Late meningeal effects of myelographic contrast media with special reference to metrizamide

The leptomeninges as a critical organ for normal CNS development and function: First patient and public involved systematic review of arachnoiditis (chronic meningitis)

BACKGROUND & IMPORTANCE

This patient and public-involved systematic review originally focused on arachnoiditis, a supposedly rare "iatrogenic chronic meningitis" causing permanent neurologic damage and intractable pain. We sought to prove disease existence, causation, symptoms, and inform future directions. After 63 terms for the same pathology were found, the study was renamed Diseases of the Leptomeninges (DLMs). We present results that nullify traditional clinical thinking about DLMs, answer study questions, and create a unified path forward.

METHODS

The prospective PRISMA protocol is published at Arcsology.org. We used four platforms, 10 sources, extraction software, and critical review with ≥2 researchers at each phase. All human sources to 12/6/2020 were eligible for qualitative synthesis utilizing R. Weekly updates since cutoff strengthen conclusions.

RESULTS

Included were 887/14286 sources containing 12721 DLMs patients. Pathology involves the subarachnoid space (SAS) and pia. DLMs occurred in all countries as a contributor to the top 10 causes of disability-adjusted life years lost, with communicable diseases (CDs) predominating. In the USA, the ratio of CDs to iatrogenic causes is 2.4:1, contradicting arachnoiditis literature. Spinal fusion surgery comprised 54.7% of the iatrogenic category, with rhBMP-2 resulting in 2.4x more DLMs than no use (p<0.0001). Spinal injections and neuraxial anesthesia procedures cause 1.1%, and 0.2% permanent DLMs, respectively. Syringomyelia, hydrocephalus, and arachnoid cysts are complications caused by blocked CSF flow. CNS neuron death occurs due to insufficient arterial supply from compromised vasculature and nerves traversing the SAS. Contrast MRI is currently the diagnostic test of choice. Lack of radiologist recognition is problematic.

DISCUSSION & CONCLUSION

DLMs are common. The LM clinically functions as an organ with critical CNS-sustaining roles involving the SAS-pia structure, enclosed cells, lymphatics, and biologic pathways. Cases involve all specialties. Causes are numerous, symptoms predictable, and outcomes dependent on time to treatment and extent of residual SAS damage. An international disease classification and possible treatment trials are proposed.

Neurologic deficits and arachnoiditis following neuroaxial anesthesia

Of late, regional anesthesia has enjoyed unprecedented popularity; this increase in cases has brought a higher frequency of instances of neurological deficit and arachnoiditis that may appear as transient nerve root irritation, cauda equina, and conus medullaris syndromes, and later as radiculitis, clumped nerve roots, fibrosis, scarring dural sac deformities, pachymeningitis, pseudomeningocele, and syringomyelia, etc., all associated with arachnoiditis. Arachnoiditis may be caused by infections, myelograms (mostly from oil-based dyes), blood in the intrathecal space, neuroirritant, neurotoxic and/or neurolytic substances, surgical interventions in the spine, intrathecal corticosteroids, and trauma. Regarding regional anesthesia in the neuroaxis, arachnoiditis has resulted from epidural abscesses, traumatic punctures (blood), local anesthetics, detergents, antiseptics or other substances unintentionally injected into the spinal canal. Direct trauma to nerve roots or the spinal cord may be manifested as paraesthesia that has not been considered an injurious event; however, it usually implies dural penetration, as there are no nerve roots in the epidural space posteriorly. Sudden severe headache while or shortly after an epidural block using the loss of resistance to air approach usually suggests pneumocephalus from an intradural injection of air. Burning severe pain in the lower back and lower extremities, dysesthesia and numbness not following the usual dermatome distribution, along with bladder, bowel and/or sexual dysfunction, are the most common symptoms of direct trauma to the spinal cord. Such patients should be subjected to a neurological examination followed by an MRI of the effected area. Further spinal procedures are best avoided and the prompt administration of IV corticosteroids and NSAIDs need to be considered in the hope of preventing the inflammatory response from evolving into the proliferative phase of arachnoiditis.

Familial spinal arachnoiditis with secondary syringomyelia: clinical studies and MRI findings

We report the clinical and MRI findings of two patients with familial spinal arachnoiditis. Although their initial symptoms were various, they both showed spastic paraparesis and sensory disturbance below the thoracic level. Cytokines and WBC in the CSF were studied, but they were not elevated at all. The spinal magnetic resonance images of each showed extensive arachnoiditis and a cystic structure. The other impressive features included: (i) an enhancement within the thickened arachnoid and an adhesion between the spinal cord and the dura mater, (ii) deformation of the thoracic cord where the arachnoid adhered, and (iii) secondary syrinx formation. Laminectomy may have an adverse outcome for such patients.

