Epidural Catheter




Sacral Canal Labeled

Figure 10.5. (A) Lateral view of apparent RK needle placement in the sacral canal. (B) AP view of apparent spread of contrast in the sacral canal.

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Caudal Epidurogram
Figure 10.5. Continued. (C) Lateral view of contrast showing superficial spread outside the sacral canal.

Space-occupying lesions producing pain can be along the proximal nerve root but are most often distal within the neuroforamen and ventral in the epidural space. Once a SOL has been identified as consistent with the patient's symptomatology, localized catheterization is needed.

At this point some attention must be given to several other epiduro-graphic abnormalities that could be encountered. The following is a short list of some of these findings that must be recognized.

Complications in Epidurography

Vascular Runoff: Vascular runoff is seen frequently and surprisingly often is associated with negative aspiration. This is due to venous compression by the epidural fibrosis. Large venous plexuses develop, making vascular cannulation likely, as well as hazardous if unrecognized. Figure 10.6A demonstrates venous runoff of contrast on the same side as the catheter, but contralateral venous uptake can also occur, as shown in Figure 10.6B. Figure 10.7 demonstrates similar unexpected vascular uptake after cannulation at the C5 level. In each of these examples, negative aspiration preceded contrast injection. Loculation of Contrast: Complete loculation of contrast (Figure 10.8A) can produce very high pressure gradients. Without cephalad, caudal,

Lumbarization Vertebral Body
Figure 10.6. Attempted epidurolysis of (A) right S1 with ipsilateral vascular runoff and (B) left L4 with contralateral vascular runoff.
Epidurolysis Ventral Epidural Space

Figure 10.7. (A) Cannulation of right C5 medial neuroforamen. C5 with extensive ipsilateral vascular runoff.

(B) Attempted epidurolysis of right

Figure 10.7. (A) Cannulation of right C5 medial neuroforamen. C5 with extensive ipsilateral vascular runoff.

(B) Attempted epidurolysis of right

Figure 10.8. (A) Caudal epidurogram with complete loculation of contrast medium. (B) Subsequent cannulation of right L5 neuroforamen with decompression adhesiolysis and runoff.

or lateral runoff, very small volumes of injected contrast or other agents can produce intraspinal pressures high enough to cause permanent barotrauma to sensitive nerve roots.4,27 If loculation is noted and paresthesias develop, the injection should be terminated and adhesiolysis attempted to improve runoff prior to further injection (Figure 10.8B). If a runoff cannot be produced and/or can-nulation above the loculation is not possible, further injection is contraindicated. Figure 10.9 demonstrates complete loculation due to previously undiagnosed grade 4 spondylolithesis of L4 on L5. Further injection here could easily have produced permanent neurological damage.

Subdural and Subarachnoid Injections: Subdural and subarachnoid spreads are two subtle abnormalities often seen with epidurography. Each has a specific appearance distinct from, but quite similar to, a pathological epidural spread. Patients who have undergone multiple lumbar surgeries have often lost their well-defined epidural space, making cannulation of the subdural or subarachnoid space likely. Recognition of dye spread deep to the epidural space is critical to the safety and efficacy of the procedure.

Characteristic of a subdural spread are the smooth rounded edges of the contrast often accompanied by a "shifting lake" appearance: that is, the contrast moves freely in the lateral projection (Figure 10.10).

A subarachnoid or intrathecal spread is recognized by initial loss of resistance to advancement of the catheter as it enters the space filled with cerebrospinal fluid (CSF). The injected contrast material is seen to dissipate rapidly and to spread uniformly in all directions with a dilutional effect on its appearance (see Figure 10.11A,B). The exception to this is the patient with extensive arachnoid adhesions, which add resistance to catheter advancement; with loculations of contrast, the appearance can closely resemble an epidural spread.

