Chronic Pain Market Looks to Dorsal Root Therapies

by James Cavuoto, editor

Researchers and commercial firms involved with treating chronic pain are investigating new forms of neuromodulation to treat the condition. Several teams and a startup neurotechnology vendors are looking at the dorsal root ganglion of the spinal cord as an alternative site for neuro­stimulation, which could expand treatment options for patients with chronic pain who have no other alternative and for whom spinal cord stimulation is not effective.

At the 17th Napa Pain Conference held in California earlier this month, investigators affiliated with Spinal Modulation Inc., the Menlo Park, CA manufacturer of neuromodulation systems, presented results from early work in this area. Eric Grigsby of the Napa Pain Institute discussed advanced treatment options for treating a wide variety of pain conditions using either neurostimulation or intrathecal pumps. He noted several opportunities for improvement in neuromodulation therapies, including thoracic nerve root pain, axial back pain, peripheral nerve injury, and failed intraspinal infusion and SCS treatments.
Grigsby also described his participation in a proof of principle study of a temporary DRG stimulator sponsored by Spinal Modulation. He enrolled five patients at the Napa Pain Institute. The procedure involved epidural access using fluoroscopy. In one patient, with upper abdominal pain, he placed leads at T8-9, T10-11, and T12-L1.

Intraoperative stimulation allowed him to map the paresthesia to their painful areas. This patient received 90 percent pain relief during the trial period. In another case, a 25-year old female who failed to respond to medications, epidural injections, and a traditional SCS system, the patient reported 50 percent pain relief and a satisfaction level of 7 on a scale of 0 to 10. Grigsby reported improvements in secondary measures such as physical function, sleep, and activity levels also improved with DRG stimulation. There were no adverse events from lead delivery, stimulation of tissue or lead removal.
Robert Levy from Northwestern University cited mounting evidence implicating cells in the DRG as playing a key role in the development and maintenance of chronic pain. DRG is an interesting neurological target, he said, because the pain pathways are dermatone specific and there a re multi-segmental pathways with cross-level communication.

Levy cited previous pharmacologic and neurostimulation studies of DRG neuromodulation, which showed short-term pain relief. He believes there is potential for long-term relief with the development of advanced DRG neuromodulation techniques.

Thus far, Spinal Modulation has im­planted 10 patients at four sites in the U.S. The company plans to present preliminary results at the North American Neuromodulation Society meeting in December. Lynn Elliot, the company’s CTO, will make a presentation at the Neurotech Leaders Forum September 23-24.

“There are large groups of patients for whom SCS does not work well,” said president and CEO David Wood. “The major drawbacks of SCS include the high energy requirements needed to drive stimulation through the cerebral spinal fluid and the ability to treat patients with pain stemming from the axial back, the thorax, and the extremities. We hope to provide another option for patients in chronic pain.”