The nerve-sparing (NS) technique may reduce urinary and erectile dysfunction in patients with localized prostate cancer undergoing robot-assisted radical prostatectomy (RARP). However, the influence of NS dissection depth on functional outcomes remains unclear. We aimed to evaluate the impact of NS grades, based on a four-layer dissection model, on urinary continence and nerve function using subjective and objective outcome measures. This was a retrospective cohort of 600 consecutive patients undergoing RARP (December 2012–September 2023), with NS graded I–IV (intrafascial to extrafascial) using surgical records/videos. Maximum NS grade (mNSG) was defined as the highest grade on either side. Continence was defined as using no safety pad or only one safety pad/day. Urodynamic study and intraoperative electrical stimulation were used in a subset to evaluate urinary and nerve function. Associations between NS grade and outcomes were assessed using logistic regression. Patients with mNSG I showed significantly better continence at 3, 6, and 12 months (p < 0.001, p < 0.001, p = 0.017, respectively). A total number of both sides of ≥ 3 (NS grade I to IV = point 3 to 0) was also associated with better continence. mNSG I remained an independent predictor at 3 and 6 months. Urodynamic study parameters were largely comparable, except for higher voiding volume in mNSG I (p = 0.006). Greater preservation of intraurethral pressure after stimulation was observed in mNSG I. Limitations include the retrospective design and selection bias. Even unilateral intrafascial NS (mNSG I) may improve continence and nerve function. Layer-specific dissection may optimize outcomes after RARP.
