Tolerance of iohexol, iopamidol, and metrizamide in lumbar myelography

Status epilepticus after myelography with iohexol (Omnipaque)

Myelography has been of great use as a diagnostic modality, especially when other modalities were not conclusive.However, considering the invasive nature of myelography, it should receive the attention of medical personnel for them to be aware of its possible complications, especially when newer agents are applied as the contrast media. Myelography could lead to some common adverse effects and complications, but in this case report, we will present one of the most serious and uncommon complications accompanied with myelography using Omnipaque, a nonionic second-generation contrast agent. These complications include lower-extremity myoclonic spasms, tonic seizure leading to status epilepticus, rhabdomyolysis, disseminated intravascular coagulation and anaphylactic shock. Having the knowledge of possible complications and available solutions, particularly fatal ones, could prepare medical staff beforehand for primary and secondary preventions.

Malignant Cerebral Edema following CT Myelogram Using Isovue-M 300 Intrathecal Nonionic Water-Soluble Contrast: A Case Report

Lumbar myelogram utilizing nonionic contrast is a commonly performed procedure to identify spinal pathology. Complication rates are low. Cerebral edema has been shown to occur following intrathecal injection of ionic contrast; however, no current literature has documented this complication relating to the ubiquitously used nonionic contrast medium. We report a case of a patient who developed malignant cerebral edema following a lumbar myelogram with Isovue-M 300 nonionic water-soluble intrathecal contrast. We believe this is the first reported case of cerebral edema resulting from the use of a nonionic contrast.

Aseptic meningoencephalitis after iohexol CT myelography

We describe the case of a patient with aseptic meningoencephalitis after intrathecal iohexol injection for myelography and review the previous literature on similar cases of contrast-induced neurotoxicity.

Rhabdomyolysis after intraoperative myelography

This case report suggests that the nonionic contrast agents may cause myoclonic spasms and seizures like the ionic ones. A 14-year-old female with congenital scoliosis was scheduled for T2-L3 scoliosis surgery. She had no medical history of a seizure disorder. After a negative wake-up test, myelography was performed with iohexol. Myoclonic spasms, disseminated intravascular coagulopathy (DIC) and rhabdomyolysis were diagnosed postoperatively. Anaesthesiologists should be aware of the complications which may occur after the use of nonionic and water-soluble contrast agents.

Brain penetration of intrathecal iomeprol in dogs

PURPOSE

Iomeprol, a new nonionic iodinated compound for intravascular use, is being evaluated as a myelographic contrast agent because of its low neurotoxicity. This study aimed to assess the degree of brain penetration of iomeprol after intrathecal administration.

MATERIAL AND METHODS

Brain penetration in dogs was investigated by CT and compared with that of iopamidol, iohexol, and ioversol, currently used as myelographic contrast media (CM). Nervous tissue density was determined in different brain structures by recording Hounsfield values.

RESULTS

The experiments revealed that CM diffused from the cisternae into the parenchyma, reaching a maximum at 5-24 h after injection. The density of the examined brain regions was still higher than the preinjection levels 24 h later. No differences in brain penetration were observed among the CM investigated.

CONCLUSION

The study has shown that iomeprol penetrates into the brain to the same extent as the most widely used myelographic CM.

Conditioned taste aversion in rats following intrathecal administration of contrast media

PURPOSE

The occurrence of side-effects such as visceral malaise after intrathecal administration of the non-ionic radiography contrast media iomeprol, iopamidol, and iotrolan was assessed in rats by the conditioned tasted aversion procedure.

METHODS

Reduced preference towards a saccharose solution compared with normal water following intraventricular administration of a contrast medium was used as a measure of the aversive response.

RESULTS

At a dose of 100 mg I/kg none of the tested contrast media induced aversion. At 200 and 300 mg I/kg, both iopamidol and iomeprol induced significant aversive responses with respect to control, although the response of the iomeprol group appeared milder than that of the iopamidol group at a dose of 200 mg I/kg. Iotrolan could be tested only at the lowest dose since the high doses caused excessive mortality.

CONCLUSION

Intrathecally administered iomeprol appeared to be well tolerated in rats at doses higher than those suggested for clinical use.

Neurotoxicity of water-soluble contrast media

A review is given of the development of the water-soluble contrast media (CM) with particular attention to the frquency of neurological complications. A remarkable improvement was achieved following the introduction of the nonionic agent metrizamide in 1974, and a further decrease in neurotoxicity was obtained with the newer nonionic monomers, which have multlple hydroxyl groups included at different sites of the molecule. Theoretical considerations and experimental studies suggest that the neurotoxicity of the new nonionic dimeric agents shuold be at least within the low range seen with the monomeric ones, but further experience is needed before definite conclusions can be drawn in this respect. The mechanisms responsible for the neurological complications seen with CM are unknown but certain critical groups on the CM molecules are known. Several animal models have been developd, which may help predict the degree of neurotoxicity.

