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Myelography Complications and Current Practice Patterns

Department of Radiology, Eastern Virginia Medical School, Hofheimer Hall, Ste. 541, 825 Fairfax Ave., Norfolk, VA 23507.

Received July 2, 2004; accepted after revision November 2, 2004.

 
Address correspondence to J. F. Donnal.

Presented at the 2004 annual meeting of the American Roentgen Ray Society, Miami Beach, FL.

Abstract

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OBJECTIVE. Relatively few data are available in the literature on postmyelography complications. Also, no consensus exists on the need to screen myelography patients for use of potentially epileptogenic drugs, metformin, and aspirin or other nonsteroidal antiinflammatory drugs (NSAIDs) or to routinely check prothrombin time (PT) and partial thromboplastin time (PTT). We designed a Web-based survey to obtain information on myelography complications and current practice patterns.

MATERIALS AND METHODS. An e-mailing was sent to 2,296 members of the American Society of Neuroradiology (ASNR), requesting their participation in a survey, and 351 responses (15%) were received. The survey included questions on the number of myelography examinations performed and the number of seizures and other complications observed in myelography patients; questions on screening for potentially epileptogenic drugs, metformin, and aspirin or other NSAIDs; and a question on checking PT and PTT.

RESULTS. Most responding ASNR members (88%) reported no postmyelography seizures, and 82% observed no other significant complications in the past 5 years. A majority of practitioners (63%) screens patients for potentially epileptogenic drugs, 63% of respondents do not advise patients to discontinue metformin use after myelography, 58% do not advise patients to discontinue aspirin or other NSAIDs, and 73% do not routinely check PT and PTT.

CONCLUSION. Myelography is generally safe, with a low risk of seizures, contrast reactions, and other significant complications. The results of this study show that a majority of practitioners screens patients for use of potentially epileptogenic drugs, but a majority does not require patients to discontinue use of metformin and aspirin or other NSAIDs, nor do they routinely check PT and PTT before the procedure. These common practice patterns are considered to be appropriate for the safe and efficient performance of myelography.

Introduction

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Myelography is an important diagnostic procedure for specific indications, although its frequency has declined over the past decade as MRI has gained widespread acceptance for most spinal studies. Although the incidence of complications from myelography is generally believed to be quite low, a number of questions remain regarding management necessary to prevent seizures, contrast reactions, bleeding, and other significant postmyelography complications. Current myelography protocols in many practices include screening for use of medications that lower the seizure threshold, obtaining laboratory test results (e.g., prothrombin time [PT], partial thromboplastin time [PTT], blood urea nitrogen, and creatinine), withholding metformin, and discontinuing aspirin or other nonsteroidal antiinflammatory drugs (NSAIDs) before myelography. However, practice guidelines for management of myelography patients are unavailable, and some practitioners do not believe that routine screening or laboratory testing is necessary before myelography. In addition, referring clinicians and patients can become frustrated by such requirements, particularly when they result in modification of medication regimens or rescheduling of procedures.

Data are clearly needed on preparation of patients before myelography and complications after myelography, but such information would be difficult to obtain using either a prospective or a retrospective study design. Survey methodology, on the other hand, lends itself to efficient collection of descriptive information and has been used in previous studies of cervical myelography [1]. We designed a Web-based survey to obtain information on myelography complications and current practice patterns.

Materials and Methods

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An e-mailing was sent to the 2,296 U.S. members of the American Society of Neuroradiology (ASNR) with valid e-mail addresses, requesting their participation in a Web-based survey, and 351 responses (15%) were received. The survey included questions on the number of myelography procedures performed and the number of seizures and other complications observed in myelography patients; questions on screening for potentially epileptogenic drugs, metformin, and aspirin or other NSAIDs; and a question on checking PT and PTT. Written comments were also requested. Results were compiled and percentages calculated by EventHandler Professional software (UbiDog Productions).

