EFFECTS OF POSTMYELOGRAPHIC REMOVAL OF METRIZAMIDE IN DOGS

Using a paired crossover trial, the effects of postmyelographic removal of metrizamide injected via the cerebellomedullary cistern were studied in 16 normal dogs. Each animal received a routine and a withdrawal myelogram. Seizure activity, changes in spinal evoked motor potentials and body temperature were measured following each myelogram. The amount of metrizamide removed was determined by densitometrically analyzing radiographs of cerebrospinal fluid/metrizamide aliquots recovered during the withdrawal procedure. There was a significant decrease in the number of seizures for withdrawal versus nonwithdrawal myelography (p < 0.01). The mean amount of metrizamide withdrawn per dog was 29% of the total injected.     

Cerebrospinal fluid changes after iopamidol and metrizamide myelography in clinically normal dogs.

Cerebrospinal fluid samples from 2 groups of clinically normal dogs were compared after iopamidol (n = 9) and metrizamide (n = 8) myelography. Iopamidol (200 mg of I/ml) and metrizamide (170 mg of I/ml) were administered by cerebellomedullary injection at dosage of 0.45 ml/kg of body weight. In dogs of both groups, postmyelographic CSF changes included high specific gravity, Pandy score, protein concentration, and WBC count. The high specific gravity and Pandy score were false-positive effects attributed to nonionic contrast media. Although postmyelographic protein concentration and total WBC count were greater in CSF samples from dogs given metrizamide than in those given iopamidol, differences were not statistically significant. The differential WBC counts were consistent with mild, acute leptomeningitis; these findings were supported by results of histologic examination. Iopamidol and metrizamide should be considered low-grade leptomeningeal irritants in dogs.     

Comparison of nonionic contrast agents iohexol and iotrolan for cisternal myelography in dogs

During this investigation, the use of iohexol was compared with iotrolan for canine cisternal myelography. Iohexol and iotrolan myelography was done in 6 dogs by cisternal puncture with a 6-week interval between both procedures; each dog served as its own control. Cerebrospinal fluid (CSF) was collected for baseline analysis from each dog immediately before the contrast agent was injected. Cerebrospinal fluid samples were obtained at 1, 3, 7, and 14 days after injection of each contrast medium for cytologic and chemical analysis. Total CSF leucocyte count and glucose concentration did not change significantly in comparison with baseline data in any of the samples. After the injection of iohexol, protein concentration increased significantly in the 24-hour sample, and lactate dehydrogenase activity increased significantly in the 3-day sample. Significant difference was not found between the different samples collected at 1, 3, 7, and 14 days, compared with both contrast media. None of the dogs had seizure activity during a 5-hour postmyelographic observation period. Pathologic changes were not found by gross or microscopic examination of the spinal cord. Although a degradation in time of radiographic quality of all myelograms took place, the average radiographic score decreased more rapidly with iohexol. The average score at 90 minutes with iotrolan was comparable with the score at 45 minutes with iohexol, and the average score at 150 minutes with iotrolan was better than the score at 90 minutes with iohexol. At 5 and 10 minutes after cisternal injection, no significant difference was observable between the myelograms, but from 45 minutes onward, myelograms with iotrolan were superior.     

Prevention of postmetrizamide myelographic seizures in dogs, using 5% dextrose solution

Diuresis by IV administration of 5% dextrose in a balanced electrolyte solution (BES) reduced the frequency of occurrence of postmyelographic seizures in dogs. In the first study, a single myelogram was obtained in 8 dogs without dextrose diuresis. Two of these dogs weighed greater than 15 kg and both had seizures after metrizamide myelography. The remaining 6 dogs weighed less than 15 kg and only 2 had seizures. Greater body weight may have increased the risk of postmyelographic convulsions. In a crossover study, myelograms were obtained in 12 dogs weighing 20 to 31 kg. Six dogs were given 5% dextrose in BES (20 ml/kg of body weight/hr [diuresed]) and 6 were given BES alone (10 ml/kg/hr [not diuresed]). When myelography was repeated 10 days later, the 6 dogs that had been given 5% dextrose in BES were given BES only and the 6 dogs that had been given BES alone were given 5% dextrose in BES. The frequency of convulsions after metrizamide myelography was lower when dogs were given dextrose (33%) than when they were not (100%).     

