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Spontaneous intracranial hypotension (SIH) is a disorder of CSF dynamics that causes a complex clinical syndrome and severe disability. SIH is challenging to diagnose because of the variability of its presenting clinical symptoms, the potential for subtle imaging findings to be easily overlooked, and the need for specialized diagnostic testing. Once SIH is suggested by clinical history and/or supported by initial neuroim-aging, many patients may undergo initial nontargeted epidural blood patching with variable and indefinite benefit. However, data suggest that precise localization of the CSF leak or CSF-venous fistula (CVF) can lead to more effective and durable treatment strategies. Leak localization can be achieved using a variety of advanced diagnostic imaging techniques, although these may not be widely performed at nontertiary medical centers, leaving many patients with the potential for inadequate workup or treatment. This review describes imaging techniques including dynamic fluoroscopic and CT myelography as well as delayed MR myelography and treatment options including percutaneous, endovascular, and surgical approaches for SIH. These are summarized by an algorithmic framework for radiologists to approach the workup and treatment of patients with suspected SIH. The importance of a multidisciplinary approach is emphasized.

OBJECTIVE. Myelography is a commonly used procedure to evaluate the spinal canal. However, the procedure is not without risk, chiefly risk of seizure after intrathecal administration of iodinated contrast material. CONCLUSION. The risk of seizure remains an important concern for radiologists, who should strongly consider practice parameter guidelines that address this risk.

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.

Objective: We compared traditional bevel-tip end-hole spinal needles and pencil-point-tip side-hole needles for the incidence, severity, and duration of spinal headaches in subjects who had myelograms. Age, sex, and myelographic findings were examined., Subjects and Methods: We studied 138 subjects referred for myelograms. For 108 procedures, we randomly used 22-gauge Quinke bevel-tip end-hole needles or 22-gauge Sprotte pencil-point-tip needles. The 30 additional subjects were examined with Gertie Marx pencil-point-tip needles. All myelograms were performed by one of two neuroradiologists using recommended doses of iohexol. The myelograms were examined by an independent neuroradiologist for quality of image and presence of extraarachnoid contrast material. Five to 14 days after myelography, subjects were telephoned by an independent observer and asked about the presence, severity, duration, and positional quality of headache. Spinal headache is defined by positional quality and increases in severity when the subject moves from horizontal to sitting or standing., Results: We found that four (8%) of 52 subjects who had myelograms with Sprotte needles had spinal headaches. Likewise, 14 (25%) of 56 subjects who had myelograms with Quinke needles had spinal headaches. We calculated a statistically significant difference in the incidence of spinal headaches using chi-square analysis (p = .02). The average grade and duration of the spinal headaches did not differ significantly, although they were less marked in the Sprotte group. Spinal headaches occurred more frequently in young and middle-aged subjects than in older subjects. We found one definite extraarachnoid injection in each group. For the Gertie Marx needles, two (7%) of 30 subjects had spinal headaches. The average grade of postmyelogram headache was 2.5, and the mean duration was 1 day. There were no mixed injections., Conclusion: We found a significant reduction in spinal headaches after myelograms when we used the pencil-point-tip side-hole needle. These results support the routine use of these needles for myelography in young and middle-aged patients.

A series of myelographies performed with a smaller than customary dose (3.75 g) of metrizamide was compared with a series using the larger customary dose. While little decrease in the incidence of headache and vomiting resulted from the decreased dose, there was a heartening drop in the incidence of psychoneurologic side effects. Little difference in diagnostic quality between the two series resulted when the contrast agent was injected close to the site of main interest, but total spinal canal myelography performed with the low dose is often inadequate.

Bloody cerebrospinal fluid is thought to increase the risk of arachnoiditis from myelography with iophendylate, but not with aqueous media. An experimental study was undertaken of the effects of metrizamide, iocarmate, and blood, independently and in mixtures, on the production of arachnoid fibrosis. Monkeys exposed to a mixture of iocarmate or metrizamide and blood developed no more significant arachnoid fibrosis than animals exposed to the contrast medium alone. Lumbar puncture with bloody cerebrospinal fluid, although a possible cause of adverse effects, is not a contraindication to proceeding with metrizamide myelography.

