Lower Extremity Somatosensory Evoked Potential (SSEP) Collision Testing for Guidance of Nerve Root Stimulation Placement for Chronic Pain
Rohit Gummi1, Nicholas Meyers1, Mark Keroles1, Sungho Cho1, Scheherazade Le1, Leslie Lee1, Ankita Tippur1, Jaime Lopez1, Ashwin Ramayya1
1Stanford Medicine
Objective:
This case report highlights the use of collision studies to enhance nerve root stimulator placement for refractory chronic pain management.
Background:
Chronic pain is often treated with increasingly invasive therapies, starting with behavioral techniques and medications, and progressing to surgery. Spinal cord stimulators (SCS) and nerve root stimulators (NRS) represent alternative approaches in refractory cases, targeting large afferent nerve fiber roots to effectively block the transmission of pain signals between the peripheral nerve and the brain. Intraoperative neurophysiological monitoring (IONM) techniques, including somatosensory evoked potential (SSEP) collision testing, can be used to provide real-time feedback for the accurate placement of SCS under general anesthesia; however, a similar technique for NRS is not currently available.
Results:
We present a case involving a 38-year-old female with persistent back pain and hyperalgesia following schwannoma resection. Collision testing demonstrated a significant decrease in SSEP amplitudes upon stimulating the L4 nerve root, indicating its role in pain transmission. This localized the L4 nerve root's contribution to sensory signaling from the dorsum of the foot and guided placement of the NRS. Postoperatively, the patient experienced substantial pain relief in the tested area, though pain in other locations necessitated a spinal cord stimulator placement afterwards.
Conclusions:
In this case, we demonstrated a change in cortical SSEP during collision studies of the L4 nerve root while stimulating the dorsal aspect of the foot. This change correlated with postoperative pain relief in the foot after NRS placement at the L4 nerve root. These findings suggest that collision studies may accurately predict the contribution of the individual nerve roots in transmitting sensory signals from various dermatomes. This case highlights the therapeutic potential of targeted NRS placement and supports further investigation into personalized pain management through precise nerve root stimulation and collision studies.
Disclaimer: Abstracts were not reviewed by Neurology® and do not reflect the views of Neurology® editors or staff.