Diagnosis of Cauda Equina Abnormalities By Using Electromyography, Discography, and Epidurography in Dogs

Electromyography (EMG), L7-S1 discography and epidurography were investigated in 15 dogs with clinical signs of cauda equina dysfunction and in 7 control dogs without such clinical signs. Electromyography of paraspinal and pelvic limb muscles was done in 13 of 15 affected dogs. An L7-S1 discogram followed by an epidurogram was performed in all 22 dogs using 20% iopamidol. Results of discograms, epidurograms, and gross necropsy examinations were normal in six of seven control dogs. The one dog in which these studies were abnormal had a mild L7-S1 disc protrusion that did not result in nerve root compression at necropsy. Electromyographic analysis was 100% accurate in predicting the presence or absence of cauda equina disease. None of the results of discograms were falsely negative. Twelve of 15 discograms in clinically affected dogs indicated dorsal disc protrusion, but 2 of these protrusions were found to be noncompressive at surgery (13% error). Abnormal epidurograms occurred in 9 of 15 clinically affected dogs. There was one false positive and two false negatives (20% error). Electromyography was a sensitive screening technique for the presence of cauda equina disease. Discography may be more sensitive for detection of L7-S1 disc protrusion than epidurography. An abnormal radiographic contrast study of the cauda equina may only be useful when combined with an abnormal EMG.     

A SACRAL LESION RESEMBLING OSTEOCHONDROSIS IN THE GERMAN SHEPHERD DOG

More than 30% (21 of 65) of German Shepherd dogs with clinical signs of cauda equina compression had radiographic and pathologic abnormalities compatible with osteochondrosis of the sacral endplate. Most of these dogs had a defect in the dorsal part of the sacral endplate and a detached bone fragment in the vertebral canal. Similar lesions were also found in growing and young adult dogs without clinical signs. The dogs with clinical signs of cauda equina compression also had severe degenerative disc disease with protrusion of the lumbosacral disc and compression of the cauda equina, suggesting that the signs of cauda equina compression more likely were related to the secondary degenerative changes (disc protrusions) rather than the primary disease. Clinically normal German Shepherds with sacral osteochondrosis usually were younger than 18 months, the dogs with cauda equina compression and sacral osteochondrosis older than 18 months (mean age 4.8 years). On the average, these dogs were two years younger as compared to dogs with cauda equina compression without sacral osteochondrosis. Male dogs are more often affected than females (5:1). There is a breed predisposition: in dogs other than German Shepherds, osteochondrosis of the sacral endplate seems to be extremely rare.     

The diagnosis and treatment of cauda equina lesions in the dog

The case details of 46 dogs with cauda equina syndrome are reviewed. The causes were variable and included lumbosacral spondylosis, disc protrusion, discospondylitis, fractures, dislocations and neoplasia. Dogs with discospondylitis generally responded well to prolonged antibiotic therapy but the response to conservative treatment of lumbosacral spondylosis or disc protrusion was transient or incomplete. Ten dogs with cauda equina syndrome were treated surgically; the techniques are described and results presented.     

MAGNETIC RESONANCE IMAGING OF ARTICULAR PROCESS JOINT GEOMETRY AND INTERVERTEBRAL DISK DEGENERATION IN THE CAUDAL LUMBAR SPINE (L5–S1) OF DOGS WITH CLINICAL SIGNS OF CAUDA EQUINA COMPRESSION

The geometry of the lumbosacral region has been suspected to play a role in the development of degenerative lumbosacral stenosis in the dog. In this study, 50 dogs (21 German Shepherd dogs and 29 dogs of other breeds) with clinical signs of cauda equina compression were studied by magnetic resonance (MR) imaging. The orientation of the articular process joints in the L5-S1 region and the angle difference between two adjacent motion segments were calculated. Intervertebral disc degeneration of the same region was identified and classified in four stages. A positive association between MR-imaging stage and articular process joint angle difference in the transverse plane was found in the two groups of animals. German Shepherd dogs and dogs of other breeds had different geometry of the lumbosacral region with different articular process joint angles in the transverse plane and statistically different stages of disc degeneration.     

