Puborectalis Nerve Denervation: Clinical Presentation
Puborectalis nerve denervation typically manifests as progressive fecal incontinence with or without urinary symptoms, often accompanied by perineal descent, reduced anal squeeze pressure, and in some cases chronic perineal or rectal pain—though many patients remain asymptomatic until denervation becomes severe.
Sensory and Motor Symptoms
Patients with partial puborectalis denervation are often asymptomatic or experience only subtle functional decline, such as difficulty keeping up during athletic activities or chronic constipation that was attributed to other causes 1, 2.
Progressive fecal incontinence is the hallmark symptom when denervation becomes severe, particularly when both the puborectalis and external anal sphincter are affected; patients may experience urgency, passive leakage, or complete loss of bowel control 1, 2.
Urinary symptoms—including urgency, urge incontinence, stress incontinence, frequency, and nocturia—frequently coexist with fecal incontinence when denervation affects the broader pelvic floor 3.
Chronic perineal, rectal, or anal pain may occur, ranging from dull aching to sharp, lancinating, or electrical sensations; pain can radiate into the groin, genitals, or perianal region and may worsen with sitting, straining, or prolonged activity 3, 4, 5.
Sensory changes are often subtle or absent because the puborectalis is primarily a motor structure; however, patients may report altered rectal sensation, reduced awareness of rectal filling, or difficulty sensing the urge to defecate 3, 2.
Physical and Functional Findings
Perineal descent during straining is a common physical finding; the perineum may descend more than 2 cm below the ischial tuberosities, reflecting loss of pelvic floor support 6.
Muscle atrophy and orthopedic deformities can develop with long-standing denervation, including thinning of the pelvic floor musculature and secondary changes in gait or posture 3.
Reduced anal resting and squeeze pressures are measurable on anorectal manometry, reflecting weakness of both the internal and external anal sphincters as well as the puborectalis sling 1, 2.
Acute worsening after sudden back stretching—such as during childbirth, falls onto the buttocks, or vigorous sporting activities—is characteristic of underlying tethered or stretched nerve pathology 3.
Electrophysiological and Diagnostic Correlates
Prolonged pudendal nerve terminal motor latency (PNTML) is found in approximately 68% of patients with idiopathic fecal incontinence, indicating distal nerve damage 2.
Increased motor unit potential duration and fibre density on EMG confirm chronic denervation and reinnervation; the puborectalis shows these changes in 60% of incontinent patients, while the external anal sphincter is affected in 75% 2.
Acute straining transiently prolongs PNTML and blunts anal sensation, with changes returning to baseline after 3 minutes; this demonstrates that functional nerve impairment can occur even without permanent structural damage 6.
Bilateral denervation is more common than unilateral, particularly in women with chronic straining or obstetric trauma; bilateral changes are seen in 86% of affected females 5.
Clinical Pitfalls and Diagnostic Considerations
Partial denervation of the external anal sphincter can occur independently of puborectalis denervation in patients who strain at stool; only when severe changes affect both muscles does incontinence typically develop 1.
Patients may have a long history of subtle abnormalities—such as being "slow" athletically, chronic constipation, late toilet training, or prior orthopedic deformities—that were never recognized as neurogenic in origin 3.
Pudendal neuropathy, altered anal sensation, and perineal descent do not always correlate in the same patient, so the absence of one finding does not exclude denervation 6.
Age is an independent predictor of both sensory and motor dysfunction; older patients have significantly worse anal sensation and longer PNTML even in the absence of overt symptoms 6.
Management Implications
Anorectal manometry with sensory testing and EMG evaluation should be performed to confirm denervation and quantify the degree of motor and sensory impairment before initiating therapy 7, 2.
Pelvic floor biofeedback with sensory retraining is the first-line definitive treatment, achieving success rates exceeding 70% when denervation is not complete and the patient can still generate voluntary contraction 7.
Sacral nerve stimulation may be considered as a second-line option after a minimum 3-month biofeedback trial fails, though evidence for functional improvement in denervation cases is limited 7.
Surgical decompression or neurectomy is reserved for refractory pudendal neuralgia when conservative and interventional measures fail 4.