Bertolotti syndrome (BS) is defined as a condition characterized by chronic pain resulting from the presence of lumbosacral transitional vertebra (LSTV). Therefore, radiological and clinical diagnoses should be concurrently performed. Owing to the similarity in clinical presentation to other conditions that cause low back pain, diagnosis can be challenging. Various treatment modalities, ranging from conservative to surgical approaches, have been implemented to manage this condition. However, there are currently no standardized treatment protocols or approaches, and new approaches continue to emerge [1-3]. Pulsed radiofrequency ablation, which applies radiofrequency energy near the sensory nerve roots, offers long-term pain relief by inducing minimal nerve destruction and blocking pain conduction and nerve modulation [4]. Moreover, reports from 2010 and 2020 have described the use of pulsed radiofrequency ablation in the LSTV in patients with BS [5,6].

In this report, we present the case of a 23-year-old male diagnosed with BS, who showed a significant response to a diagnostic block of the ipsilateral L4 root. Subsequently, pulsed radiofrequency ablation of the L4 dorsal root ganglion was performed, resulting in a reduction in pain from a visual analog scale (VAS) score of 7 to 4.

A 23-year-old male patient, with no underlying medical conditions, visited the hospital as an outpatient because of severe left lower back and ipsilateral radiating leg pain. This had been ongoing for 6 years and had substantially worsened over the past year, with a VAS score of 9. Additionally, the patient reported worsening pain during prolonged standing or sitting, long-distance walking, and lying on one side. Initial evaluation, including lumbosacral spine magnetic resonance imaging (MRI) at the onset of symptoms, did not reveal any significant findings, such as disc abnormalities or neural foraminal stenosis. Physical examination revealed tenderness over the quadratus lumborum muscle, pain radiating to the left lateral thigh and inguinal area, and left hip flexion. Considering the his age and clinical presentation, the patient was initially diagnosed with spondylosis and paraspinal myofascial pain syndrome.

Trigger point injections targeting the psoas and quadratus lumborum muscles were administered to temporarily relieve the symptoms. However, symptoms recurred over time, necessitating repeated treatments with minimal long-term relief. Following pelvic and lumbosacral spine MRI examinations, which encompassed the sacroiliac joint, the results revealed the presence of an LSTV positioned between the left L5 transverse process and the left sacrum (Fig. 1). Furthermore, considering the possibility of symptoms related to BS, diagnostic blocks were performed at the LSTV pseudoarticulation area using a 0.125% chirocaine solution, resulting in temporary symptom relief. Subsequent interventions, such as steroid injections and superior cluneal nerve blocks, led to an improvement in the lower back pain; however, radiating pain in the left leg persisted.

Figure 1. (A) An anteroposterior (AP) view of pelvis image showing enlargement of L5 left transverse process with pseudoarticulation. (B) A Transverse view of T2 weighted MRI revealing lumbosacral transient vertebra between Lt L5 transverse process and sacrum.

A diagnostic L4 nerve block procedure was performed (Fig. 2), during which the L4 exit nerve root may be compressed by the enlarged L5 transverse process. The patient reported concordance between the sensations experienced during the injection and the typical symptoms associated with the condition. Follow-up assessments showed gradual improvement in the VAS score from 7 to 6, and ultimately to 4. Furthermore, to achieve long-term pain relief with conservative treatment rather than surgical intervention, pulsed radiofrequency treatment was applied to the left L4 dorsal root ganglion. During the procedure, the patient reported that the stimulated area aligned with the typical symptoms. Subsequently, the patient experienced relief from pain, registering a VAS score within the 4-point range.

Figure 2. (A) Contrast spreading patterns in left L4 selective nerve root block – an anteroposterior fluoroscopic image. (B) Contrast spreading patterns in left L4 selective nerve root block – a lateral fluoroscopic image.