Synovial cysts associated with cauda equina syndrome in two dogs

OBJECTIVE: To report synovial cysts associated with cauda equina syndrome in 2 dogs. STUDY DESIGN: Clinical cases. ANIMALS: Two German Shepherd dogs. METHODS: After magnetic resonance imaging detection, cysts were surgically removed via dorsal laminectomy. RESULTS: Six and 8 months after surgery, both dogs were free of clinical signs and no pain was elicited on lumbosacral joint manipulation. CONCLUSION: Although described in dogs, cysts at the lumbosacral joint might cause compression of the cauda equina nerve roots. Radical excision of the cyst capsule can result in resolution of clinical signs. CLINICAL RELEVANCE: Synovial cysts should be considered in the differential diagnosis of dogs with cauda equina compression syndrome when lumbosacral degenerative joint disease is present.     

Measurements on the lumbosacral junction in normal dogs and those with cauda equine compression

Comparative measurements on lateral plain radiographs of the lumbosacral junction in neutral position, in flexion, and in extension, were made of 41 clinically and radiographically normal dogs (21 German shepherd dogs [GSDs], 12 Bernese mountain dogs, eight labrador retrievers) and 58 GSDs with clinical signs of cauda equina compression due to malformation and, or, malarticulation. The comparison of these measurements between sexes, between normal and affected GSDs and between normal GSDs and the two other breeds of dogs showed several statistically significant results. One was that the affected GSDs showed a reduced flexion ability at this junction compared to the normal ones. However, no difference was observed in the degree of sub-luxation of the sacrum between normal and affected GSDs. It was concluded that plain radiographs of the lumbosacral junction in flexion could help in determining a reduced flexion ability, which could be a characteristic of the GSD with cauda equina compression.     

Magnetic Resonance Imaging in the Diagnosis of Degenerative Lumbosacral Stenosis in Four Dogs

Magnetic resonance imaging was used to diagnose degenerative lumbosacral stenosis in four dogs that had physical and neurologic signs consistent with a cauda equina lesion. Nerve root displacement by protruding disc material and loss of epidural fat were identified. In all dogs, the diagnosis was confirmed by dorsal laminectomy of the lumbosacral area.     

MR-imaging of lumbosacral intervertebral disc degeneration in clinically sound German shepherd dogs compared to other breeds

German shepherd dogs are overrepresented in the group of dogs with cauda equina compression syndrome due to degenerative lumbosacral stenosis. A congenital predisposition for early degeneration of the lumbosacral intervertebral disc has been suspected. Our aims were to assess the morphologic appearance of the lumbosacral intervertebral disc and the lumbosacral junction in healthy German shepherd dogs compared to other breeds and to evaluate for an early onset of degenerative changes. The lumbosacral spine of 110 clinically sound German shepherd dogs and 47 healthy dogs of other large breeds was examined using magnetic resonance (MR) imaging. The degeneration of every intervertebral disc was graded using an established classification system. Signal intensity of the entire lumbosacral disc and the nucleus pulposus was determined independently. Lumbosacral malalignment was assessed according to a previously described method. The findings for the German shepherd dogs were compared to those of the other breeds. Although most dogs were younger than 18 months at the date of examination, significantly higher grades of degeneration were detected for the lumbosacral intervertebral disc of German shepherd dogs (P < 0.003). Degeneration of the lumbosacral intervertebral disc was independent from findings in the other lumbar discs. We conclude that the German shepherd dog has a predisposition for degenerative changes in the lumbosacral intervertebral disc.     

Asymmetrical, transitional, lumbosacral vertebral segments in six dogs: a characteristic spinal syndrome

Clinical findings in six dogs with asymmetrical, transitional, lumbosacral vertebral segments are reported. All dogs exhibited low back pain and varying degrees of asymmetrical cauda equina dysfunction. Results of myelography, epidurography, and magnetic resonance imaging (MRI) indicated a unilateral disk protrusion in all dogs. In the dogs with MRIs, focal degenerative alterations in the vertebral end plates and adjacent body of the vertebra were detected. All dogs were treated with a dorsal laminectomy or hemilaminectomy. Results following surgery were good or excellent in all six dogs.     

COMPARISON BETWEEN COMPUTED TOMOGRAPHIC AND SURGICAL FINDINGS IN NINE LARGE-BREED DOGS WITH LUMBOSACRAL STENOSIS

In a three-year prospective study, computed tomographic (CT) and surgical findings were compared for nine large breed dogs with lumbosacral stenosis. Surgically-excised tissue was examined histologically in seven dogs and additional necropsy evaluation was performed in one dog. The CT abnormalities observed at sites of confirmed cauda equina compression were: loss of epidural fat, increased soft tissue opacity, bulging of the intervertebral disc margin, spondylosis, thecal sac displacement, narrowed intervertebral foramen, narrowed vertebral canal, thickened articular process, articular process subluxation, articular process osteophyte, and telescoped sacral lamina. The CT characteristics of lumbosacral degenerative disease and discospondylitis were similar to those described in humans. In three dogs, CT findings at the site of cauda equina compression were consistent with congenital or developmental spinal stenosis, but the method of surgical exposure precluded confirmation. Epidural fibrosis (eight dogs) and multi-level CT abnormalities (six dogs) were identified but the cause(s) and significance were unknown.     

