated that the occurrence of syrinx is significantly correlated with spinal stenosis after treatment, and that an inadequate reduction of the spine may lead to the formation of syrinx. This reported case describes a patient in whom post-traumatic syringomyelia began to develop 3 weeks after injury, which improved neurologically after adequate decompression. SUMMARY OF BACKGROUND DATA: A 30-year-old man sustained a 20-foot fall at work. He presented with a complete spinal cord injury below T4 secondary to a T4 fracture dislocation. The patient underwent open reduction and internal fixation of T1-T8. After 3 weeks, the patient was noted to have ascending weakness in his bilateral upper extremities and some clawing of both hands. METHODS: A computed tomography myelogram demonstrated inability of contrast to pass through the T4-T5 region from a lumbar puncture. An incomplete reduction was noted. The canal showed significant stenosis. A magnetic resonance image of the patient's C-spine showed increased signal in the substance of the cord extending into the C1-C2 area. The patient returned to the operating room for T3-T5 decompressive laminectomy and posterolateral decompression including the pedicles, disc, and posterior aspect of the body. Intraoperative ultrasound monitoring showed a good flow of cerebrospinal fluid past the injured segment. RESULTS: On postoperative day 1, the clawing posture of the patient's hands was significantly diminished, and the patient noted an immediate improvement in his hand and arm strength. Over the next few days, the patient's strength in the bilateral upper extremities increased to motor Grade 4/5 on manual testing. A magnetic resonance image 4 weeks after decompression showed significant improvement in the cord diameter and signal. CONCLUSIONS: Post-traumatic syringomyelia has not been reported at so early a stage after injury. This disorder is an important clinical entity that must be recognized to prevent potentially fatal or devastating complications. As evidenced by the reported patient and the literature, if this disorder is discovered and treated early, permanent deficit can be avoided. The prevention of post-traumatic syringomyelia requires anatomic realignment and stabilization of the spine without stenosis, even in the case of complete injuries, to maintain the proper dynamics of cerebrospinal fluid flow.

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

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

Hemilaminectomy for the treatment of thoracolumbar disc disease in the dog: a follow-up study 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.

Incidence of contralateral versus ipsilateral 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.

Thoracolumbar intervertebral disk disease in large, nonchondrodystrophic dogs: a retrospective study.

Medical records of 62 large, nonchondrodystrophic dogs diagnosed with thoracolumbar intervertebral disk disease between March 1986 and February 1996 were reviewed. Fifty-seven (92%), primarily mixed-breed dogs (mean age, 6.6 years) had Hansen type I disease. Fifty-eight percent had acute onset. The interspace between the first (L1) and second (L2) lumbar vertebrae was affected most commonly. The outcomes of the 48 dogs available for follow-up after undergoing laminectomies were evaluated. Surgical success rate and mean time to walking for nonambulatory dogs with deep pain perception was 90% and seven weeks, respectively. Thirty-nine percent had residual deficits. Following surgery, 12% had recurrence of disk protrusion/extrusion at a different site.