Magnetic resonance imaging in the diagnosis of degenerative lumbosacral stenosis in four dogs

Transitional lumbosacral vertebrae in black Norwegian elkhound and Brittany dogs: Clinical findings and its association with degenerative lumbosacral stenosis

BACKGROUND

Lumbosacral transitional vertebra (LTV) is a congenital anomaly in dogs and have been proposed to be associated with cauda equina syndrome (CES) in German Shepherd dogs. This prospective study, including 32 dogs from two breeds, aims to investigate if LTV is associated with lower back pain in dogs. The study compared owners' assessment of their dogs' well-being and clinical evaluation with advanced diagnostic imaging to identify changes that might explain clinical findings.

RESULTS

Dogs with LTV type 2 (57.0%) and with LTV type 3 (70.0%) exhibited mild lower back pain, which was significantly more frequent (P = 0.012) compared to dogs with LTV type 0 and LTV type 1. Advanced diagnostic imaging identified a plausible cause for this pain. Dogs diagnosed with LTV types 2 and 3 with lower back pain tended to be lighter (median 14.50 kg) and younger (median 4.10 years) than breeds typically reported for degenerative lumbosacral stenosis (DLSS). Based on the owners' assessment of their dogs, they considered them pain-free.

CONCLUSIONS

The study identified a correlation between LTV types 2 and 3 and lower back pain in these dog breeds. Advanced diagnostic imaging findings confirmed that dogs with these LTV types were more likely to exhibit pathological changes associated with DLSS.

Neurogenic Bladder in Dogs, Cats and Humans: A Comparative Review of Neurological Diseases

Lower urinary tract disease (LUTD) includes abnormalities in the structure and function of the bladder and the urethra. LUTD caused by neurological disease is defined neurogenic bladder (NB). The integrity of the central nervous system (CNS) and peripheral nervous system (PNS) is required to explicate normal micturition, maintaining the proper function of bladder and urethra. The location and type of neurological lesions influence the pattern of clinical manifestations, potential treatment, and prognosis. Though, in dogs and cats, spinal cord injury is considered mainly responsible for bladder and/or urethra incompetence, other disorders, congenital or acquired, involving CNS or PNS, could play a role in NB. In veterinary medicine, the information about the epidemiology, prevalence, etiopathogenesis, diagnosis and treatment of NB are scattered. The aim of this study is to provide an overview of the epidemiology, prevalence, clinical findings, diagnosis and prognosis for NB in dogs and cats compared with humans.

Evaluation of L7-S1 nerve root pathology with low-field MRI in dogs with lumbosacral foraminal stenosis

OBJECTIVE

To describe low-field MRI findings associated with lumbosacral foraminal stenosis and radiculopathy and correlate these with clinical signs.

STUDY DESIGN

Retrospective study.

ANIMALS

Client-owned dogs (n = 240) that underwent a clinical examination and standardized MRI protocol of the lumbosacral junction.

METHODS

Medical records of dogs with degenerative lumbosacral stenosis with neurological clinical evaluation and MRI of the lumbosacral junction were used to describe imaging pathologies and relate them to clinical status.

RESULTS

In total, 480 L7 neuroforamina were evaluated. A loss of foraminal fat signal was identified in 364 of 480 neuroforamina of which 87.9% (n=320) showed also concurrent nerve root changes. Magnetic resonance imaging features of L7 radiculopathy included nerve root enlargement and hyperintensity to surrounding connective tissue in dorsal oblique gradient echo short time inversion recovery sequences and specific changes in shape, size, or position of the nerve root in transverse T1-weighted sequences. Radiculopathy was noted as a consequence of either circumferential (entrapment) or focal (impingement) foraminal stenosis. Lateral vertebral spondylotic and intervertebral facet joint changes were the most common underlying spinal and neuroforaminal pathologies. Clinical signs were present in the ipsilateral hind leg in 85% (n = 65) of dogs with unilateral lumbosacral imaging findings.

