Clinical evaluation of metrizamide as a myelographic agent in the dog.

Metrizamide, a new, water-soluble contrast agent, was clinically evaluated as a myelographic agent in 17 dogs. Nine dogs were given lumbar subarachnoid injections and six were given cisternal injections. Two dogs were given cisternal and lumbar injections; in one dog, both injections were given on the same day. The dosage ranged from 0.3 to 0.57 ml/kg of body weight, using an isotonic solution of metrizamide. Of eight dogs given cisternal injections, two experienced convulsive activity requiring diazepam treatment during the anesthetic recovery period. The lumbar injections did not cause convulsions. Satisfactory radiographic density persisted up to 45 minutes after injection, allowing time for several views to be obtained. In general, metrizamide appeared to be an adequate myelographic agent in the dog.     

A MYELOGRAPHIC TECHNIQUE FOR AVIAN SPECIES

A post-mortem myelogram was used to diagnose a vertebral fracture in a Red-tailed Hawk ( Buteo jamaicenis ). This diagnosis led the authors to believe that myelography would be useful in live birds. In a pilot study using live adult female chickens (Gallus domesticus) , mammalian myelographic techniques were modified for avian anatomic differences. A thoracolumbar puncture site was used rather than the lumbar or cisternal site which is commonly used in mammals. The volume of contrast medium needed to produce a diagnostic myelogram in birds(0.8–1.2 ml/kg) was found to be approximately four times that needed in mammals. A 25 gauge spinal needle was used rather than a 23 gauge needle. Myelograms of diagnostic quality were obtained with normal subject recovery. Seizures, the most common post-myelographic complication in mammals, were not observed in any of the birds studied. Avian myelography was found to be a cost effective and humane technique with potential application to avian practice.     

犬脊髓造影技术

采用脊髓蛛网膜下腔穿刺将造影剂注入椎管 ,分别对 1 6只不同年龄犬行欧乃派克 ( omnipaque,每毫升含碘 30 0 mg)脊髓造影 ,对 1 1只犬行碘化油 (含碘 4 0 % )脊髓造影。造影后拍摄颈段、胸段、腰荐段正、侧位脊髓造影照片并评定造影结果 ,研究比较水溶性造影剂欧乃派克和脂溶性造影剂碘化油用于不同年龄犬的脊髓造影技术 ,分析了犬正常脊髓造影影像。研究表明 ,每毫升含碘 30 0 mg的欧乃派克可安全地用于犬的脊髓造影 ;不同年龄犬造影剂用量相同 ,每公斤体重 0 .4 5m L时全段脊髓同时清楚显示 ,0 .30 m L时局部 (颈段、胸段或腰荐段 )脊髓显示清楚 ,0 .2 0 m L以下时脊髓显示较模糊。碘化油毒副作用较大 ,不宜再用于犬的脊髓造影     

Thoraco-Lumbar Myelography with Water-Soluble Contrast Medium in Dogs I. Technique of Myelography; Side-effects and Complications

Abstract— A technique previously devised by the author for filling the greater part of the spinal subarachnoid space with water-soluble contrast medium (Kontrast U^R) has been tested for myelographic localization, of thoracic and lumbar compression of the spinal cord in the dog. The principle for the myelographic examination has been to inject the medium in the lumbar region in a sufficient dose for it to be forced beyond the compressed part of the subarachnoid space, to permit demonstration of both the posterior and anterior limit of the compression. A single injection of 20 per cent Kontrast U into the subarachnoid space in the dose generally used (0·3 ml/kg of body weight) does not seem to have any detrimental effect on the spinal cord. On the other hand, morphologic lesions of the spinal cord, presumably to be ascribed to the preparation in question, have been observed after repeated injections of contrast medium at the same examination.     

Absence of cerebrospinal fluid abnormalities and spinal cord lesions after iotrolan cervical myelography in normal cats: an open placebo-controlled study

Iotrolan (Isovist 300, Schering AG) at a volume of 0.5 ml/kg B.W. was injected into the cerebellomedullary cistern of 12 cats (Isovist group); the same volume of normal saline was injected in four other cats (control group). Two ml of CSF was collected from each anaesthetized cat by cisternal tap immediately before, and 7 and 15 days after, injection. The physical characteristics, specific gravity, total cell count and total protein concentration of each CSF sample were recorded. The cats were euthanized on day 15 immediately after CSF samples and spinal cord specimens had been obtained. Spinal cord histopathology was examined with the aid of light and transmission electron microscopy. The physical characteristics of all the CSF samples were within the reference range. No significant differences were found for CSF specific gravity, total cell count and total protein concentration between the pre-injection samples and those collected 7 and 15 days post-injection in both groups; no spinal cord lesions were detected in histopathology.     

