Asterixis and encephalopathy following metrizamide myelography: investigations into possible mechanisms and review of the literature

A Comprehensive Biological and Synthetic Perspective on 2-Deoxy-d-Glucose (2-DG), A Sweet Molecule with Therapeutic and Diagnostic Potentials

Glucose, the primary substrate for ATP synthesis, is catabolized during glycolysis to generate ATP and precursors for the synthesis of other vital biomolecules. Opportunistic viruses and cancer cells often hijack this metabolic machinery to obtain energy and components needed for their replication and proliferation. One way to halt such energy-dependent processes is by interfering with the glycolytic pathway. 2-Deoxy-d-glucose (2-DG) is a synthetic glucose analogue that can inhibit key enzymes in the glycolytic pathway. The efficacy of 2-DG has been reported across an array of diseases and disorders, thereby demonstrating its broad therapeutic potential. Recent approval of 2-DG in India as a therapeutic approach for the management of the COVID-19 pandemic has brought renewed attention to this molecule. The purpose of this perspective is to present updated therapeutic avenues as well as a variety of chemical synthetic strategies for this medically useful sugar derivative, 2-DG.

Critical Assessment of Myelography Practices: A Call for Rational Guideline Revision

BACKGROUND AND PURPOSE

Patient preparation for myelography and postprocedural monitoring varies widely between practices, despite published guidelines. Our aim was to examine the current practice variations in discontinuing reportedly seizure threshold-lowering medications before myelography and to assess the reported incidence of postmyelographic seizures.

MATERIALS AND METHODS

An e-mail survey was sent to American Society of Neuroradiology members concerning the number of postmyelographic seizures experienced in the past 5 years, the presence of an institutional policy for discontinuing seizure threshold-lowering medications, and the type of myelographic contrast used. We compared the postmyelographic seizure frequency in the responses.

RESULTS

Of 700 survey responses, 57% reported that they do not discontinue seizure threshold-lowering medications before myelography. Most (97%) indicated never having a patient experience a seizure following myelography. The number of postmyelographic seizures between those who discontinue seizure threshold-lowering medications and those who do not was not statistically significant (OR = 2.13; 95% CI, 0.91-4.98; P = .08). Most (95%) reported using nonionic hypo-osmolar agents.

CONCLUSIONS

Survey results revealed widely variable practices for patient myelography preparation and postprocedural monitoring. We found no difference in reported seizures between those who discontinued seizure threshold-lowering medications and those who did not. In light of our findings, we propose that discontinuing reportedly seizure threshold-lowering medications is not warranted with the current nonionic water-soluble contrast agents and may be potentially harmful in some instances. This work supports revision of existing recommendations to withhold such medications before myelography.

Asterixis: a study of 103 patients

In 1949, asterixis was first described in patients with hepatic encephalopathy. It was quickly recognized that this phenomenon also occurs in other generalized encephalopathies and sometimes results from structural brain lesions. This paper is a study of asterixis in the general neurology clinic and on the inpatient neurology consultation service. The neurologists recorded the findings on inpatients and clinic patients for 12 consecutive months. Of the 1,109 inpatients with adequate examination, asterixis was documented in 97. Eighteen of the 97 cases were unilateral (18.6%) and 79 cases were bilateral (81.4%). Of the 614 outpatient visits with well documented examination, 6 (1%) individuals had asterixis. Since a small number of patients were examined more than once, the study yielded 103 individuals with adequate data for analysis. Asterixis resulted from varied causes: medications, renal disorder, hepatic dysfunction, pulmonary insufficiency, stroke and other brain lesions (including malignancy, subdural hematoma, and epidural abscess). Asterixis occurred in various patterns: in some cases it was easier to elicit in the upper extremities, in some it was easier to elicit in the lower limbs, and some it was solely or predominantly unilateral. The findings are discussed in light of the literature on asterixis with regard to its varied causes, patterns and presentations. Lastly, asterixis is examined from a historical perspective and the terminology is elucidated.

