Background and Aims:
Evoked compound action potential (ECAP) recording during spinal cord stimulation (SCS), to measure neural recruitment (Aβ mechanoreceptor fibers) and correlation of ECAP amplitude with paresthesia coverage, has been reported.1 A new SCS system, with ECAP recording, can measure patients’ therapeutic window (TW) for SCS.2 Maintaining ECAP amplitude within the TW could improve efficacy with fewer side-effects.3,4 We present data from a patient undergoing SCS for chronic pain, while reducing medication.

Methods:
Data collection occurred during set medication adjustments (Table), encompassing ECAPs (including conduction velocities), TW (threshold, comfort, maximum), and strength-duration curves (chronaxie, rheobase).

Results:
As gabapentin and oxycodone dose decreased, so did TW size. The patient’s ECAP amplitudes decreased without gabapentin and decreased further without oxycodone; stimulation amplitude required appeared independent of medication dose. New data, 7 months later, remain consistent (Figure). No observable correlation with medication dose existed between conduction velocity or chronaxie and rheobase.

Conclusion:
Data correlate with previous work showing ECAP amplitude decreased with pregabalin dose reduction.5 Once off medication, ECAP amplitude may need maintaining within a smaller TW. Closed-loop SCS continuously measures ECAP amplitude, maintaining it within the TW. ECAPs may facilitate titration and optimized dosing of anticonvulsants and opioids. No correlation between stimulation amplitude and medication dose indicates measuring neural recruitment (eg, ECAP) is necessary to monitor effects. Data imply stimulation duration and/or concomitant medication could affect SCS outcomes. If reproducible (research ongoing), this could impact understanding of SCS mechanisms of action.

EVOKED COMPOUND ACTION POTENTIAL RECORDING TO FURTHER UNDERSTAND EFFECT OF TITRATING MEDICATION WITH SPINAL CORD STIMULATION - CASE STUDY