Urologic changes after cauda equina compression in dogs

Effects of body position, imaging plane, and observer on computed tomographic measurements of the lumbosacral intervertebral foraminal area in dogs

OBJECTIVE

To evaluate effects of imaging plane, flexion and extension, patient weight, and observer on computed tomographic (CT) image measurements of the area of the lumbosacral (L7-S1) intervertebral foramen (LSIF) in dogs.

SAMPLE

12 dog cadavers (2 were excluded because of foraminal stenosis).

PROCEDURES

In each cadaver, sagittal, sagittal oblique, transverse oblique, and double oblique CT images were obtained at 3 zones (entrance, middle, and exit zones) of the region of the lateral lumbar spinal canal that comprises the LSIF while the lumbosacral junction (LSJ) was positioned in flexion or extension. Barium-impregnated polymethylmethacrylate was used to fill the intervertebral foramina to aid boundary detection. Measurements of interest were obtained.

RESULTS

Among the dog cadavers, there was large variability in LSIF cross-sectional areas (range, 0.12 to 0.44 cm2; SD, 0.1 cm2) and in foraminal angles required to obtain a double oblique plane in LSJ extension (SD, 8 ° to 9 °). For LSIF area measurements in standard sagittal CT images, interobserver variability was 23% to 44% and intraobserver variability was 4% to 5%. Sagittal oblique images obtained during LSJ extension yielded smaller mean LSIF areas (0.30 cm2), compared with findings in sagittal images (0.37 to 0.52 cm2). The exit and middle zone areas were smaller than the entrance zone area in sagittal images obtained during LSJ extension.

CONCLUSIONS AND CLINICAL RELEVANCE

Repeated measurements of the LSIF area in images obtained during LSJ extension may be unreliable as a result of interobserver variability and the effects of dog positioning and CT slice orientation.

Cauda equina syndrome: factors affecting long-term functional and sphincteric outcome

STUDY DESIGN

Retrospective cohort study with prospective clinical follow-up.

OBJECTIVE

To determine the factors that influence outcome after surgery for cauda equina syndrome (CES).

SUMMARY OF BACKGROUND DATA

CES is a rare but serious consequence of lumbar disc prolapse and can have devastating long-lasting neurologic consequences. The timing of surgical decompression remains controversial.

METHODS

Fifty-six patients with evidence of a sphincteric disturbance who underwent urgent surgery were identified and invited to follow-up. The outcome measures comprised history and examination and several validated self-assessment questionnaires.

RESULTS

Forty-two patients (78%) attended with a mean follow-up of 60 months (range, 25-114 months). Mean age at onset was 41 years (range, 24-67 years) with 23 males and 19 females. Twenty-six patients were operated on within 48 hours of onset of sphincteric symptoms; 5 of these were within 24 hours. Acute onset of sphincteric symptoms and the time to operation did not influence the outcomes. Leg weakness at onset persisted in a significant number of patients at follow-up (P < 0.005). Urinary disturbance at presentation did not affect the outcomes. At follow-up, significantly more females had urinary incontinence (P < 0.005). Bowel dysfunction at presentation was associated with sexual problems at follow-up (P < 0.005). The 13 patients who failed their post operative trial without catheter had worse outcomes. The SF-36 scores at follow-up were reduced compared with age-matched controls in the population. The mean ODI was 29, Low Back Outcome Score 42, and VAS 4.5. The time elapsed from operation to follow-up was not found to influence the outcomes.

CONCLUSIONS

In our series, the symptom duration before operation and the speed of onset do not affect the outcome more than 2 years after surgery. Based on the SF-36, ODI, and Low Back Outcome Scores, patients who have had CES do not return to a normal status.

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.

Clinical and radiologic features of lumbar spinal stenosis and disc herniation with neuropathic bladder

STUDY DESIGN

Clinical and radiologic findings of patients with lumbar spinal stenosis and lumbar disc herniation presenting with neuropathic bladder were prospectively analyzed.

OBJECTIVES

To study the relationship between the degree of cauda equina compression and prevalence of neuropathic bladder in patients with lumbar spinal stenosis and lumbar disc herniation.

SUMMARY OF BACKGROUND DATA

Bladder dysfunction has frequently been noted in patients with lumbar spinal stenosis and lumbar disc herniation. However, there have been few studies that have demonstrated the correlation between bladder function and the degree of stenotic compression of the cauda equina seen on radiologic findings in patients with lumbar spinal stenosis and lumbar disc herniation.