Association of cauda equina compression on magnetic resonance images and clinical signs in dogs with degenerative lumbosacral stenosis

Magnetic resonance imaging (MRI) was used to examine the lumbosacral spine of 27 dogs with degenerative lumbosacral stenosis. Four normal dogs were also similarly imaged. Compression of the soft-tissue structures within the vertebral canal at the lumbosacral space was assessed in two ways: by measuring dorsoventral diameter on T1-weighted sagittal images and cross-sectional area on transverse images. The severity of the clinical signs was compared to the severity of cauda equina compression. No significant correlation was found. It is concluded that degree of compression as determined by MRI at time of presentation is independent of disease severity.     

DISCOGRAPHY AND EPIDUROGRAPHY FOR EVALUATION OF THE LUMBOSACRAL JUNCTION IN DOGS WITH CAUDA EQUINA SYNDROME

Cauda equina syndrome in the dog is a common neurologic disorder caused by compression of the spinal cord, nerve roots and spinal nerves caudal to the fifth lumbar vertebra. This paper describes the clinical signs, radiographic findings of discography and/or epidurography, and comparison with surgery or necropsy of 21 dogs with cauda equina syndrome. Discograms were performed by using a 20- or 22-gauge spinal needle introduced in a sagittal plane into the lumbosacral (LS) disc space under fluoroscopic guidance. Epidurograms were performed following discography by injecting contrast medium after repositioning the tip of the needle into the ventral epidural space at the level of the LS junction. Direct examination of the LS junction was performed in all dogs by surgical exploration and/or necropsy. On survey radiographs, the most common findings were spondylosis, malalignment of the sacrum to the last lumbar vertebra, collapse of the LS disc space, stenosis of the vertebral canal at the LS junction, and transitional vertebral segments. Discography was considered of diagnostic quality in 19/21 (90%) of the dogs, showing disc protrusion in 14/21 (67%). Epidurography was of diagnostic quality in 18/18 (100%) dogs, showing abnormal findings in 14/18 (78%). No adverse reaction was noted to the radiographic procedure when dogs were allowed to recover from anesthesia before surgery. Based on macroscopic findings, combination of survey radiographs and disco-epidurography was correctly positive in 16/18 dogs (89%). It is concluded that discography associated with epidurography is a valuable procedure for evaluation of the LS junction in the dog. A combination of both procedures reduces the possibility of technical artifacts by outlining both sides of the compressive lesion, i.e., the disc and the epidural space.     

Force plate analysis before and after dorsal decompression for treatment of degenerative lumbosacral stenosis in dogs

OBJECTIVE: Using force plate analysis (FPA), determine ground reaction forces in dogs with degenerative lumbosacral stenosis (DLS) and evaluate the effects of lumbosacral decompressive surgery. STUDY DESIGN: Prospective clinical study. ANIMALS: Twelve dogs with DLS. METHODS: DLS was diagnosed by clinical signs, radiography, computed tomography, and/or magnetic resonance imaging. FPA was performed before surgery, and 3 days, 6 weeks, and 6 months after surgery. The mean peak braking (Fy+), peak propulsive (Fy-), and peak vertical (Fz+) forces of 8 consecutive strides were determined. The ratio between the total Fy- of the pelvic limbs and the total Fy- of the thoracic limbs (P/TFy-), reflecting the distribution of Fy-, was analyzed to evaluate any changes in locomotion pattern postoperatively. Ground reaction force data for DLS dogs were compared with data derived from 24 healthy dogs (control). RESULTS: In dogs with DLS, the propulsive forces (Fy-) of the pelvic limbs were significantly smaller than those of controls. P/TFy- was significantly smaller in dogs with DLS than in control dogs, and increased during the follow-up period, reaching normal values 6 months after surgery. CONCLUSIONS: Cauda equina compression in dogs with DLS decreases the propulsive force of the pelvic limbs and surgical treatment restores the propulsive force of the pelvic limbs in a 6-month period. CLINICAL RELEVANCE: In dogs with DLS, FPA is an effective method in evaluating the response to surgical treatment. Normal propulsive force in the pelvic limbs was restored during 6 months after decompressive surgery.     