Individual responses in the raw data were analyzed for consistency by cross-matching the responses between related questions within a group, and those responses that were considered to be invalid were discarded from the final data. For example, in Table 1, a response of "0" to the first question, "How many patients had seizures in last 5 years?" should have resulted in the respondent's skipping the second question, "Did patient have a seizure history?" and the third question, "Was patient taking potentially epileptogenic drugs?" However, if a response of "0" to the first question was followed by a response of "Yes" or "No" to the second or third question, those incompatible responses were considered to be invalid. In addition, cross-matching analysis for Table 1 included comparison of responses between the fourth and fifth questions and between the fourth and sixth questions. Similar analysis was performed for Table 3 by comparing responses between the first and second questions and between the first and third questions.

Results

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The survey shows that 42% (147/351) of responding ASNR members performed more than 100 myelography examinations, 41% (145/351) performed 20-100, and 17% performed fewer than 20 yearly. Questions regarding seizures (Table 1) indicate that few seizures were observed in myelography patients, with 88% of respondents reporting no seizures and only 12% reporting one or two seizures in the past 5 years. A majority of the seizures (59%) were observed by practitioners performing more than 100 myelography examinations per year (data not shown). Most of the seizures (88%) were in patients who were not taking potentially epileptogenic drugs, and most (78%) occurred in practices that screen for such drugs (data not shown). One of the practitioners responding to the survey commented that he had performed "thousands of myelograms, and had never observed a seizure." Another stated "we do five to 15 myelograms per day and we haven't seen a medication-induced seizure."

Of the respondents whose patients experienced seizures, 40% indicated that those patients had a history of seizure, and only 14% reported that the patients had been taking potentially epileptogenic drugs. A majority of respondents (63%) indicated that they screen for such drugs, with 43% reporting screening for one to 10 drugs and 38% reporting screening for more than 10 drugs. Respondents who screen for potentially epileptogenic drugs indicated that patients must refrain from taking the drugs before myelography for either 1 day (27%), 2 days (54%), or 3 days (19%). A question about metformin (Table 2) revealed that a majority of respondents (63%) does not advise patients to discontinue metformin use after myelography.

Other complications (Table 3) were reported to be relatively uncommon in myelography patients, with 78% of respondents reporting no contrast reactions and only 19% reporting 1-2 contrast reactions in the last 5 years. Most respondents (81%) indicated that patients with contrast reactions did not have a history of contrast allergy, and most (88%) reported that the contrast reactions were minor. However, nine respondents did report major reactions, including "shortness of breath," "airway compromise," and "laryngeal edema" (written comments). A majority of the contrast reactions (67%) occurred in practices performing more than 100 myelography examinations per year (data not shown). Most of the respondents (82%) reported no other significant complications of myelography, although 18% did observe significant complications in the last 5 years. The most serious complications included nine cases of "cord puncture" or "conus puncture" and two cases of "injection of nonmyelographic contrast" (written comments).

A question about screening for potential bleeding complications (Table 4) in myelography patients revealed that 27% of respondents routinely check PT and PTT in patients without specific risk factors, whereas 73% do not. Also, 42% of respondents advise patients to discontinue aspirin or other NSAIDs, whereas 58% do not give such advice.

Discussion

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The findings reported here show that seizures resulting from myelography are infrequent, with most responding ASNR members (88%) reporting no seizures in the last 5 years (Table 1). According to a recent review of the literature, seizures rarely occur with the use of current nonionic intrathecal contrast agents, with only three case reports of seizures after use of iohexol in the past 15 years [2]. In contrast, seizures had been reported to occur in up to 0.6% of myelography examinations performed with metrizamide [2]. Although there have been no well-designed studies to confirm an increased seizure risk in myelography patients who take medications that lower the seizure threshold, some practitioners recommend that drugs that lower the seizure threshold be avoided 48 hr before and 24 hr after administration of myelographic contrast medium [3]. In the present study, a majority (63%) of respondents reports screening for potentially epileptogenic drugs and advising that patients withdraw from such medications before myelography. However, a significant minority (37%) does not screen for such drugs. Further study is encouraged to better define the association, if any, between drugs that lower the seizure threshold and myelography-associated seizures.

