Significance of neurovascular bundle formation observed on preoperative magnetic resonance imaging regarding postoperative erectile function after nerve-sparing radical retropubic prostatectomy

OBJECTIVES To investigate the significance of variations in neurovascular bundle (NVB) formation observed on preoperative magnetic resonance imaging (MRI) regarding postoperative potency after nerve-sparing radical retropubic prostatectomy (RRP). METHODS Preoperative MRI was performed in 93 patients who underwent bilateral nerve-sparing RRP for clinically localized prostate cancer and were followed up for at least 12 months after surgery. Judging from the MRI scans, patients were categorized into three groups: group 1, patients with no definite NVB observed on MRI, group 2, those with probable NVB formation observed on MRI but not definite, and group 3, those with NVB more definitely observed on MRI. Patients' erectile function status was assessed preoperatively and postoperatively using the International Index Erectile Function 5-item (IIEF-5) questionnaire. RESULTS Of the 93 patients, 40.9% were in group 1, 21.5% in group 2, and 37.6% in group 3 according to the MRI findings. The patient characteristics, including age, serum prostate-specific antigen, pathologic Gleason score, and preoperative IIEF-5 scores, were not significantly different among the three groups. However, the changes in the IIEF-5 scores after bilateral nerve-sparing RRP demonstrated a significantly larger decrease for group 1 compared with groups 2 and 3. Similar trends were observed when patients 60 years old or younger and those older than 60 years were analyzed separately. CONCLUSIONS In patients with no definite NVB formation observed on MRI, the nerves associated with erectile function may run along both sides of the prostate and spread more anteriorly than those with the NVB more definitely observed. Thus, to preserve the NVBs completely at all times, it would be important to widely dissect the lateral aspects of the prostate during nerve-sparing RRPs.