The value of oblique versus ventrodorsal myelographic views for lesion lateralisation in canine thoracolumbar disc disease

OBJECTIVE: To determine the value of oblique versus ventrodorsal myelographic views for lesion lateralisation in canine thoracolumbar disc disease. METHODS: The ventrodorsal and oblique views from 196 lumbar myelograms of dogs with single thoracolumbar disc extrusions or protrusions were blindly and independently reviewed by two of the authors for evidence of lesion lateralisation. Medical records were reviewed for details regarding hemilaminectomy surgery. The side (left versus right) of the surgery and whether or not the disc material was retrieved were noted. RESULTS: Both reviewers lateralised significantly more disc lesions from the oblique views (93 and 95 per cent) than from the ventrodorsal views (59 and 70 per cent) (P<0.001). Using a combination of oblique and ventrodorsal views, 194 (99 per cent) and 195 (99.5 per cent) lesions were lateralised. Unilateral hemilaminectomy was performed in 193 dogs with myelographic lateralisation and in one dog without myelographic lateralisation. The side of spinal cord decompression corresponded with the myelographic findings in all dogs showing lateralisation on myelography. In the dog without myelographic lateralisation, a left (randomly chosen) hemilaminectomy revealed dorsal protrusion of the annulus fibrosus. CLINICAL SIGNIFICANCE: Myelography, including oblique, ventrodorsal and lateral views, is an accurate method for determining lateralisation of extruded or protruded disc material in the vertebral canal before decompressive surgery. Combined oblique and ventrodorsal views are more useful than either view alone and should be routinely obtained in all lumbar myelographic studies when investigating thoracolumbar disc disease.     

Myelographic localization of spinal cord compression in dogs. A comparison between cisternal and lumbar injections of metrizamide "Amipaque" in diagnosing and locating spinal cord compression.

Metrizamide is a new water-soluble contrast medium possessing unique properties, one of which is that even in an isotonic solution it has a radiographic density sufficient for a diagnostic myelogram. Whereas in the past myelography with water-soluble preparations invariably entailed lumbar injections, which are technically difficult in dogs, the fact that isotonic metrizamide causes so little tissue irritation has made it possible to inject the contrast solution into the cisterna magna. The author has compared metrizamide myelograms obtained with both cisternal and lumbar injections. Myelography with a cisternal injection is preferable for demonstrating cervical cord compressions and also in cases in which it is desirable to obtain myelographic information on both the cervical and the thoraco-lumbar areas. If, on the other hand, it is necessary to determine exactly the extent of a thoraco-lumbar compression before decompressive laminectomy, the contrast should be injected in the lumbar region in such an amount and at a pressure high enough to ensure that the contrast is forced past the site of the compression. The safety of metrizamide will probably enable a better prognosis following surgery than was previously possible.     

Comparison of metrizamide and iohexol for cisternal myelographic examination of dogs

A double-blind study, using metrizamide, iohexol, or Ringer's solution (control) as cisternal myelographic agents, was performed on 25 dogs. Before myelographic examination was done, each dog was subjected to physical, clinical pathologic, and neurologic examinations, as well as examinations by electroencephalography and computerized tomography. These were repeated 24 hours after completion of the myelographic examination. The group of dogs given metrizamide (group II) had a significantly greater occurrence of seizure activity (6 of 10) than did the control dogs (group I; 0 of 5) or dogs given iohexol (group III; 0 of 10; P less than 0.003). In group II, the CSF microprotein concentration was significantly greater 24 hours after myelography was done than were the values in groups I and III (P less than 0.003). Myelograms of the group II dogs (metrizamide) and group III dogs (iohexol) had similar diagnostic qualities. At 24 hours after myelographic examination was done, computerized tomography scan revealed that each dog given metrizamide and iohexol had myelographic contrast material in the brain and cervical spinal cord parenchyma. Seemingly, iohexol has good diagnostic quality, but is less epileptogenic than metrizamide when used in cervical myelographic examinations of dogs.     

