04:12 PM Abstract No. 401 Natural history of motor nerve cryoablation: a retrospective cohort analysis

Abstract

There are no reported descriptions of motor nerve cryoablation in humans. As a result, physicians faced with inadvertent motor nerve cryoablation during palliative or therapeutic procedures for established indications are forced to rely on preclinical studies to manage patient expectations. (1, 2) In addition, potential applications of motor nerve cryoablation, such as for management of spasticity and pain, have been avoided because of the unknown prognosis following cryoneurolysis of mixed or motor nerves. The purpose of this study was to retrospectively analyze and report the outcomes of patients who have undergone inadvertent or deliberate motor nerve cryoablation at our institutions, and generate a predictive model for recovery. Patients who underwent inadvertent or deliberate motor nerve cryoablation were identified (n=7) and a detailed chart review performed. Neurological exam muscle activation assessments from follow up visits were extracted and plotted against time and approximate distance from the ablation site. The rate of recovery was calculated by performing a standard least-squares regression and compared to established rates of nerve regeneration following reversible injury (1mm/day). In addition, numerical strength scores immediately following ablation and the most recent interval for the most improved muscle group in each patient were compared using a Mann-Whitney t-test. At the time of analysis, the range of subject follow up post injury was 4-36 months (15± 9.9). Nerve regeneration as reflected by muscle group activation was not significantly different than the predicted 1mm/day (p=0.0002). A standard least-squares regression analysis, showed there was a valid model (p=0.0002, by ANOVA) that demonstrated the rate of nerve regeneration to be 1.0mm/d (95% CI 0.57-1.48mm/d). Muscle groups more proximal to the ablation site regained full function faster than distal muscle groups, and muscular strength at the end of the follow-up period was significantly improved compared to immediately following cryoablation (p < 0.0006). Regeneration of motor nerves following cryoablation occurs at the expected rate for nerves that undergo reversible injury.