CONCLUSION

A loss of foraminal fat signal was likely to be associated with L7 radiculopathy and foraminal stenosis. Unilateral lesions were generally associated with clinical signs on the ipsilateral limb.

CLINICAL SIGNIFICANCE

Loss of foraminal fat signal revealed by low-field MRI should prompt the assessment of concurrent radiculopathy and underlying stenosis, and in coherence with clinical findings, when is combined with clinical findings, improves the diagnosis of lumbosacral foraminal stenosis.

Lumbosacral foraminal ratios and areas using MRI in medium-sized dogs

Objective: To examine conventional magnetic resonance imaging planes of the lumbosacral foramina to obtain objective measurements of foraminal size in mediumsized (20–28 kg) normal dogs.

Method: Ten canine cadavers were evaluated using magnetic resonance imaging in neutral, flexed and extended position. Foraminal ratios, areas and lumbosacral angles were calculated and their relationship to body weight was evaluated.

Results: Foraminal ratios were found to be independent of body weight in medium sized dogs (p >0.42). Foraminal areas were dependent on body weight (p <0.05). Flexion and extension were shown to significantly change both the foraminal ratio and area.

Clinical significance: Lumbosacral foraminal stenosis is common in working dogs. Foraminal ratios were evaluated in mediumsized dogs and were found to be independent of body weight, which may provide objective evaluation of surgical decompression techniques if calculated pre- and post-surgery. Foraminal areas were not independent of body weight.

Agreement between computed tomography, magnetic resonance imaging, and surgical findings in dogs with degenerative lumbosacral stenosis

OBJECTIVE

To assess the extent of agreement between computed tomography (CT), magnetic resonance imaging (MRI), and surgical findings in dogs with degenerative lumbosacral stenosis.

DESIGN

Observational study.

ANIMALS

35 dogs with degenerative lumbosacral stenosis.

PROCEDURES

Results of preoperative CT and MRI were compared with surgical findings with respect to degree and location of disk protrusion, position of the dural sac, amount of epidural fat, and swelling of spinal nerve roots.

RESULTS

A lumbosacral step was seen on radiographic images from 22 of 32 (69%) dogs, on CT images from 23 of 35 (66%) dogs, and on MR images from 21 of 35 (60%) dogs. Most dogs had slight or moderate disk protrusion that was centrally located. There was substantial or near perfect agreement between CT and MRI findings in regard to degree of disk protrusion (kappa, 0.88), location of disk protrusion (0.63), position of the dural sac (0.89), amount of epidural fat (0.72), and swelling of spinal nerve roots (0.60). The degree of agreement between CT and surgical findings and between MRI and surgical findings was moderate in regard to degree and location of disk protrusion (kappa, 0.44 to 0.56) and swelling of spinal nerve roots (0.40 and 0.50).

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicate that there is a high degree of agreement between CT and MRI findings in dogs with degenerative lumbosacral stenosis but that the degree of agreement between diagnostic imaging findings and surgical findings is lower.

Magnetic resonance imaging findings in dogs with thoracolumbar intervertebral disk disease: 69 cases (1997-2005)

OBJECTIVE

To determine magnetic resonance imaging (MRI) abnormalities in dogs with intervertebral disk disease (IVDD) and develop a classification scheme for IVDD in dogs based on MRI findings.

DESIGN

Retrospective case series.

ANIMALS

69 dogs.

PROCEDURE

Medical records of dogs admitted because of thoracolumbar IVDD in which MRI of T9 through L7 had been performed were reviewed.

RESULTS

A total of 759 intervertebral disk spaces were examined. Of these, 342 (45.1%) were classified as having a normal MRI appearance; the remaining 417 (54.9%) had various types of IVDD. Disk degeneration was identified in 276 disk spaces in 56 dogs, bulging of the intervertebral disk was identified in 37 disk spaces in 24 dogs, disk protrusion was identified in 54 disk spaces in 32 dogs, and disk extrusion was identified in 50 disk spaces in 48 dogs. Cartilage endplate changes were identified in 35 vertebrae in 17 dogs, and increased signal intensity of the spinal cord was identified in 21 dogs.

