Does choice of imaging modality affect outcome in dogs with thoracolumbar spinal conditions?

OBJECTIVES: A retrospective cross-sectional study was done to look for differences in outcome in canine spinal patients that had myelography compared to those that had magnetic resonance imaging. METHODS: Medical records of dogs with spinal conditions in the period January 2004 to December 2007 were reviewed. Data on patient age, gender, breed, size, neurolocalisation, rate of onset, imaging modality, time taken to image, type of treatment, neurological grade at admission and discharge, length and cost of hospitalisation and status at discharge were collected. Only dogs with neurological grade 3 to 6 with signs referable to the thoracolumbar spine were included. RESULTS: Of 107 dogs that met the inclusion criteria, 66 (62%) had myelography and 41 (38%) had magnetic resonance imaging. Using multivariable analyses, non-chondrodystrophoid breed, increasing age and higher neurological grade at admission were found to be associated negatively with survival. Neurological grade 5 at admission was found to be associated positively with likelihood of neurological improvement. Male gender, higher neurological grade at admission and medical treatment were associated negatively with length of hospitalisation. magnetic resonance imaging, surgical treatment and period of hospitalisation were associated positively with total cost of hospitalisation. CLINICAL SIGNIFICANCE: No significant association was found between type of imaging and any patient outcome variables except cost of hospitalisation, which was higher for dogs having magnetic resonance imaging. Although magnetic resonance imaging may be considered advantageous compared to myelography because it is non-invasive and provides superior anatomical detail for surgical guidance, no beneficial effect on outcome of dogs with non-ambulatory thoracolumbar spinal disease was found.

A myelographic technique for avian species.

A post-mortem myelogram was used to diagnose a vertabral fracture in a Red-tailed Hawk (Buteo jamaicensis). This diagnosis led the authors to believe that myelography would be useful in live birds. In a pilot study using live adult female chickens (Gallus domesticus), mammalian myelographic techniques were modified for avian anatomic differences. A thoracolumbar puncture site was used rather than the lumbar or cisternal site which is commonly used in mammals. The volume of contrast medium needed to produce a diagnostic myelogram in birds (0.8-1.2 ml/kg) was found to be approximately four times that needed in mammals. A 25 gauge spinal needle was used rather than a 23 gauge needle. Myelograms of diagnostic quality were obtained with normal subject recovery. Seizures, the most common post-myelographic complication in mammals, were not observed in any of the birds studied. Avian myelography was found to be a cost effective and humane technique with potential application to avian practice.

Imaging in hydrocephalus and spinal dysraphism.

Hydrocephalus and spinal dysraphism are two commonly encountered clinical entities where imaging plays a vital role. Sonography, Computed Tomography and Magnetic Resonance Imaging are the modalities used for the evaluation of hydrocephalus. Ultrasound is useful in small infants with open fontanella, is non-invasive and can be performed at cribside. However, it has limitation in identifying the etiology. CT is the most cost effective modality in the evaluation of hydrocephalus and gives detailed anatomical information. MRI offers the added advantage of multiplanar display and can also assess stenosis/patency of CSF pathways, using phase contrast cine techniques. MRI is the modality of choice for evaluating spinal dysraphism and gives excellent information regarding contents of back mass, spinal cord status and associated anomalies like Chiari malformation. Myelography coupled with CT should be reserved for equivocal cases or in centres where MRI is not available.

MR imaging as the primary modality for neuroradiologic evaluation of the lumbar spine. Effects on cost and number of examinations.

