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.

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.

Central nervous system reactions to cervical myelography

In a double blind prospective study of side effects to cervical myelography 38 patients were evaluated with neurologic examination, electroencephalography (EEG), brainstem evoked response (BER), somatosensory evoked responses (SSER), and continuous reaction times prior to and at 6 h and 24 h after myelography with either metrizamide or iohexol. A difference in the incidence of side effects (for example headache, dizziness, nausea, and neck pain) to the two different contrast media indicated that the inconveniences related to myelography were not only due to the spinal puncture. A contrast medium effect on the central nervous system varying from one agent to another was present. A high frequency of EEG deteriorations among patients with adverse clinical reactions and on only discrete affection upon BER indicated the reaction to be located to the cerebral cortex. Weakened tendon reflexes and reduced strength in the upper extremities were probably caused by blockade in the motor roots as SSER were normal indicating no affection of the sensory pathways. This hypothesis is in agreement with the fact that the patients were in the prone position in the first phase of the investigation causing the highest concentration of contrast medium around the motor roots and the anterior part of the spinal cord. Difference in metabolic effect may explain differences in side effects of metrizamide and iohexol.

Complications of lateral C1-2 puncture myelography

This study reviewed the technical complication of 112 cases of lateral C1-2 puncture myelography for cervical spinal cord disorders. Spinal cord puncture and contrast injection, puncture between the occiput and C1, and blood vessel puncture were the main complications. These principally depended on the positioning of the patient's neck (hyperextension) and misdirection of the x-ray beam. For preventing major arterial puncture, the authors also reviewed 164 vertebral angiograms and determined the pathway of the vertebral arteries and the incidence of anomaly.

Sex and age related differences in postmyelographic adverse reactions. A prospective study of 1765 myelographies

Differences in frequency of postmyelographic adverse reactions were analyzed with respect to sex and age in a prospective study including 1026 patients injected with metrizamide and 739 injected with iohexol. Regardless of the type of contrast medium or myelography, all types of adverse reactions were 1.4-3.8 times as frequent in women as in men. Most of the differences were statistically significant. Headache was more frequent, while vomiting and dizziness were less frequent in both women and men aged 26-50 years compared with those over 50 years of age. Dizziness and increased low back pain were consistently reported spontaneously by the patients less frequently than emerged via formal interview. The large differences between the sexes suggest that further research on contrast media toxicity would be best performed with separation of the data by gender.

Serial EEG recordings following intrathecal metrizamide administration

EEG recordings were obtained before and after intrathecal metrizamide injection in 50 consecutive patients who underwent metrizamide myelography or cisternography. EEG tracings were recorded daily until the pattern returned to baseline. One patient (2%) developed seizures. The most frequent EEG abnormality was generalized slowing of various degrees. In 15 patients (30%), the EEG record was normal throughout the study. In 4 patients (8%), EEG disturbances were seen up to the fifth day after the procedure. Patients who had undergone cervical myelography and cisternography had a marginally higher frequency of EEG disturbances than patients who underwent lumbar myelography. The causes inducing these time-related disturbances are discussed, as compared to pharmacokinetics of intrathecally administered metrizamide.

[The effects of metrizamide myelography on electroencephalographic changes]

Metrizamide, a non-ionic water soluble contrast medium, is used in myelography for detecting spinal cord lesions. Because it is an injection in the subarachnoid space, the effects on the central nervous system following metrizamide myelography should be studied. Electroencephalography can offer a non-invasive and objective method for evaluating the functions of the central nervous system. From September to December 1986, 30 cases which had received cervical or lumbar metrizamide myelography were collected. After myelography, in addition to a history review and neurologic examination, electro-encephalography was carried out within 24 hours. If the EEG record revealed abnormal, a series of EEG follow-ups were conducted until recordings were normal. The incidence of clinical adverse effects following Metrizamide myelography was 53.3% and 66.6% respectively in cervical and lumbar injections. No significant difference was found between the two groups. Secondly, the abnormal rate of the EEG record was 40.0% and 60.0% following cervical and lumbar myelography. The difference was also not significant. Lastly, the relation between clinical adverse effects and an abnormal EEG records was poor in cervical metrizamide myelography but good in lumbar myelography. The conclusions suggested by this research that the clinical adverse effects and the abnormal EEG record after metrizamide myelography are transient and are reversible changes. The mechanism of complications following cervical and lumbar metrizamide are different. Although complications may occur following cervical and lumbar metrizamide myelography, it remains a practical method in detecting spinal cord lesions.

