Thoracolumbar Disc Herniation Research Articles

Successful medical management of lumbar intervertebral disc prolapse in a ferret

Thoracolumbar disc herniation was diagnosed in a two-year-old ferret using a myelogram followed by a computed tomography scan. The ferret was paraplegic with no control over urination and defecation. Conservative treatment that included cage rest and passive range of motion exercises for three weeks followed by extensive physiotherapy and hydrotherapy resulted in full recovery two months after the onset of treatment. Although intervertebral disc disease has been reported previously in four ferrets, this is the first report in which a postmyelogram computed tomography was used to demonstrate the herniated disc, and physiotherapy was used as principal treatment modality.

Magnetic Resonance Imaging in Dogs with Neurologic Impairment Due to Acute Thoracic and Lumbar Intervertebral Disk Herniation

Magnetic resonance imaging (MRI) is a correlate to physical examination in various myelopathies and a predictor of functional outcome. To describe associations among MRI features, neurological dysfunction before MRI, and functional outcome in dogs with disk herniation. One hundred and fifty-nine dogs with acute thoracolumbar disk herniation. Retrospective case series. Signalment, initial neurological function as assessed by a modified Frankel score (MFS), and ambulatory outcome at hospital discharge and >3 months (long-term) follow-up were recorded from medical records and telephone interview of owners. Associations were estimated between these parameters and MRI signal and morphometric data. Dogs with intramedullary T2W hyperintensity had more severe pre-MRI MFS (median 2, range 0-4) and lower ambulatory proportion at long-term follow-up (0.76) than those dogs lacking hyperintensity (median MFS 3, range 0-5; ambulatory proportion, 0.93) (P=.001 and .013, respectively). Each unit of T2W length ratio was associated with a 1.9 times lower odds of long-term ambulation when adjusted for pre-MRI MFS (95% confidence interval 1.0-3.52, P=.05). Dogs with a compressive length ratio >1.31 (which was the median ratio within this population) had more severe pre-MRI MFS (median 3, range 0-5) compared with those with ratios < or =1.31 (median MFS 3, range 0-4; P=.006). MRI features were associated with initial injury severity in dogs with thoracolumbar disk herniation. Based on results of this study, the T2W length ratio and presence of T2W intramedullary hyperintensity appear to be predictive of long-term ambulatory status.

Description and repeatability of a newly developed spinal cord injury scale for dogs

The objectives of this study were to describe a new spinal cord injury scale for dogs, evaluate repeatability through determining inter-rater variability of scores, compare these scores to another established system (a modified Frankel scale), and determine if the modified Frankel scale and the newly developed scale were useful as prognostic indicators for return to ambulation. A group of client-owned dogs with spinal cord injury were examined by 2 independent observers who applied the new Texas Spinal Cord Injury Score (TSCIS) and a modified Frankel scale that has been used previously. The newly developed scale was designed to describe gait, postural reactions and nociception in each limb. Weighted kappa statistics were utilized to determine inter-rater variability for the modified Frankel scale and individual components of the TSCIS. Comparisons were made between raters for the overall TSCIS score and between scales using Spearman's ρ. An additional group of dogs with surgically treated thoracolumbar disk herniation was enrolled to look at correlation of both scores with spinal cord signal characteristics on magnetic resonance imaging (MRI) and ambulatory outcome at discharge. The actual agreement between raters for the modified Frankel scale was 88%, with a weighted kappa value of 0.93. The TSCIS had weighted kappa scores for gait, proprioceptive positioning and nociception components that ranged from 0.72 to 0.94. Correlation between raters for the overall TSCIS score was Spearman's ρ = 0.99 ( P < 0.001). Comparison of the overall TSCIS score to the modified Frankel score resulted in a Spearman's ρ value of 0.90 ( P < 0.001). The modified Frankel score was weakly correlated with the length of hyperintensity of the spinal cord: L2 vertebral body length ratio on mid-sagittal T2-weighted MRI (Spearman's ρ = −0.45, P = 0.042) as was the overall TSCIS score (Spearman's ρ = −0.47, P = 0.037). There was also a significant difference in admitting modified Frankel scores ( P = 0.029) and admitting overall TSCIS scores ( P = 0.02) between dogs that were ambulatory at discharge and those that were not. Results from this study suggest that the TSCIS is an easy to administer scale for evaluating canine spinal cord injury based on the standard neurological exam and correlates well with a previously described modified Frankel scale.