Recognition of these areas of contrast spread is important because many steroid solutions contain preservatives and are still suspected by some to cause arachnoiditis if injected intrathecally. More important, inadvertent subdural or intrathecal administration of 10% hypertonic saline can cause permanent neurological dysfunction.28-30 Epidural administration has been shown to be safe by dural permeability studies31 and by the long-term clinical use of the procedure in thousands of cases at multiple centers since the mid-1980s. Extremely rare reports, however, suggest that anachnoiditis may result.29 Novice and experienced pain professionals should still carry a high index of suspicion regarding inadvertent puncture of the intrathecal space; whenever there is doubt, hypertonic saline anytime should not be used. The addition of hypertonic saline adds benefit to the procedure26 but is not essential to patient improvement and therefore should be treated as an adjunct to epidurolysis.

Catheter Placement (Mechanical Epidurolysis)

Catheter placement into the specific area of pain generating epidural fibrosis is a learned skill. One can easily thread a catheter near the general area of pathology. Guiding the catheter tip laterally into a neuroforamen filled with engorged veins and fibrosis (often thick, dense postoperative scarring) is a more challenging task. The light touch required to guide the specialized catheter into a space-occupying lesion has been described by Racz as "an elegant maneuver, as if sipping tea" (with the little finger held extended). Catheter placement is a skill that cannot be taught, only learned. This critical component of the epidurolysis

Racz Catheter Epidurolysis

Figure 10.9. (A) Epidurogram with complete loculation and paresthesias at 3 cc injected. Injection terminated owing to loculation and paresthesias. (B) Lateral view of (A) demonstrating loculation secondary to grade 4 spondylolithesis of L4 on L5 (vertebral bodies enhanced to show detail).

Figure 10.9. (A) Epidurogram with complete loculation and paresthesias at 3 cc injected. Injection terminated owing to loculation and paresthesias. (B) Lateral view of (A) demonstrating loculation secondary to grade 4 spondylolithesis of L4 on L5 (vertebral bodies enhanced to show detail).

Spinal Subdural Dye Injection

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Figure 10.10. Subdural spread of contrast with typical smooth rounded edges loculated in the (A) spinal canal, AP view, and (B) the dorsal spinal canal (less often seen in a ventral location), lateral view.

Adhesiolysis Epidural

Figure 10.11. (A) Epidural catheter position at right L4 with predominantly epidural spread. (B) Sub-arachnoid spread of contrast seen diffusely with dilutional effect and smooth dissemination. Note the presence of small nerve root evaginations and darker areas of subarachnoid adhesions with loculation (arrow).

Figure 10.11. (A) Epidural catheter position at right L4 with predominantly epidural spread. (B) Sub-arachnoid spread of contrast seen diffusely with dilutional effect and smooth dissemination. Note the presence of small nerve root evaginations and darker areas of subarachnoid adhesions with loculation (arrow).

procedure can be a source of much frustration to expert and novice alike. The familiar edict "first do no harm" is the rule. Sensitive neural structures can be damaged if the technique is not given due respect or if an overly aggressive attempt is made to cannulated specific areas. Such areas of disc or neural pathology not accessible to epidurolysis on initial attempt may be more easily and safely cannulated later, on subsequent attempts. In addition to the mechanical lysis of adhesions that takes place with cannulation, injection of hyaluronidase and steroid softens epidural scarring and creates a more porous adhesion that can often be easily lysed 10 days to 2 weeks later. Subsequent epidurography demonstrates significantly improved filling of the neu-roforamen and distal neural sheath, consistent with the clinical improvement of the patient (Figures 10.12).

I recommend routine follow-up evaluation approximately 2 weeks after initial epidurolysis to assess the patient's response, whereupon a repeat procedure may be considered. A second lysis of adhesions in this time frame seems to produce better outcomes, although this has not been confirmed by clinical studies. Anecdotal experience has demonstrated that more lasting clinical improvement is achieved with a second consecutive lesion-specific steroid injection. A more extensive decompression of scarred nerve roots is possible following exposure of the inflamed neural tissues by an initial epidural adhesiolysis procedure.