PURPOSE: To evaluate the effects on cost, and number of primary and supplementary neuroradiologic examinations, after introducing MR imaging as the primary modality in the evaluation of the lumbar spine. MATERIAL AND METHODS: Two 5-month periods were compared: period 1--before MR; and period 2--after introduction of a 2nd MR device. In period 1, patients were examined with myelography and/or CT after referral from specialists only, whereas in period 2 both specialists and general practitioners could refer patients for MR imaging. The direct cost (neuroradiologic methods and hospitalization) and indirect cost (sick-leave and estimated loss of production caused by the diagnostic procedure) were estimated. RESULTS AND CONCLUSION: In period 1, investigations were started in 75 patients (62 myelographies and 13 CT examinations); in period 2, in 227 patients (198 MR, 21 CT, and 8 myelographies). The estimated total cost increased from SEK 825,000 to 1,265,000 (53%), the cost per investigated patient decreasing from 11,000 to 5565 (50%), and the cost of preoperative investigation per operated patient decreasing from 8616 to 5563 (35%). The number of supplementary examinations was unchanged.

Cost effectiveness and outcome assessment of magnetic resonance imaging in diagnosing cord compression.

BACKGROUND: This study was designed to investigate the costs associated with the use of magnetic resonance imaging (MRI) in the workup of spinal cord compression caused by metastatic disease, an area in which it has proven to be diagnostically useful. METHODS: The study was divided into two parts. Part 1 consisted of a retrospective review of the hospital charts of 46 patients, half of whom were diagnosed with cord compression in the pre-MRI era and the other half diagnosed after MRI availability; costs for these two groups were compared. Part 2 consisted of a review of several major studies comparing the sensitivities and specificities of MRI with alternative imaging techniques, usually myelography. Cost effectiveness and cost/cost ratios were derived for diagnostic usefulness using prevalence, sensitivity, specificity, and cost estimates of MRI and its alternatives, including costs of false-negative and false-positive testing. RESULTS: Our hospital-based experience yielded an average cost of $ 3664 per patient without MRI and $ 2283 per patient when MRI was available (1991 dollar amounts). The cost of diagnosis was 65% more expensive without MRI. Use of the literature-based experience demonstrated that the cost of diagnosis was at least 82% more costly without MRI than when it was available. However, when key variables were altered during sensitivity analysis, this difference of increased cost of diagnosis without MRI ranged from 25% to 98%. CONCLUSION: This work suggests that MRI may result in significant economic benefits in diagnosing metastatic cord compression, but further work is needed on physician behavior and referral patterns with MRI versus myelography as is long term follow-up for potential reductions in patient debility using MRI.

Lumbar herniated disk disease: comparison of MRI, myelography, and post-myelographic CT scan with surgical findings.

One hundred eighty patients with suspected lumbar disk disease were evaluated preoperatively with magnetic resonance imaging (MRI), myelography, and post-myelogram computerized tomography (CT) scan. Sixty patients underwent surgery on 102 disk levels, allowing for anatomic confirmation of the diagnosis. Eight negative explorations were performed. The correlation between preoperative interpretations of each test and the observed surgical findings was analyzed statistically. Based on this analysis, MRI accurately predicted the operative findings in 98 of 102 disk levels (96%), while the accuracy of myelography (81%) and post-myelogram CT scan (57%) was significantly less. When myelography and CT scan were utilized jointly, the accuracy was 84%, a significant improvement over either test alone, as a diagnostic modality. There was only one false positive MRI study in the evaluation of lumbar herniated disk. The results of this study reflect that MRI is a clinically superior diagnostic test in the evaluation of patients with suspected lumbar disk herniation, and that it should be the diagnostic study of choice when available. Its noninvasive nature, multiplanar capabilities, and the lack of ionizing radiation are particularly desirable for patient and physician.

The role of nonionic myelography in the diagnosis of lumbar disc herniation.

