What is the role of the pudendal nerve in a patient with decreased ejaculation intensity and altered rectal sensation?

Role of the Pudendal Nerve in Decreased Ejaculation Intensity and Altered Rectal Sensation

The pudendal nerve is the primary sensory and motor nerve of the perineum, controlling genital sensation (including ejaculatory sensation), voluntary sphincter function, and rectal sensation—making pudendal neuropathy a likely cause when both ejaculatory intensity and rectal sensation are simultaneously impaired. 1, 2

Anatomical and Functional Overview

The pudendal nerve originates primarily from the S3 sacral root (with contributions from S2 and S4) and serves three critical functional domains relevant to your patient's presentation 1, 3:

Sensory Functions

• Genital sensation: Innervates the glans penis/clitoris, providing the sensory substrate for sexual arousal and orgasmic sensation 1, 2
• Perineal sensation: Supplies skin of the scrotum/labia majora and central perineal body 1
• Rectal sensation: The inferior rectal nerve branch provides sensory innervation to the anal canal and distal rectum 3

Motor Functions

• Erectile function: Pudendal nerve branches communicate with cavernous nerves and contain nitric oxide synthase-positive fibers essential for erectile rigidity 2
• Ejaculation: Controls the bulbocavernosus and ischiocavernosus muscles responsible for ejaculatory force and penile rigidity during orgasm 1, 2
• Sphincter control: Innervates the external anal sphincter and urethral sphincter, providing voluntary continence 1

Clinical Significance in Your Patient's Presentation

Decreased Ejaculation Intensity

The pudendal nerve's motor branches to the bulbocavernosus muscle are directly responsible for the rhythmic contractions that generate ejaculatory force 2. Pudendal neuropathy impairs these contractions, resulting in:

• Reduced ejaculatory volume expulsion
• Decreased orgasmic sensation intensity
• Potential retrograde ejaculation if sphincter coordination is affected 4

Altered Rectal Sensation

The inferior rectal nerve branch provides critical sensory feedback for:

• Discrimination between gas, liquid, and solid stool 4
• Urge sensation for defecation 4
• Coordination of voluntary sphincter relaxation during defecation 5

Impaired rectal sensation from pudendal neuropathy manifests as reduced awareness of rectal filling, difficulty distinguishing stool consistency, and impaired defecatory coordination 4.

Diagnostic Approach for Suspected Pudendal Neuropathy

Essential Clinical Examination

Perform pinprick sensory testing of all six pudendal nerve branches bilaterally 6:

• Dorsal nerve of penis/clitoris
• Perineal nerves (medial and lateral)
• Inferior rectal nerves (bilateral)

This simple bedside test diagnoses pudendal neuropathy in 92% of cases 6.

Key Historical Features

• Positional pain: Pain worsened by sitting suggests pudendal nerve compression (tunnel syndrome) 1, 7
• Absence of nocturnal pain: Pain that does not wake the patient supports pudendal neuralgia rather than inflammatory or malignant causes 7
• Associated symptoms: Inquire about urinary hesitancy, incomplete bladder emptying, or fecal incontinence, which indicate broader pudendal dysfunction 4

Neurophysiologic Confirmation

If clinical examination suggests pudendal neuropathy, obtain 6:

• Pudendal nerve somatosensory evoked potentials (SSEP)
• Bulbocavernosus reflex latency testing
• Electromyography of perineal muscles

Two abnormal neurophysiologic tests combined with characteristic symptoms establish "definite" pudendal neuropathy 6.

Anatomical Compression Sites

The pudendal nerve is vulnerable to compression at three primary locations 1, 6:

1. Interligamentary space: Between sacrotuberous and sacrospinous ligaments (most common)
2. Alcock canal (pudendal canal): Within the obturator fascia along the lateral pelvic wall
3. Anomalous pathways: Through layers of the sacrotuberous ligament or separate inferior rectal nerve pathways

Therapeutic Algorithm

First-Line Conservative Management (14 weeks minimum) 6

• Nerve protection: Avoid prolonged sitting, use cushions with perineal cutouts
• Neuropathic pain medications: Gabapentin or pregabalin for pain control
• Physical therapy: Pelvic floor muscle relaxation techniques (avoid strengthening exercises that may worsen compression)

Second-Line Interventional Treatment

If conservative measures fail after 14 weeks, proceed with fluoroscopy-guided transgluteal pudendal nerve blocks 7:

• Administer series of three perineural injections at 4-week intervals
• Success defined as ≥30% pain reduction
• Short-term success rate of 49.4% at 2 weeks 7
• Additional benefits include reduced medication use and improved activities of daily living 7

Third-Line Surgical Decompression

Surgical neurolysis via transgluteal approach is recommended only after failure of both conservative and injection therapies 6:

• Indicated in approximately 35% of patients with definite pudendal neuropathy
• Success rate of 75% in properly selected patients 1
• Addresses compression at all three anatomical sites through single incision 6
• Long-term cure rates documented beyond 13 years 6

Differential Considerations

Diabetic Autonomic Neuropathy

If your patient has diabetes, consider diabetic cystopathy and autonomic neuropathy as alternative or coexisting diagnoses 4:

• Perform post-void residual volume measurement 8
• Assess for other autonomic symptoms (gastroparesis, orthostatic hypotension)
• Pudendal SSEP abnormalities correlate with bladder dysfunction in diabetes 4

Defecatory Disorders

Altered rectal sensation may indicate a primary defecatory disorder rather than isolated pudendal neuropathy 4, 5:

• Perform anorectal manometry to assess rectal sensory thresholds and sphincter coordination 5
• If defecatory disorder confirmed, biofeedback therapy is superior to continued medical management with >70% success rates 5

Critical Pitfalls to Avoid

• Do not attribute symptoms to psychological causes without objective sensory testing—pudendal neuropathy has clear diagnostic criteria 6, 7
• Do not proceed directly to surgery without adequate conservative trial and diagnostic confirmation 6
• Do not overlook coexisting conditions: Pudendal neuropathy frequently coexists with pelvic floor dysfunction, requiring combined treatment approaches 5
• Do not assume normal examination excludes pudendal neuropathy: Pinprick testing of all six branches is essential, as compression may affect only specific branches 6