Epidurography and epidurolysis can be performed at any level of the spine from the sacral hiatus to the foramen magnum. The details provided here are generalized to all areas (sacral, lumbar, thoracic, and cervical) unless identified as specific to a particular area of the spine.
Once it has been determined that a patient meets the accepted criteria for diagnostic epidurography, a detailed discussion of the potential ciii iinm i n hi h ciii iinm i n hi h
Figure 10.3. (A) Loculated contrast filling with no epidural runoff of contrast. (B) Cannulated right L5 neuroforamen. (C) Epidurolysis (decompression) of right L5 neuroforaminal soft tissue stenosis (graded 5/5A).
Figure 10.3. Continued.
Figure 10.3. Continued.
risks and reasonable benefits of the procedure should take place. The risks are those typically associated with an intraspinal procedure and should be made clear to the patient both verbally and in written form.
Risks associated with infection and hemorrhage can be minimized with basic laboratory data. A complete blood count with differential and clotting studies should be standard and normal. Prolonged bleeding times, elevated prothrombin and partial prothromboplastin times, and platelet dysfunction should be evaluated and corrected before any intraspinal procedure is undertaken. Patients should be asked whenever possible to stop all anticoagulants 2 weeks prior to the procedure. Persistent abnormalities should be referred to an internist or hematologist for evaluation.
Intravenous access is advisable in case of inadvertent subdural or in-travascular injection and for mild sedation as required. The injection procedure into areas of neural inflammation can be quite painful. The injection procedure is generally well tolerated by patients who are not sedated but have been well prepared by learning relaxation techniques and the technique of distraction. An awake, alert patient is requested to give the physician feedback regarding the intensity and distribution of the paresthesias elicited by the injection sequence or catheterization. If sedation is required, a small amount of midazelam (1-2 mg) and fen-tanyl (25-50 ^g) will suffice for most patients.
Monitoring should consist of noninvasive blood pressure, electrocardiography, and pulse oximetry. The ability to watch trends and record vital signs is recommended.
The patient is placed prone on a cushioned fluoroscopy table. The lumbar lordosis is straightened by pillows placed under the hips for elevation. The patient's legs should be slightly spread and the toes inverted. This allows ease of access to the sacral hiatus by helping relax the gluteal musculature.
For cervical procedures, pillows are used to elevate the chest to allow the head and neck to fall naturally into a slightly flexed, direct an-teroposterior (AP) position. A lateral position is often recommended to help limit patient movement during the procedure; however, the prone position allows better visualization of the spine and can make specific catheter positioning less frustrating.
Protection from harmful radiation overexposure in the form of protective gloves, glasses, thyroid shield, and lead apron should be used ritualistically with every procedure. A lead table apron is also advisable to help reduce scatter from the source (usually located beneath the table) to the gonads. This is the most often neglected source of radiation exposure and can be the most damaging. The C-arm fluoro-scope is likewise of supreme importance. One should select equipment with a low scattergram and pulse mode capability. Real-time fluoroscopy can be approximated with a pulse mode of 4 pulses per second, thereby reducing radiation exposure by as much as 80%.
No protection, however, can overcome poor technique. Frequent direct beam exposure of even shielded areas of the body such as hands and forearms will produce radiation burns. The same is true for indirect exposure to the cheeks and nose. Consistent use of radiation badges should be required for all medical staff in the room. Lead-lined walls, though not required for C-arm fluoroscopic suites, are highly recommended.
Lysis of adhesions located within the sacral spine to the lower thoracic spine can be best accomplished by access through the sacral hiatus. After appropriate local anesthetic infiltration of the area, needle entry is made caudal to the hiatus on the contralateral side from the anticipated epidural lesion. It is generally recommended that equipment specifically designed for the task of epidurography and epidurolysis be used. Many needles and catheters are available, but only the 16-gauge RK needle and the Racz catheter (Epimed International, Inc.) are designed specifically for this purpose. A 20-gauge needle and catheter system is now available and may offer some technical advantages over the larger needle and catheter.
The needle is advanced through the sacral hiatus across the midline, assuring proper positioning within the sacral canal by means of a lateral fluoroscopic view (Figure 10.4A). A small amount of nonionic contrast (1 mL) is injected to confirm spread within the sacral canal in both lateral (Figure 10.4B) and AP views (Figure 10.4C,D). Both views are necessary because, as seen in Figure 10.5, a needle that appears to be within the canal in one view can be clearly outside the canal in the other view. Once the needle has been confirmed to be within the canal, the tip should not be advanced past the inferior ischial spine (S3 level), since the thecal sac extends to this level in some patients, presenting the risk of an inadvertent puncture. Additionally, since catheterization of the ventral epidural space is favored, passing the catheter laterally and ventrally prior to the S3 level is the most advantageous approach.
For cervical or thoracic procedures, an interlaminar approach, approximately 5 mm off of the midline ipsilaterally, is preferred, but if anatomical difficulties arise, a contralateral paramedian approach can be utilized to enter the epidural space. Ideal entry is 3 to 4 segments below the anticipated space-occupying lesion, such that the initial needle entry does not disrupt the epidural anatomy prior to the epiduro-gram. A typical entry level for cervical epidurography is T1-2 or T2-3.
Without a technically proficient epidurogram, the therapeutic accuracy of epidurolysis is reduced. In this diagnostic portion of the procedure, good and consistent technique is essential, and a knowledgeable eye for both normal and abnormal anatomy is required. This section will address both these issues.
Once the epidural needle has been positioned, nonionic contrast medium is injected. Inadvertent injection of ionic contrast into the sub-arachnoid space can cause catastrophic and permanent damage to the spinal cord and nerve roots. Nonionic contrast approved for intrathe-cal use is suggested for epidurography.
Figures 10.1 and 10.2 demonstrate typical differences between a normal and an abnormal epidurogram. Many variations of the contrast spread are seen with epidurography. There is so much variation that it could be said that the epidurogram is the fingerprint of a patient's spinal pain. Only after seeing hundreds of epidurograms will a practitioner begin to acquire expertise at recognizing pathology and likely sources of pain pathology. However, even the novice can see the obvious defects of filling that so often exactly match the patient's pain description and distribution.
Figure 10.4. (A) Lateral view of RK needle placement within sacral canal. (B) View of initial contrast injection within sacral canal.
Figure 10.4. Continued. (C) AP view of initial contrast injection within the sacral canal (note that the RK needle is pointed toward the side of the anticipated lesion). (D) Completed epidurogram demonstrating complete loculation of contrast at the L5-S1 disc level.
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