[Neurotropic effects of non-ionic contrast media]

Effects of non-ionic contrast media on the central nervous system were compared in order to clarify any differences due to the side-chain structures among iopamidol, iotrolan, iocibidol, iohexol, iopromide, iosimide and metrizamide. The study included a primary screening test based on Irwin's method, antielectric convulsive tests using mice, measurement of the blood pressure using rats and electroencephalography using rats and rabbits. The general behavior of mice in the primary screening test revealed that tolerance to iopamidol, iotrolan and iocibidol was excellent; that to iopromide and iohexol was moderate; and that to iosimide and metrizamide was poor. Iosimide and iohexol suppressed the transient increase of blood pressure upon intravenous administration in the normal rats but not in the pithed rats. Electric stimulus increased the mortality of mice pretreated with iosimide and iohexol. Abnormal EEG with epileptic seizures, slow wave and/or flattening were observed with the administration of iopromide, iosimide or metrizamide as well as ionic contrast media. From these results, it was concluded that iopromide and metrizamide were not well tolerated in general behavior and EEG; iohexol, in general behavior, electroshock and blood pressure; and iosimide, in all experiments, while iopamidol, iotrolan and iocibidol were well tolerated. Therefore, small differences in their side-chain structures among these contrast media are considered to cause different effects on the central nervous system.

[Adverse reactions and intracranial contrast medium after myelography]

Correlation between adverse reactions and intracranial contrast media after myelography was studied. Myelography was carried out for 12 cases with metrizamide and 14 with iotrolan. In all patients, cranial CT scans were performed 18 approximately 22 hours after myelography. CT attenuation value of subarachnoid cistern was higher than the gray matter in 12 cases and lower in 14 cases. Six cases suffered from adverse reactions, but only 1 case belongs to the higher group. No correlation between adverse reactions and residual amount of contrast medium on CT was recognized.

F-responses after metrizamide and iohexol lumbar myelography

We measured several F- and averaged F-response variables before and after lumbar myelography with metrizamide and iohexol in order to evaluate possible effects of these contrast agents upon proximal motor nerve conduction and motor neurone exitability. Averaged F-response onset latency increased while both duration and amplitude decreased after iohexol myelography. These changes were interpreted as signs of minor neural depression but they were slight and without clinical significance in the individual patient. F-response variables were not affected after metrizamide myelography.

[Metrizamide encephalopathy in a child with hydrocephalus--effects of L-threo-DOPS on persistent disturbance of consciousness and L-dopa on extrapyramidal symptoms]

This report describes a case of metrizamide encephalopathy with persistent disturbance of consciousness and extrapyramidal symptoms. These two conditions have rarely been reported among the various adverse effects of metrizamide. An 11-year-old girl had been in almost good health until she was ten years old, at which time she received a ventriculo-peritoneal shunt operation, suffering from hydrocephalus of unknown etiology. At the age of eleven, she was admitted to our hospital due to hydrocephalus recurrence. She was examined by metrizamide shunt-gram (1200 mg iodide/4 ml). On the next day, she became drowsy. The CT scan disclosed the periventricular penetration of metrizamide into the medial part of the thalamus and the caudate nucleus. Thirteen days later, disturbance of consciousness continued, and extrapyramidal symptoms, that is, rigo-spasticity and postural tremor, were observed. Oral administration of L-threo-DOPS, the direct precursor of noradrenaline, was effective against the persistent disturbance of consciousness and L-DOPA was effective against the extrapyramidal symptoms. She soon recovered almost to normal and no neurological deficit remained. We thus conclude that the CT scan findings and effects of L-threo-DOPS and L-DOPA suggest that metrizamide encephalopathy in this case were respectively due to its periventricular penetration into the medial part of the thalamus and the caudate nucleus, and the resultant deficiency of the ascending noradrenergic reticular activating system and the nigrostriatal dopaminergic system.