Peroperative prednisolone fails to improve the clinical outcome following surgery for prolapsed lumbar intervertebral disc. A randomized controlled trial

Ninety three patients undergoing their first conventional hemilaminectomy for lumbar disc protusion were randomized to a double blind clinical trial. Half of the patients were treated immediately following surgery with prednisolone; 50 mg per day for fourteen days and then 25 mg per day for another 14 days. The other patients were treated for the same time period with placebo tablets. Assessments using subjective and objective outcome criteria at 26 weeks, 52 weeks and 156 weeks of follow-up, demonstrated no statistically significant differences between the randomized groups. It is concluded that systemic prednisolone administration in the pre- and postoperative period does not in this study improve the clinical outcome after first time lumbar discectomy.

Spinal cord stimulation in 112 patients with epi-/intradural fibrosis following operation for lumbar disc herniation

A total of 112 patients with epi-/intradural fibrosis following operation for lumbar disc herniation were treated by spinal cord stimulation. Lumbosacral spinal fibrosis is seen particularly often after extensive and repeated operations. Radicular pain responds better to stimulation than back pain. A favourable long-term effect on radicular pain has been observed in 67% of patients treated by epidural implantation, the corresponding average follow-up period being 4 1/2 years. 40% of these patients needed less analgesics after the operation, while 25% of them showed an improved fitness for work. Among about 5,000 patients who underwent surgical treatment for lumbar disc herniation, an indication for spinal cord stimulation was found in 1.5%. By comparison, the frequency of the "last resort" procedure of microsurgical cordotomy was 0.3%. We no longer use other ablative methods like extirpation of spinal ganglia.

Vascular damage, fibrosis, and chronic inflammation in mechanical back pain problems

Our current hypothesis is that mechanical damage in the spine such as a disc prolapse can lead directly to pain. However, pain arising for this reason is usually of short duration. In many subjects, however, the mechanical problems lead to vascular damage and, in particular, venous obstruction and dilatation with endothelial damage, fibrin deposition, and intravascular thromboses. In turn, this is associated with perineural and intraneural fibrosis. There is a defect in the fibrinolytic system in the peripheral blood that may be the result of vascular damage but in turn may contribute to the persistence of this problem. Therefore, it seems likely that in many patients with chronic mechanical back pain there are important vascular, fibrotic, and inflammatory components to the problem. Treatment in the future should be directed specifically at these aspects of the disorder and hopefully can lead to better control of symptoms.

A fibrinolytic defect in chronic back pain syndromes

Blood fibrinolytic activity was measured in 18 subjects with severe chronic back pain and 18 age and sex matched controls. The patients showed evidence of defective fibrinolysis--namely, significant prolongation of the euglobulin clot-lysis time, reduction in fibrin-plate lysis-area and plasminogen levels, and increase in levels of the fibrinolytic inhibitors, alpha 2 antiplasmin and alpha 2 macroglobulin. This defect could be associated with fibrin deposition and scar formation and be responsible for the development and/or perpetuation of chronic inflammation and scarring at sites of damage in the spine. Enhancement of fibrinolytic activity may offer a new approach to the management of these back problems, and a double-blind controlled trial is in progress.

Steroid-induced arachnoiditis

Eighteen cases are reported in which the myelographic appearances of adhesive arachnoiditis were found. These patients have had intrathecal steroid injections as either the only procedure or the most likely procedure that could have induced such changes. Adhesive arachnoiditis has not been found at this hospital in the absence of some type of intervention. Other possible iatrogenic causes of arachnoiditis have been excluded in this group. The literature on the aetiology and symptomatology of steroid-induced arachnoiditis is reviewed.

Iopamidol in lumbar myelography

Iopamidol is a new, nonionic, water-soluble contrast material currently undergoing clinical trials for intravascular and intrathecal use in Europe and the United States. In this study, 12 patients underwent lumbar myelography with this agent. For each subject, up to 12 mL of iopamidol (at 200 mg I/mL) was employed. The myelograms obtained were highly satisfactory. No serious adverse reactions were observed. The most common side effect--headache--occurred in seven patients. However, six of the seven headaches were mild and transient, and did not require treatment. Nausea occurred in two patients, back pain in two patients, hypotension and hypertension each in one patient. All of these reactions were mild and self-limited. Iopamidol appears to be a safe and conveniently used agent for lumbar myelography.

Myelography--a case for audit

The radiographic findings and clinical outcome of 54 patients having a myelogram at the request of the Department of Rheumatology over a period of five years are described. Fortynine of the patients had either clinical features of an intervertebral disc protrusion or chronic back pain of obscure aetiology. Abnormalities which could have accounted for the symptoms and signs were found in 28 of these. Although useful information was obtained in regard to therapy the investigation did not lead to surgical treatment in any of the patients without clinical evidence of lumbar root compression. No unexpected malignancies were found. Morbidity was common, but usually mild.

Spinal arachnoiditis

A review of the literature points to the many causes of arachnoiditis and the failure of treatment to arrest or reverse its effects. The true incidence cannot be determined, although it is probably lower than might at first appear from the published articles. In the radiological literature the diagnosis seems to derive from an examination of the films alone, often without reference to the clinical findings or appearance at operation. While attempts at treatment are usually unsuccessful, some iatrogenic cases can be prevented by the avoidance of intrathecal steroid injections or unduly rough or repeated surgical exploration of the lumbar vertebral canal.