A specialized spring-tipped catheter designed specifically for epidurolysis is recommended.32 This catheter has a wire stylus that can be curved, giving it steerability while maintaining its coiled-spring tip. The soft tip enhances the safety to intentional cannulation of sensitive injured nerve root areas.

Injection Sequence (Injection Epidurolysis)

A detailed review of all substances discussed in this section was provided by Lewandowski in 1997.26

Contrast Injection

Once the catheter has been properly positioned, contrast medium is injected again to demonstrate the spread of injectate and the degree to which the filling defect is opened or lysed (injection epidurolysis). This is limited to a volume of 2 to 4 mL. The patient's response to this injection is noteworthy because the reproduction of a familiar pattern of painful paresthesias likely indicates the pathology responsible for the clinical symptoms.

Both the final position of the catheter tip in relation to the neuro-foramen and the extent to which the contrast spreads within the neu-roforamen affect the adequacy of the epidurolysis. A simple grading scale has been developed to document both results. A grading scale of 1 to 5 is employed, utilizing the neuroforamen as a reference point. The catheter tip position (all positions are assumed to be ventral epidural) is designated in one of the following ways:

1. Medial or midline ipsilateral or contralateral epidural space

2. Lateral epidural space, but still proximal to the medial border of the neuroforamen

Borders Epidural Space
Figure 10.12. (A) Initial epidurogram demonstrating a filling defect of the left L5 neuroforamen consistent with a clinical presentation of left L5 radiculopathy. (B) Cannulation of the left L5 neuroforamen prior to epidurolysis.
Figure 10.12. Continued. (C) Epidurolysis with spread of contrast transforaminally (graded 4/5B) prior to administration of hyaluronidase, local anesthetic, and steroid. (D) Epidurogram 4 weeks later, with resolution of radicular pain.

3. Intraforaminal space, not extending to the lateral border of the neu-roforamen

4. Intraforaminal space extending to the lateral border, but not beyond

5. Catheter tip positioned beyond the lateral border of the neuroforamen

The extent of contrast spread is designated as follows:

1. Medial or midline ipsilateral or contralateral epidural spread

2. Lateral epidural spread, but still proximal to the medial border of the neuroforamen

3. Intraforaminal spread, not extending to the lateral border of the neu-roforamen

4. Intraforaminal spread extending to the lateral border, but not beyond

5. Contrast spread beyond the lateral border of the neuroforamen

The relative volume of contrast seen within the space occupying lesion is likewise graded. Designations of A, B, or C are given to this characteristic of the contrast spread:

A. Large volume noted with minimal striation or trabeculations (a "full" filling of the space)

B. Medium volume noted with some striations or trabeculations

C. Small to no amount of contrast filling of the space, with predominance of striations and trabeculations

A grading of a catheter tip placement and subsequent contrast injection of 1/1B indicates a fairly poor epidurolytic result, with the catheter tip in a medial epidural position and the contrast limited to a modest, trabeculated filling of the medial epidural space. A grade of 3/3C indicates a catheter tip positioned intraforaminally with a very poor, highly trabeculated filling within the neuroforamen, not extending all the way to the lateral border of the foramen. A grade of 5/5A similarly denotes a catheter tip positioned well outside the lateral border of the neuroforamen with a large amount of contrast spread both proximally and distally within the neural sheath.

This A, B, C grading method provides a way of scoring the adequacy of the epidurolysis for later comparison to the clinical results, which in turn helps to determine the reasonableness of a subsequent epidurol-ysis procedure. For instance, a poor clinical response to a well-placed and adequately decompressed neural sheath (5/5A) would make it unlikely that a second epidurolysis would yield any further clinical benefit. On the other hand, a 2/3B result with short-term clinical improvement might make a second attempt 2 to 4 weeks later well worthwhile.

I recommend recording hard copy radiographs or thermograms to provide evidence of the initial epidural adhesions, subsequent injection sequences, and the results of epidurolysis. This often provides the only evidence of the pathology responsible for the low back pain and radicular symptoms presented. Without such evidence, many patients are unfairly labeled as malingerers or "symptom magnifiers." The pain may not be sufficient to produce an objectifiable physical limitation.

