Lumbar Myelography

Abstract

Lumbar myelography is a radiographic study that is used to evaluate central and neuroforaminal stenosis, bony lesions, and cord compression. It is also a fairly reliable alternative for patients who are unable to undergo magnetic resonance imaging (MRI). Although MRI is preferred for the evaluation of disc pathology, soft tissue, and neural compression, computed tomography (CT)-myelography remains an option for diagnostic testing. Metal from surgery or trauma can cause artifacts on MRI that limit imaging of the central spinal canal, which can be better assessed by CT-myelography. CT enables better assessment of hardware, such as pedicle screws, to assess for osteolysis. In addition, CT-myelography is often used, and sometimes preferred, by surgeons as the diagnostic imaging study for preoperative planning.

Keywords

Contrast, Contrast Flow, Epidurogram, Fluoroscopy

Note: Please see pages ii , iii for a list of anatomic terms/abbreviations used throughout this book.

Lumbar myelography is a radiographic study that is used to evaluate central and neuroforaminal stenosis, bony lesions, and cord compression. It is also a fairly reliable alternative for patients who are unable to undergo magnetic resonance imaging (MRI). Although MRI is preferred for the evaluation of disc pathology, soft tissue, and neural compression, computed tomography (CT)-myelography remains an option for diagnostic testing. Metal from previous surgery or trauma may cause artifact on MRI imaging that may limit the image quality within the central spinal canal, which is better assessed and visualized with CT myelogram. CT enables better assessment of hardware, such as pedicle screws, to assess for osteolysis. In addition, CT-myelography is often used, and sometimes preferred, by surgeons as the diagnostic imaging study for preoperative planning.

Proper sterile precautions and techniques in performing myelography are essential to decrease adverse effects such as headache, hemorrhage, fever, meningitis, altered mental status, and seizures. The most common complication is spinal headache, ranging from 32% to 70% incidence, which may require intravenous hydration or a blood patch.

Trajectory View: The Trajectory/Anteroposterior View Is Also a Multiplanar View

▪

The patient should be in a prone position with pillows under the pelvis, the goal being to flatten the lumbar lordosis.
▪

Review available studies to evaluate for stenosis, previous surgeries, and hardware so that a proper needle entry level can be chosen.
▪

Confirm the level (under the anteroposterior [AP] view). It is preferable to enter below the conus, typically at the L2-L3 interspace or below. If an MRI is available, it can be useful to confirm the level. Because the target is the intrathecal space, the needle can often be introduced into the site of a previous laminectomy (unlike the strategy for a lumbar epidural injection).
▪

It is preferable to enter in the interspace at the vertebral body, rather than the disc space. If there is a significant herniated disc and/or central stenosis at the chosen interspace, the thecal sac is narrowed, making entry into the thecal space more difficult and causing pain to the patient (see Figs. 14.5 and 14.10 ).
▪

The image intensifier is tilted caudad or cephalad to open up the target interlaminar space and facilitate easier entry between the two adjacent laminae. Here we demonstrate minimal obliquity for entry. However, the image intensifier can be obliqued 5 to 10 degrees to the right or left for the initial trajectory view. The needle should be placed parallel to the fluoroscopic beam, and the needle should be advanced toward the midline ( Fig. 14.1A ) .

Fig. 14.1

A, Trajectory/anteroposterior (AP) view of the lumbar spine with the ideal needle position for L1-L2 interlaminar entry with a target that avoids the disc space. B, Radiopaque structures, AP/trajectory view. C, Radiolucent structures, AP/trajectory view.

Notes on Positioning in the Anteroposterior/Trajectory View

▪

In the setting of an intact lamina, the initial approach is either straight AP or slightly oblique, similar to that of an interlaminar epidural steroid injection.
▪

Because the contrast dye is denser than the cerebrospinal fluid (CSF), the Trendelenburg or reverse Trendelenburg position is utilized during the procedure so that the contrast dye is able to stay in the lumbar region or flow cephalad toward the cervical spine (see Fig. 14.7B ), depending on the targeted segments to be imaged.
▪

A smaller bore spinal needle (22 or 25 G) is preferred to lower the risk of bleeding and postprocedural headache.
▪

Target over a vertebral body and NOT over an intervertebral disc space.
▪

If radicular paresthesias or pain are elicited during ventral advancement of the needle, the needle should be repositioned. However, a mild radicular pressure sensation is not unusual when contrast dye is administered.
▪

The needle should be maintained midline in line with the vertebral body.
▪

This view should be used only to assess the mediolateral and superoinferior needle position; it should not be used for any substantial ventral needle advancement.
▪

To help determine the depth of the needle, contralateral oblique and/or lateral views are obtained.

There are typically no other radiolucent structures that are safety considerations in this trajectory view aside from advancing the needle too far ventrally. Please use the other views for needle advancement to best visualize the corresponding landmarks.

Only gold members can continue reading. Log In or Register to continue