Chapter 6 Ganglion Impar Injection

The ganglion impar (i.e., the ganglion of Walther) is the most inferiorly located of all of the ganglia of the sympathetic nervous system. It is the only sympathetic ganglion that is solitary and midline (rather than paired, like the right and left paravertebral). The ganglion impar is located just anterior to the upper coccyx or the lower sacrum in the retrorectal space.^1–3

The ganglion impar has been implicated in “sympathetically maintained” pain in the pelvic region. Ganglion impar injections have been reported to be useful for relieving pelvic and perineal pain that is caused by either malignant intrapelvic pathology (e.g., prostate, cervical, and colon cancers) or nonmalignant pathology.^1,2 The underlying cause of the pain should be evaluated before beginning these injections, and this evaluation should include screening for underlying pelvic malignancies.

The technique described in this chapter approaches the ganglion impar through the sacrococcygeal or intercoccygeal disc space. Paracoccygeal and analcoccygeal approaches will also be briefly discussed. The main safety consideration is to avoid bowel perforation by going too far lateral on the anteroposterior (AP) view and too far ventral on the lateral view.

Note: Please see page ii for a list of anatomical terms/abbreviations used in this book.

Trajectory View

The Trajectory View Is Also a Multiplanar View

Confirm the level (with the cross-table lateral view) by noting any visible landmarks (e.g., the coccygeal cornu, the sacrococcygeal joint, any intracoccygeal joints) through which the approach may be planned. Mark this site with a skin marker or a metallic pointer. This tells you how superior or inferior the block should be initiated.

The C-arm is then brought to the AP position, and the needle is inserted in the midline at the predetermined superoinferior position, just deep enough to obtain skin purchase and to maintain a perpendicular trajectory needle position “down the beam.”

Cephalad or caudad tilt of the image intensifier to “line up” the disc space for entry (Figure 6–1

Figure 6–1 A, Fluoroscopic image of a trajectory view with the needle in position at the sacrococcygeal junction and in line to enter through the center of the disc. B, Radiopaque structures, trajectory anteroposterior view. C, Radiolucent structures, trajectory anteroposterior view.

Notes on Optimal Needle Positioning in the AP/Trajectory View

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

Direct the needle midline to access the ganglion impar.

).

Trajectory Anteroposterior View Safety Considerations

If the needle strays from midline, it may potentially cause the inadvertent blockade of other pelvic nerves or rectal perforation.

Optimal Needle Positioning in the Anteroposterior View

Lateral View (Figure 6–2)

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