The intradural space: the fourth place to go astray during epidural block

Epidural, Inadvertent Subdural, and Combined Epidural-Subdural Anesthesia in Lumbar Spine Surgery: A Retrospective Analysis

This study aimed to categorize contrast media images associated with epidural, subdural, and combined epidural-subdural anesthesia in patients who had undergone fluoroscopy-guided epidural anesthesia using contrast media combined with monitored anesthesia care (MAC) targeted at deep sedation, incorporating capnography over 5 years. Additionally, a correlation was established between the anesthetic effects and radiographic findings according to the categorized imaging appearances. This study included 628 patients who underwent endoscopic, open, or fusion surgery under epidural anesthesia at Nanoori Hospital in Gangnam between March 2018 and September 2023. Fluoroscopy-guided epidural anesthesia using contrast media combined with MAC and capnography was used. The dataset included detailed radiographic imaging, nursing, and anesthesia records. Distinct patterns of anesthesia administration were observed, with 49%, 19.6%, and 31% of patients receiving epidural, subdural, and combined epidural-subdural anesthesia, respectively. The incidence and duration of motor block were significantly different among the three groups. Additionally, subdural anesthesia displayed a higher incidence of motor block and a prolonged motor deficit duration than epidural anesthesia. Fluoroscopic guidance using a contrast medium for epidural and subdural anesthesia ensures precise space identification and prevents serious anesthetic complications. Our findings suggest the potential to achieve stable anesthesia, particularly using subdural and combined epidural-subdural anesthesia.

A review of epidural and non-epidural contrast flow patterns during fluoroscopic and CT-guided epidural steroid injections

Epidural steroid injections are commonly performed using fluoroscopic or CT guidance. With both modalities, the injection of contrast material is necessary before steroid administration to ensure adequate epidural flow and exclude non-epidural flow. While fluoroscopic guidance is conventional, CT is utilized at some centers and can be particularly helpful in the setting of challenging or postoperative anatomy. It is important for proceduralists to be adept at evaluating contrast media flow patterns under both modalities. The goal of this review article is to describe and provide examples of epidural and non-epidural flow patterns on both conventional fluoroscopy and CT. Specific non-epidural patterns discussed include intrathecal flow, intradural/subdural flow, vascular uptake, flow into the retrodural space of Okada, inadvertent facet joint flow, and intradiscal flow.

Assessing the impact of adding bupivacaine on immediate and delayed post-procedure pain scores in interlaminar epidural steroid injections

OBJECTIVE

A local anesthetic is frequently administered as part of a lumbar epidural steroid injection (LESI); however, there is a rare potential for this to result in transient paralysis if administered incorrectly. The purpose of this retrospective study is to determine if the addition of bupivacaine significantly improves patient-reported pain scores.

MATERIALS AND METHODS

This retrospective review includes patients undergoing LESI over an approximately 1 year time span. Pre-procedure, immediate post-procedure, and 1-week integer scaled pain scores were recorded. Ordinal regression was used to compare the distributions of the aggregated ordinal pain score categories between bupivacaine- and non-bupivacaine-injected patients.

RESULTS

Two hundred fifty-eight patients met the inclusion criteria (126F:132 M, mean age 64.7 years) with 164 receiving bupivacaine and steroids and 94 receiving steroids alone. The relative frequency distributions for pre-injection pain did not differ between the bupivacaine patients and the non-bupivacaine patients (p = 0.114). Similarly, the relative frequency distributions for immediate and 1-week post-procedure pain did not differ between the bupivacaine patients and the non-bupivacaine patients (p = 0.293 at immediate time point and p = 0.306 at 1-week time point). Odds ratios comparing pain severity change between the bupivacaine and non-bupivacaine patients also were not significantly different at either the immediate post-procedure (p = 0.769) or 1-week (p = 0.203) time points.

CONCLUSION

The lack of a significant downward shift in the bupivacaine patients' post-procedure pain scores compared to the non-bupivacaine patients' post-procedure pain scores raises doubts about bupivacaine's utility as a standard component of a lumbar epidural injection.

Lumbar Epidural Contrast Spread Patterns for the Interlaminar Approach: Three-Dimensional Analysis Using Antero-Posterior, Lateral, and Contralateral Oblique Views

OBJECTIVE

To describe and analyze lumbar epidural contrast spread patterns in antero-posterior (AP), lateral, and contralateral oblique (CLO) views.

METHODS

Lumbar epidural contrast spread patterns after interlaminar injection were prospectively collected in AP, lateral, and several CLO views and analyzed for multiple variables; three-dimensional mapping was also performed.