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

To describe the influence of fenestration at the disc herniation site on recurrence in thoracolumbar disc disease of chondrodystrophoid dogs. Prospective clinical study. Chondrodystrophic dogs (n=19). 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. 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). In thoracolumbar disc herniation, fenestration of the affected intervertebral disc space prevents further extrusion of disc material. Fenestration reduces the risk of early recurrence of disc herniation and associated postoperative complications.

Adverse effects and outcome associated with dexamethasone administration in dogs with acute thoracolumbar intervertebral disk herniation: 161 cases (2000–2006)

To determine complications and neurologic outcomes associated with dexamethasone administration to dogs with surgically treated thoracolumbar intervertebral disk herniation, compared with dogs not receiving dexamethasone. Retrospective case series. 161 dogs with surgically confirmed thoracolumbar disk herniation. Medical records from 2 hospitals were used to identify dogs that had received dexamethasone < 48 hours prior to admission (dexamethasone group dogs), dogs that received glucocorticoids other than dexamethasone < 48 hours prior to admission (other-glucocorticoid group dogs), and dogs that received no glucocorticoids (nontreatment group dogs). Signalment, neurologic injury grade, laboratory data, and complications were extracted from medical records. Dexamethasone group dogs were 3.4 times as likely to have a complication, compared with other-glucocorticoid or nontreatment group dogs. Dexamethasone group dogs were 11.4 times as likely to have a urinary tract infection and 3.5 times as likely to have diarrhea, compared with other-glucocorticoid or nontreatment group dogs. No differences in neurologic function at discharge or recheck evaluation were detected among groups. Results indicated that treatment with dexamethasone before surgery is associated with more adverse effects, compared with treatment with glucocorticoids other than dexamethasone or no treatment with glucocorticoids, in dogs with thoracolumbar intervertebral disk herniation. In this study population, no difference in outcome was found among groups. These findings suggest that the value of dexamethasone administration before surgery in dogs with thoracolumbar disk herniation should be reconsidered.

Evaluation of the Success of Medical Management for Presumptive Cervical Intervertebral Disk Herniation in Dogs

To determine the success of medical management of presumptive cervical disk herniation in dogs and variables associated with treatment outcome. Retrospective case series. Dogs (n=88) with presumptive cervical disk herniation. Dogs with presumptive cervical and thoracolumbar disk herniation were identified from medical records at 2 clinics and clients were mailed a questionnaire related to the success of therapy, clinical recurrence of signs, and quality of life (QOL) as interpreted by the owner. Signalment, duration and degree of neurologic dysfunction, and medication administration were determined from medical records. Ninety-seven percent of dogs (84/87) with complete information were described as ambulatory at initial evaluation. Successful treatment was reported for 48.9% of dogs with 33% having recurrence of clinical signs and 18.1% having therapeutic failure. Bivariable logistic regression showed that non-steroidal anti-inflammatory drug (NSAID) administration was associated with success (P=.035; odds ratio [OR]=2.52). Duration of cage rest and glucocorticoid administration were not significantly associated with success or QOL. Dogs with less-severe neurologic dysfunction were more likely to have a successful outcome (OR=2.56), but this association was not significant (P=.051). Medical management can lead to an acceptable outcome in many dogs with presumptive cervical disk herniation. Based on these data, NSAIDs should be considered as part of the therapeutic regimen. Cage rest duration and glucocorticoid administration do not appear to benefit these dogs, but this should be interpreted cautiously because of the retrospective data collection and use of client self-administered questionnaire follow-up. These results provide insight into the success of medical management for presumptive cervical disk herniation in dogs and may allow for refinement of treatment protocols.

