How does prostate removal cause erectile dysfunction?

Mechanism of Erectile Dysfunction After Prostate Removal

Prostate removal causes erectile dysfunction primarily through surgical injury to the cavernous nerves that run along the anterolateral aspect of the prostate and control penile erection. 1

Anatomical Basis of Nerve Injury

The cavernous nerves are the critical structures responsible for erectile function, and their proximity to the prostate makes them vulnerable during radical prostatectomy. 1 Even with nerve-sparing surgical techniques, these nerves sustain damage during prostate removal, leading to temporary or permanent erectile dysfunction. 2, 3

Recovery of erectile function is directly related to the degree of preservation of the cavernous nerves during surgery. 4 The extent of nerve damage determines whether erectile dysfunction will be temporary and reversible or permanent. 1

Molecular Pathophysiology

When the cavernous nerves are injured, several molecular pathways are disrupted:

• Loss of nitric oxide (NO) signaling through the NOS/NO pathway, which is essential for smooth muscle relaxation and penile blood flow 1
• Oxidative stress in penile tissues due to lack of nerve-mediated oxygenation 1
• Activation of the RhoA/ROCK pathway, which promotes smooth muscle contraction and fibrosis 1
• Upregulation of transforming growth factor-β (TGF-β), leading to cavernosal fibrosis 1
• Loss of nocturnal erections, which normally oxygenate penile tissue and prevent structural damage 2

Structural Consequences of Denervation

The absence of nerve function after surgery leads to progressive penile structural changes:

• Cavernosal fibrosis develops in the absence of regular tissue oxygenation from nocturnal erections 2, 1
• Penile atrophy occurs when erectile dysfunction remains untreated 5
• These structural changes can become irreversible if nerve regeneration does not occur or is delayed 1

Factors Determining Recovery

Recovery of erectile function depends on three critical factors: patient age at surgery, preoperative erectile function, and the extent of neurovascular bundle preservation. 4

The data demonstrate dramatic differences in outcomes:

• 76% of men younger than 60 years with full preoperative erections who had bilateral nerve-sparing surgery recovered full erections 4
• Only 7.5% of men older than 65 years with diminished preoperative erections who had unilateral bundle resection recovered potency 4

Timeline of Recovery

Recovery of erectile function is gradual and often delayed, with maximal function sometimes not returning until 12-24 months after surgery. 4, 6 Early recovery of natural erectile function is uncommon even with expert nerve-sparing technique. 3 Many patients experience erectile dysfunction for up to 2 years after the procedure. 3

Clinical Implications

The mechanism of injury explains why:

• Nerve-sparing techniques significantly improve outcomes but do not eliminate erectile dysfunction 3, 7
• Early penile rehabilitation may prevent irreversible structural damage by promoting tissue oxygenation and nerve regeneration 2, 1
• Phosphodiesterase-5 inhibitors (like tadalafil) can aid recovery by promoting blood flow and potentially supporting nerve regeneration 4, 8
• Nerve grafts to replace resected nerves do not appear effective, highlighting that prevention of injury is more important than attempted repair 4