EFFECTS OF METRIZAMIDE MYELOGRAPHY ON CEREBROSPINAL FLUID ANALYSIS IN THE DOG

The effect of metrizamide myelography on the composition of cerebrospinal fluid (CSF) was studied. Seven dogs received an intracisternal injection of metrizamide. An intracisternal puncture was performed in three additional dogs that did not receive metrizamide. CSF was collected before myelography and 24, 72, and 144 hours after myelography from all dogs. A significant increase in the percentage of neutrophils (p<0.05) and a pleocytosis noted 24 hours after myelography (p<0.02) were attributed to the effect of metrizamide. Significant increases in total protein concentration (p<0.001) and erythrocyte count (p<0.05), and a decrease in the percentage of small mononuclear cells (p<0.01) were attributed to repeated intracisternal puncture. No significant changes were observed for CSF creatine phosphokinase activity or the percentage of large mononuclear cells.     

Incidence of seizures associated with iopamidol or iomeprol myelography in dogs with intervertebral disk disease: 161 cases (2000–2002)

Objective – To compare the incidence of seizures in dogs with intervertebral disk disease after iopamidol or iomeprol myelography, and to assess whether the incidence of seizures differed between the 2 agents when severity of neurological deficits, location of cord compression, duration of anesthesia, site of myelogram, volume of contrast, and concentration of contrast were evaluated. Design – Retrospective study. Setting – Veterinary teaching hospital. Animals – One hundred and sixty‐one client‐owned dogs with intervertebral disk disease. Interventions – Subarachnoid injection of contrast medium. Measurements and Main Results – One hundred and sixty‐one dogs with intervertebral disk disease were subjected to myelography using iopamidol (n=74) or iomeprol (n=87). Cranial myelography was performed in 31 dogs, caudal myelography in 125 and both cranial and caudal myelography in 5. Seizures occurred in 23 of 161 (14%) dogs. There was no significant difference overall between iopamidol and iomeprol myelography. However, in dogs with thoracolumbar disk extrusion and paraplegia, seizures occurred more frequently after caudal myelography using iopamidol compared with iomeprol. Conclusions – Both iomeprol and iopamidol are suitable for myelography in dogs. Iomeprol is recommended for caudal myelography in paraplegic dogs with thoracolumbar disk extrusion due to the higher incidence of seizures in this group when iopamidol was used.     

Effect of intravenous administration of dextrose or lactated Ringer's solution on seizure development in dogs after cervical myelography with metrizamide

The effect of fluid (5% dextrose in water or lactated Ringer's solution) administered intravenously on the development of seizures after cervical myelography with metrizamide was studied in 10 dogs. In a crossover experimental design, 8 dogs were used twice. Urine output was measured during the second part of the study to determine whether diuresis was a factor affecting seizure development. Dogs given 5% dextrose in water had significantly (P less than 0.05) fewer seizures than did dogs given lactated Ringer's solution. This was attributed to an increase in CSF glucose concentration and was not associated with diuresis.     

Risk factors associated with development of seizures after use of iohexol for myelography in dogs: 182 cases (1998)

OBJECTIVE: To determine prevalence of seizures after use of iohexol for myelography and identify associated risk factors in dogs. DESIGN: Retrospective study. ANIMALS: 182 dogs that received iohexol for myelography in 1998. PROCEDURE: Medical records were reviewed for age, breed, sex, weight, dose and total volume of iohexol, injection site, number of injections, lesion type and location, total duration of anesthesia, duration from time of iohexol injection to recovery, presence and number of seizures, and whether surgery followed the myelogram. RESULTS: 39 (21.4%) dogs had at least 1 generalized seizure during or after myelography. Injection site was strongly associated with prevalence of seizures, and risk of seizure was significantly higher after cerebellomedullary injections, compared with lumbar injections. Mean total volume of iohexol administered to dogs that had seizures was significantly higher, compared with that administered to dogs that did not have seizures, although dosage did not differ between groups. Weight was significantly correlated with risk of seizure, and dogs that weighed > 20 kg (44 lb) had higher prevalence of seizures than dogs that weighed < 20 kg. CONCLUSIONS AND CLINICAL RELEVANCE: It is preferential to administer iohexol via the L5-6 intervertebral space to minimize the risk of seizures. Higher prevalence of seizures in large dogs, compared with smaller dogs, may be caused by administration of larger total volumes of contrast agent per volume of CSF.     