Evaluation of the Success of Medical Management for Presumptive Thoracolumbar Intervertebral Disk Herniation in Dogs

To determine the success of medical management of presumptive thoracolumbar disk herniation in dogs and the variables associated with treatment outcome. Retrospective case series. Dogs (n=223) with presumptive thoracolumbar disk herniation. Medical records from 2 clinics were used to identify affected dogs, and owners were mailed a questionnaire about success of therapy, recurrence of clinical signs, and quality of life (QOL) as interpreted by the owner. Signalment, duration and degree of neurologic dysfunction, and medication administration were determined from medical records. Eighty-three percent of dogs (185/223) were ambulatory at initial evaluation. Successful treatment was reported for 54.7% of dogs, with 30.9% having recurrence of clinical signs and 14.4% classified as therapeutic failures. From bivariable logistic regression, glucocorticoid administration was negatively associated with success (P=.008; odds ratio [OR]=.48) and QOL scores (P=.004; OR=.48). The duration of cage rest was not significantly associated with success or QOL. Nonambulatory dogs were more likely to have lower QOL scores (P=.01; OR=2.34). Medical management can lead to an acceptable outcome in many dogs with presumptive thoracolumbar disk herniation. Cage rest duration does not seem to affect outcome and glucocorticoids may negatively impact success and QOL. The conclusions in this report should be interpreted cautiously because of the retrospective data collection and the use of client self-administered questionnaire follow-up. These results provide an insight into the success of medical management for presumptive thoracolumbar disk herniation in dogs and may allow for refinement of treatment protocols.

Thoracolumbar Lateral Corpectomy for Treatment of Chronic Disk Herniation: Technique Description and Use in 15 Dogs

To describe a technique for thoracolumbar lateral corpectomy and to evaluate its use for treatment of chronic thoracolumbar disk disease in dogs. Retrospective study. Fifteen dogs with signs of chronic thoracolumbar disk herniation. After a dorsal or lateral approach to the spine, a lateral slot was created in 2 adjacent vertebral bodies on either side of the herniated disk and extruded/protruded material was removed. Data collected included history, duration of clinical signs, presurgical assessment of neurologic status, postsurgical neurologic status, complications, and outcome. Ambulatory capacity was maintained or regained, and neurologic status improved by 1 grade (3 dogs), 2 grades (8), 3 grades (2), or 4 grades (2). Eleven dogs were considered free of disease. A seroma in 1 dog was the sole complication observed. Lateral corpectomy permits relatively easy removal of protruded-extruded disk material from within the vertebral canal in chronic disk disease without further iatrogenic injury to the spinal cord. Lateral corpectomy is an alternative to dorsal decompression for treatment of ventral and lateroventral thoracolumbar chronic disk disease in dogs.

Recovery of pelvic limb function in dogs following acute intervertebral disc herniations.

Chondrodystrophoid breeds of dog are prone to explosive herniation of mineralized disc material into the thoracolumbar spinal canal. The resulting acute spinal cord injury may represent an excellent spontaneous model of acute traumatic spinal cord injury. The aims of this study were to quantify the recovery of dogs following acute disc herniations, to evaluate external factors that influence recovery, and to identify a group of dogs suitable for use in clinical trials on neuroprotective drugs. The gait of 88 dogs with thoracolumbar disc herniations was scored at the time of injury and 2, 4, and 12 weeks after surgical decompression. Dogs were placed into four groups dependent on the severity of presenting signs; dogs in group 1 had the most severe injury severity. Group 1 dogs showed a variable but incomplete recovery by 12 weeks. Dogs in groups 2 and 3 recovered uniformly but more completely, while dogs in group 4 made a rapid and excellent recovery and were deemed unsuitable for clinical trials. Combining dogs in groups 1, 2 and 3 produced a population of dogs with incomplete recovery by 12 weeks. Power analysis revealed that 87 such dogs would be needed per treatment group to detect a 20% change in function with a power of 95%. The number needed reduced drastically to 19 by eliminating dogs in group 1, but this produced less room for functional improvement. External factors did not appear to influence outcome. We conclude that dogs with spontaneous disc herniations provide a useful model of acute spinal cord injury for clinical trials.