CONCLUSIONS AND CLINICAL RELEVANCE

Four types of IVDD (disk degeneration, bulging of the intervertebral disk, disk protrusion, and disk extrusion) were identified on the basis of MRI findings in dogs with thoracolumbar IVDD. We recommend that a standardized nomenclature be adopted for the various types of thoracolumbar IVDD in dogs.

LOW-FIELD MAGNETIC RESONANCE IMAGING OF BONE MARROW IN THE LUMBAR SPINE, PELVIS, AND FEMUR IN THE ADULT DOG

The purpose of this study was to describe the appearance of normal bone marrow in seven adult dogs using low-field (0.3T) magnetic resonance (MR) imaging. The areas imaged included the lumbar spine, pelvis, and femur. T1-weighted, fast spin-echo T2-weighted, and short tau (T1) inversion recovery (STIR) sequences were obtained at all locations. Histopathology was performed on sections from the sixth lumbar vertebral body, the wing of the ilium, and the femur (head and neck, mid-diaphysis, and condyle) for evaluation of cellularity and fat content. The lumbar spine and pelvic marrow MR images were similar in all dogs. The lumbar vertebral bone marrow was uniform, intermediate signal intensity, and isointense to muscle on all sequences. There was variation between dogs in the bone marrow distribution with MR imaging of the femur. In the proximal and mid-diaphysis of the femur there was patchy high-signal intensity on T1- and T2-weighted images, and hypointense foci on the STIR images. The distal femoral metaphysis had a variable pattern ranging from intermediate-to-high signal on T1- and T2-weighted images and intermediate-to-low signal on STIR images. The femoral condyles were uniformly high signal on T1- and T2-weighted images and hypointense on STIR images. Histopathologically there was a normal variation in the bone marrow cellularity. The marrow was normocellular (25-75% cellularity) for all sites examined except the femoral condyles, which were hypocellular (<25% cellularity).

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.

Magnetic resonance imaging in the diagnosis and surgical management of sacral osteochondrosis in a mastiff dog

The clinical, radiographic, magnetic resonance imaging (MRI), surgical and pathological findings related to an osteochondral lesion of the sacrum in a mastiff dog are described. The dog showed chronic signs of pain in its pelvic limbs. Radiography revealed a triangular mineralised opacity at the craniodorsal aspect of the sacrum consistent with sacral osteochondrosis. A T2-weighted spin-echo MRI revealed dorsal and lateral compression of the cauda equina. The osteochondral fragment was removed via a dorsal laminectomy, and the clinical signs resolved. Histological abnormalities in the fragment were consistent with a diagnosis of osteochondrosis.

Endoscopic-Assisted Lumbosacral Foraminotomy in the Dog

OBJECTIVE

To determine if endoscopic-assisted foraminotomy significantly increased the area of the L7-S1 intervertebral foramen and if, over 12 weeks, stenosis would occur.

STUDY DESIGN

Prospective, experimental study.

ANIMAL POPULATION

Six clinically normal, 22-29 kg, adult dogs.

METHODS

Using endoscopic assistance, unilateral L7-S1 foraminotomy was performed. Computed tomography of L7-S1 was performed preoperatively, immediately postoperatively, and at 12 weeks. Parasagittal foramen area (PFA) measurements were obtained at the entry, middle, and exit zones of the treated and control foramen for each period. Objective and subjective data were compared among dogs by time period and treatment status.

RESULTS

Endoscopic-assisted foraminotomy resulted in a significant increase in the mean PFA of the entry and middle zones immediately postoperatively. The exit zone was not significantly larger at any time. The foramen remained significantly larger at 12 weeks only in the middle zone; however, some decrease in the surgically created foramen enlargement occurred at all 3 levels. The procedure was well tolerated but dogs did have transient, mild delay of functional return postoperatively.

CONCLUSIONS

Endoscopic-assisted foraminotomy in dogs can be performed for certain foraminal regions, allowing enhanced visibility of the spinal canal. The foramen can be surgically enlarged at the entry and middle zones using this technique; however, some reduction of the foraminal enlargement occurs by 12 weeks. The clinical implications of this reduction cannot be determined from this study.