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.

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.

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.

Capgras syndrome associated with metrizamide myelography

A case of Capgras' Syndrome secondary to an Organic Mental Disorder associated with metrizamide myelography is presented. The relationship of Capgras' symptom to reduplicative paramnesia and prosopagnosia is discussed.

Metrizamide and the EEG: three case reports and a review

Three patients are described who developed cerebral complications and an EEG abnormality for several days after metrizamide myelography. Clinically, the patients showed a fluctuating confusional state with dysphasia and retrograde amnesia, while their EEGs were dominated by runs of slow wave activity interspersed with frequent spikes. The runs appeared either continuously or in paroxysmal bursts. The clinical symptoms and the EEG are compatible with complex partial status epilepticus and are similar to the symptomatology of ten patients described in the literature. This rare clinical entity should be distinguished from a more common complication of metrizamide--non-specific slow wave abnormality of variable degree in the EEG with or without clinical signs. Clinical manifestations may include transient aphasia and weakness of the limbs with pyramidal signs.

Metabolic effect of topical application of metrizamide to rat brain cortex

The x-ray contrast material metrizamide is structurally related to 2-deoxyglucose and inhibits brain glucose phosphorylation both in vitro and in vivo. in vivo. In vivo, however, the present autoradiographic study with labeled 2-deoxyglucose revealed a local increase of glucose metabolic rate in an area of direct metrizamide application to the cerebral cortex. The local increase was 137% above the metabolic rate calculated for the contralateral region. Regions outside the application site showed no difference between the glucose metabolic rates of the ipsi- and contralateral hemispheres. Evidence from the literature suggests that metrizamide may stimulate cortical activity by inhibiting acetylcholinesterase.

Neural tissue uptake and clearance of iohexol following lumbar myelography in rabbits

The diffusion of water-soluble contrast media (CM) into the extracellular space of the central nervous system following injection into the subarachnoid space has previously been shown. As a result of this, water-soluble CM will come in direct contact with the neurons and may interfere with their normal function. The toxic effects would thus be a result both of the molecular properties of the CM as well as the local tissue concentration. The neuronal tissue uptake and clearance of metrizamide in rabbits following lumbar myelography was described in a previous study by our group. This study indicated some retention of metrizamide in the spinal cord probably as a result of binding of the CM to the cell membrane. The mechanism for this has not yet been shown although it may relate to the binding of metrizamide via its 2-deoxy-D-glucose (2-DG) portion and the specific glucose membrane carrier. The present investigation was performed to evaluate the diffusion kinetics of a new non-ionic CM. With iohexol, which lacks a 2-DG component in its molecule a direct relationship between the neural tissue and CSF concentration was found which seems to follow a simple diffusion model. Since iohexol shows no sign of entrapment in the tissue, the contact time for neurons will be shorter than that seen with metrizamide assuming that their rate of drainage from the CSF is identical.

EEG changes 24 hours after myelography with metrizamide

A prospective study of EEG changes following metrizamide myelography was made on 34 patients aged 17-79 years. EEGs were recorded just before and 22-26 hours after myelography. Usually 8-10 ml of metrizamide was injected by either lumbar or lateral cervical puncture. The concentration of metrizamide was relatively high. EEGs were abnormal in 15 out of the 20 patients whose baseline EEGs were normal. EEGs deteriorated in 10 of the 14 patients whose control tracings were abnormal. High voltage delta activity and/or a great deal of theta activity were common abnormalities. Three patients showed triphasic waves. No relationships were found between the EEG changes and clinical variables. But central nervous system involvements by metrizamide tended to be accompanied by a severe EEG slowing.

