Treatment of external urethral sphincter hypertonicity by pudendal nerve block using phenol solution in patients with spinal cord injury

Abstract

We report our experience utilizing the technique of phenol block of the pudendal nerve in the treatment of voiding dysfunction due to hypertonicity of the external urethral sphincter. We have performed 13 pudendal nerve blocks using a 7% phenol solution in seven patients with spinal cord injury who could not obtain relaxation of the external urethral sphincter with a large postvoid urine residual (150 ml to 600 ml) despite large doses of antispasticity drugs and intermittent catheterisations over three weeks. These drugs were discontinued at least 48 hours before this procedure. The efficacy of the pudendal nerve block could also be tested by the ease of facilitating micturition during or just after the block and measuring the amount of postvoid residual urine and intravesical leak pressure. A pudendal nerve block was produced by injecting a 7% phenol solution medial to the ischial tuberosity having specifically localized the nerve by electrical stimulation. This procedure improved the voiding pattern dramatically, leading to a full stream of urine and a remarkable decrease of postvoid residual volume and intravesical leak pressure. The mean difference of the postvoid residual volume and the intravesical leak pressure before and after pudendal nerve block was 255.7 ml and 57.5 cmH2O, respectively. We conclude that pudendal nerve block with a phenol solution as a treatment of external urethral sphincter hypertonicity was effective, easy to perform, and had no complication. This treatment should be considered as a possible alternative to more invasive surgical procedures.