Pudendal Neuropathy Treatments and Their Effect on Continence
Pudendal neuropathy treatments can improve continence outcomes, but the presence and severity of pudendal nerve damage fundamentally determines treatment success—patients with severe bilateral neuropathy have poor prognosis for continence improvement, while those with mild or unilateral neuropathy can achieve meaningful gains through conservative and surgical interventions. 1, 2
Impact of Pudendal Neuropathy on Treatment Outcomes
Conservative Treatment Effects
Biofeedback therapy improves continence in patients with mild fecal incontinence and no pudendal neuropathy, with significant improvements in external anal sphincter function (amplitude and duration of voluntary contraction). 1
Patients with severe incontinence (incontinence to solids) and pudendal neuropathy fail to improve their maximum voluntary contraction amplitude and duration after biofeedback therapy. 1
Pudendal neuropathy and severity of incontinence are two factors of poor prognosis for favorable manometric results after biofeedback therapy, though clinical improvement may still occur despite lack of objective manometric changes. 1
The American College of Physicians recommends pelvic floor muscle training (PFMT) as effective treatment for stress and mixed urinary incontinence, with number needed to treat of 2-3 for improvement. 3
Surgical Treatment Effects
Both pudendal nerves must be intact to achieve normal continence after sphincter repair—patients with unilateral pudendal neuropathy are more likely to have poor than good postoperative function after anal sphincteroplasty. 2
All patients achieving excellent results after sphincter repair had normal pudendal nerve terminal motor latency bilaterally, while those with unilateral or bilateral neuropathy predominantly had improved or failed outcomes. 2
Pudendal canal decompression (PCD) is effective for treating fecal incontinence associated with complete rectal prolapse, with 53.8% of patients with partial incontinence and 62.5% with complete incontinence achieving full fecal control after decompression surgery. 4
The degree of response to pudendal canal decompression relates directly to the degree of pudendal nerve damage—nonimprovement occurs due to irreversible nerve damage or incomplete decompression. 4
Clinical Significance of Unilateral vs. Bilateral Neuropathy
Unilateral pudendal neuropathy is common in fecal incontinence (38% of patients with neuropathy) and is significantly associated with reduced anal resting pressures and squeeze increments. 5
Functional asymmetry exists in pudendal innervation—dominant pudendal nerve stimulation induces greater facilitation of cortically evoked responses than non-dominant nerve stimulation, explaining why unilateral injury can still disrupt continence. 6
In patients with intact sphincters, unilateral neuropathy reduces squeeze increments (41 vs. 52 cm H₂O; P<0.01) but has less impact on resting pressures compared to bilateral neuropathy. 5
Treatment Algorithm for Patients with Pre-existing Fistula and Straining History
Initial Assessment and Conservative Management
Initiate at least 3 months of structured pelvic floor biofeedback therapy before considering any surgical intervention in patients with baseline sphincter dysfunction. 7, 8
Document baseline sphincter function with anorectal manometry and pudendal nerve terminal motor latency testing to identify pre-existing defects and guide treatment selection. 7, 8
The biofeedback program should include electronic and mechanical devices to improve pelvic floor strength, scheduled defecation programs, and toilet training techniques. 7, 8
Surgical Considerations
Sphincteroplasty success rates decline with time—only 28% remain continent at 40 months, with predicted median time to relapse of 5 years, making it primarily reserved for postpartum fecal incontinence. 3
Age, gender, extent of sphincter injury, etiology, duration of incontinence, presence of pudendal neuropathy, and surgical technique have all been considered as prognostic factors, but none consistently demonstrates clear correlation with sphincteroplasty outcomes. 3
Sacral nerve stimulation (SNS) should be considered for moderate or severe fecal incontinence after failed conservative measures, with 89% therapeutic success at 5 years, though 36% achieve complete continence. 3
Fistula-Specific Management
Major anatomic defects including fistula in ano should be rectified with surgery as part of the treatment algorithm. 3
LIFT procedure (ligation of intersphincteric fistula tract) has lower incontinence rates (1.6%) compared to advancement flaps (7.8%), and 53% of LIFT patients experience improvement in fecal continence postoperatively. 3, 9
Smoking at time of LIFT surgery significantly increases failure risk (HR 3.2), and active proctitis trends toward increased failure (HR 2.0). 3, 9
Critical Pitfalls to Avoid
Do not proceed with fistulotomy without at least 3 months of documented pelvic floor therapy in patients with baseline sphincter dysfunction, as this increases risk of permanent incontinence. 7, 8
Avoid fistulotomy in the anterior perineum of female patients due to asymmetrical anatomy and short anterior sphincter, which has high chance of jeopardizing continence. 3
Never use cutting setons in perianal disease—this technique has 100% fistula closure but 57% incontinence rate due to forced sphincter transection. 3
Aggressive probing during examination of failed LIFT can convert manageable recurrence into complex fistula requiring more extensive intervention. 9
Progression Algorithm When Conservative Measures Fail
If biofeedback fails after 3 months, progression should be: perianal bulking agents (52% response rate with dextranomer), then sacral nerve stimulation, then sphincteroplasty. 3, 8
Consider temporary fecal diversion in patients with uncontrollable diarrhea or severe limitations preventing adequate perineal hygiene. 9
Long-term loose seton placement combined with medical therapy may be considered as alternative to repeat definitive surgery for patients unable to maintain adequate hygiene. 9