Absence status epilepticus with computed tomographic brain changes following metrizamide myelography

Absence status epilepticus following metrizamide myelography was associated with computed tomographic scan evidence of a high concentration of the dye in brain gray matter. We suggest that absence status epilepticus is due to the direct effect of metrizamide on the cortex and that this clinically treatable condition may have escaped diagnosis in previous reports.

[EEG study after cervical myelography with iopamidol and metrizamide]

In an open investigation on 100 patients, changes in the electroencephalogram following ascending cervical myelography with iopamidol 250 or metrizamide were studied. In the postmyelographic EEG, there were normal findings in 36 patients after iopamidol and 26 after metrizamide. A comparison of the pathological results after iopamidol and metrizamide yielded a relation of 6:2 for mild, 2:5 for moderate, and 0:6 for severe degree of slowing, 4:6 for basal theta wave activation, and 2:5 for increased cerebral excitability. The results were statistically significant on the 5% level according to the chi-square test.

Absence status epilepticus resulting from metrizamide and omnipaque myelography

Two cases of absence status are described, one case following metrizamide myelography and the other from omnipaque myelography. Metrizamide has been well known to cause convulsive seizures even in patients without epilepsy. The exact mechanism is not known but appears to be direct neuronal toxic effects possibly due to competitive inhibition of hexokinase activity. The acute confusional state following myelography from water soluble agents is reviewed. In view of the difficulty in clinical diagnosis and the excellent response to anticonvulsant therapy, the possibility of this clinical entity should be specifically excluded by EEG in any person suffering from prolonged confusion following myelography with water soluble agents.

Absence status following metrizamide myelography: management of nonresponders

Acute confusional state following metrizamide myelography has been reported to occur in up to 2% of patients. These patients have been diagnosed as having toxic encephalopathy. Recently, various cases have been reported to have a nonconvulsive status (absence status or complex partial status) who responded well to diazepam or clonazepam therapy. However, some authors have described cases of nonresponders to anticonvulsive therapy. Failure of therapy can be dose-related. For this reason, our patient was closely monitored by EEG to determine if dose adjustment was warranted, thereby achieving good results.

Reduction of the gastrointestinal side effects of metrizamide myelography with oral dexamethasone

A prospective, double-blind study was undertaken to assess the effectiveness of oral dexamethasone premedication in reducing a variety of side effects associated with metrizamide myelography. We also examined the relationship between side effects and needle size, total metrizamide dose, radiographic findings, and personality. Patients were randomly assigned to either a placebo group (44 patients) or a dexamethasone group (38 patients). All patients completed a 24-item symptom checklist before and 24 hr after lumbar myelography. In addition, all patients completed the Minnesota Multiphasic Personality Inventory prior to myelography. Analysis of variance demonstrated a statistically significant decrease in the frequency of gastrointestinal side effects (loss of appetite, nausea, vomiting) in the dexamethasone group. There were no significant differences between the two groups for the other 21 symptoms examined. We concluded that premedication with oral dexamethasone significantly reduces the gastrointestinal side effects associated with metrizamide myelography. This reduction was especially important in older patients.

Hemodynamic and electrocardiographic consequences of high- and low-osmolality contrast agents for left ventricular angiography

The cardiovascular effects of two nonionic contrast agents with low osmolality (iohexol and metrizamide) were compared with one standard ionic, high-osmolality contrast agent (metrizoate) used for left ventricular (LV) angiography in patients with coronary heart disease. Metrizoate induced a marked elevation of LV end-diastolic pressure and LV systolic pressure and an increase in cardiac output after a delay of a few minutes. All these changes were significantly less severe with iohexol and metrizamide. Hypotension occurring 30 sec after LV angiography was observed only with use of metrizoate. All agents increased heart rate, but the increase after metrizoate was significantly more pronounced and prolonged. The PQ and QT interval was prolonged only by metrizoate. The subjective symptoms were significantly more marked with metrizoate than with the two other agents. Thus the new nonionic contrast agent iohexol and metrizamide produced markedly less hemodynamic and electrocardiographic disturbance than the ionic agent metrizoate.