Blood-brain transfer of galactose in experimental galactosemia, with special reference to the competitive interaction between galactose and glucose

The interaction between glucose and galactose during transport across the cerebral capillary endothelium was studied in anesthetized rats. Although galactose is present in the diet of suckling mammals and is a potential substrate for brain metabolism in adult mammals, its effect on glucose transport in adult rats is unknown. A kinetic model was formulated to analyze the effect of chronically elevated galactose levels on glucose transport in adult rats. The analysis indicated that galactose and glucose compete for the same transport mechanism in the cerebral capillary endothelium. The Tmax of glucose and galactose were both about 380 mumol 100 g-1 min-1 and the Kt of galactose (30 mM) was about three times that of glucose (10 mM). During prolonged galactosemia in adult rats, neither the Tmax, nor the Kt of either competitor changed substantially when compared with rats subjected to acute galactosemia. At 10 mM galactose in plasma in rats with acute galactosemia, the inhibition of glucose transport, simulated a 25% reduction of plasma glucose, and in rats with chronic galactosemia a 20% reduction. This moderate effect is in contrast to the effect of galactose in suckling rats in which 10 mM galactose in plasma reduced the glucose transport to a level corresponding to a 50% reduction of the plasma glucose concentration.

Non-ionic water soluble contrast medium 3-deoxy-3-iodo-D-glucose (DIG) for use in the CSF space. An experimental study with mongrel and beagle dogs

A non-ionic water soluble contrast medium, 3-Deoxy-3-Iodo-D-Glucose (DIG), was experimentally evaluated for use in the cerebrospinal fluid (CSF) space, and compared with other contrast media. Two ml (180 mgI/ml) of DIG were injected either intraventricularly or intracisternally in 15 adult mongrel dogs (average weight: 6.4 kg), and X-ray photographic, CSF, EEG, and histological studies were then performed. Additional tests were made on four beagle dogs (average weight: 9.8 kg), focussing particularly on changes in cell count and protein in the CSF following alternate intracisternal injections of 2 ml (170 mgI/ml) of DIG and metrizamide (Amipaque), and on epileptogenicity following intracisternal injection of 3 ml (300 mgI/ml) of DIG. That DIG provides adequate definition was demonstrated both by the ventriculograms and cisternograms, and by comparison with metrizamide. Neither epileptic discharges in the EEG nor epileptic symptoms were seen in any of the dogs used in the studies. In the CSF drawn 24 hours after the injection, protein tended to increase moderately with DIG, but pleocytosis was mild with both media. Histological studies of the central nervous system structures around the cisterna magna revealed no definite abnormal findings. Neither fibrosis nor arachnoid adhesions were seen in scanning electron microscopic observations of the basal subarachnoid spaces.

Nonconvulsive status epilepticus following metrizamide myelography

Epileptic seizures are a known complication of metrizamide myelography. To our knowledge, this is the first report of a case of nonconvulsive status epilepticus of the absence type following metrizamide myelography. There was symptomatic and electroencephalographic improvement after intravenous administration of antiepileptic drugs, and there was no neurological residual. Nonconvulsive status epilepticus should be considered when impairment of consciousness supervenes after radiographic procedures using metrizamide.

The effect of metrizamide on regional brain glucose metabolism in the rat

The X-ray contrast material metrizamide is structurally related to 2-deoxyglucose and inhibits brain glucose phosphorylation in vitro. In vivo, the present autoradiographic study with labeled 2-deoxyglucose revealed a global reduction of brain glucose phosphorylation after metrizamide administration in the cisterna magna of rats. The reduction averaged 18% of all regions.

Competitive inhibition of human brain hexokinase by metrizamide and related compounds