Neurotoxicologic effects of the nonionic contrast agent iopamidol on the leptomeninges of the dog

The effect of iopamidol on the leptomeninges was tested and compared with that of metrizamide and normal saline solution in 18 dogs. Pathologic and clinical effects were evaluated at 24 hours and 14 days after cisternal injection of iopamidol, metrizamide, or normal saline solution. Pathologic changes were evaluated by microscopic examination of serial CSF samples and of sections of brain and spinal cord with the leptomeninges intact. Clinical changes were subjectively evaluated. Electromyograms and EEG were performed on each dog after physical and neurologic examination. There were no changes seen in neurologic status, electromyogram, or EEG in any of the dogs immediately after subarachnoid injection nor at 24 hours or 14 days later. Pathologic changes were limited to mild, moderate, or severe patchy hemorrhagic leptomeningitis seen at 24 hours after iopamidol or metrizamide was injected. The severity of changes were judged to be similar with both these agents. The CSF analysis and histologic evaluation of brain and spinal cord sections revealed a neutrophilic response to iopamidol and a mononuclear response to metrizamide. These findings indicate that iopamidol has minimal neurotoxicologic effect on the leptomeninges and therefore has merit as a myelographic agent.     

Sparing effect of a low dose of intrathecal morphine on fentanyl requirements during spinal surgery: a preliminary clinical investigation in dogs

Objective— To evaluate the effect of preoperative intrathecal administration of a low dose of morphine on intraoperative fentanyl requirements in dogs undergoing cervical and thoracolumbar spinal surgery.
Study Design— Prospective randomized clinical study.
Animals— Dogs (n=18) matched by surgical procedure administered intrathecal morphine (MG) or no-treatment (control group, CG).
Methods— After premedication with romifidine (4 μg/kg, intravenously) and induction with propofol, anesthesia was maintained with sevoflurane in oxygen. Intrathecal morphine 0.03 (0.023–0.034) mg/kg was administered at lumbar level 41 (25–65) minutes before surgery in MG. Ketamine (0.5 mg/kg) was administered hourly, starting before incision. Fentanyl infusion (1.2 and 4.2 μg/kg/h in MG and CG, respectively) was administered after a loading dose (5 and 10 μg/kg in MG and CG, respectively), and boluses were given if an increase >20% in heart rate and arterial blood pressure was observed. Total amount of fentanyl administered was recorded, to calculate hourly requirements and predict plasma concentration using a computer simulation.
Results— Hourly fentanyl consumption and predicted plasma concentrations at the time of response to surgery were significantly lower in MG compared with CG.
Conclusions— Preoperative administration of a low dose of intrathecal morphine has a sparing effect on intraoperative fentanyl requirements.
Clinical Relevance— Preoperative intrathecal administration of a low dose of morphine at the lumbar level represented a safe and effective mean of providing intraoperative analgesia in dogs undergoing cervical and thoracolumbar spinal surgery.     

Absence of postmyelographic adverse effects and high radiographic resolution of iotrolan used in the cervical myelography for the clinically normal cat: an open-placebo controlled study

Iotrolan solution at 300 mgI/ml (Isovist 300, Schering AG), was injected into the cerebromedullary cistern in 8 cats (Isovist group), at a volume of 0.5 ml/Kg BW and over one minute. In 3 cats (control group), normal saline was also injected at a same volume and speed. During the subarachnoid injection and at 1, 5 and 10 min thereafter all the cats were being monitored for evidence of respiratory arrest, bradycardia or changes in the arterial blood pressure. The cats were also checked for postmyelographic adverse effects for at least 3 h after their complete recovery from anaesthesia. Postmyelographic neurologic examination was done for 3 consecutive days and the myelographic quality of the films taken at 5 and 15 min postinjection was evaluated. No significant differences were detected between the Isovist and the control groups for all the variables evaluated immediately before, during and up to 3 days after the injection. No actual post-myelographic adverse effects were seen in the animals of both groups. At 15 and 30 min postinjection the opacity, the distention of the subarachnoid space and the detail of all the myelograms obtained were assessed as highly diagnostic.     

Metrizamide myelography in sixty-eight dogs

The results of 68 metrizamide myelograms in the dog are recorded, involving both cisternal and lumbar punctures. The technical considerations are described together with interpretation of the normal myelogram and the diagnostic signs. Failure to obtain a good contrast column occurred in 14 dogs, and post myelographic signs were observed in eight.     

