CT-guided Botox Injections Show Promise in Easing Pelvic Pain

By Elizabeth Gardner

One in seven U.S. women experience pelvic pain, which accounts for 10 percent of gynecology visits and $2.8 billion in healthcare costs every year. While pelvic pain has a variety of causes, about one in 50 women are diagnosed with myofascial pain in their pelvic floor muscles.

In addition to chronic pain, this condition can cause painful intercourse and urination, urinary retention and constipation. About 40 percent of women diagnosed with myofascial pelvic pain (MPP) don't respond to first-line treatments like physical therapy, acupuncture, biofeedback, NSAIDs, opioids or muscle relaxers. But Botulinum Toxin A (Botox) injections can help relieve their symptoms and may help to an even greater degree with fewer side effects if delivered using CT-guided injections.

A research team at Johns Hopkins studied pain relief in 57 MPP patients who received Botox injections, and found that the CT-guided injections were 100 percent successful in reaching their targeted muscles, with fewer complications than injections guided solely by physical exam landmarks—the standard practice when injections are administered in a gynecologist's office.

Left to right: a CT-guided Botox injection into the obturator internus, piriformis and levator ani muscles. (Click to enlarge)  — Image courtesy of Anna Moreland, MD

In a Monday session, presenter Anna Moreland, MD, a radiology resident at Johns Hopkins and a consultant for NeuWave Medical, which creates probes used for tumor ablation, said the procedure minimizes the amount of Botox needed as well as the risk that it will spread to unintended areas. As a result, the image-guided technique reduces the risk of temporary, but miserable, side effects such as urinary retention and fecal incontinence that occur in 7 to 10 percent of cases where Botox is injected without image guidance. Botox inhibits the release of acetylcholine, causing flaccid paralysis of the muscles and relieving muscle spasm.

"The doses we're using are a half to a sixth of the doses used in a gynecologist's office, but we get the results because we're targeting injections where they are needed," Dr. Moreland said.

The study population consisted of patients referred by gynecologists who specialized in chronic pelvic pain and requested injections of specific pelvic floor muscles according to point tenderness on pelvic exam. The patients' median age was 39 with a range from 21 to 68. Fifteen percent had had prior Botox injections without image guidance.

Patients were moderately sedated. Following scout CT, a 22-gauge needle was placed into each target muscle under CT fluoroscopic guidance. Botox suspended in saline was injected into the piriformis, obturator internus and/or levator ani. Most patients had only one session, but some had up to three. The median number of muscles injected during a session was two, though some patients had as many as six muscles injected during a single session.

The amount of Botox varied depending on the muscle: 50 units were used in the piriformis or obturator, and 25 units were used in the levator. If a muscle had previously under–responded to 50 units, the dose was increased to 100 units.

None of the patients had complications, either major or minor, and 73 percent reported improvement in symptoms.

Further research is needed on cost and efficacy comparisons between the two treatment techniques and settings. While using CT increases the cost of a treatment, it may also reduce the need for multiple treatments, as well as reducing the outlay for the Botox itself. The image-guided treatments typically use 50 units (at $1 each), whereas treatments in a gynecology office might use 100 to 300 units, Dr. Moreland said.