Chronic pelvic pain and the use of ganglion impar block and amitriptyline
Chronic pelvic pain is made up of a large and diverse variety of conditions from idiopathic pudendal neuralgia to interstitial cystitis to chronic perineal pain post radiotherapy for cancer, all with varying pain and symptom patterns.
There are many associated challenges in pelvic pain management, none more prevalent than the associated mood disorder. Broadly speaking, depression is considered to be s times as common in the pelvic pain population than those without and anxiety similarly so.
This newsletter isn't focused on chronic pelvic pain and just highlights for education purpose one intervention and one medication that are used in chronic pain management including pelvic pain management. However, it is clear to see from any discussion of it that multidisciplinary management is essential.
Most pain specialists would consider working with a specialist pelvic physiotherapist and psychologist to be essential for both female and male chronic pelvic pain.
Intervention: Ganglion impar block
AB always, interventional pain management only makes up one option for the management of chronic pain. A ganglion impar block is no different, but can aid a number of syndromes including tenesmus, vulvodynia 2 and the frequently difficult to treat but surprisingly common coccydynia. It should be considered and considered early, particularly in coccydynia as the outcome is profoundly affected by duration of symptoms, as in many chronic pain conditions.
Coccydynia can occur after even relatively innocuous trauma such as a short fall onto a hard surface. Scans are unreliable in the assessment of coccydynia as the normal coccyx can show a multitude of configurations. Spinal surgery for manipulation or correction of a coccygeal deformity is rarely warranted and frequently challenging.
Image 1. Contrast seen on the anterior surface of the sacrococcygeal region where the ganglion impar sits.
The Ganglion impar block is a quick, well-tolerated, under light sedation, day-case procedure that, for some, can provide effective analgesia with the symptoms described above. Local and steroid is applied via a very fine needle to the anterior surface of the sacrum and coccyx where the ganglion impar sits. It is a safe procedure with an extremely low risk of serious complications. In the image shown here, the needle can be seen through the coccygeal disc space with contrast to the anterior surface of the sacrum.
The block is often repeated or may have pulsed radiofrequency applied. Pain specialists often quote about 50% pain relief for duration of weeks to months: however, considerations should include the ability to wean stronger medications or make other treatment procedures such as pelvic floor physiotherapy easier to undertake.
Medication: Amitriptyline
Amitriptyline is commonly used for the management of chronic pain yet from the outset it's important to remember this is chronic nerve pain only as outlined by the NPS amitriptyline for nerve pain fact sheet.
Many pain specialists still use this commonly, particularly for nerve pain syndromes with many positive features such as allodynia or hyperaesthesia. Anecdotally only it appears to be less successful for the more negative feature neuropathic pains - eg associated with hypoaesthesia. It's therefore worth undertaking a full neuropathic pain assessment and using tools such as the DN4 pain questionnaire. (to be outlined in a future newsletter).
The mechanism of action appears to be mainly noradrenergic and serotonergic and affecting descending inhibition of pain signals in the pain pathway.
Start low and build up slowly. In many cases a starting dose as low as 10mg (or even 5mg in an older patient) is a good starting point and building up slowly eg increasing the dose by 10mg per week. Careful discussion with your patient of side effects and cautions such as driving is essential.
Extra caution in the older patient. It should be considered lower down the treatment algorithm in older patients due to the relative contraindications in cardiac disease and risk of urinary retention. It may still be required for someone with refractory pain so the above applies even more so.
Beware serotonin syndrome. Whilst it's a very rare complication it can be extremely severe. In addition medications with serotonergic effects are more common than expected. Obvious examples include many antidepressants but also tramadol, the Triptans in migraine management, anti-emetics such as granisetron and over the counter supplements such as St Johns Wort.
References:
1. Ghi Huang, Ai-Lien Le, et al. A Systematic Review of the Cost of Chronic Pelvic Pain in Women. Journal of Obstetrics and Gynaecology Canada, Volume 44, Issue 3,2022, Pages 286-293.
2. Hong DG,et al. Efficacy of ganglion impar block on vulvodynia: Case series and results of midand long-term follow-up. Medicine 2021 Jul 30;100(30)