Ultrasound Guided Phenol Block of the Obturator Nerve for Severe Adductor Spasticity: A Pilot Study

Abstract

Objective: To assess the efficacy of phenol block of the obturator nerve in treating severe adductor spasticity. Design: A prospective pilot study. Setting: Outpatient rehabilitation clinics. Participants: We recruited 5 participants with severe adductor spasticity. Four were persons with multiple sclerosis and one was a person with adult cerebral palsy. All participants were women and had an average age of 60.4 years; four participants had bilateral severe adductor spasticity and one had unilateral severe adductor spasticity. Interventions: A total of 9 phenol blocks of the obturator nerve were performed. Five were performed with ultrasound guidance, followed by localization of the obturator nerve by peripheral nerve stimulator. Four were performed using anatomic landmark and peripheral nerve stimulator for localization. Outcome Measures: The primary outcome measure was the Modified Ashworth Scale score of the hip adductor at 1 month after the obturator nerve block. The secondary outcomes measures include Modified Ashworth Scale (MAS) score of the hip adductors at 6 months, distance between the right and left medial femur condyles in supine with hip extended to neutral, Disability Assessment Scale (DAS) score, Goal Attainment Scale (GAS) score, Spasticity Numeric Rating Scale score and Subjects’ and Physician Global Impression of Changes scores. Results: There was statistically significant decrease in the MAS score at 1-month compared to baseline (2.43 vs. 4; P=0.001). There was no statistically significant difference in the secondary outcomes. There were no reported adverse effects of procedure. Conclusion: This study suggests that phenol block of the obturator nerve is effective in treating severe adductor spasticity. We recommend a larger study with more participants and longer follow up period to allow further assessment of the efficacy of the phenol block of the obturator nerve in treating severe adductor spasticity.