RESULTS

Epidural contrast patterns were prospectively analyzed in 28 subjects. The median volume of contrast injected was 2 mL; the AP view was more sensitive than the lateral view to detect foraminal uptake (13/28, 46%, 95% confidence interval [CI] = 27-66%, vs 7/28, 25%, 95% CI = 11-45% subjects). CLO view demonstrated the most consistent location for epidural contrast spread, with contrast contacting the ventral laminar margin in 28/28 (100%, 95% CI = 87-100%) patients. The most common location of contrast spread in the lateral view was at the facet joint lucency, with only 8/28 (29%, 95% CI = 13%-49%) subjects showing contrast contacting the spinolaminar junction. Lateral view was more sensitive than the CLO view in ventral epidural contrast spread detection. The extent and distribution of the spread did not bear any relationship to the volume injected or to the needle location in AP view.

CONCLUSIONS

CLO view provides the most consistent landmark for lumbar epidural contrast spread, and lateral view is most suited to confirming ventral epidural spread. The AP view may be the most optimal for determining target access when considering access to the dorsal root ganglia; in an individual patient, the volume injected and needle location in AP view do not reliably predict target access. The volume to be injected and the need to re-access or obtain multisite access must be prospectively determined, based upon observation of the spread.

Time to Resolution of Inadvertent Subdural Contrast Injection during a Myelogram: When Can the Study Be Reattempted?

BACKGROUND AND PURPOSE

Inadvertent subdural contrast injections can occur during any myelogram. Currently, there are no guidelines defining when residual subdural iodinated contrast will be cleared and no longer interfere with subsequent procedure and imaging. We investigated the time to resolution of subdural contrast using a 2-day lateral decubitus digital subtraction myelogram and associated CT myelogram data in patients undergoing evaluation for spontaneous intracranial hypotension.

MATERIALS AND METHODS

Retrospective review of 63 patients with lateral decubitus digital subtraction myelograms from September 4, 2018, to October 1, 2019, was performed. Patients with 2-day lateral decubitus digital subtraction myelograms on 2 consecutive days, with or without a same-day CT myelogram on day 1 and with a same-day CT myelogram on day 2, were included. Patients with next-day CT covering at least the abdomen and pelvis after either-day injection were also included. In cases of subdural injection, next-day CT scans were evaluated for residual subdural contrast.

RESULTS

Of 49 included patients, 5 had subdural injection on day 1, with the second-day CT myelogram available for review. One of these 5 patients had subdural injections on 2 different days and subsequently had chest/abdomen/pelvis CTA a day after the second subdural injection. In all 6 cases of subdural injections, there was complete resolution of subdural contrast on the next-day CT, with the shortest time to resolution of approximately 20.5 hours (range, 20.5-28.5 hours).

CONCLUSIONS

Our study suggests that resolution of inadvertently injected subdural contrast occurs within 1 day, and the myelogram can be reattempted as early as the next day.

Spinal subdural abscess following repeat lumbar microdiscectomy: A case report of imaging findings for a rare infection

Spinal subdural abscess is a rare central nervous system infection with just over a hundred cases reported. It is much less common than spinal epidural abscess. While most case reports have focused on route of infection and treatment options, there have not been any reports that focused on the unique MRI findings of spinal subdural abscess. We describe a case of spinal subdural abscess diagnosed by MRI in a 33-year-old male who presented with headaches after undergoing a microdiscectomy procedure, and review the underlying anatomic features of the spinal meninges which produce the appearance of a spinal subdural abscess.

An Anatomical Study of the Intradural Space

We have previously postulated that it is possible to accidentally insert an epidural needle or catheter into the substance of the dura during attempted epidural block, creating an intradural space. It appears that injection of local anaesthetic into an intradural space leads to an initially inadequate neuraxial block but further doses may produce an extensive life-threatening block. In the laboratory, 54 samples of human thoraco-lumbar dura were obtained from six cadavers and prepared for scanning electron microscopy. Images from these dehydrated specimens were assessed for the presence of spaces within the dura, and attempts were made to insert an epidural catheter, under optical microscopy, into the substance of the dura in 32 cases. Electron microscopy revealed the concentric laminae that compose the dura and the presence of artefactual spaces between some of these. It was possible to insert an epidural catheter into the substance of the dura in eight specimens, creating intradural spaces which remained following catheter removal. If this represents the clinical situation, it may help to explain previously reported cases of atypical neuraxial block and their associated radiological findings.

Accidental intradural injection during attempted epidural block -A case report-

Several cases of accidental subdural injection have been reported, but only few of them are known to be accidental intradural injection during epidural block. Therefore we would like to report our experience of accidental intradural injection. A 68-year-old female was referred to our pain clinic due to severe metastatic spinal pain. We performed a diagnostic epidural injection at T9/10 interspace under the C-arm guided X-ray view. Unlike the usual process of block, onset was delayed and sensory dermatomes were irregular range. We found out a dense collection of localized radio-opaque contrast media on the reviewed X-ray findings. These are characteristic of intradural injection and clearly different from the narrow wispy bands of contrast in the subdural space.