Somatosensory evoked potentials after iohexol myelography

Tibial nerve and S1 dermatome somatosensory evoked potentials (SSEPs) were recorded before and after iohexol lumbar myelography in order to evaluate possible neurotoxic effects of this contrast medium. No significant change in SSEP latencies nor amplitudes was noted after iohexol myelography, supporting the low neurotoxic profile of this contrast agent. Results were compared to those of a control group of patients before and after lumbar puncture (LP), without injection of contrast agent. In this group also no significant change in SSEP components was found, indicating that a preceding LP does not affect this electrophysiological examination.

Water-soluble contrast CT cisternography in CSF fistulas

High resolution C.T. cisternography with water-soluble contrast media was performed in eight patients with C.S.F. rhinorrhea and suspected C.S.F. fistula. This technique, aided by video fluoroscopy, proved successful in documenting the precise anatomical localisation of the fistulous track in all eight patients. Surgical exploration and correction was done in every case with confirmation of the radiological findings.

The influence of needle size and other factors on the incidence of adverse effects caused by myelography

A randomized prospective trial of 26 G versus 22 G spinal needles was performed in 284 consecutive patients referred for myelography, during which contrast medium was introduced by lumbar puncture. Use of the fine (26 G) gauge needle resulted in a significant decrease in moderately or severely painful needle placements and moderate, severe or postural headaches following myelography. The incidence of other side effects was not significantly influenced by needle size. The incidence of headaches and other side effects was significantly higher in female patients. Back pain, the commonest side effect, was significantly more common in patients who had normal lumbar myelograms than in those in whom lumbar root compression was demonstrated. The incidence of neck stiffness was significantly higher following cervicothoracic myelograms than lumbar myelograms but there was no significant difference in the incidence of other side effects. The use of 4.5 g instead of 3.0 g of iodine resulted in no increase in symptoms. The experience of the operator had no significant effect on the incidence of side effects. Some side effects of myelography appear to be due mainly to cerebrospinal fluid leakage at the site of puncture and are strongly influenced by psychological factors.

The clinical application of radiopharmaceuticals

This article highlights the choices and the arguments in the selection of appropriate contrast materials in radiological examinations--nonionic versus ionic contrast material--and aims to assist the physician in decision-making. Various authors have raised questions concerning the proposed advantages of nonionic contrast material. However, studies in low risk patients have shown more complications with the use of ionic contrast than nonionic contrast materials; this is the important group of patients since in high risk patients nonionics are used almost exclusively. The important factor that increases the controversy is cost, which is significant since nonionic agents cost 10 to 15 times more than ionic agents in the USA. Thus, cost-benefit considerations are important because price sensitivity and cost may determine fund availability for equipment or materials that also may be necessary or important in improving patient care. In magnetic resonance imaging (MRI), as in computed tomography (CT), the use of contrast material has improved diagnostic accuracy and the ability to reveal lesions not otherwise easily detected in brain and spinal cord imaging. These include separating scan from disc, meningitis, meningeal spread of tumour, tumour seeding, small metastases, intracanalicular tumours, separating major mass from oedema, determining bulk tumour size and ability to demonstrate blood vessels so dynamic circulatory changes may be revealed.

Which factors affect reported headache incidences after lumbar myelography? A statistical analysis of publications in the literature

Nineteen publications were reviewed and subjected to a combined statistical analysis (meta-analysis) regarding the influence of study design factors upon reported headache and total symptom incidences after lumbar iohexol myelography. A significant association was found between reported side effects on one hand and needle diameter, follow up time and the method of questioning respectively on the other. The combination of long follow-up time and specific questioning and the combination between larger diameter (20G) needles and long follow-up time, both seemed to be strong predictors for reporting high side effect incidences. Nine studies were similarly analyzed regarding the influence of early ambulation and contrast type upon reported headache incidences. Early ambulation significantly increased headache after iohexol or iopamidol lumbar myelography as opposed to metrizamide myelography.

Outpatient myelography with iohexol and iopamidol; pilot study and contrast trial

50 patients underwent myelography on an outpatient basis; the incidence and severity of side effects were compared, in a prospective study, with 180 inpatient examinations over the same period. In addition, in the initial 200 myelograms (36 outpatients and 164 inpatient) iohexol and iopamidol were compared in a double blind trial. Headache was the most common side effect in both patient groups, recorded in 50% of outpatients and 25% of inpatients. Other side effects were of comparable incidence. 84% of outpatients undergoing myelography found it "acceptable", and did not consider a night in hospital necessary after the procedure. No difference in side effects was demonstrated between the two contrast media. This pilot study suggests that outpatient myelography is practical and safe, with considerable cost saving implications.