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.

Effects of route of fluid administration on severity of side effects with post-metrizamide myelogram

The effect of route of hydration on the severity of side effects of nausea, vomiting, and headaches for 13 patients receiving a metrizamide myelogram was studied. Six patients were hydrated by mouth only and seven by mouth and intravenously. Severity was measured 24 hours postmyelogram with a visual analogue scale for each side effect. Controlling for the volume of all fluid received, significantly more severe headaches were reported by patients hydrated only orally. For this small sample, no significant differences were found for severity of nausea or vomiting. The study and its implications for nursing are described.

Metrizamide myelography in patients with iodine allergy or previous adverse reactions to iodinated contrast media

Twenty-seven metrizamide myelographies were performed in 26 patients who had a history of iodine allergy or adverse reactions to iodinated contrast media. Three of the patients had had adverse reactions from a previous myelography procedure. All patients received atropine, diazepam, and metoclopramide as premedication. In ten examinations corticosteroids were also given. No patient, during or after myelography, had any reaction that could be related to hypersensitivity to the contrast medium. The incidence of headache, the most frequent side effect, was almost the same in patients who had corticosteroids in their premedication (30%) as in patients without (35%). These observations indicate that metrizamide myelography may be performed despite previous adverse reactions to contrast media.

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.

Side effects following metrizamide myelography and lumbar laminectomy

A retrospective study of 50 patients was undertaken to observe the postoperative side effects experienced by patients undergoing metrizamide (Amipaque) myelography followed by laminectomy on the same day and to compare them with side effects experienced if the laminectomy was postponed at least one day. Results documented that the incidence of nausea was statistically greater in Group 1 (myelogram and surgery the same day) than in Group 2 (delayed surgery). While the occurrence of vomiting and headache in Group 1 was also greater, the numbers did not reach statistical significance. Group 1 did require significantly more doses of antiemetics for a longer period of time. The groups did not differ in the length of time an intravenous (IV) infusion was in place, but Group 1 patients required a significantly greater number of urinary catheterizations for retention and residual for longer than three days. The length of stay and the time from surgery to discharge was the same for both groups.

Multiple subcortical haemorrhages following lumbar metrizamide myelography

The case is presented of a patient showing multiple subcortical haemorrhages after lumbar metrizamide myelography. This complication after intrathecally administered metrizamide contrast medium appears not to have been reported before. Several different possible explanations are proposed for the phenomena observed in this case.

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.

The effect of intrathecal iohexol on visual evoked response latency: a comparison including incidence of headache with iopamidol and metrizamide in myeloradiculography

Fifty consecutive unselected patients referred for myeloradiculography and examined by the same radiologist, when facilities for measuring the visual evoked response were available, are considered. The effect on the visual evoked response of the examination and the incidence of headache following the use of iohexol as the contrast medium are compared with those after the use of iopamidol and metrizamide reported in a previous study. A total of 400 cases examined with iopamidol and 200 cases examined with iohexol are reviewed with regard to the incidence of headache. Whereas iopamidol and, to a greater extent metrizamide, were found to cause significant lengthening of the visual evoked response latency 20 hours after the radiological examination, iohexol did not. Furthermore there was no significant difference in the 20 hour reading following the use of iohexol compared with the original control group of patients who underwent lumbar puncture alone. There was a lower incidence and severity of headache following the use of iohexol than with iopamidol and a markedly reduced incidence compared with metrizamide. Iohexol is considered less neurotoxic than iopamidol which had previously superceded metrizamide as the contrast medium used for myeloradiculography in the Royal Surrey County Hospital. Volumes of up to 14 ml of iohexol 300 mg I/ml have been used for lumbar radiculography and for total myelography and up to 10 ml for direct lateral cervical puncture. In 350 cases examined to date with iohexol the only serious sequel was a case of chemical meningitis following the lumbar injection of 10 ml of the 300 mg I/ml solution for a cervical examination. The patient made an uneventful recovery.