Another concern among myelographers has been the pre- and postmyelography management of patients taking metformin. Because of the theoretic risk of contrast-induced renal insufficiency and subsequent lethal lactic acidosis, it has been suggested that patients undergoing myelography should discontinue metformin after contrast administration [3]. However, it has recently been pointed out that the risk of contrast-induced nephrotoxicity is extremely low in procedures such as myelography, which involve administration of small volumes of contrast medium [4]. Furthermore, to our knowledge, there have been no reports to date of such a reaction in a myelography patient. The results of the present study (Table 2) show that a majority (63%) of respondents do not advise patients to discontinue metformin use after myelography.

This study shows that complications other than seizures are also uncommon in myelography patients, with 78% of respondents reporting no contrast reactions and 82% reporting no other significant complications (Table 3). However, 18% of respondents reported significant complications, including nine cases of spinal cord or conus medullaris injection (written comments). Several cases of spinal cord puncture or contrast injection were previously observed as a complication of cervical myelography [1]. This rare complication can be avoided by careful attention to spontaneous flow of cerebrospinal fluid from the needle hub before injection and by careful fluoroscopic observation of contrast flowing away from the needle (i.e., no pooling in the parenchyma) during injection. In addition, two respondents reported injection of nonmyelographic contrast medium (written comments), but this reportedly lethal complication [5] can easily be prevented with strict attention to technique [6]. Finally, it has been suggested that anticoagulants and anti-platelet agents be discontinued and that PT and PTT be documented in myelography patients [3] to decrease bleeding risk. Our results show that a majority of the respondents (73%) does not check PT and PTT routinely and a majority of the respondents (58%) does not advise patients to discontinue aspirin or other NSAIDs. These findings should be considered in light of several limitations of the survey methods used. The low response rate of 15% is consistent with rates obtained in other e-mail surveys, which tend to be lower than in conventional mail surveys [7]. A second shortcoming is that sample selection was limited to a subset of ASNR members in the United States with valid e-mail addresses listed in the ASNR directory. Because this sample is not representative of the entire ASNR membership or of non-member practitioners, the results cannot be generalized to all myelography practitioners. In addition, a significant limitation of the survey method is the inaccuracy of responses that depend on the memory of the respondents, especially with respect to questions on patient complications and history during the past 5 years. Finally, minor discrepancies in the numeric data are apparent when comparing related questions within a group and are primarily related to respondents' not answering some of the questions.

In summary, myelography is safe, with a low risk of seizures, contrast reactions, and other significant complications. The results of this study show that a majority of practitioners screens patients for use of potentially epileptogenic drugs, but a majority does not require that patients discontinue use of metformin and aspirin and other NSAIDs, nor do they routinely check PT and PTT before the procedure. These common practice patterns are considered to be appropriate for the safe and efficient performance of myelography and should help to prevent unnecessary modification of medication regimens, decrease costly laboratory testing, and avoid disruptive rescheduling of procedures.

Acknowledgments
 
We thank all the respondents for their kind participation in the survey. We also thank Kim Lewandowski for her skill in producing the Web page and Marleen Viola for her generous assistance with the e-mailing.

References

Top Abstract Introduction Materials and Methods Results Discussion References

 

1. Robertson HJ, Smith RD. Cervical myelography: survey of modes of practice and major complications. Radiology1990; 174:79 -83[Abstract/Free Full Text]
2. Fedutes BA, Ansani NT. Seizure potential of concomitant medications and radiographic contrast media agents. Ann Pharmacother 2003; 37:1506 -1510[Abstract/Free Full Text]
3. Smith RR. Myelographic complications associated with drug interactions. (answer to question) AJR2001; 177:713[Free Full Text]
4. Henry WD. Metformin hydrochloride in patients undergoing myelography (letter). AJR 2002;178 : 1289[Free Full Text]
5. van der Leede H, Jorens PG, Parizel P, Cras P. In-advertent intrathecal use of ionic contrast agent. Eur Radiol2002; 12[suppl 3]:S86 -S93
6. ISMP Medication Safety Alert. Intrathecal injection of ionic contrast media may be fatal. November 27, 2003. Available at: www.ismp.org/MSAarticles/fatal.htm. Accessed May 15, 2005
7. Wald C, Luchs J, Davila J, et al. Residents' perceptions of MRI training in the United States. JACR 2004;1 : 331-337

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