How to assess the pudendal nerve function?

From the Guidelines

Testing the pudendal nerve is most effectively done through the pudendal nerve terminal motor latency test (PNTML), which measures the time it takes for an electrical stimulus to travel through the nerve, with normal latency being less than 2.2 milliseconds. This method is crucial for evaluating the function of the pudendal nerve, especially in the context of diagnosing conditions such as pudendal neuralgia, pelvic floor disorders, or fecal incontinence.

Clinical Assessments

When assessing the pudendal nerve, several clinical evaluations can be performed, including:

• Testing sensation in the perineal region using light touch, pinprick, or temperature stimuli, as the pudendal nerve provides sensory innervation to the external genitalia, perineum, and perianal area.
• Evaluating motor function by assessing the strength of the external anal sphincter through digital rectal examination.
• Testing the bulbocavernosus reflex, which involves stroking the glans penis or clitoris and observing for anal sphincter contraction. These assessments are vital for understanding the nerve's function and identifying any potential issues. Although studies like 1 discuss anorectal testing, including anal manometry and imaging with ultrasound or MRI for identifying anal sphincter defects and other conditions, the PNTML test remains the most direct method for specifically evaluating pudendal nerve function.

From the Research

Testing the Pudendal Nerve

To test the pudendal nerve, several electrophysiological methods can be employed, including:

• Bulbocavernosus muscle electromyography (EMG) 2, 3
• Measurements of the bulbocavernosus reflex latencies (BCRLs) 2, 3
• Somatosensory evoked potentials of the pudendal nerve (SEPPNs) 2
• Sensory conduction velocity of the dorsal nerve of the penis (SCVDNP) 2
• Pudendal nerve terminal motor latencies (PNTMLs) 2

Diagnostic Value of Tests

The diagnostic value of these tests varies:

• Anal sphincter electromyography (EMG) is the most sensitive technique in diagnosing chronic pudendal lesions 3
• The bulbocavernosus reflex (BCR) can distinguish between afferent and efferent lesions of the sacral reflex arc 3
• Pudendal somatosensory evoked potentials (SEP) can detect pure afferent lesions 3

Clinical Utility

These tests have clinical utility in:

• Confirming pudendal neuropathy 2
• Providing prognostic information 2
• Evaluating pelvic floor disorders 4
• Assessing anal tone and its alterations 5
• Diagnosing and managing pudendal neuralgia related to entrapment syndrome 6