The probability of pancreatitis after pancreatic parenchymatography with a non-ionic contrast medium. A sequentially designed clinical trial

Endoscopic retrograde pancreatography (ERP) with parenchymatous contrast filling may result in clinical pancreatitis. The aim of the present prospective trial was to assess the frequency of acute pancreatitis after pancreatic parenchymatography with a non-ionic contrast medium, metrizamide. For ethical reasons the examination was designed as a sequential study with clearly defined stopping rules. None of the 48 patients studied developed clinical pancreatitis. This indicates that the probability of pancreatitis after parenchymatography is less than 5%. A high degree of contrast filling was obtained both in patients with normal and in those with pathologic pancreatic ducts. The contrast filling of the ducts was associated with not more than a slight pain. The rise in serum amylase was considerable but was not associated with clinical pancreatitis and returned to preexamination levels within 48 h. The examination shows that the non-ionic contrast medium used is well tolerated in ERP.

Tolerance of iohexol, iopamidol, and metrizamide in lumbar myelography

Iohexol and iopamidol, two new nonionic contrast media, have been extensively studied in comparison with metrizamide for lumbar myelography. Review of the literature with statistical analysis indicates both agents are superior to metrizamide in terms of number of patients with adverse reactions (p less than 0.001). Preliminary data suggest, but do not prove, that use of iohexol may result in fewer side effects than iopamidol.

Chemical meningitis in metrizamide myelography. A report of seven cases

Seven patients with acute chemical meningitis after metrizamide myelography are described. Five of the cases occurred within a time span of two months. Clinical and cerebrospinal fluid findings in the acute stage of the illness were similar to findings in acute bacterial meningitis. Possible causes of this complication are discussed.

Cognitive and affective changes after myelography: a comparison of metrizamide and iohexol

A battery of brief cognitive tests and a mood scale were administered to 42 patients before and after cervical myelography with either metrizamide (20 patients) or iohexol (22 patients). The patients receiving metrizamide experienced a deterioration in mood after myelography and a relatively greater decline in cognitive test performance than did those receiving iohexol. These two side effects tended to occur together in the metrizamide group, suggesting a common underlying cause; but there was no correlation between changes in mood and cognitive function after myelography with iohexol. These results suggest that metrizamide has a greater neurotoxic effect than iohexol.

CT of extraarachnoid metrizamide instillation

Because CT of spinal extraarachnoid metrizamide collections may be misleading, we reviewed the postmetrizamide CT scans of 425 patients in order to characterize the appearance of subdural or epidural metrizamide. Eight patients were found to have extraarachnoid metrizamide contrast collections. In all patients, both the subarachnoid space and the extraarachnoid collection were opacified with metrizamide. In seven patients, a subdural collection of metrizamide created a mass upon the opacified subarachnoid space. Three of these subdural collections were less dense than the opacified subarachnoid compartment and simulated soft-tissue disease, including tumor and an arteriovenous malformation. The hypodense collections are probably a result of leakage of metrizamide and cerebrospinal fluid through the spinal needle defect. CT clues for diagnosing these potentially misleading subdural collections include preservation of the normal dural and epidural interface, identification of small islands of metrizamide within a suspected soft-tissue "mass," the presence of concomitant epidural contrast material collections, and the absence of adjacent vertebral-body destruction.

Low-dose metrizamide spinal computed tomography in outpatients

Delineation of the thecal sac in CT can be improved by the presence of intrathecal metrizamide. This may be especially helpful in postoperative patients in whom the landmarks are often obscured by epidural scarring. Metrizamide-enhanced CT was performed on outpatients using 2 1/2 ml metrizamide (170 mg I/ml). Follow-up is available on 40 patients. The procedure was well tolerated with only three instances of severe headache, one case of vomiting, and no reported seizures. Adequate opacification was obtained at 92% of the levels examined with fair opacification at the remainder of the levels. This technique is considered a safe and useful outpatient procedure.

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.