Tibial nerve somatosensory evoked potentials in dogs with degenerative lumbosacral stenosis

OBJECTIVE: To determine somatosensory evoked potentials (SEPs) in dogs with degenerative lumbosacral stenosis (DLS) and in healthy dogs. STUDY DESIGN: Clinical and experimental study. ANIMALS: Dogs with DLS (n = 21) and 11 clinically normal dogs, age, and weight matched. METHODS: Under anesthesia, the tibial nerve was stimulated at the caudolateral aspect of the stifle, and lumbar SEP (LSEP) were recorded percutaneously from S1 to T13 at each interspinous space. Cortical SEP (CSEP) were recorded from the scalp. RESULTS: LSEP were identified as the N1-P1 (latency 3-6 ms) and N2-P2 (latency 7-13 ms) wave complexes in the recordings of dogs with DLS and control dogs. Latency of N1-P1 increased and that of N2-P2 decreased as the active recording electrode was moved cranially from S1 to T13. Compared with controls, latencies were significantly delayed in DLS dogs: .8 ms for N1-P1 and 1.7 ms for the N2-P2 complex. CSEP were not different between groups. CONCLUSIONS: Surface needle recording of tibial nerve SEP can be used to monitor somatosensory nerve function of pelvic limbs in dogs. In dogs with DLS, the latency of LSEP, but not of CSEP, is prolonged compared with normal dogs. CLINICAL RELEVANCE: In dogs with lumbosacral pain from DLS, the cauda equina compression is sufficient to affect LSEP at the lumbar level.     

Facet joint geometry and intervertebral disk degeneration in the L5-S1 region of the vertebral column in German Shepherd dogs

OBJECTIVE: To evaluate the possible association between facet joint geometry and intervertebral disk degeneration in German Shepherd Dogs. ANIMALS: 25 German Shepherd Dogs and 11 control dogs of similar body weight and condition. PROCEDURE: Facet joint angles in the caudal portion of the lumbar region of the vertebral column (L5-S1) were measured by use of computed tomography, and the intervertebral discs were evaluated microscopically. The relationship between facet joint geometry and disk degeneration was evaluated by use of statistical methods. RESULTS: German Shepherd Dogs had significantly more facet joint tropism than control dogs, but an association with disk degeneration was not found. However, German Shepherd Dogs had a different facet joint conformation, with more sagittally oriented facet joints at L5-L6 and L6-L7 and a larger angle difference between the lumbar and lumbosacral facet joints, compared with control dogs. CONCLUSIONS AND CLINICAL RELEVANCE: A large difference between facet joint angles at L6-L7 and L7-S1 in German Shepherd Dogs may be associated with the frequent occurrence of lumbosacral disk degeneration in this breed.     

A REVIEW OF IMAGING TECHNIQUES FOR CANINE CAUDA EQUINA SYNDROME

There are many imaging modalities available for evaluating the canine lumbosacral region. These include conventional radiography, stress radiography, myelography, epidurography, transosseous and intravenous venography, discography, linear tomography, computed tomography, and magnetic resonance imaging. Myelography, epidurography and discography are commonly used, but often lack sensitivity. Myelography is of little value when evaluating the cauda equina because the dural sac is elevated from the vertebral canal floor and frequently ends before the lumbosacral junction. Epidurography will identify a ventrally located compressive lesion and discography can delineate the dorsal extent of the diseased disc; however, both are sometimes difficult to interpret. Therefore, more than one of these imaging techniques must be used in order to make a diagnosis. Computed tomography and magnetic resonance imaging have become valuable in evaluating the lumbosacral region in dogs. These modalities have proven to be both sensitive and specific for determining cauda equina compression in both humans and in dogs.     