CLINICAL RELEVANCE

Endoscopic-assisted foraminotomy could be used to improve intraoperative visualization in dogs with foraminal stenosis as a component of degenerative lumbosacral stenosis.

Three-dimensional motion pattern of the caudal lumbar and lumbosacral portions of the vertebral column of dogs

OBJECTIVE

To evaluate the 3-dimensional motion pattern including main and coupled motions of the caudal lumbar and lumbosacral portions of the vertebral column of dogs.

ANIMALS

Vertebral columns of 9 German Shepherd Dogs (GSDs) and 16 dogs of other breeds with similar body weights and body conditions.

PROCEDURE

Main and coupled motions of the caudal lumbar and lumbosacral portions of the vertebral column (L4 to S1) were determined by use of a testing apparatus that permitted precise application of known pure moments to the vertebral column. Motion was compared between GSDs and dogs of other breeds.

RESULTS

All specimens had a similar motion pattern consisting of main motion and a certain amount of coupled motion including translation. Vertebral columns of GSDs had significantly less main motion in all directions than that of dogs of other breeds. Translation was similar in GSDs and dogs of other breeds and was smallest at the lumbosacral motion segment.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that motion in the caudal lumbar and lumbosacral portions of the vertebral column of dogs is complex and provided a basis for further studies evaluating abnormal vertebral columns.

Staging of lumbar intervertebral disc degeneration in nonchondrodystrophic dogs using low-field magnetic resonance imaging

Recognition of disc degeneration in vivo is important in the investigation of the pathophysiology of intervertebral disc disease as well as the assessment of patients. The purpose of this study was to compare low-field magnetic resonance imaging and histopathologic findings of disc degeneration in the canine caudal lumbar spine. A simple four-stage classification system for disc degeneration is proposed. Most common signs of disc degeneration in magnetic resonance imaging included nuclear clefts, decreased signal intensity of the nucleus pulposus and tears of the annulus fibrosus, or disc herniations. The association between magnetic resonance images and histopathologic findings was highly significant. A sensitivity of 100% and specificity of 79% for magnetic resonance imaging was calculated using histopathology as the gold standard.

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.

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.

Comparison of fast spin-echo and conventional spin-echo magnetic resonance spinal imaging techniques in four normal dogs

Various magnetic resonance (MR) imaging techniques have been used to assess lumbar spinal abnormalities in people. Four, young adult, clinically normal dogs were used to compare images of the spinal cord acquired using conventional spin-echo and rapid acquisition relaxation-enhanced (RARE), commonly called fast spin-echo (FSE), magnetic resonance imaging techniques. Lateral myelograms were made as an anatomic control. The T2-weighted FSE technique was characterized by better image quality than the T2-weighted conventional spin-echo technique. The short acquisition time with the FSE technique allowed increases in the matrix size and number of excitations, thus improving resolution and signal-to-noise ratio. In canine lumbar spinal MR imaging, use of a FSE technique is recommended to reduce the overall time for imaging and to improve image quality.

Association between postoperative outcome and results of magnetic resonance imaging and computed tomography in working dogs with degenerative lumbosacral stenosis

OBJECTIVE

To determine whether results of magnetic resonance imaging (MRI) and computed tomography (CT) are associated with postoperative outcome in working dogs with degenerative lumbosacral stenosis.

DESIGN

Prospective cohort study.

ANIMALS

12 dogs treated surgically for degenerative lumbosacral stenosis.

PROCEDURE

The lumbosacral vertebral column was examined before surgery by use of MRI and CT and after surgery by use of CT. Outcome, based on performance in standardized training exercises, was assessed 6 months after decompressive surgery. Associations between imaging results and postoperative outcome were determined by use of a Fisher exact test and logistic regression.

RESULTS

None of the dogs were able to perform their duties before surgery. By 6 months after surgery, 8 of 12 dogs had been returned to full active duty. Nerve tissue compression was effectively localized by use of CT and MRI. Significant associations between results of imaging studies and postoperative outcome were not identified.

