Nerve block procedure: WHRIA  (Women’s Health & Research Institute of Australia)
Prof. Thierry Vancaillie.  Oct. 2011

A study on the ‘natural history of pudendal nerve block’ which we recently finished (a manuscript has been submitted for publication last month) shows that there is substantial improvement in at least 40% of the patients. And that is after a single injection of anaesthetic alone. This has convinced me to continue improving the injection technique first and then to look into using different substances to improve the outcome.

Improvement in injection technique was aimed at making sure the injected medication is actually delivered into Alcock’s canal and the infra-piriformis canal. We achieved that by introducing dynamic fluoroscopy: radio-opaque dye is used to localise Alcock canal and we observe how the dye as well as the anaesthetic spreads along both canals toward the perineum as well as toward the sacrum. Patients who received blocks prior to introduction of that technique and are now getting a repeat block with dynamic fluoroscopy, report a marked difference in result.

Parallell to this development, we have started working with Dr. Toos Sachinwalla from Northside Imaging and have developed a specific pudendal neuralgia protocol for MRI (neuro-MRI). We have now realised that combining the MRI and the neurography (=dynamic fluoroscopy) technology gives us a far better understanding of the anatomy. We can now see the true dimensions of Alcock canal and abnormalities such as compression by the falciform ligament, narrow canal etc. We also believe (but can’t prove yet) that we can actually visualise true compression of the pudendal nerve along its course. The most common site for compression, at least identified by this new combination of techniques, appears to be between the sacro-spinous and sacro-tuberous ligaments. We have however also observed that the anatomy is not ‘fixed’ over time. We are able in some cases to ‘unblock’ a compression, using large volumes of injected fluid in combination with cortisone.