Pudendal Nerve Compression (Alcock Canal Syndrome)

Pudendal Nerve Compression (Alcock Canal Syndrome) is a rare and difficult to diagnose cause of chronic pelvic pain.

Pudendal nerve compression, also known as Alcock Canal Syndrome, is an underdiagnosed cause of chronic pelvic pain. It refers to a pathologic and very severe pain that is caused by compression of the pudendal nerve in its course. 

It can often be compressed between ligaments (Sacrospinous and Sacrotuberous ligament) and if it is compressed when passing through the Alcock Canal, also called the Pudendal Canal, it is called Alcock Canal Syndrome.

What are the Complaints of Patients?

This pain occurs in areas innervated by the pudendal nerve or its branches. These areas are the clitoris, mons pubis (where genital hair grows), vulva, lower 1/3 of the vagina and labias in women. But often the pain can be felt in the entire pelvis, even if it is unilateral.

Symptoms may start suddenly or may increase over time. Typically, the pain gradually increases throughout the day and worsens with sitting. The pain may be unilateral or bilateral, depending on which nerve branches are affected. However, in clinical practice, it is usually seen in the form of unilateral somatic pain. The skin in these areas may also be more sensitive to touch and pressure.

Possible symptoms include burning, numbness, tenderness, pain like electric shock or stabbing, foreign body or mass sensation in the vagina and rectum, twisting or squeezing sensation, constipation, pain during bowel movements, burning during urination, pain during sexual intercourse, sexual dysfunction and loss of sensation in innervated areas.

What Causes This Painful Disease?

Causes include repetitive mechanical trauma to the pelvic area (sitting for long periods of time, cycling for many years, lifting weights), heavy pregnancy, difficult delivery, inflammatory or autoimmune disease, endometriosis, recurrent infections, accident - fall or surgery affecting the pelvic area. But it can also occur without any obvious clinical history.

How is the diagnosis made?

There is no definitive diagnostic test for pudendal nerve compression. The diagnosis is based on the patient's history, symptoms, identification of conditions that make the pain better or worse and a good neuropelveologic examination. There are very few doctors in the world who have a special training in neuropelveology. On examination, the affected nerve root is examined for pain and loss of function. The entire pelvic region can be investigated by MRI and CT for the presence of a mass that may cause compression on the nerve. Today, the most important imaging method used in diagnosis is 3 Tesla MRI and tractography. PNMLT (pudendal nerve motor latency test) is a test similar to EMG that helps to evaluate the nerve.

What is a Pudendal Nerve Block? How is it done?

It is a local anesthetic drug injection around the nerve using a very fine and long needle to heal or reduce the pain that develops as a result of the nerve compression. The block is usually applied vaginally to the ischial bone prominence area where the nerve is compressed between the sacrospinous and the sacrotuberous ligaments. Local anesthetic medications are administered by controlling this area with a finger. Disappearance or reduction of the pain during the effect of anesthetic agent lasts suggests the presence of compression of the pudendal nerve. Pudendal nerve block is a very safe procedure when it is performed in experienced hands. It should be done by people who have received special training on this subject.