CONCLUSIONS AND CLINICAL RELEVANCE

Surgical intervention is justified in high-performance working dogs with degenerative lumbosacral stenosis. However, results of imaging studies may be less important than clinical or surgical factors for predicting outcome in affected dogs.

Magnetic resonance, computed tomographic and radiologic findings in a dog with discospondylitis

Magnetic resonance (MR), computed tomographic and radiographic imaging were conducted in a dog with discospondylitis. The MR findings were increased T2 and decreased T1 signal intensity of the soft tissues ventral to vertebral bodies, the end plates of the same vertebral bodies and the intervertebral disc, and are similar to those described in human with discospondylitis.

Degenerative lumbosacral stenosis

This article reviews the management of degenerative lumbosacral stenosis. Degenerative lumbosacral stenosis occurs when soft tissue and bony changes, possibly in conjunction with abnormal motion of the lumbosacral joint, impinge on the nerve roots or vasculature of the cauda equina. It occurs most frequently in middle-aged dogs of medium to large breed, especially the German Shepherd dog. Common signs are lumbosacral pain, lameness, pelvic limb weakness and ataxia, and urinary incontinence. Diagnosis is based on clinical features and imaging studies. Decompressive surgery is effective in most patients.

The spine

Computed tomography (CT) and magnetic resonance imaging (MRI) are becoming increasingly accessible in veterinary medicine. Because of their ability to image the bony spine and spinal cord noninvasively and with exceptional detail, these techniques have revolutionized the way spinal disorders are diagnosed in both people and animals. Although the veterinary literature on this topic is limited, interpretation of CT and MR images of the spine are facilitated by the similarity of human and animal disease processes. This article provides an overview of imaging strategies, normal anatomy, and the CT and MRI features of degenerative, infectious, neoplastic, and vascular diseases of the spine.

The advantage of magnetic resonance imaging in diagnosis of cauda equina syndrome in dogs

Three dogs were evaluated in our study using magnetic resonance imaging (MRI) to reveal the anatomical deformity and the degree of the lesion of cauda equina. In all dogs, MRI revealed soft tissue, such as cauda equina, epidural fat, and intervertebral disc, at the lumbosacral region clearly without contrast medium. Our results suggest that MRI has some advantages in evaluating cauda equina syndrome in dogs.

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.

Magnetic resonance imaging of presumptive lumbosacral discospondylitis in a dog

A three-year-old male Boxer dog had hyperesthesia, symmetrical epaxial, gluteal and hind limb muscular atrophy and rear limb ataxia. Neurological deficits included decreased conscious proprioception of the left hind limb, decreased withdrawal and increased patellar reflexes of both hind limbs. The dog had a urinary tract infection with positive culture for Staphylococcus intermedius. On survey radiography of the lumbosacral spine there was active bone proliferation spanning the L7 S1 intervertebral disc space with an epidural filling defect at the ventral aspect of the vertebral canal on epidurography. On magnetic resonance imaging (MRI), findings were similar to those described for human diskospondylitis including altered signal intensity and nonuniform contrast enhancement of the L7-S1 intervertebral disc, adjacent vertebral end plates and epidural and sublumbar soft tissues. Although skeletal radiography is usually sufficient to reach a diagnosis of discospondylitis, MRI of this patient made it possible to reach a presumptive diagnosis of discospondylitis prior to development of definitive radiographic abnormalities.

Common neurologic diseases of older animals

Of the various neurologic diseases that affect dogs and cats, some are more often encountered in older animals. Physical diagnosis may be challenging, as multiple disease processes that may minic neurologic disease can be present in the same animal. A diligent, complete neurologic examination should lend for an accurate neuroanatomical diagnosis. Once a level of involvement is determined, knowledge of diseases affecting the particular area of the nervous system will provide for appropriate diagnosis, treatment, and prognosis. Although neurologic diseases are still often devastating, successful management of many of these diseases will afford better quality of life during the geriatric years.