BS is a condition that causes pain due to the presence of transitional lumbosacral vertebra (LSTV). The reported prevalence ranges from 4% to 36%; however, not all cases of LSTV are diagnosed as BS. Confirmation of BS as the cause of a patient’s pain is essential, highlighting the necessity to conduct thorough assessments for an accurate diagnosis. Moreover, BS is often classified using the Castellvi classification, which considers the direction and degree of fusion of the LSTV [1]. According to Zhu et al [3], the average age of diagnosed patients is 47.7 years [3]. LSTV can alter the biomechanics of the spine by reducing mobility at L5-S1 and causing hypermobility above the transitional segment [1]. Additionally, Desai et al. [7] reported a notably higher pelvic incidence in patients with BS, whereas McGrath et al. [8] found thinner iliolumbar ligaments on the affected side in patients with unilateral LSTV. Various pathophysiological mechanisms, such as secondary scoliosis, joint inflammation, quadratus lumborum, psoas muscle strain, and herniated discs, can contribute to the diverse clinical presentations of this syndrome. Jain et al. [9] reported that pain in BS predominantly arises in the following order: ipsilateral L5-S1 facet joint, LSTV in situ, SI joint, and disc degeneration. Moreover, Elster et al. [10] found that herniated discs are most common just above the LSTV segment. Knopf et al. [11] proposed the Onyiuke grading and treatment algorithm to enhance the clinical utility of Castellvi types. Jenkins et al. [12] introduced the Jenkins classification, noting that Castellvi types do not encompass all anatomical variations.

The treatment options for BS range from conservative medical therapy to physical therapy, minimally invasive interventions, and surgery. Zhu et al. [3] reported that 63% of their patients underwent surgical treatment, 11% received local anesthesia and steroid injections, and 5% underwent radiofrequency ablation at the LSTV site. Burnham et al. [5] and Kanematsu et al. [6] reported symptom relief with heated and pulsed RF; however, these procedures were limited to the LSTV pseudoarticulation site.

Pulsed radiofrequency is a minimally invasive procedure that applies a low-energy electrical field with rapid pulsation to modulate nerves and nearby microglia, thereby affecting neurotransmitters, ion channels, inflammatory cytokines, and synaptic functions. Furthermore, when applied to patients with lumbosacral radicular pain, pulsed radiofrequency provided longer-lasting symptom relief compared with transforaminal epidural injection [13]. It is noteworthy that pulsed radiofrequency ablation is considered less ablative, and its effects are relatively short-lived compared with those of conventional radiofrequency ablation [4,14,15].

As exemplified by our case, young patients complaining of persistent lower back and radiating leg pain can be challenging, because pain associated with LSTV is often overlooked in younger populations [16,17]. Moreover, even when LSTV is detected, attributing the symptoms to BS can be difficult, given the various clinical presentations. In this case, the patient exhibited findings suggestive of the left LSTV on external lumbar spine MRI, which were initially overlooked. Upon symptom relapse, additional imaging and diagnostic blocks were performed, leading to symptom improvement. A literature review was performed during the clinical course, which revealed findings from Kojo et al. [2], who observed secondary compression of the L5 root within a narrow tunnel formed by the connective tissue due to LSTV in patients with BS through imaging. This finding prompted us to consider the possibility of nerve root compression. It is noteworthy that the hypothesis suggesting possible compression of the ipsilateral L4 root is by an enlarged ipsilateral L5 transverse process excludes patients with other concurrent spinal pathologies that mimic the clinical profile of the patient in this case [18]. In this study, ipsilateral L4 root decompression was performed and these interventions yielded significant therapeutic benefits. Drawing inspiration from Ju et al. [18], a diagnostic L4 root block was administered in our case, and the patient experienced symptom relief. Subsequently, in pursuit of long-term therapeutic effects, L4 pulsed radiofrequency treatment was administered.

BS has a high incidence and diverse clinical presentations. Interpretation can be challenging when other concurrent spinal conditions are present and the syndrome can induce secondary biomechanical changes. Given these complexities, it is crucial to adopt an individualized treatment approach, considering various possibilities. For patients with radicular pain due to BS without concurrent spinal conditions, diagnostic nerve root block and pulsed radiofrequency ablation of the ipsilateral nerve root can be considered if a positive response is observed.

This study was approved by the Institutional Review Board (IRB) of the Seoul National University Hospital (Seoul, Republic of Korea) (IRB no. H-2310-055-1474).

No potential conflict of interest relevant to this article was reported.