We have compared the competitive inhibitory effects of 2-deoxyglucose, glucosamine, N-acetylglucosamine, N-benzoylglucosamine, and the commonly used radiographic and density gradient agent metrizamide (2-[3-acetamido-2,4,6-triiodo-5-(N-methylacetamido) benzamido]-2-deoxyglucose) on the mitochondrial and soluble forms of human brain hexokinase. Metrizamide produces a classical competitive inhibition with glucose for human brain hexokinase, with Kis of 2.8 and 2.5 mM, respectively, for the mitochondrial and soluble forms. Glucosamine exhibited Kis of 0.58 and 0.29 mM, while 2-deoxyglucose exhibited Kis of 0.074 and 0.15 mM and N-acetylglucosamine 0.098 and 0.092 mM for these two forms, respectively. N-Benzoylglucosamine was by far the most effective inhibitor tested, with Ki values of 0.0086 and 0.022 mM, respectively. In order of increasing potency as a competitive inhibitor for mitochondrial hexokinase are metrizamide, glucosamine, N-acetylglucosamine, 2-deoxyglucose, and N-benzoylglucosamine. For the soluble form of the enzyme in increasing potency are metrizamide, glucosamine, 2-deoxyglucose, N-acetylglucosamine, and N-benzoylglucosamine. Since N-benzoylglucosamine was over 100 times more potent than metrizamide, some of the effects of metrizamide could be due to contamination by N-benzoylglucosamine. However, gas chromatography-mass spectrometry analysis of metrizamide did not indicate the presence of N-benzoyl-glucosamine. In addition, column chromatographic separation of commercially available metrizamide and reconstitution of freeze-dried eluate fractions localized the inhibitory effect to the metrizamide peak.

Occipital dysplasia and Chiari type I deformity in a family. Clinical and radiological study of three generations

Three generations of a family affected by a craniocervical malformation (CCM) were subjected to clinical and radiological studies. Occipital dysplasia (OD) and Chiari type I deformity (CD.I) were the main features, inheritance being autosomal-dominant. The malformation was variably expressed; it ranged from OD with basilar impression (BI) to OD without BI and from CD.I with OD to CD.I without obvious osseous malformation. Its pathogenesis, and that of other related familial disorders (Klippel-Feil syndrome and syringomyelia), is discussed, the conclusion being drawn that all were elements of one genetic disorder which finds expression in a very variable sequence. The value of high-resolution CT in the detection of asymptomatic carriers is emphasized.

Drug-induced neurological disorders

When a patient presents with a neurological or neuromuscular disorder, it is essential to consider drugs as a possible cause. Drugs can affect virtually any part of the neuraxis and the resulting disorders can usually be classified in terms of the anatomical site affected and the clinical presentation. In general, the signs and symptoms of drug-induced neurological disorders are virtually indistinguishable from those seen in naturally occurring disease but are usually reversible if diagnosed early enough. Cortical depression may produce coma, particularly in overdose cases, but a large number of drugs can also initiate seizures in susceptible individuals. The effects of drugs in the pathogenesis of headaches are certainly underestimated, and the eye, hearing and balance mechanisms can be severely damaged by certain drugs before symptoms prompt investigation. The long term effects of antipsychotic drugs on basal ganglia demand that these drugs are used only when absolutely essential and for as short a period as possible. Finally, there is increasing awareness of the role of drugs in the development of neuromuscular disorders such as peripheral neuropathies, myasthenic syndromes and myopathies.

Neurotoxicity of radiological contrast agents

The most important complications of intravascular administration of contrast agents include idiosyncratic (anaphylactoid) reactions, shock, congestive heart failure, cardiac arrhythmias, acute renal failure, and neurotoxic effects. The incidence of serious neurotoxic effects is low. Entry of contrast agents into the central nervous system normally is limited but may be increased by osmotic opening of the blood-brain barrier with cerebral arteriography or arch aortography. Most neurotoxic effects are thought to represent direct effects of the contrast agent on brain or spinal cord. Adverse effects with arteriography include seizures, transient cortical blindness, brain edema, and spinal cord injury. Most cases of focal brain deficit (other than cortical blindness) are attributed to embolism secondary to the catheter. Seizures may occur with intravenous administration, especially in patients with brain tumors or other processes disrupting the blood-brain barrier. The most important adverse effects observed with myelographic agents include acute and chronic meningeal reactions with iophendylate, and seizures and transient encephalopathy with metrizamide.