A PROSPECTIVE CLINICAL TRIAL COMPARING METRIZAMIDE AND IOHEXOL FOR EQUINE MYELOGRAPHY

A prospective clinical trial comparing adverse postmyelographic effects and myelographic quality of metrizamide and iohexol was conducted. Using a predetermined, randomized assignment, 24 horses exhibiting neurologic signs were administered either metrizamide (180 mgl/ml) or iohexol (180 mgl/ml) via cerebellomedullary puncture. Each horse was evaluated postmyelographically for adverse effects. Myelographic quality was assessed by a numerical scoring method. Adverse effects were observed more frequently with metrizamide (21) compared with iohexol (6) myelography (p < 0.05). Seizures, intensification of preexisting neurologic signs and prolonged anesthetic recovery were the most common complications after myelography. There was no difference in myelographic quality (p > 0.05). We conclude that iohexol is safer than metrizamide for equine myelography and that quality myelograms can be obtained with either contrast medium.     

Beta-2-microglobulin levels in the cerebrospinal fluid of normal dogs and dogs with neurological disease

BACKGROUND: Cerebrospinal fluid (CSF) analysis is the basis for establishing a diagnosis of central nervous system (CNS) inflammation. However, the information provided by routine CSF analysis is limited. Determination of CSF beta-2-microglobulin (beta2m) concentration has been used diagnostically in humans to identify inflammatory CNS disease; we hypothesized that it may have similar value in dogs. OBJECTIVES: The objective of this study was to measure (beta2m concentration in the CSF of clinically healthy dogs and compare the values to those observed in dogs with inflammatory CNS disease and intervertebral disc disease (IVDD). METHODS: CSF was collected from 10 clinically healthy laboratory dogs and 11 dogs each with inflammatory CNS disease and IVDD. Routine CSF analysis was performed, and (beta2m concentration was measured by ELISA. CSF (beta2m concentration and CSF:serum (beta2m ratio were compared between groups by ANOVA. Linear relationships between CSF total nucleated cell count (TNCC), RBC count, total protein concentration, and (beta2m concentration were assessed by regression analysis. RESULTS: The mean (+/- SD) CSF (beta2m concentration in clinically healthy dogs was 0.36 (+/- 0.05 microg/mL (cisternal) and 0.40 (+/- 0.07 microg/mL (lumbar). Median CSF (beta2m concentration in dogs with IVDD (0.46 microg/mL) and inflammatory CNS disease (0.85 microg/mL) differed from that of controls (0.36 microg/mL; P=.002). The concentration also differed between the 2 disease groups (P=.01). Five dogs with inflammatory CNS disease had CSF:serum (beta2m ratios >1. A correlation was identified between TNCC and (beta2m concentration (r=0.69, P=.0003). CONCLUSIONS: CSF (beta2m concentration is higher in dogs with IVDD and inflammatory CNS disease, with highest values seen with inflammatory disease. This may be attributed in part to the correlation between CSF (beta2m concentration and TNCC, but also may reflect intrathecal immune activation.     

Canine intervertebral disc disease: Changes in the cerebrospinal fluid

Data was obtained from 118 cerebrospinal fluid (CSF) samples from dogs with intervertebral disc disease. The effect of lesion location and the severity and duration of clinical signs was studied. Ninety-seven samples were obtained from the cerebellomedullary cistern and 21 from the lumbar cistern. Changes in CSF were identified in 84.7 per cent of the lumbar samples, compared with only 37.1 per cent of the cerebellomedullary samples. More pronounced pleocytosis and protein level increases were seen in dogs with acute and clinically severe lesions. The protein concentration was more commonly elevated than the total white blood cell count. These results indicate that marked protein and white blood cell count elevations can occur in association with intervertebral disc extrusion. Such findings, therefore, should not necessarily preclude myelographic examination in dogs presented for paralysis.     