METHODS

Thirty-four patients admitted for treatment for lumbar spinal stenosis or lumbar disc herniation underwent urodynamic studies, and computed tomographic scans after myelography were obtained to determine the degree of cauda equina compression. The cross-sectional area and anteroposterior diameter of the dural sac were measured at their smallest transverse area.

RESULTS

Twenty (58.8%) of the 34 patients were diagnosed with positive neuropathic bladder. There was no significant difference in the cross-sectional area of dural sac between the patients with positive neuropathic bladder and with negative neuropathic bladder. However, the dural sac anteroposterior diameter in positive neuropathic bladder patients was significantly shorter than that in patients with negative neuropathic bladder. A critical size for the dural sac of patients with neuropathic bladder was revealed as 8 mm in this study.

CONCLUSIONS

The prevalence of neuropathic bladder is more significantly associated with dural sac anteroposterior diameter than with the cross-sectional area of dural sac. Therefore, dural sac anteroposterior diameter might be an important factor predicting the existence of neuropathic bladder.

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.

Spinal trauma: therapy--options and outcomes

The management of patients with spinal trauma is based on the following goals: (1) the preservation of life; (2) preserving and maximising the neurological function; and (3) providing a stable, painless vertebral column. There have been advances in both non operative as well operative modalities of treatment of patients with spinal injuries. These advances have led to renewed interest in the management of a spinally injured patient. However, despite these advances controversies exist regarding the classification of these fractures, the use of pharmacological intervention, the timing of surgical intervention and indeed the use of surgical intervention itself in the management of these fractures. Most of these controversies surround the treatment of thoracic and lumbar fractures. The purpose of this article is to provide an over view of the therapy options available in the treatment of these fractures. The article shall also look at some of the controversies surrounding the management of these fractures.

Clinical symptoms and surgical outcome in lumbar spinal stenosis patients with neuropathic bladder

We evaluated the clinical and radiologic features of patients with lumbar spinal stenosis with neuropathic bladder. Based on cystometrogram analysis, the patients were divided into two groups--the neuropathic bladder (NB) group: the NB+ group (23 patients), and the nonneuropathic bladder group: the NB- group (14 patients). The symptom of incontinence was characteristic in patients in the NB+ group. Patients in the NB+ group had a more severe neurologic disturbance, compared with those in the NB- group. The more severe neurologic disturbance was caused by the more striking finding of degenerative spinal stenosis associated with developmental narrowing of the spinal canal. Decompressive surgery had a beneficial effect on the recovery of the neurologic symptoms in both groups. Residual urine volume was reduced after surgery. Postoperative cystometrogram was carried out in nine patients in the NB+ group. It showed a normal pattern in six patients; however, three patients remained in an underactive pattern. Furthermore, four patients still required clear intermittent self-catheterization after surgery.

Electrically stimulated detrusor myoplasty

PURPOSE

Many children with spina bifida and other causes of neurogenic bladder rely on clean intermittent catheterization to empty the hyporeflexic or areflexic bladder. Direct bladder and sacral nerve root stimulation have been met with limited success. We studied the electrical stimulation of a rectus abdominis muscle flap wrapped around the bladder to achieve bladder contractility and emptying.

MATERIALS AND METHODS

The feasibility of performing rectus detrusor myoplasty in humans was first studied in 8 cadavers. In male and female cadavers it was possible to wrap the distended bladder completely with the rectus abdominis muscle. The rectus abdominis muscle was surgically dissected with preservation of its insertion on the pubis bone and rotation of its mid section behind the bladder to effect a complete bladder wrap. The deep inferior epigastric artery and veins, and 2 most caudal intercostal nerves were preserved. This unilateral rectus abdominis muscle flap was then electrically stimulated with 2 pairs of bipolar electrodes inserted into the muscle near the nerve entrance. Stimulation frequencies of 40, 60 and 80 Hz. were used in each of the 8 dogs. The increase in intravesical pressure over baseline, compliance and post-void residual were measured. Paired Student's t tests were used for statistical comparisons.