Symptoms of thoracolumbar junction disc herniation.

A retrospective clinical review of patients with thoracolumbar junction disc herniation. To evaluate the clinical features of thoracolumbar junction disc herniation and to prepare a chart for the level diagnosis in the neurologic findings and symptoms. Thoracolumbar junction disc herniations show a variety of signs and symptoms because of the complexity of the upper and lower neurons of the spinal cord, cauda equina, and nerve roots. Furthermore, much is still unknown about thoracolumbar junction disc herniations because of their rare frequency. The clinical features of 26 patients who had undergone operations for single disc herniations at T10-T11 through L2-L3 were investigated. Affected levels were as follows: 2 patients with disc herniation at T10-T11 disc, 4 patients at T11-T12, 3 patients at T12-L1, 6 patients at L1-L2, and 11 patients at L2-L3. The level of disc space of interest was confirmed with whole-spine plain roentgenograms. The caudal end of the cord was judged by magnetic resonance imaging and computed tomographic myelogram. Two patients with T10-T11 disc herniation showed moderate lower extremity weakness, increased patellar tendon reflex, and sensory disturbance of the entire lower extremities. Three of four patients with T11-T12 disc herniation experienced lower extremity weakness, and three patients had accentuated patellar tendon reflex. Sensory disturbance was observed in the anterolateral aspect of the thigh in one patient and on the entire leg in three patients. Bowel and bladder dysfunction was noted in three patients. In the T12-L1 disc herniation group (n = 3), muscle weakness and atrophy below the leg were advanced, and bowel and bladder dysfunction were also noted. Two of these three patients had bilateral drop foot, and one patient had unilateral drop foot; sensory disturbance was noted in the sole or foot and around the circumference of the anus, and the patellar tendon reflex and Achilles tendon reflex were absent. All six patients with L1-L2 disc herniation showed severe thigh pain and sensory disturbance at the anterior aspect or lateral aspect of the thigh. On the other hand, there were no clear signs of lower extremity weakness, muscle atrophy, deep tendon reflex, or bowel and bladder dysfunction in these patients. In the L2-L3 disc herniation group (n = 11), all patients had severe thigh pain and sensory disturbance of the anterior aspect or the lateral aspect of the thigh. Weakness in the quadriceps was noted in five patients and weakness in the tibialis anterior in two patients. Decreased or absence of patellar tendon reflex was observed in nine patients. Five patients had positive straight leg raising test results, and eight patients showed positive femoral nerve stretch test results. Among thoracolumbar junction disc herniations, T10-T11 and T11-T12 disc herniations were considered upper neuron disorders, T12-L1 disc herniations were considered lower neuron disorders, L1-L2 disc herniations were considered mild disorders of the cauda equina and radiculopathy, and L2-L3 disc herniations were considered radiculopathy. These findings had relatively distinct differences among herniated disc levels.

Chronic and acute compressive spinal cord lesions in dogs due to intervertebral disc herniation are associated with elevation in lumbar cerebrospinal fluid glutamate concentration.

Acute injury to the central nervous system initiates a series of biochemical events that cause secondary tissue damage. The accumulation of excessive concentrations of glutamate in the extracellular space causes excitotoxic damage, and is incriminated as a mediator of this secondary tissue damage. The aim of this study was to measure the concentration of glutamate in cerebrospinal fluid (CSF) obtained from the cerebellomedullary cistern and lumbar subarachnoid space in dogs with acute and chronic compressive injuries of the cervical and thoracolumbar spinal cord, and to correlate the glutamate concentration with injury severity. The results demonstrate that focal injuries of the spinal cord do not affect the glutamate concentration in CSF taken from the cerebellomedullary cistern. However, dogs with severe, acute thoracolumbar disc herniations have two- to 10-fold increases in glutamate concentration in their lumbar CSF at intervals of >12 h after injury. Moreover, the severity of their clinical signs is directly related to the glutamate concentration. Dogs with chronic compressive thoracolumbar lesions have a two-fold elevation of CSF glutamate concentration, suggesting that excitotoxicity may also be a component of chronic spinal cord compression.