Transitional lumbosacral vertebral anomaly in the dog: a radiographic study

Transitional lumbosacral vertebral anomalies have for some time been suggested as a possible cause of cauda equina syndrome (especially in the German shepherd dog [GSD]), a condition recently thought to be inherited. The frequency of this condition within a large clinical population and the radiographic features used in its detection are reported. In a group of 143 patients, the sexes were similarly represented and the GSD was greatly overrepresented. The anomaly is characterised by separation of the first sacral segment that was identified on the lateral view by the presence of a radiolucent disc space between what are normally the first and second sacral segments. On the ventrodorsal view, the anomaly was characterised by separation of the spinous processes between what are normally the first and second sacral segments. In the presence of the transitional segment, the nature of the sacroiliac joint at the level of the anomalous segment varies from a strong ilial attachment, with the presence of a wing-like lateral process, to a weakened ilial attachment because of the presence of a lateral process, shaped as that seen on a lumbar segment. These patterns were present unilaterally or bilaterally and result in symmetrical or asymmetrical patterns. The effect of the weakening of the sacroiliac attachment was thought to result in premature disc degeneration, which, together with spinal canal stenosis, resulted in potential compression of the overlying spinal nerves and creation of a cauda equina syndrome. The condition is thought to have clinical significance and should be selected against in breeding, especially in the GSD.     

Predictors of outcome after dorsal decompressive laminectomy for degenerative lumbosacral stenosis in dogs: 69 cases (1987-1997)

OBJECTIVE: To identify predictive factors of long-term outcome after dorsal decompressive laminectomy for the treatment of degenerative lumbosacral stenosis (DLSS) in dogs. DESIGN: Retrospective study. SAMPLE POPULATION: 69 client-owned dogs. PROCEDURE: Medical records of dogs that had undergone dorsal laminectomy at North Carolina State University and the University of Tennessee between 1987 and 1997 were reviewed. Dogs with diskospondylitis, traumatic lesions, or neoplasia of the lumbosacral region were excluded. All dogs had evidence of cauda equina compression on myelography, epidurography, computed tomography, or magnetic resonance imaging, along with subsequent confirmation of the lesion at surgery. Follow-up was performed by telephone inquiries to the referring veterinarian, the owner, or both, using a detailed questionnaire. RESULTS: The outcome was excellent or good in 54 of 69 (78%) dogs over a mean follow-up period of 38+/-22 months. Five of these 54 dogs had been incontinent for a median of 2 weeks prior to surgery. Six of the 15 dogs with a poor outcome had been incontinent for a median of 8 weeks before surgery. A significant correlation was detected between the presence of urinary and fecal incontinence prior to surgery and outcome. When duration of signs was considered, urinary incontinence was the only variable that significantly affected outcome. CONCLUSIONS AND CLINICAL RELEVANCE: Decompressive laminectomy is an effective treatment for DLSS, although dogs with urinary or fecal incontinence have a worse prognosis than dogs that are continent before surgery. Chronic urinary incontinence is a predictor of poor outcome for dogs with DLSS.     

The lumbosacral junction in working german shepherd dogs -- neurological and radiological evaluation

The clinical and radiological incidence of lumbosacral (LS) disease was studied on 57 German Shepherd dogs (GSDs) used in active service. The study included a clinical history, a neurological examination, and plain radiographs of the caudal lumbar vertebrae. The neurological examinations revealed lower back pain and/or neural deficits in 21 dogs, of which 14 had a history of pain or pelvic gait abnormalities. Radiographic findings were spondylosis at L7-S1, degeneration of L7-S1 disc, LS malalignment, transitional LS vertebrae and/or primary spinal canal stenosis in 15 dogs with neurological abnormalities and/or back pain and in 18 dogs with no clinical signs. No correlation between the neurological and the radiographic findings were found. This study demonstrates that even prominent radiographic LS abnormalities are of minimal value in the evaluation of LS disease in the GSD.     

FLEXION-EXTENSION MYELOGRAPHY OF THE CANINE CAUDA EQUINA

The radiographic appearance of the canine dural end-sac and its behavior during flexion and extension of the spine is described in a myelographic study in 22 normal dogs and 26 dogs with cauda equina compression syndrome. In more than 80% of the dogs, the dural sac ended at the level of the sacrum. There were relatively large individual differences in shape and size of the dural end-sac. In contrast, shape, length, position, and diameter of the dural end-sac at the level of the lumbosacral articulation is extremely constant during flexion and extension in normal individuals. In the 26 dogs with lesions affecting the cauda equina and nerve roots between L6 and the first caudal vertebra, myelography was diagnostic in 21 dogs. Myelographic diagnosis of cauda equina compression was possible in seven dogs with spine in flexion. In 14 dogs, overextension of the spine and imaging in lateral and dorsal recumbency was necessary to establish a diagnosis. The five dogs with nondiagnostic myelograms had either a dural end-sac ending cranially to the lesion (two dogs), diseases not associated with compression (two dogs), or only slight indentations of the contrast medium column (one dog).