Ultrasound as a Viable Treatment Modality for Pain

LAS VEGAS — Although ultrasound technology has improved dramatically over the years, there is still more work to be done in relation to its use in managing pain—particularly chronic pain. Ultrasound is a valuable tool for imaging soft-tissue structures and bony surfaces; however, more studies will be needed to assess the safety and efficacy of pain-relief techniques guided by ultrasound.

Michael Bottros, MD, director of the Acute Pain Service and assistant professor in the Division of Pain Medicine of the Department of Anesthesiology at Washington University School of Medicine, provided the audience at PAINWeek with a history lesson on ultrasound technology: its beginnings and how it actually works.

Karl Theodore Dussik, a 20th century psychiatrist and neurologist, began studying ultrasonography during the late 1930s. His primary interest was in diagnosing intracranial tumors, and he was one of the first physicians to use ultrasound for diagnostic purposes in 1942.¹ Although he was able to visualize the brain, the imaging was unsuccessful because artifacts were produced that interfered with the image. By 1947, Dussik and his brother had constructed ultrasonic equipment that was capable of producing images of intracranial regions that provided enough information to diagnose tumors.²

The first paper on the use of ultrasound was published in 1978 and focused on a Doppler ultrasound blood flow detector used to facilitate supraclavicular brachial plexus block.³ Dr. Bottros reported that at the time of the paper’s release, ultrasound technology was not suitable for visualization of nerves.

Fast forward to 1988, when Bruno Fornage published a report on how ultrasonography could be use for peripheral nerve imaging.⁴ The trend continued into 1994, when Stephan Kapral published a report on the first direct use of ultrasound for a regional block.⁵

Modern ultrasound in the United States primarily uses a pulse-echo approach with a brightness-mode (B-mode) display. For diagnostic purposes, small pulses of ultrasound echo are transmitted from a transducer into the body. Ultrasound transducers work both as a speaker (generating sound waves) and a microphone (receiving sound waves).

Ultrasound waves must be emitted in pulses with sufficient time to allow signal to reach the target and the echo reflected back to the transducer before the next pulse is generated. The peak frequency ratio for medical imaging devices typically ranges from 1 to 10 kHz. 

Dr. Bottros pointed out several benefits to using ultrasound: there is no radiation exposure, it may be safer than some procedures, and it may require less medication use due to visualization of medication spread. There has also been reported to be improvement in performance time, onset time, quality, and safety.

Ultrasound technology has been used to identify different causes of pain. In one instance, researchers learned that bedside ultrasound can accurately identify various causes of acute abdominal pain.⁶ The study revealed that emergency medicine physicians who performed bedside ultrasound examination had 78% diagnostic accuracy. 

Visualization of the facet joints for assessment of low back pain represents another ultrasound application.⁷ First introduced for use in regional anesthesia, this procedure involves minimal risk and is suitable for a large part of the population. 

David Rosenblum, MD, a member of Clinical Pain Advisor’s editorial board, discussed several main advantages to using ultrasound technology for clinicians searching for ways to manage and treat pain in patients. 

“Some of the main advantages are obvious,” he said. “Actually seeing the nerve, as opposed to a blind approach, is very attractive and may lead to better diagnostic and procedural quality, although there are no data that I know of that show ultrasound to be superior to fluoroscopy for these procedures.”

Dr. Rosenblum also noted that he has used ultrasound to perform several types of injections, including of the “suprascapular nerve for patients with postoperative shoulder pain, as well as occipital nerve block.”

He added: “Using ultrasound for occipital nerve blocks has enabled me to decrease the volume of local anesthetic while increasing the accuracy of the shot.”

Dr. Bottros cautioned that just because a clinician can use ultrasound, it doesn’t mean that it should be used. “Poorly performed ultrasound—such as failure to image the needle or misinterpretation of artifacts—or novice behavior might actually increase the risk of injury.” 

He added: “The literature is silent with regard to patient- or situation-specific safety outcomes where ultrasound may prove to be particularly useful.” Dr. Bottros acknowledged that “the application of ultrasound in chronic pain management remains in an embryonic state.”

The reasons provided for the paucity of studies involving ultrasound use in chronic pain include the following: image quality has been historically poor and interpretation has been difficult; few experts have the required skills; diagnostic soft-tissue ultrasound is generally abandoned in favor of magnetic resonance imaging; and there is a deeply rooted acceptance of fluoroscopy and computed tomography as the gold standard of imaging in pain.

References

1. Dussik KT. On the possibility of using ultrasound waves as a diagnostic aid. Z Neurol Psychiatr. 1942;174:153-168.
2. Dussik KT, Dussik F, Wyt L. Auf dem wege zur hyperphonographie des gehirnes. Wiener Medizinische Wochenschrift. 1947;97:425-429.
3. La Grange P, Foster PA, Pretorius LK. Application of the Doppler ultrasound bloodflow detector in supraclavicular brachial plexus block. Br J Anaesth. 1978;50(9):965-967.
4. Fornage BD. Peripheral nerves of the extremities: imaging with ultrasound. Radiology. 1977;167:179-182.
5. Kapral A, Krafft P, Eibenberger K, Fitzgerald R, Gosch M, Weinstabl C. Ultrasound-guided supraclavicular approach for regional anesthesia of the brachial plexus. Anesth Analg. 1994;78(3):507-513.
6. Hasani SA, Fathi M, Daadpey M, Zare MA, Tavakoli N, Abbasi S. Accuracy of bedside emergency physical performed ultrasound in diagnosing different causes of acute abdominal pain: a prospective study. Clin Imaging. 2015;39(3):476-479.