Analysis of cerebrospinal fluid from the cerebellomedullary and lumbar cisterns of dogs with focal neurologic disease: 145 cases (1985-1987)

Data were obtained from 158 CSF samples from 145 dogs with focal, noninfectious/noninflammatory neurologic disease. The effect of lesion location and the duration and severity of clinical signs were studied. One hundred and twenty-five samples were obtained from the cerebellomedullary cistern (CMC), and 33 were obtained from the lumbar cistern (LC). Intracranial and cervical disease affected the CSF from the CMC more often than did thoracolumbar disease. However, lumbar CSF was more frequently affected by disease anywhere along the neuraxis. For compressive spinal cord disease, the protein concentration at both cisterns was more often high in acute, clinically severe lesions. Intracranial lesions consistently caused abnormalities in CSF from both the CMC (7 of 7; 100%) and LC (2 of 2; 100%). Abnormalities were identified in 16 of 38 (42%) and 5 of 7 (71%) CMC and LC samples, respectively, in dogs with cervical disease. In dogs with thoracolumbar lesions, only 22 of 80 (27.5%) CMC samples were abnormal, compared with 21 of 24 (87.5%) LC samples. These findings suggest that CSF collected cranial to the lesion may be normal or only mildly altered by focal neurologic disease. Fluid obtained caudal to the lesion presumably is more substantially altered because of the predominant caudal flow of CSF. To maximize the yield of diagnostic information from CSF analysis, the fluid should preferably be obtained caudad to the disease site; however, because of problems associated with lumbar puncture, we suggest that CSF from the CMC also be obtained.     

Transient leakage across the blood-cerebrospinal fluid barrier after intrathecal metrizamide administration to dogs

Cerebrospinal fluid samples from 9 dogs given 84 mg of metrizamide/kg of body weight intrathecally were collected at intervals from 3 hours to 30 days after treatment and were compared with CSF samples collected before metrizamide treatment (base line) and with samples taken at similar intervals from 2 nontreated control dogs. Increased CSF albumin (mean 19.2 mg/dl) and immunoglobulin (Ig) G (mean 5.91 mg/dl) concentrations occurred 1 day after myelography, compared with base-line concentrations (6.15 and 1.24 mg/dl, respectively) and with concentrations from controls. Immunoglobulin M and IgA concentrations also were increased in some of these samples. However, immediately after myelography (3 hours after treatment) CSF albumin and IgG concentrations were comparable with those of controls, and these values returned to base line within 5 days of myelography and remained so for 30 days. A high correlation between albumin and IgG concentrations of individual CSF samples indicated the likelihood that leakage across the blood-CSF barrier was the origin of the increased values. A transient increase in CSF leukocytes, consisting of mononuclear cells and neutrophils, was also noticed 1 day after treatment but not at other times and not in controls. Nonsuppurative, predominately histiocytic meningitis of decreasing intensity was noticed in dogs euthanatized at 1 or 5 days, but not in dogs euthanatized at 10, 20, or 30 days after treatment. The meningeal cells stained intensely with periodic acid-Schiff stain and intracellular contrast medium was ultrastructurally apparent in phagolysosomes. Control dogs killed after 30 days did not have these changes. The intrathecal administration of metrizamide resulted in transient leakage of serum components into CSF and an accompanying transient meningitis.     

Complications associated with the use of iohexol for myelography of the cervical vertebral column in dogs: 66 cases (1988-1990).

Medical records of 66 dogs that had undergone myelography, using iohexol (240 mg of iodine/ml, 0.3 to 0.5 ml/kg of body weight) during a 2-year period, were reviewed. In 3 dogs, myelography was performed twice during different anesthetic procedures. Neurologic abnormalities were more pronounced the day after myelography in dogs with caudal cervical spondylomyelopathy (P less than 0.01), meningitis (P less than 0.01), or extradural tumors (P less than 0.05). Neither anesthetic regimen nor duration of anesthesia significantly affected the frequency of complications. Seizures occurred after myelography in 6 dogs, and 1 dog had seizures after each of 2 myelographic procedures. The frequency of seizures was significantly greater in male Doberman Pinschers afflicted with caudal cervical spondylomyelopathy. Male dogs (P less than 0.01) and Doberman Pinschers (P less than 0.001) had higher prevalence of seizures. Caudal cervical spondylomyelopathy was associated with higher prevalence of seizures, compared with all other diagnoses (P less than 0.001). Seizures were significantly more prevalent when body weight was greater than or equal to 29 kg (P less than 0.001), when greater than or equal to 2 injections of contrast medium were administered (P less than 0.016), or when 2 injections of contrast medium were given at the cisterna magna (P less than 0.015). The 10% prevalence of seizures after myelography with iohexol in the study reported here is greater than in previous reports, but is lower than that reported after myelography using metrizamide.     