RESULTS

The increase in intravesical pressure ranged 35 +/- 5 to 45 +/- 7 cm. H2O at stimulation frequency 40 and 80 Hz., respectively. Post-void residual was 27 +/- 4%, 22 +/- 3% and 26 +/- 3% at stimulation frequencies 40, 60 and 80 Hz., respectively. Intravesical pressure was significantly increased over baseline bladder pressure (p <0.05).

CONCLUSIONS

Electrically stimulated detrusor myoplasty results in uniform increases in intravesical pressure and reasonable bladder emptying in an animal model. We are currently investigating detrusor myoplasty in a chronic study to determine whether it can be used for enhanced bladder emptying in children with poor detrusor contractility.

Surgical treatment of degenerative lumbosacral stenosis in dogs

OBJECTIVE

To study the epidemiology, clinical findings, and long-term outcome of surgical treatment of degenerative lumbosacral stenosis (DLSS) in dogs.

STUDY DESIGN

Retrospective study.

SAMPLE POPULATION

131 client-owned dogs with DLSS.

METHODS

The medical records of dogs with DLSS treated by dorsal laminectomy and dorsal fenestration were reviewed. The clinical diagnosis had been verified by diskography, epidurography or myelography, or a combination thereof.

RESULTS

The German shepherd breed was over-represented (56.5%), and males were more often affected than females (2:1). Historically, reluctance or pain when jumping, rising from a prone position, or climbing stairs (92.4%) and signs of pain or stiffness during extensive physical activity (85.5%) were the most frequent concerns. The most common physical and neurologic examination findings were pain in the lumbosacral area during hyperextension (97.7%) and on direct digital palpation (84.7%). A total of 93.2% of the dogs were improved clinically within the follow-up period (mean 26 +/- 17 months). Recurrence of clinical signs resembling DLSS was reported by the owner or diagnosed by clinical examination in 17.6% of the dogs with a mean onset of signs at 18 +/- 13 months postoperatively.

CONCLUSIONS

Surgical treatment of DLSS with dorsal laminectomy and fenestration generally resulted in good to excellent clinical outcome.

Pathophysiology of spinal cord injury. Recovery after immediate and delayed decompression

We evaluated the effect of the timing of decompression of the spinal cord after compression of 50 per cent of the diameter of the spinal cord at the fourth lumbar level in thirty purebred dogs. The dogs were divided into five groups of six dogs each on the basis of the duration of the compression. Decompression was performed immediately (Group I), one hour (Group II), six hours (Group III), twenty-four hours (Group IV), or one week (Group V) after the compression. Monitoring of somatosensory evoked potentials, daily neurological examinations, and histological and electron microscopic studies at the time of the autopsy were performed for all of the dogs. Initially, all of the dogs were paraplegic after the compression of the spinal cord. The dogs that had immediate decompression or decompression after one hour of compression recovered the ability to walk (grades 4 and 5, according to Tarlov's system) as well as control of the bowel and bladder, and the somatosensory evoked potentials improved an average of 85 and 72 per cent, respectively. However, when compression lasted six hours or more, there was no neurological recovery and there was progressive necrosis of the spinal cord. Somatosensory evoked potentials improved 29 per cent in Group III, 26 per cent in Group IV, and 10 per cent in Group V. The percentage of recovery of the somatosensory evoked potentials by six weeks after the decompression was significantly related to the duration of the compression (p < 0.0008).

Voiding dysfunction and urodynamic findings in patients with lumbar spinal stenosis and the effect of decompressive laminectomy

Eighteen consecutive patients (12 men and 6 women, mean age 55) with clinically and radiologically verified lumbar spinal stenosis underwent urodynamic examinations before decompressive laminectomy (n = 16) and 15 afterwards. Twelve of the patients (67%) had symptoms of voiding dysfunction preoperatively but urodynamic findings were normal in most cases only one patient showing detrusor hyperreflexia and one obstruction. Three patients reported an improvement in voiding postoperatively. Three patients showed obstructive voiding postoperatively, one undergoing TURP with a good outcome. One patient developed detrusor areflexia after the operation, with difficulties in bladder emptying. The only statistically significant changes in urodynamic parameters were rises in the maximum urethral pressure and urethral closure pressure. When considering the radicular symptoms and back pains the overall outcome was assessed as excellent or good in 6 cases, 6 had a fair outcome and 4 poor. Decompressive laminectomy gives acceptable results but the effects on bladder and urethral function remain controversial and unexpected. Electrophysiological investigations are needed for more detailed analysis of these cases.