A double-blind clinical trial of iopamidol versus metrizamide for lumbosacral myelography

A double-blind study was performed to compare metrizamide with the new iodinated water-soluble nonionic contrast medium, iopamidol, for conventional and computerized tomography lumbosacral myelography. Both contrast agents were used in 30 patients, and were equivalent in terms of image quality and clinical accuracy. Headaches and nausea were less severe using iopamidol. The most striking difference was found in adverse neurobehavioral reactions and associated electroencephalographic abnormalities, which were noted in 17% of the metrizamide group but were not seen with the use of iopamidol. Iopamidol appears to be superior to metrizamide for intrathecal applications. An explanation of the differential neurotoxicity is provided.

Neurodegenerative diseases of infancy and childhood

The neurodegenerative diseases of infancy and childhood include disorders in which there is progressive loss of neurological function due to structural abnormalities of the central nervous system. Well over six hundred disorders, many of which are rarely seen, can be included in this category. Yet, the conditions represent collectively over one-fourth of all admissions to pediatric neurology services. Five-year samples of admission characteristics of 1218 patients from two medical centers over twenty-two years permit an estimate of the frequency of the neurodegenerative diseases. The six most-encountered diagnoses, in declining order, were: subacute sclerosing panencephalitis; neuronal ceroid lipofuscinosis; tuberous sclerosis with degeneration; West disease, or idiopathic degenerative encephalopathy associated with infantile spasms; Werdnig-Hoffmann disease, and hereditary spastic paraplegia. A classification is offered grouping the neurodegenerative disorders into five major categories: polioencephalopathies, leukoencephalopathies, corencephalopathies, spinocerebellopathies, and diffuse encephalopathies. Disorders in each subgroup may be either genetic or nongenetic. Neurodegenerative diseases have multiple causes, including metabolic, viral, immunopathic, environmental, and epileptogenic. The cause of many remains unknown.

Iopamidol vs metrizamide: a double blind study for cervical myelography

A double-blind study was performed on 20 patients comparing the safety and efficacy of Iopamidol and Metrizamide in cervical myelography. The radiographic qualities of the Iopamidol and Metrizamide examinations were equivalent when using the same volume (12 to 13 ml), concentration (200 mg I/ml), and a C1-2 route of administration. The performance of a CT scan on selected patients in specified areas of interest provided additional diagnostic information in some patients (e.g syringomyelia, degenerative spondylosis). The adverse reactions were mild in the Iopamidol group with 4 of the 10 patients experiencing no adverse reactions. The more severe reactions, including disorientation, agitation, dysarthria, asterixis, hyperreflexia and EEG abnormalities were limited to the Metrizamide group with one or more occurring in 2 of the 10 patients studied. Only one Metrizamide patient experienced no adverse reactions. In this study containing a limited number of patients, Iopamidol was shown to be a diagnostically effective and safer contrast medium for performing cervical myelography.

Competitive inhibition of rat brain hexokinase by 2-deoxyglucose, glucosamine, and metrizamide

The effects of metrizamide on the kinetics of rat brain hexokinase were compared in vitro with those of 2-deoxyglucose and glucosamine. Although metrizamide, 2-deoxyglucose, and glucosamine are known to be competitive inhibitors of approximately equal potency for glucose of yeast hexokinase (Ki approximately 0.7 mM for all three), metrizamide is a much weaker competitive inhibitor (Ki about 20 mM) of rat brain hexokinase than either 2-deoxyglucose or glucosamine (Ki about 0.3 mM for both). This indicates a greater active site specificity of rat brain hexokinase than of yeast hexokinase. Rat brain hexokinase activity is enhanced approximately threefold in the presence of 0.05, 0.2, and 0.8 mg/ml bovine serum albumin, while yeast hexokinase is only enhanced by 50% under these conditions. Despite the high Ki value for metrizamide, interference with glucose metabolism may occur whenever metrizamide is present in much higher concentrations than glucose. Myelography in humans is one such situation.