Use of iohexol for myelography in the horse

The use of iohexol as a contrast agent for myelography is reported in two groups of horses. Group 1 (n = 6) were used only for myelography and to assess the clinical and pathological effects of intrathecal administration of iohexol. A volume of 20 ml at a concentration of 300 or 350 mg iodine/ml gave satisfactory myelographic detail with no serious clinical or neurological side effects. Only a minimal inflammatory response could be demonstrated in cerebrospinal fluid at four and 14 days after injection. At post mortem examination 14 days after myelography there was no evidence of meningitis nor was any other pathological change detected. Group 2 (n = 19) comprised a series of clinical cases of suspected cervical vertebral malformation. The only untoward sequelae recorded involved two horses in which iohexol was diluted with sterile water prior in intrathecal injection. A progressive necrotising meningitis developed in both cases which necessitated euthanasia. It was concluded that the major advantages of iohexol for use in the horse were its diagnostic quality, safety and low cost.     

Autoantibodies against structures of the central nervous system in steroid responsive meningitis-arteriitis in dogs

Steroid-responsive meningitis-arteriitis (SRMA) is a disease of dogs familiar in small animal practice for decades. A combined evaluation of IgA in serum and cerebrospinal fluid (CSF) is an important diagnostic tool. It is suspected that immunpathological mechanisms are involved in the pathogenesis of SRMA because of the marked response to steroids. Excessive production of IgA seems to play a central role and might be caused by an immune reaction to self-antigens of the central nervous system (CNS). To test this hypothesis, we analyzed CSF samples from 55 dogs with SRMA using the western blot method. After blotting canine brain tissue, IgA, IgM and IgG of the CSF samples were tested for their binding to CNS antigens. We also evaluated CSF samples from 45 dogs with other brain diseases, including different encephalitides and intracranial tumors, and from healthy dogs as controls. Positive reactions (mostly IgA) were observed in the CSF samples from dogs with SRMA, different encephalitides and brain tumors (a total of 8% positive samples). The occurrence of autoantibodies against CNS structures was significantly higher in the control group "other brain diseases" than in the SRMA group (p = 0.0135). There was no significant difference in the number of positive samples between dogs with SRMA and the negative control group (healthy dogs, p = 0.1535). Despite the small number of positive samples, only dogs with abnormal findings in the CSF analysis also had autoantibodies in the CSF. There was no significant correlation between the occurrence of autoantibodies and levels of IgA, protein content and cell counts in the cerebrospinal fluid. However, there was a certain trend toward positive reactions in CSF samples with high protein content. The occurrence of autoantibodies in dogs with SRMA thus seems to be an epiphenomenona rather than the cause of the disease.     

Detection of oligoclonal bands in cerebrospinal fluid from German Shepherd dogs with degenerative myelopathy by isoelectric focusing and immunofixation

BACKGROUND: Detection of intrathecal IgG synthesis is important in evaluating inflammatory diseases in the central nervous system. Isoelectric focusing (IEF) is currently the most sensitive method to demonstrate intrathecal IgG synthesis and may have diagnostic value for German Shepherd degenerative myelopathy (GSDM). OBJECTIVE: The objective of this study was to adapt a modified IEF and immunofixation method for the detection of oligoclonal bands in cerebrospinal fluid (CSF) from dogs with GSDM. METHODS: Serum and lumbar CSF samples were collected from 6 German Shepherd dogs clinically diagnosed with GSDM. Samples were also collected from 6 clinically healthy dogs for comparison. The concentration of IgG was measured by quantitative ELISA and the concentration of total protein was measured by the Bradford protein assay. The presence of oligoclonal bands was evaluated by use of modified IEF followed by immunofixation. RESULTS: The concentrations of total protein and IgG, and the IgG/total protein ratio in CSF samples, were not significantly different between GSDM patients and control dogs. Four GSDM patients had oligoclonal bands in their CSF based on IEF-immunofixation. No oligoclonal bands were found in CSF from control dogs. CONCLUSION: The results suggest that the detection of oligoclonal bands by IEF-immunofixation may have diagnostic value for GSDM, and support the idea that humoral immune responses may play a role in the pathogenesis of GSDM.     