USE OF CONTRAST‐ENHANCED COMPUTED TOMOGRAPHY TO STUDY THE CRANIAL MIGRATION OF A LUMBOSACRAL INJECTATE IN CADAVER DOGS

Volumes used in lumbosacral epidural injections for anesthesia have remained unchanged since the 1960s. The goals of this cross‐sectional observational study were to characterize the three‐dimensional spread of a lumbosacral epidural injection, as well as confirm that the commonly used volume of 0.2 ml/kg injected into the lumbosacral epidural space reaches the thoracolumbar (TL) junction in the majority (≥80%) of dogs. Ten clinically normal, adult, nonpregnant, mixed‐breed dogs were obtained within five minutes of euthanasia and 0.2 ml/kg of radiopaque contrast medium was injected into the lumbosacral epidural space. A computed tomography scan of the TL spine was performed immediately following the injection. Migration of contrast reached the TL junction in 8 of 10 (80%) dogs. Contrast was well visualized in all epidural planes with contrast travelling predominantly in the dorsal epidural space in 7 of 10 (70%) dogs. There was no significant difference in the weight of dogs where the epidural injectate reached the TL junction and those where it did not (P = 0.16), or in the weight of dogs where the cranial‐most point of the contrast column was in the dorsal versus the ventral epidural space (P = 0.32). This preliminary study supports the use of computed tomography to characterize injectate distribution in the canine thoracolumbar epidural space and provides evidence that a 0.2‐ml/kg volume is likely to reache the TL junction in most dogs. Further studies are needed in live dogs to determine if variables affecting human epidural injectate doses have similar effects in the dog.     

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.     

Spinal fluid concentrations of mepivacaine in horses and procaine in cows after thoracolumbar subarachnoid analgesia

The CSF concentrations of mepivacaine in 10 Standardbred horses and of procaine in 10 Holstein cows given the drugs by thoracolumbar subarachnoid injection were determined. Mepivacaine hydrochloride was injected into the horses (502 +/- 60.5 kg) at an average dosage of 30 mg (1.5 ml of 20 mg/ml solution). Analgesia was produced 7.5 +/- 4.3 minutes after injection, extended between spinal cord segments T13 and L3 on both sides of the spinal column, and lasted 47 +/- 18.7 minutes at the T18 dermatome. Procaine hydrochloride was injected into cows (614 +/- 51.5 kg) at a dosage ranging between 75 mg and 100 mg (1.5 ml and 2 ml of 50 mg/ml solution). Analgesia was produced 8.2 +/- 2.0 minutes after injection, extended between spinal cord segments T11 and L4 on both sides of the spinal column, and lasted 47 +/- 17.5 minutes at the T13 dermatome. The critical CSF concentrations of local anesthetics required to eliminate response to pinprick stimulation were 204.4 +/- 90.3 micrograms of mepivacaine/ml in horses and 197.0 +/- 86.1 micrograms of procaine/ml in cows. Average CSF concentrations at 120 minutes after injections were made were 16.8 +/- 15.5 micrograms of mepivacaine/ml and 30.6 +/- 17.1 micrograms of procaine/ml. In in vitro experiments to determine the rates of hydrolysis of mepivacaine and procaine in CSF, significant changes (P greater than 0.05) were not seen in the CSF concentrations of mepivacaine in horses and procaine in cattle after a 120-minute incubation (37 C). The analgesic threshold concentrations of mepivacaine in CSF of horses and procaine in CSF of cows were similar.(ABSTRACT TRUNCATED AT 250 WORDS)     

THE RADIOLOGICAL DIAGNOSIS OF THORACOLUMBAR DISC DISEASE IN THE DACHSHUND

The accuracy of survey radiographs in the diagnosis of acute thoracolumbar disc disease in 36 Dachshunds was determined by comparison with lumbar myelographic findings using iohexol. The value of making radiographs immediately after injection of contrast medium and the effectiveness of oblique radiographs in determining the exact circumferential distribution of extruding or protruding disc material were assessed. The presence of a double contrast medium column, resistance to injection and the presence of cerebrospinal fluid flow during needle placement was also evaluated. The location of the affected disc was accurately determined on survey radiographs in only 26 dogs. The myelographic technique used in this study resulted in the correct intervertebral space being identified, together with the exact circumferential distribution of disc material, in 35 dogs. Survey radiographs alone are inadequate for localization of protruding or extruding disc material.     

RELATIONSHIP OF CERVICAL SPINAL CORD DIAMETER TO VERTEBRAL DIMENSIONS: A RADIOGRAPHIC STUDY OF NORMAL DOGS

Cervical spinal cord abnormalities are often unapparent on myelographic studies, because no normal values for cervical spinal cord diameter are currently available. The purpose of this study was to establish, myelographically, the normal sagittal diameter of the cervical spinal cord in large and small breed dogs and its relationship to the sagittal diameter of the vertebral canal and sagittal height/length of the corresponding vertebral bodies. Forty-one adult dogs underwent cervical radiography and myelography. Spinal cord and vertebral canal sagittal diameter, vertebral body height at C2 to 5, body length at C3 to 5, and dorsal spine length of C2 were measured on lateral views. Ratios of spinal cord:vertebral canal diameter, spinal cord:body height, and spinal cord:body length/spine were calculated, and a normal range was determined for small and large breed dogs. The spinal cord:vertebral canal ratios showed that small breeds have a higher cervical cord-to-canal ratio than large breeds. The mean values and ranges of 14 ratios are reported. The ratios of spinal cord:body length at C2 to 4 in small breeds and spinal cord:body height at C3 to 5 in large breeds were found to be the most accurate for assessing spinal cord sagittal diameter. These normal ranges would allow quantitative and objective evaluation of the cervical spinal cord by myelography and early identification of dogs with altered spinal cord diameter, which could be further evaluated by means of alternative imaging techniques.     

