Bertolotti syndrome presenting as pudendal neuralgia: A case report

Introduction

Bertolotti syndrome is a condition stemming from an aberrant lumbosacral transitional vertebra (LSTV). ¹ Although LSTV occur in 4%–36% of the population, the condition is diagnosed only when this abnormality is identified as the pain generator. ²

Bertolotti syndrome often presents as lower back pain due to a transverse process (TP) rub site, adjacent level facet joint strain or degenerative disc disease, myofascial pain, or nerve root irritation caused by altered biomechanical forces secondary to the LSTV. It may also mimic sacroiliac, hip, or knee pain via referred pain patterns. ¹ Bertolotti syndrome’s inconsistent pain patterns contribute to high rates of misdiagnosis and delayed diagnosis, prompting increased research to better understand the condition’s clinical characteristics and to establish therapeutic guidelines.^3,4 While Bertolotti syndrome is traditionally described by the Castellvi classification, the newly proposed Jenkins et al. classification system may better predict its presence. This updated classification system measures the gap between the TP and sacral ala to more comprehensively describe the functional anatomy.

Genital pain mimicking pudendal neuralgia is a unique presentation for Bertolotti syndrome not previously reported. Pudendal neuralgia, often caused by pudendal nerve compression from activities such as cycling or prolonged sitting, typically presents with pain in the external genitalia, anus, perineum, and aspects of the rectum. Diagnosis is guided by the Nantes criteria and traditional treatments range from conservative measures such as activity modifications and pelvic physical therapy (PT), to medications, injections, neuromodulation, and decompression surgery. ⁵

We present a patient with 30 years of genital pain resembling pudendal neuralgia, which was refractory to pudendal nerve blocks. Although appropriate anesthesia was achieved with pudendal nerve blocks, indicating successful blocks, the pain persisted, indicating the pudendal nerve was not the pain generator. Coincidentally, after performing a Bertolotti block to diagnose her lower back pain, she experienced significant genital pain relief, confirmed with a subsequent block. This case demonstrates a unique presentation of Bertolotti syndrome not discussed in the existing literature and thus contributes toward the larger scale effort to understand the breadth of symptomatology associated with LSTV. While the pathomechanism is not fully elucidated and may vary between patients depending on which structures are involved, it is reasonable to conclude that the genital pain is another possible referral site of LSTV pain.

Case description

A 68-year-old female presented with 30 years of progressive right greater than left vulvodynia. She described a sharp pain with paresthesias radiating from the coccyx with associated vaginal spasms extending to the pelvic floor and weakness with defecation. She also reported chronic lower back pain. Her medical history was significant for a coccyx fracture at age 18, which resolved without pain for over 20 years.

Her exam was notable for tenderness over the right L5 TP, radiating pain to the right groin with palpation of the coccyx, intact strength and sensation, and bilateral FABER tests reproducing pain in her lower back. Lumbar X-ray demonstrated peaked sacral alae which appeared to abut the L5 TP (Figure 1). A pelvic CT measured the gap between the sacral ala and L5 TP at 3 mm bilaterally, classified as Jenkins type 1b LSTV (Figure 2). Lumbar MRI showed L4/5 and L5/S1 degenerative changes. Gluteal ultrasound (US) demonstrated thickening of the right sacrospinous ligament.

OPEN IN VIEWER

Figure 1.

Anterior-posterior lumbar X-ray demonstrating bilateral peaked sacral ala.

OPEN IN VIEWER

Figure 2.

Coronal lumbar CT demonstrating 3 mm gaps bilaterally between the peaked sacral ala and L5 transverse processes indicating Jenkins type 1b LSTV

She tried various pharmacologic options, including amitriptyline, valium, baclofen, and ketamine suppositories, all of which were discontinued due to side effects. Additionally, symptoms persisted despite more than 6 weeks of pelvic floor and lower back PT. An initial US-guided bilateral pudendal nerve block at the level of the sacrospinous ligament with bupivacaine and triamcinolone resulted in appropriate numbness in the pudendal nerve distribution but did not diminish her pain. After 4 months, a repeat bilateral pudendal nerve block was performed and the patient again reported appropriate numbness without pain relief. Specifically, she reported ongoing vaginal pain extending to the rectum. Over the next 6 months, she attempted to manage the residual pain with oral medications and PT but continued to report vulvodynia extending to her rectum. She subsequently underwent two rounds of vaginal botulinum injections which did not provide relief of pain or spasms. Given her prior coccyx fracture, a fluoroscopic-guided ganglion impar block with bupivacaine and triamcinolone was performed with a negative diagnostic response. She did however report a 1-week delayed onset pain relief lasting 3 weeks which was attributed to the steroid injected. A repeat ganglion impar injection with bupivacaine alone was diagnostically negative. She ultimately underwent bilateral diagnostic fluoroscopic-guided LSTV rub site injections with lidocaine and experienced 60%–70% resolution of her vaginal and rectal pain for approximately 1 h. After 3 months, she underwent repeat bilateral fluoroscopic-guided LSTV rub site injections with 60%–70% improvement in genital pain and complete relief of low back pain.