Influence of anesthetic regimen on the frequency of seizures after cervical myelography in the dog

We examined the influence of various anesthetic drug combinations on the frequency of seizures in dogs after cervical myelography with metrizamide. Over a 12-month period, 78 dogs admitted to the teaching hospital for cervical myelography were assigned randomly to 1 of 6 anesthetic protocols. Myelography was performed, and the dogs were observed for signs of seizure activity after recovery from anesthesia. The person making the decision as to whether or not a dog had had a seizure was unaware of the anesthetic protocol that had been used. Preanesthetic treatment with pentobarbital (5.0 mg/kg) and maintenance of anesthesia with methoxyflurane significantly reduced the frequency of seizures (P less than 0.05). No reduction in seizure frequency was seen with any anesthetic protocol using halothane as the maintenance agent.     

Use of pentobarbital sodium to reduce seizures in dogs after cervical myelography with metrizamide

We conducted a prospective study to examine the effect of pentobarbital administration on the development of seizures in dogs that had undergone cervical myelography with metrizamide while anesthetized with halothane. Thirty dogs scheduled for cervical myelography were assigned to 3 groups. Dogs in group 1 received no pentobarbital. Those in group 2 were administered pentobarbital (5 mg/kg, IM) before induction of anesthesia, and those in group 3 received pentobarbital at the end of the procedure when the anesthetic vaporizer was turned off. Anesthesia was induced with thiamylal sodium in all dogs and was maintained with halothane. Dogs that underwent surgery immediately after the myelography were not included in the study. A significant difference was not found among the 3 groups in terms of number of dogs that had seizures, mean body weight of the dogs, duration of anesthesia after injection of metrizamide, time from extubation to first seizure, volume of metrizamide injected, or clinician performing the myelography.     

Lumbar cerebrospinal fluid in dogs with type I intervertebral disc herniation

BACKGROUND: Cerebrospinal fluid (CSF) in dogs with Hansen type I intervertebral disc herniation (IVDH) is classically described as normal or mildly inflammatory with a predominance of large mononuclear cells or neutrophils in severe acute herniations. However, we have observed a moderate to marked pleocytosis with a predominance of lymphocytes in some dogs with IVDH. HYPOTHESIS: Moderate to marked CSF pleocytosis occurs more commonly in dogs with type I IVDH than is reported in the literature. Lymphocytic predominance is more common than nonlymphocytic pleocytosis in dogs with chronic IVDH. ANIMALS: Four hundred twenty-three client-owned dogs with type I IVDH. METHODS: Retrospective study. Lumbar CSF of dogs with surgically confirmed type I IVDH was evaluated cytologically. Information obtained from medical records included signalment, prior clinical history, time from onset of signs to presentation, neurologic status, and intraoperative findings. Dogs with prior history and/or intraoperative evidence consistent with chronic IVDH before an acute herniation were termed acute-on-chronic (AOC). RESULTS: Pleocytosis (> 5 cells/uL) was present in 51% of dogs, including 23% with cervical IVDH and 61% with thoracolumbar IVDH. Moderate or marked inflammation (> or = 20 cells/uL) was identified in the CSF of 51% of dogs with thoracolumbar IVDH and pleocytosis. A predominance of lymphocytes was significantly more common in dogs examined > 7 days from onset of signs (P= .032) and in dogs with AOC IVDH (P= .0013). CONCLUSIONS AND CLINICAL IMPORTANCE: Moderate to marked CSF pleocytosis in dogs with type I IVDH is more common than previously reported. Lymphocytic pleocytosis is most common in dogs with chronic progression or AOC IVDH. Lymphocytic inflammation in the CSF of some dogs might suggest an immune-mediated response to chronically herniated disc material.