A rostrocaudal gradient for neurotransmitter metabolites and a caudorostral gradient for protein in canine cerebrospinal fluid

Neurotransmitter metabolites (dihydroxyphenylacetic acid [DOPAC], homovanillic acid [HVA], and 5-hydroxyindoleacetic acid [5-HIAA]) in CSF of 10 healthy dogs were evaluated with reverse-phase high-pressure liquid chromatography and electrochemical detection. Neurotransmitter metabolite concentrations determined in CSF collected from the cisterna magna were compared with those values in CSF collected from the lumbar dorsal subarachnoid space. Amounts of DOPAC (P = 0.0444), HVA (P = 0.0001), and 5-HIAA (P = 0.0316) were significantly lower in lumbar spinal fluid compared with those values in the cervical spinal fluid. Metabolite concentrations in cervical and lumbar CSF were: DOPAC = 2.81 +/- 0.73 ng/ml of CSF and 1.28 +/- 0.57 ng/ml; HVA = 98.29 +/- 12.42 ng/ml and 4.68 +/- 1.61 ng/ml; and 5-HIAA = 46.29 +/- 8.17 ng/ml and 36.96 +/- 4.07 ng/ml, respectively. Cytologic evaluations of cervical and lumbar CSF revealed a similar concentration of 3 +/- 1 WBC/microliters in both fluids. A significant (P = 0.0002) difference in protein concentration between the 2 regions was observed, with 16.1 +/- 1.8 mg of protein/dl in the cervical CSF and 27.2 +/- 2.3 mg of protein/dl in the lumbar CSF. Between the cisterna magna and lumbar dorsal subarachnoid space of dogs, a rostrocaudal gradient existed for neurotransmitter metabolites, and a caudorostral gradient existed for protein.     

Use of magnetic motor-evoked potentials in horses with bilateral hind limb ataxia

OBJECTIVE: To determine the usefulness of magnetic motor-evoked potentials (MMEPs) for assessing the integrity of the cervical, thoracic, and thoracolumbar spinal cord in horses with bilateral hind limb ataxia. ANIMALS: 9 horses and 1 donkey with bilateral hind limb ataxia of various degrees. PROCEDURE: The motor cortex was stimulated magnetically, and MMEPs were recorded bilaterally from the extensor carpi radialis and cranial tibial muscles. RESULTS: In 5 horses and 1 donkey, MMEPs with normal onset latencies and peak-to-peak amplitude were recorded from the extensor carpi radialis muscles, whereas abnormal onset latencies and peak-to-peak amplitudes were recorded from the cranial tibial muscles. In these animals, a spinal cord lesion in the thoracic or thoracolumbar segments was suspected. In 4 horses, onset latencies and peak-to-peak amplitude of MMEPs recorded from the extensor carpi radialis and cranial tibial muscles were abnormal. In these horses, a cervical spinal cord lesion was suspected. CONCLUSIONS AND CLINICAL RELEVANCE: Transcranial magnetic stimulation can be considered a valuable diagnostic tool for assessing the integrity of the spinal cord, and MMEPs may be used for differentiating thoracic or thoracolumbar spinal cord lesions from mild cervical spinal cord lesions that cause ataxia in the hind limbs only.     

Changes in thermal threshold response in eight cats after administration of buprenorphine, butorphanol and morphine

Thermal thresholds were measured in eight cats after the intramuscular administration of morphine (0.2 mg/kg), buprenorphine (0.01 mg/kg) or butorphanol (0.2 mg/kg), doses commonly used in clinical practice; 0.9 per cent saline (0.3 ml) was injected as a control. Groups of six cats were used and each cat participated in at least two treatments, according to a randomised design. The investigator was blinded to the treatments. The thermal thresholds were measured with a testing device developed specifically for cats, and measurements were made before and five, 30, 45 and 60 minutes and two, four, six, 12 and 24 hours after the injections. There was no significant change in thermal threshold after the injection of saline. With butorphanol, the threshold was increased only at five minutes after the injection and was decreased two hours after the injection; with morphine it was increased from between four and six hours after the injection, and with buprenorphine it was increased from between four and 12 hours after the injection.