The neurovascular bundle (NVB) is a collection of nerves and blood vessels adjacent to the prostate gland. It houses the delicate nerves responsible for controlling both erectile function and, to a degree, urinary control. Preservation of the NVB during the surgical removal of the prostate is a primary goal for many patients and surgeons, as its integrity directly influences the quality of life after the procedure. The precision required to balance complete cancer removal with the retention of these functions makes the NVB the central focus of surgical planning and technique.
Anatomy and Physiological Role
The neurovascular bundle is a tubular structure containing the cavernous nerves, small arteries, and veins that run along the prostate’s outer surface. It is situated posterolaterally on both the left and right sides of the gland, nestled between the prostatic capsule and the surrounding pelvic fascia, often referred to as Denonvilliers’ fascia. These nerves are extensions of the pelvic plexus, which carries parasympathetic nervous system input, the primary signal for initiating an erection.
The cavernous nerves travel through the NVB and continue to the corpora cavernosa, the spongy tissues in the penis that fill with blood during an erection. The parasympathetic signals transmitted through these nerves trigger the relaxation of the smooth muscle within the penile arteries, allowing increased blood flow necessary for rigidity. The NVB also contains nerve fibers that contribute to the function of the external urinary sphincter, which aids in the recovery of urinary continence.
The NVB’s close proximity to the prostatic capsule (often within a few millimeters) creates a challenge during surgical removal. Tumor extension beyond the prostate boundary, known as extracapsular extension, directly threatens these nerves. The NVB’s function depends entirely on the structural integrity of these fine nerve fibers, which are highly susceptible to damage from heat, tension, or direct cutting.
Critical Importance in Prostate Surgery
The NVB is the central point of contention during a radical prostatectomy, the surgical procedure to remove the entire prostate gland to treat localized cancer. The surgeon faces a fundamental conflict between maximizing the chance of a cure and preserving the patient’s sexual and urinary functions. The primary oncologic goal is to achieve a negative surgical margin, meaning that no cancer cells are found at the edge of the removed tissue.
To guarantee a negative margin, the surgeon would ideally remove a wide cuff of tissue surrounding the prostate, which would inevitably involve sacrificing the adjacent neurovascular bundles. Conversely, to preserve the NVB, the dissection plane must be kept extremely close to the prostate capsule, a technique known as “nerve-sparing.” This tight dissection increases the risk of a positive surgical margin, where cancer cells may be left behind.
The decision to perform a nerve-sparing procedure is an intricate trade-off, balancing the risk of cancer recurrence against the probability of maintaining quality of life. For patients with aggressive or locally advanced cancer, the oncologic imperative takes precedence, and the NVB may be intentionally removed. However, for appropriately selected patients with lower-risk disease, modern surgical techniques, particularly robot-assisted methods, allow for the precise dissection required to separate the nerves from the prostate.
The nerve-sparing approach is the main strategy for managing this conflict, but it is not universally applicable. Success hinges on the surgeon’s ability to assess the likelihood of cancer involvement at the time of surgery. The proximity of the NVB to the cancer site dictates whether a full, partial, or non-sparing approach is the safest option.
Determining Factors for Nerve Preservation
The feasibility of preserving the neurovascular bundles is determined by a careful assessment of several pre-operative and intra-operative factors. Pre-operative staging relies heavily on multi-parametric Magnetic Resonance Imaging (mpMRI), which provides detailed images of the prostate and surrounding tissues. mpMRI helps the surgeon visualize the tumor’s exact location, size, and its proximity to the prostatic capsule and the NVBs.
If mpMRI suggests a high probability of extracapsular extension (ECE), or if the tumor is a high-grade lesion (e.g., Gleason pattern \(\geq 4\)) located directly adjacent to a bundle, that NVB is typically sacrificed to ensure complete cancer removal. The imaging data can be influential enough to change the initial surgical plan, sometimes shifting a planned bilateral-sparing procedure to a unilateral or non-sparing one.
Patient characteristics are also a major determinant, especially pre-operative erectile function, or baseline potency. Men with robust erectile function prior to surgery are the most likely to benefit from nerve preservation, as their nerves are more resilient to surgical trauma. Conversely, a patient with poor pre-operative function may be less likely to gain functional benefit, making the oncologic priority of a wider margin more justifiable.
The surgical strategy is often side-specific, meaning the decision to spare is made independently for the NVB on the left and the right side of the prostate. A bilateral nerve-sparing procedure, where both bundles are preserved, is preferred for maximum functional recovery and is generally reserved for patients with low-volume, localized cancer. If the tumor is clearly confined to one side, a unilateral nerve-sparing procedure may be performed, preserving the NVB on the non-involved side while excising the bundle closest to the cancer.
Post-Surgical Quality of Life Outcomes
The degree of neurovascular bundle preservation is the strongest predictor of functional recovery following radical prostatectomy, influencing both erectile function and urinary continence. Patients who undergo a bilateral nerve-sparing procedure consistently demonstrate the highest rates of erectile function return. One study showed that at 12 months post-surgery, patients who received bilateral nerve sparing had a potency rate of approximately 69% compared to 43% for those who received unilateral sparing.
Recovery is a prolonged process that can take up to 24 months, with nerve regeneration occurring gradually over time. Achieving an erection sufficient for intercourse often requires the use of oral medications, even after successful nerve preservation. Only a minority of patients, roughly 22% in some cohorts, return to their exact pre-operative erectile function without the need for medication two years after surgery.
Age is a dominant factor in the recovery timeline and eventual outcome, as younger men have more resilient nerves and faster regeneration capacity. Patients under 60 years old typically have a higher likelihood of recovering functional erections than older patients. The extent of nerve trauma during the procedure, even in a “sparing” case, also influences the result, as stretching or thermal injury is common.
Continence recovery is also positively affected by NVB preservation, though the mechanism is less direct than for erectile function. The preservation of the nerves that contribute to the external sphincter’s control leads to a quicker and more complete return to continence. In one analysis, complete continence at one year was reported in about 97% of patients who received bilateral nerve sparing, compared to 88% of those who underwent a unilateral procedure.