Reoperative neurosurgery in dogs with thoracolumbar disc disease.

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. A retrospective case series. 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. 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. 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. 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.

Functional outcome in dogs after surgical treatment of caudal lumbar intervertebral disk herniation.

Caudal lumbar disk herniations (i.e., third lumbar [L3] to seventh lumbar [L7] intervertebral spaces) represent approximately 15% of surgically treated thoracolumbar disk herniations in dogs. A retrospective case-control study was conducted to determine the postoperative outcome of this subset of dogs in the authors' neurosurgical practice. Medical records (1985 through 1996) were reviewed for dogs with caudal lumbar disk herniation confirmed at surgery. Thirty-six cases were identified. For each case, two dogs that underwent surgical treatment for upper motor neuron thoracolumbar disk herniation (tenth thoracic [T10] to L3 intervertebral spaces) were selected as controls. Probabilities of functional recovery for cases and controls were 81% and 85%, respectively (p value of 0.49). In dogs with caudal lumbar disk herniation, complete sensorimotor loss was the only significant predictor of functional recovery (p value of 0.005). Disk herniations that occur at the thoracolumbar junction and those that occur in the caudal lumbar region should not be considered to be different in terms of surgical treatment and postoperative outcome. The lower motor neuron signs that often accompany caudal lumbar disk herniation reflect the site of spinal cord injury and do not necessarily predict a poor prognosis.

INTRAOPERATIVE SPINAL ULTRASONOGRAPHY IN DOGS: NORMAL FINDINGS AND CASE‐HISTORY REPORTS

Intraoperative spinal ultrasonography was performed in cervical and lumbar spine of 2 and 5 normal dogs, respectively, following ventral slot technique or dorsal or hemilamenectomy. The dura was hyperechoic, while the parenchyma was hypoechoic. The subarachnoid space was anechoic. An echogenic line was present in the center of the spinal cord, as seen in human. Pulsation of the spinal cord was noted during M‐mode imaging. Clinical findings of one dog with thoracolumbar disk herniation and one with thoracic vertebral fracture/subluxation confirmed the usefulness of intraoperative spinal ultrasonography for real time evaluation of spinal canal spatial abnormalities (mass lesion and degree of spinal cord compression on scanning planes) and spinal cord motion. Follow‐up ultrasound examinations were possible from 6 days postoperatively.

Investigations of the Therapeutig and Prophylactic Effects of Disc Evacuation in Cases of Thoraco-Lumbar Herniated Discs in Dogs

The author describes a method for the fenestration and evacuation of degenerated discs in the thoraco-lumbar region of the dog using a lateral approach. This lateral approach makes it possible to reach the entire area of the nucleus pulposus. With the method described, all of the discs in the region of T9/T10—L5/L6 can be evacuated at the same time. The author presents 88 operated cases which showed light or moderate signs of thoraco-lumbar disc herniation, i.e. dogs which displayed pain and/or varying grades of paresis, but retained the ability to walk on their hind legs. The author compares the results of this surgical treatment with the results of the conservative treatment of 128 cases. No significant difference in respect to the mean recovery time was seen between the 2 groups, but the progression of the attack into paraplegia did not occur in the surgically treated material, while such a progression was seen in 4 cases in the conservative material. The greatest value of the disc evacuation, according to the author's investigations, seems to be its prophylactic effect against recurrence. If all of the radiologically degenerated discs in the affected area are evacuated, it appears that one achieves almost complete prophylaxis for some years.