Rootlet Selection by Crescendo Single-Pulse Evoked Compound Muscle Action Potential Interpretation During Selective Dorsal Rhizotomy.

Abstract

Selective dorsal rhizotomy (SDR) is a surgical intervention aimed at reducing spasticity in children with cerebral palsy. This chapter introduces an innovative approach to SDR, utilizing crescendo single-pulse evoked compound muscle action potential (CMAP) interpretation for rootlet selection. The method combines preoperative spastic muscle identification, intraoperative neurophysiological monitoring, and a precise stimulation protocol to guide the selective sectioning of sensory nerve roots. The chapter outlines the setup for crescendo single-pulse stimulation-guided SDR, including preoperative muscle group identification, intraoperative monitoring channels, and surgical approach. It details the stimulation protocol and defines criteria for motor nerves, sphincter-associated sensory nerves, and lower limb-associated sensory nerves based on evoked CMAP patterns. The concept of a "rhizotomy ratio" is introduced as a potential metric correlating with the severity of the patient's condition. Midterm outcomes of this approach are presented, based on a cohort of 481 cases with a minimum 2-year follow-up across all 5 levels of the Gross Motor Function Classification System (GMFCS). Results show muscle tone decreased by an average of 1.0 level in spastic muscle groups immediately after surgery, with a tendency to continue reducing by an additional 0.8 level in the following 2 years post-SDR. Motor function improved significantly, with 39.1% of patients advancing by one or two GMFCS levels (in 432 cases with preop GMFCS levels II-V), concurrent with intensive rehabilitation programs. The greatest improvements were observed in children who underwent surgery before age six and those with less severe preoperative motor impairments. The chapter also discusses postoperative rehabilitation strategies tailored to the gradual reduction in muscle tone experienced by children following SDR. Gait analysis in mild cases indicates improved walking patterns post-SDR. Overall, this crescendo single-pulse stimulation-guided SDR approach demonstrates promising outcomes in reducing spasticity and improving motor function in children with cerebral palsy, with minimal complications reported.