The pudendal nerve (from the Latin pudendus, shameful1), is also called the internal shameful nerve. It is located in the lower part of the pelvis and innervates the perineal region, between the genitals and the anus.

Mixed nerve. The pudendal nerve is made up of motor, sensory and vegetative nerve fibers (2).

Origin. The pudendal nerve originates from the spinal cord, and more specifically from the second, third and fourth sacral roots at the level of the sacrum (2) (3) (4).

Path. The pudendal nerve leaves the pelvis through the large sciatic notch below the piriformis muscle. After passing around the sciatic spine, it enters the clamp formed by the sacrospinous and sacrotuberal ligament. It then enters a fibrous duct called the Alcock duct (2) (3) (4).

Collateral branch. The pudendal nerve gives rise to the rectal nerve which notably innervates the external sphincter of the anus (4) (5).

Terminal Branches. At the level of the Alcock canal, the pudendal nerve divides into two terminal branches (5):

• Lower branch: The perineal nerve which is subdivided into a superficial branch, innervating the scrotum or the labia majora, and a deep branch, innervating part of the elevator muscles of the anus, the ischio- and bulbo-cavernous muscles as well as the bulb of the penis.
• Upper branch: The dorsal nerve of the clitoris in women and the penis in men

Role in the mechanism of erection. Nerve activity (sensory, motor, vegetative) and innervation of the ischio- and bulbo-cavernous muscles by the pudendal nerve allow penile rigidity (5).

Role in urinary and anal continence. The pudendal nerve transmits the sensation of the need to urinate and notably innervates the anal sphincters (5).

Pudendal neuralgia. Also called pudendal pain or Alcock syndrome, it corresponds to chronic neuropathic pain (2) (3) (4) (6). Sometimes confused with urological or gynecological disorders, it manifests itself by sharp pain in the pelvis. It is linked to the compression of the pudendal nerve which can result from external causes such as intensive cycling, a fall on the buttocks or prolonged sitting; or internal causes such as neuropathy or rheumatoid arthritis (3).

Medical treatment. Certain medications may be prescribed to relieve neuropathic pain: anti-depressants, analgesics and antiepileptics (2).

Canal infiltrations. Under fluoroscopic control, corticosteroid or local anesthetic injections can be performed in areas of compression (2) (3) (4).

Neuromodulation. This technique involves implanting electrodes in the pudendal nerve (2).

Surgical treatment. As a last resort, decompression of the pudendal nerve can be performed by surgery (neurolysis) (2) (3) (4).

Physical examination. A study of the patient’s history is carried out to identify risk factors (professional activity, sports, etc.). A rectal examination can be performed to confirm the diagnosis (2) (3) (4).

Electrophysiological exploration. The electromyogram makes it possible to study the electrical activity of the pudendal nerve and to locate the sites of compression (2) (3) (4).

Vascular exploration. The diagnosis of pudendal neuralgia is often combined with a Doppler ultrasound of the pudendal arteries to identify the presence of vascular compression (2).

Pudendal anesthetic block. This examination consists of local anesthesia of the pudendal nerve to confirm the neurological origin of the pain (2).

Medical imaging. Additional examinations can be performed to identify the causes of compression of the pudendal nerve: x-ray, bone scintigraphy, MRI, etc. (4).

Alcock syndrome was first described by Professor Amarenco in 1987 as “cyclist’s perineal paralysis” (6).