Hyaluronidase Injection

Once the contrast spread has been maximized, an injection of hyaluronidase diluted with preservative-free normal saline is provided. This should have a concentration of between 150 to 500 units/mL. The volume may vary between 3 and 5 mL. There should be a noticeable washout of the contrast previously injected, along with repeat paresthesias. A delay of approximately 3 to 5 minutes should follow, allowing for the sequestration of the hyaluronidase into the adhesive tissues.

Steroid and Local Anesthetic Injection

A combination of steroid and local anesthetic is now injected again in a combined volume of 5 mL. The traditional steroid used is triamcinolone. Methylprednisolone is also used often. Each has specific properties making it more or less desirable for epidural use.26 No single steroid has shown an obvious advantage or disadvantage to date. Typical steroid preparations are 40 mg/mL.

The local anesthetic recommended is bupivacaine 0.25% (2.5 mg/mL). The bupivacaine is diluted with the steroid typically in an 18:3 ratio. This lowers the concentration of bupivacaine to 0.214% with a steroid concentration of 5.7 mg/mL. This specific combination of local anesthetic and concentration has the advantage of helping clinicians to distinguish between an epidural injection and a subdural injection. This is of particular significance when one is considering the use of a hypertonic saline solution for neurolysis following the epidurolysis. This significance is discussed next.

Subsequent Steroid and Local Anesthetic Injection

Following the initial sequence of injections just described for a distinct filling defect, a second similar series can be performed on a subsequent area of suspicious fibrosis. The original Racz procedure promoted a single injection site with volumes of 9 to 10 mL each for the various solutions. Realization that there are often multiple lesion sites has led to the modification that allows multiple sites for injection during a single epidurolysis procedure. The wire stylus is replaced and the catheter is simply repositioned. Care should be taken to avoid inadvertent protrusion of the wire stylus through the side of the catheter's spring tip (Figure 10.13). Following repositioning, the sequence described earlier in the sections on contrast injection, hyaluronidase injection, and steroid and local anesthetic injection, are repeated. The total volume of local anesthetic and steroid is 21 mL, allowing typically for four separate injection sites if necessary. Some space-occupying lesions require both proximal and distal nerve root epidurolysis when distal injection demonstrates a persistent proximal filling defect. Multiple nerve roots may be involved, requiring multilevel epidurolysis.

Each site injected must be observed closely for signs of possible sub-dural or subarachnoid spread (Figures 10.10B, 10.11B). Any suspicion of anything other than epidural spread should put an end to consideration of the use of hypertonic saline.

Epidural Catheter
Figure 10.13. Epidural catheter with wire stylus protruding through side of spring tip.

Hypertonic Saline 10% Infusion

The RK needle is removed, leaving the catheter in place. The catheter is secured with topical antibiotic ointment, sterile gauze, and tape. Depending upon the anticipated duration of the catheter placement and number of anticipated catheter injections, a 0.22 ^m filter should be placed in line to help prevent contamination and infection. Although the original epidurolysis procedure recommends repeat local anesthetic and hypertonic saline injections for 3 successive days, current modifications require only a single hypertonic saline administration on the first day with outpatient discharge.10 No filter is required for single hypertonic saline infusion with anticipated same-day discharge. Outcomes appear to be similar for the 1- and 3-day infusions, and costs are greatly reduced by outpatient single-day care.

Following the last injection of steroid and local anesthetic, a mandatory wait time of 30 minutes allows for onset of a significant sensory or motor blockade, which will occur if a subdural or subarachnoid injection has transpired. Again, no hypertonic saline should be infused. There should be radiographic verification of all injection sites, contrast spreads, and final catheter position, as well as no significant sensory or motor blockade before the use of hypertonic saline infusion is considered. If a 10 mL volume of 10% hypertonic saline is infused through the catheter via continuous infusion pump at no greater than 20 mL/h

(10mL/30 min). Should any significant pain occur during the infusion, it should be immediately terminated and the catheter removed.

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