Conclusion

Bertolotti syndrome is known for its wide variety of symptomatology. ¹ This case explores a new presentation not previously described in the literature: pelvic and genital pain suspected to be generated by a LSTV with rub between the TP and sacral ala. In this case, the patient met many of Nantes criteria leading the authors to initially pursue the diagnosis of pudendal neuralgia. However, this was ruled out by negative diagnostic pudendal nerve blocks, as she did not experience pain relief despite appropriate anesthesia.

Due to persistent pain, alternative treatments including vaginal botulinum injections and two ganglion impar blocks were performed but failed to provide relief. As the gap between the TP and sacral ala was 3 mm and thus within the 2–10 mm range for the Jenkins classification system of Bertolotti syndrome, a Bertolotti block was performed. ⁶ It was only after bilateral fluoroscopic-guided injections at the rub site between the transitional vertebra and sacrum that the patient reported improvement of her previously unrelenting vaginal and rectal pain, confirmed with two separate blocks.

The presence of a LSTV is known to alter the biomechanics of the spine through various mechanisms. Therefore, the exact pain generator is often difficult to isolate due to the multiple degenerative changes stemming from the LSTV.^1,4 In this unique case, we primarily suspect the lingering genital pain was a result of referred pain from the LSTV rub site. While this referral pattern for Bertolotti syndrome has not previously been described, other spine pathologies such as lumbar facet joint or sacroiliac joint pain, are known to present with pain at a site distant to the anatomic origin. Referred pain in Bertolotti syndrome may be related to muscle guarding within the pelvis, or there may be a viscerosomatic referral pathway. The periosteum of each bone is innervated by somatic afferents as well as postganglionic sympathetic fibers, the latter of which are common sources of referred pain. ⁷ It is therefore possible that the nociceptive fibers that travel along the pudendal nerve converge with the nociceptive fibers traveling along nerves supplying the area of the LSTV. This may cause the brain to perceive the LSTV pain as pudendal distribution pain.

Differentiating primary from referred pain can be done by administering local anesthetic to the area where pain is felt. In this case, pain persisted after pudendal nerve blocks, consistent with referred pain. As described by Jin et al. ⁸ referred pain is often challenging to isolate as it can span multiple dermatomes and overlap with other sources, thus making diagnostic blocks essential for primary source localization.

An additional pathomechanism to consider includes altered biomechanics due to the LSTV which induces additional stress on the pudendal nerve at one of the common compression sites along the nerve’s path such as between the sacrospinous and sacrotuberous ligaments or beneath the piriformis at the exit of the greater sciatic foramen. ⁹ While this is a possible explanation, it would not explain the lack of relief following pudendal nerve blocks. Regardless of the proposed pathomechanisms described above, providing an anesthetic block to this patient’s root cause of pain, the LSTV, alleviated the source and thus more distal symptomatology improved.

Bertolotti syndrome remains a prevalent yet poorly understood condition in which clear treatment guidelines are an increasingly important area of ongoing research. This case supports a stepwise treatment algorithm when managing Bertolotti syndrome, beginning with conservative measures such as activity modifications, PT, and anti-inflammatories, progressing to diagnostic and therapeutic injections, and ultimately to surgical interventions if required. ⁴ Within a review of 388 patients with Bertolotti syndrome by Zhu et al., 17.8% of cases underwent either injection therapy or radiofrequency ablation and 68.3% of cases required surgical intervention. This case underscores the value of diagnostic LSTV rub site injections as part of the treatment algorithm. As pointed out in a review of treatment options for Bertolotti syndrome by Holm et al., ¹⁰ research regarding diagnostic injections targeting the LSTV remains sparse and thus an area of high demand for ongoing research.

To the authors’ knowledge, this is the first case to describe Bertolotti syndrome as the source of genital pain. While this remains a case study with a pathomechanism not entirely understood, the authors primarily suspect the pain may be generated via a referral mechanism. This case adds to the increasing demand for further research into the variety of presentations for Bertolotti syndrome as well as its clinical management. As Bertolotti syndrome is known for its high rate of misdiagnosis and prolonged time to diagnosis, the authors suspect there may be similar cases of unremitting genital pain secondary to LSTV, for which this case may help provide clinical guidance. The authors encourage providers to consider including Bertolotti syndrome in their differential diagnosis in cases of unremitting genital pain in patients with aberrant LSTV, especially if other treatment methods addressing more common diagnoses such as pudendal neuralgia have failed to provide relief. The authors hope this case may also stem additional investigation and research to further illuminate the pathomechanism behind this unique presentation.