RATIONALE AND OBJECTIVES: The accuracy and safety of nonionic myelography, unenhanced computed tomography (CT), and magnetic resonance (MR) in the diagnosis of lumbar disc herniation are reviewed. The comparative costs of these tests are also considered. METHODS: The accuracy of imaging tests that diagnose disc herniations was established by conducting a Medline search between 1985 and 1992. The morbidity associated with these tests are less formally established from selected articles. Finally, the mediocre reimbursement rates of these tests are reviewed. RESULTS AND CONCLUSIONS: The evolution of nonionic contrast media from the first to the second generation has been accompanied by a notable decrease in adverse reactions. Although nonionic myelograms are now better tolerated by patients, noninvasive imaging with CT and MR imaging has become as accurate as or more accurate than lumbar myelography, and should replace it as a screening test. Computed tomography may have advantages over MR imaging when issues of availability and cost are considered. In contrast to lumbar myelography, CT myelography may continue to be a useful method for clarifying ambiguous results of noninvasive tests. The morbidity associated with CT myelography can be minimized by using low doses of a nonionic agent, keeping the patient well hydrated, and using a small lumbar puncture needle. The incidence of adverse reactions can be expected to decrease further as new nonionic dimers become clinically available.

Value of a programmed investigation unit: an audit study.

A programmed investigation unit (PIU) was set up in a regional neuroscience centre. Its effects were assessed by measuring the savings associated with one particular investigation, myelography, which accounted for 50% of admissions to the PIU. Substantial savings appear to be possible, but accounting techniques allow wide variations in the estimated amounts. These benefits have to be measured against improvements which occurred simultaneously on the other wards.

Comparing the cost of spinal MR with conventional myelography and radiculography.

All spinal magnetic resonance imaging examinations carried out during a three month period were analysed retrospectively in order to determine the clinical reasons for the scan requests. Technical details of the examinations they received and the clinical profiles formed a data set which revealed 10 separate "Clinical groups" for management purposes. Hardware, salary and expendables were costed as though the imaging unit had been sited within a National Health Service radiology department. A spread sheet was designed capable of calculating costs per patient for a variety of types of working week and of different staffing structures, sensitive to the mixture of clinical groups referred for examination. The spreadsheet also accomodated straight line depreciation for hardware value and interest rates for borrowed capital. A second, prospectively observed, sample of spinal MR examinations was used to improve the accuracy of the timing of the length of patient examinations. Costs were compared with those for patients submitted for myelography and radiculography at the adjacent hospital during the same period. The comparison indicated that spinal MR was less costly than myelography and radiculography. The most important element of the extra cost of myelography related to the need to admit patients to hospital for at least one night for this examination because of the likelihood of headache and other common (though usually minor) complications following lumbar puncture and/or the injection of contrast medium. From the limited information that it was possible to obtain in the period of follow up, it appeared that MR had either been superior or equivalent to myelography or radiculography in all the clinical groups of patients where both could be tested. There were a number of groups in which no myelograms had been requested, presumably because clinical suspicions had pointed toward conditions like tumours, developmental abnormalities and demyelinating diseases in which neurologists and neurosurgeons have already made up their minds about the superiority of MR.

A prospective audit of the use and costs of myelography in a regional neuroscience unit.

A consecutive series of 397 myelograms performed in 385 patients over a six month period at the Mersey Regional Neurosciences Unit is reported. The reasons for performing the myelogram were to identify the cause of a radicular lesion in 54% of patients, a chronic spinal cord lesion in 30%, an acute cord lesion in 9%, suspected disease at the level of the foramen magnum 6%, and for a variety of other conditions in 8%. For the 385 patients undergoing a myelogram in the study period, the median interval from admission to request, request to myelography and from myelography to discharge was nought, one and three days respectively. The proportion of patients submitted to myelography by individual consultants ranged from 7% to 28%. There was a two-fold variation in the delays in the time to requesting and performing myelograms. There was room for improvement in the clinical information supplied on the myelography request form. The role of ancillary investigations and their effect on myelography was unclear. Only 16 of the patients with suspected cord disease had visual evoked responses performed before myelography. Five of them had myelography after an abnormal result. The estimated annual direct cost of myelography in the unit was at least 486,000 pounds. Reorganisation might have yielded hypothetical "savings" of between 30,000 pounds (6%) and 155,000 pounds (32%), though in practical terms these "savings" represented resources which might have been freed for use in other higher priority clinical problems within the unit, rather than true reductions in monetary cost.