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

Marked asterixis occurred in two patients following metrizamide myelography. One also suffered generalized seizures and the other had severe stuttering speech for seven days. The spectrum of toxic manifestations of metrizamide is reviewed with emphasis on the unusual lethargy and other depressive effects seen with this relatively safe agent. The hypothesis that metrizamide exerts a ouabain-like effect on the cortical surface was tested. Metrizamide in concentrations as high as 20 mM had no inhibitory effect on rat cerebral K+-para-nitrophenylphosphatase, a partial reaction of (Na+K+)-adenosine triphosphatase. Because metrizamide is a 2-deoxyglucose analogue, a competitive inhibition of hexokinase at the first step in glycolysis was also postulated. Metrizamide was found to competitively inhibit commercial (microbial) hexokinase. The Michaelis constant for glucose rises from 0.13 to 0.25 to 0.33 to 0.91 mM in the presence of 0, 0.4, 1.0, and 2.0 mM metrizamide, respectively. Since the concentration of metrizamide over the cerebral cortex after routine myelography may be approximately 50 mM compared with a glucose concentration of only 3.6 mM (65 mg/dl), it is postulated that impaired brain glucose metabolism may be responsible for some of the toxic effects of metrizamide.

Subacute reactions to intrathecal amipaque (metrizamide), conray and dimer X: a structural and ultrastructural study

Adult New Zealand rabbits were injected intrathecally with 200 or 300 mgI/ml of metrizamide, meglumine iocarmate or meglumine iothalamate. They were placed in the Trendelenburg position for 20 min and allowed to survive for 1, 2 or 3 weeks. Sacrifice was by intraarterial perfusion of aldehydes under anesthesia followed by preparation of brain and major venous sinuses for light and electron microscopy. Major findings were subpial edema and inflammatory reaction of superficial brain, leptomeninges, subarachnoid space and arachnoid granulations. They were most severe after iothalamate and milder after metrizamide. The severity decreased with time. It is of significance that severe reactions occurred after 300 mgI/ml concentration of metrizamide.

Spinal arachnoiditis: disease or coincidence?

In 86% of 63 patients with spinal arachnoiditis the localization was lumbosacral, and in 14% it was cervical or thoracic. The most important aetiological factor was the combination of one or more myelographies with one or more operations. It is remarkable that in most patients with lumbosacral arachnoiditis the clinical picture did not show new or typical signs of arachnoiditis, but was the same as before the arachnoiditis had developed. In only 20% of patients with lumbosacral arachnoiditis, and in all patients with cervical or thoracic arachnoiditis, did new signs and symptoms occur concomitantly with and due to the development of the arachnoiditis. The results of this retrospective study suggest that lumbosacral arachnoiditis is a coincidental finding in the majority of cases, without clinical consequences.

Mental disorders after myelography with metrizamide and other water-soluble contrast media

Water-soluble contrast media, which have been employed in the examination of the lumbar spinal canal for 30 years, can sometimes result in severe complications, such as arachnoiditis, epileptic seizures, and myoclonic spasm. These complications have been seen less frequently since the advent of metrizamide, a new non-ionic water-soluble contrast medium. However, a further neurological complication has now arisen--mental disorder, varying in kind and degree; for example, organic psychosis and perceptual disturbance. Some characteristic cases are described. A series of 75 patients, all of whom received varying amounts of metrizamide for the purpose of cervical, thoracic and lumbar myelography, has been studied. Seven patients were found to have a pronounced organic psychosis and three patients had visual illusions or hallucinations. It is suggested that there is some degree of correlation between the total amount of iodine received and patient age. By careful enquiry and examination, similar disturbances were also found some 4-8 h after myelography with other water-soluble contrast media.

Minimising side effects in lumbar radiculography

An attempt was made to reduce the side effects associated with the use of Metrizamide in lumbar radiculography by the removal of the contrast medium on completion of the examination. Almost complete removal was achieved in 103 patients and of these 73% had no symptoms after examination, while 8% had severe symptoms. Eleven of 14 patients in whom removal was not attempted or was not successful had significant symptoms after examination. It is concluded that aspiration of Metrizamide will reduce the incidence and severity of the side effects associated with the use of this contrast medium.

Computed tomography and spinal dysraphism: clinical and phantom studies

Two cases illustrating the value of CT in the assessment of spinal dysraphic tissue are presented. In one case, the configuration and origins of two osseous diastematomyelic spurs were shown well; in the second case, the CT recognition of a sacral lipoma led to air myelographic confirmation of the tumor and tethered cord. CT phantom studies indicated that dysraphic tissues, such as fat, cartilage, and fibrous tissue, are better identified and quantitated in the spinal canal when surrounded by air. Varying degrees of image degradation occur with water (simulating CSF) or metrizamide.