This prospective study of 90 patients after lumbar metrizamide myelography indicates that the semiupright position at 45 degrees in bed or early ambulation reduces postprocedure vomiting but does not reduce the frequency of headache. Ambulatory patients have less frequent nausea than patients kept in bed.

Myelography with meglumine iocarmate, a dilute meglumine iocarmate solution, or gas was performed in macaque monkeys. Twelve weeks later the animals were examined myelographically and histologically for evidence of arachnoiditis. Arachnoiditis in the animals treated with dilute meglumine iocarmate and gas was significantly less than in those treated with meglumine iocarmate.

Scanning electron microscopy demonstrated starch powder contamination on the stylet tip from a spinal needle after it was lightly touched with nonwashed surgical gloves. A sterile solution of Pantopaque was injected through the spinal needle after the stylet was withdrawn and carried particulate contaminants to a 0.2 micrometer millipore filter. Using both scanning electron microscopy and energy dispersive x-ray analysis, particles of various sized (mostly 5-10 microns) and variable compositions, including starch, talc, and other elements, were identified. Also, glass particles from the Pantopaque vial and plastic particles from the plastic syringe and tubing used in drawing up the Pantopaque were seen. These observations indicate that strict attention to proper technique in myelography is essential in order to eliminate potential cerebrospinal fluid contamination.

Recognized risk factors for metrizamide myelography are seizure disorder, seizure-threshold-lowering drugs, dehydration, and possibly age. After observing serious neurologic complications in diabetic patients after routine metrizamide myelography, a retrospective study was conducted to determine if diabetes should be considered another independent and important risk factor. Forty-one diabetic patients who had lumbar metrizamide myelograms were compared with a control group of 110 nondiabetic patients. A significantly higher incidence was found of severe vomiting (15% vs. 3%, p less than 0.01) and neurologic complications (20% vs. 2%, p less than 0.001) in the diabetic population. Neurologic complications included one case each of seizure, severe encephalopathy, auditory and visual hallucinations, and prolonged somnolence and four cases of confusion-anxiety. Four of the diabetic patients had major transient elevations of blood pressure. These findings suggest that diabetics are a high-risk population for metrizamide myelography. The dose of metrizamide should be minimized, whenever possible. The new nonionic myelographic agents may prove to be safer in this population, but caution and careful follow-up should be exercised in the initial trials with these patients.

A prospective study of 110 patients having iohexol lumbar myelograms indicates that patient positioning does not significantly influence the frequency of adverse postprocedural reactions. Thus, after the procedure, patients may be allowed to choose either ambulation or bed rest with their heads raised.

One hundred patients were questioned after metrizamide myelography about the side effects of the examination. The number and type of side effects were tabulated and correlated with investigated region (e.g., cervical, lumbar) and with use of medication (e.g., analgesics, diuretics). The number of side effects, particularly neuropsychologic, were higher than previously reported. The most common side effects were minor meningeal irritations (headache, nausea, dizziness, and vomiting) and were regarded by the patients as inconsequential. All side effects became apparent during the first 24 hr after myelography and all were transitory. The side effects, being minor, should not limit the use of metrizamide for myelography. However, those caring for patients who have undergone the study should be aware of the possible side effects.

Myelography in monkeys was performed with either meglumine iocarmate or metrizamide. The severity of resultant arachnoiditis in each animal 12 weeks later was evaluated by repeat myelography and by histologic study of the arachnoid. Three of the four animals examined with meglumine iocarmate had severe arachnoiditis; none of the four animals examined with metrizamide had as severe changes. The difference between the two groups was statistically significant (P less than .05).

Postmyelography headaches are produced mostly by CSF leakage at the dural puncture site and are therefore largely dependent on the size of the needle used. Our study of 300 consecutive outpatients who had lumbar myelograms performed with 25- and 26-gauge spinal needles shows that the procedure has become virtually innocuous. We recommend that 26-gauge spinal needles be widely adopted as the standard for fluoroscopically controlled intrathecal injections of contrast material.