CSF TRAP: a procedure to improve laboratory testing with myelography.

CSF TRAP (Transport and Rapid Accessioning for Additional Procedures) is a procedure that provides storage of and rapid access to cerebrospinal fluid (CSF) specimens and allows clinicians to review initial findings before ordering low-yield CSF studies. The cost-effectiveness of routinely using the CSF TRAP procedure with myelography is examined in a study group of 819 patients, 74% with disc diseases, spinal stenosis, spondylolisthesis, or pain syndromes, 10% with cancer, and 16% with neuropathies and miscellaneous conditions. Routine studies on CSF obtained during myelography provided little additional clinical information, except for patients with cancer (of 80 patients with cancer, the results of cytological examination of the CSF were positive in 12) and patients with multiple sclerosis, for whom oligoclonal band and IgG analysis provided supportive diagnostic data. The utilization of the CSF TRAP procedure with elimination of unnecessary culture and cytological studies on patients with disc diseases, spinal stenosis, spondylolisthesis, and pain syndromes, reduces myelographic CSF procedures by 20%, for a savings exceeding $14,000. The CSF TRAP procedure allows for a more cost-efficient analysis of CSF obtained using myelography, while providing fluid for analysis in patients with unexpected findings.

Outpatient myelography: an acceptable and cost-effective technique.

Sixty-five patients with stable low back pain had their lumbar myelography performed as outpatients, staying in the department for 1 h after the examination. The incidence of post-myelogram headache was similar to that reported for inpatients. No serious after-effects occurred in the study group. The vast majority of patients preferred to be at home following the study. It is concluded that outpatient myelography is safe, less expensive and preferred by the patients.

Outpatient metrizamide myelography: prospective evaluation of safety and cost effectiveness.

A group of 228 consecutive patients undergoing metrizamide myelography was prospectively evaluated for postprocedure symptoms. The observed prevalence of these symptoms concurs with previously reported inpatient studies, with the most common sequelae being exacerbation or onset of spine or extremity pain, headache, nausea, and paresthesia. Limitation of administered dose of metrizamide in lumbar myelography may slightly reduce the occurrence of common symptoms, but withdrawal of contrast medium at the completion of examination had no impact on their occurrence. There was a higher occurrence of paresthesia in cervical myelography, but otherwise there was no significant difference in symptoms between cervical and lumbar studies. Outpatient metrizamide myelography can be performed with relative safety with the potential for significant cost savings.

Outpatient lumbar myelography with metrizamide.

A prospective study of 70 adult patients was undertaken to determine whether lumbar metrizamide myelography can be performed as an outpatient procedure without an increased incidence of side effects and without undue risk. In selected patients and with a specific protocol, the incidence of common sequelae was similar to that in previous studies of inpatients either in bed with the head elevated or ambulatory after lumbar metrizamide myelography. No patient in this series experienced seizures or other severe complications. This approach provided increased cost effectiveness without increased risk.

Radiological techniques for small acoustic tumors--a re-evaluation.

Small acoustic neuromas are not detected on conventional, computed tomography (CT) brain scans. Eighteen patients with proven acoustic tumors and negative CT brain scans were studied retrospectively to re-evaluate current radiological techniques. We found that the conventional mastoid plain film or thin section tomography is an accurate, cost effective, screening test for acoustic tumors. When these screening studies are positive and agree with the clinical and audiometric examinations, a CT brain scan should then be performed. If the latter is negative, Pantopaque myelography or air-CT should follow. The decision to proceed to invasive studies has been helped by such tests as brain stem audiometry. Since no single, noninvasive X-ray test currently exists to diagnose the small acoustic tumor, screening X-ray studies are indicated before the use of invasive, expensive studies. A protocol for the radiological work-up of small acoustic tumors is suggested.