Nerve blocks for relief of coccyx pain

See also personal experiences of nerve blocks

If the only problem someone has is pain - that is, any physical damage has healed, but the nerves still report pain - then blocking the pain signals seems an attractive option. However, the body repairs itself, so permanently blocking the pain is difficult. Various methods of blocking pain signals have been devised. They also result in some of the skin in the area becoming numb.

Placement of nerve block for coccyx pain

There are three locations where a nerve block may be placed to prevent coccyx pain:

  1. Ganglion Impar Block One place for this type of block is at the ganglion impar, a cluster of nerve cells in front of the joint between the sacrum and the coccyx. To get to this ganglion, a curved needle may be passed up from underneath the coccyx, or a needle may be passed through the sacrum/coccyx joint itself. Jerry Holubec describes this method.
  2. Caudal Epidural Injections around the nerves at the lower end of the spine are called 'caudal epidurals'. 'Caudal' means towards the end of the spine, and the 'epidural' space is the space around the spinal cord (the spinal cord is covered with a membrane called the dura mater). These nerves are inside the sacrum (the part of the pelvis to which the coccyx is attached) and are accessed through a hole towards the lower end of the sacrum, or sometimes higher up. Sally Cowell has done a diagram of where the injections are done. Note, however, that Dr Patrick Foye (see Doctors and specialists in the USA, New Jersey) points out that caudal injections are above the coccyx, and very rarely help with coccyx pain.
  3. Nerves behind the coccyx A new method of blocking pain from the coccyx is called Endoscopic Coccygeal Nerve Ablation. This uses an endoscope, a small tube through which the coccyx and its nerve supply can be directly visualized. The endoscope is passed through a 5 mm slit in the skin over the coccyx. A tool is then passed through the tube and used to burn each nerve. It is claimed that this is more effective than previous methods of nerve ablation, because individual nerves can be identified and burnt.

Duration of effectiveness of nerve block

  1. Temporary nerve block Injection of a local anesthetic such as lignocaine or bipuvicaine around the nerve. This blocks the pain for a few hours, sometimes longer or permanently if the block is repeated. Blocking the pain for even a short time is helpful because if it works, then it means that the site of the pain has been clearly identified. Patrick Foye uses this method, injecting the ganglion impar under flouroscopic guidance. He finds that repeating the injections can eliminate or at least very substantially reduce the pain in many patients. Often the degree of relief from these injections is so substantial that patients previously considering surgical treatment for coccydynia no longer feel the need to pursue such options. Other doctors use the block as a diagnostic method, before considering other treatment.
  2. Semi-permanent nerve block Freezing the nerve (cryoanalgesia) damages it and may block the pain for weeks or even months until the body repairs the damage. It can be repeated if necessary. A fuller description is given on the Baptist Hospital East site. A new alternative is pulsed radiofrequency treatment, which is a non-destructive method, intended to cause lesions to the nerves without destroying them. A fuller description is given in this paper.
  3. Permanent nerve block This is also known as rhizotomy, though strictly that means cutting the nerve. It is also called neurolysis (lysis means destruction of cells) The nerves carrying the pain are destroyed. Usually this is done by heating them by passing a high frequency electric current into them through the tip of a needle (called radiofrequency or RF heating). This method is said to be more accurate than older methods of permanent nerve block such as injection of alcohol, phenol or glycerin to destroy the nerves, which can sometimes lead to more widespread destruction than intended. A fuller description is given on Center for diagnostic imaging site. Although this method is intended to be permanent, the nerves may grow back again in a year or so, and the pain can sometimes be worse when it comes back. The treatment can be repeated.

Making a permanent nerve block more effective

A permanent nerve block has something in common with the amputation of a limb, because in both cases the signals from the nerves to the brain are cut off. I discussed pains after amputations with a physiotherapist (physical therapist in the USA). After amputation of a limb, pain can continue in the 'phantom' limb. For instance, if you have an ingrowing toenail, then have the leg cut off, the pain of the toenail may carry on - and now you can't cure it. It appears that the brain makes up for being cut off from a region of the body by supplying the signals it expects.

According to the physiotherapist, because of this effect it is now normal to try to eliminate all pain from a limb for some weeks before it is due to be amputated. It is then less likely that there will be pain in the 'phantom' limb.

This could be relevant to treatment of coccyx pain with nerve blocks. Nerve blocks cut the brain off from sensation in a region of the body, so, as with amputations, it could be helpful to temporarily eliminate the pain before using the nerve block. This might mean using powerful pain killers or avoiding sitting for a few weeks before the nerve block is applied. I must emphasise that these are my own conclusions. Please do not act on them without discussing them with a doctor. And if you can shed any further light on the subject, let me know.

There is more detailed discussion of nerve blocks in a set of five medical papers published in Jacksonville Medicine, October 1998:

Clinical evidence: A trial of cryoanalgesia found 46% of coccydynia patients received complete or good pain relief, with a median duration of improvement of 30 days (Cryoanalgesia for intractable perineal pain. Evans PJ, Lloyd JW, Jack TM). In Coccygodynia, Jerry Holubec reports success with RF heating nerve blocks around the sacrum/coccyx joint, but does not give statistics on the proportion of patients getting relief.

Updated 2010-01-17

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