Radiofrequency ablation of osteoid osteoma in the atlas: A case report

Abstract

Osteoid osteoma of the atlas has previously been reported very rarely in the published literature. The traditional standard treatment has been a surgical resection of the nidus. Recently, computed tomography (CT)-guided radiofrequency ablation (RFA) has gained favor as a more precise alternative treatment. Here, we present a case of osteoid osteoma of the C1 lateral mass treated successfully using CT-guided RFA. A 30-year-old woman who presented with a four-month history of occipital and suboccipital pain was treated by CT-guided RFA. The visual analog scale (VAS) assessed the pain before and after RFA. The patient reported significant pain relief and normal activities. The VAS score reduced from 8/7 to 1/0 after the procedure. Therefore CT-guided percutaneous RFA of C1 vertebral osteoid osteoma is a safe and effective method. The technique might be contraindicated when the nidus is less than 2 mm away from the neural structures.

Introduction

Osteoid osteoma affecting the cervical spine is very rare, accounting for approximately 2.7–6.7% of all osteoid osteomas.¹ Although radiofrequency ablation (RFA) has been a gold-standard treatment method,² most authors have excluded it in critical locations, such as spinal and intra/periarticular locations, or those in proximity to neural structures.³ From a literature search performed through PubMed, we found only seven cases of osteoid osteoma located in the atlas.^4–9 They were all treated by surgical resection (Table 1). To the best of our knowledge, our case is the first report of atlas osteoid osteoma treated by RFA, and now it is described as follows.

Table 1.

Summary of previously reported cases of osteoid osteoma involving C1.

Authors and year	Age (years), sex	Therapy method
Wedge et al., 19815	10, male	Hemilaminectomy
Jones, 19874	8, male	Hemilaminectomy
Fielding et al., 19776	Uncertain, male	En bloc resection
Amirjamshidi et al., 20107	14, male	Hemilaminectomy
De Praeter et al., 19998	21, male; 22, male	Hemilaminectomy
Zhao et al., 20129	Uncertain, uncertain	Hemilaminectomy

Case report

A 30-year-old woman was referred to our hospital because of a four-month history of occipital and suboccipital pain without traumatic history. At the first two months, the pain was mild and intermittent. However, it became more constant and severe and began to disturb her sleep. Although her pain was relieved transiently by nonsteroid anti-inflammatory drugs (NSAIDs), the amount of salicylates administered had to be increased progressively to relieve her pain. Moreover, long-term drug administration resulted in gastrointestinal side effects and was not well tolerated by this patient. A computed tomography (CT) scan showed a radiolucent nidus within surrounding bone sclerosis at the right lateral mass of C1, and the lesion was hypointense on T1-weighted magnetic resonance (MR) images and hyperintense on T2 (Figure 1). These findings were believed to be consistent with the diagnosis of osteoid osteoma. As conservative treatment showed a poor effect, and on account of the risk of damage to the spinal cord, nerve root, and/or vertebral artery carried by surgery, we decided to implement CT-guided radiofrequency ablation.

Figure 1.

(a) and (b) Axial and coronal computed tomography scan showed a radiolucent nidus within surrounding bone sclerosis in the right lateral mass of the atlas (white arrow). The maximum diameter is about 10 mm. (c) and (d) The lesion appears as hypointense signal on T1-weighted magnetic resonance imaging (MRI) images and T2-weighted MRI images.

Treatment was performed with a 16-slice helical CT (Philips, Netherlands). RFA equipment used a radiofrequency cool-tip ablation system (Covidien, Mansfield, MA, USA). Before the procedure, pethidine (Demerol) 75 mg and luminal 100 mg were injected intramuscularly for pain killing and emotional stability. The vital signs were monitored continuously during the procedure. The patient was positioned prone in the CT scanner. CT images were acquired to determine the optimal puncture approach. By the posterolateral approach, CT-guided percutaneous puncture was performed with a 16G coaxial biopsy needle (Cook, Bloomington, IN, USA) under local infiltration lidocaine anesthesia. We selected a 1 cm (RF region) electrode, which corresponded to the size of the tumor. Through the biopsy cannula, the electrode was appropriately targeted in the distal of the nidus. After checking not only that the electrode was adequately placed (Figure 2) but also that the exposed tip did not touch the cannula, the electrode was connected to the RF generator and two plates were placed over the skin of the patient, close to the puncture point, that were used as heat dissipators and to reduce the damage of skin burns. Ablation was performed by gradually warming up the needle tip. The RFA generator monitored the real-time heating temperature of the tip to maintain constancy at 90℃, which lasted for 8 minutes. After the removal of the RFA electrode, a sterile strip dressing was applied. No neurological or vascular complications occurred in this patient. She was removed from the CT scanner and reported little pain except at the needle puncture site. The next morning we used VAS to record the pain, from 8/7 preoperatively to 1/0 postoperatively.

Figure 2.

(a) and (b) Computed tomography (CT) scan during the operation showed the electrode was appropriately targeted in the distal of the nidus. (c) and (d) CT images after the operation showed no serious spinal cord and vascular injury near the ablation area.

During a five-year follow-up, the patient had complete resolution of pain without taking any painkiller, and there has been no evidence of recurrence to date (Figure 3).

Figure 3.

(a) and (b) Axial and coronal computed tomography scan performed six months after treatment showed that the lesion was ablated. (c) and (d) At the five-year follow-up, magnetic resonance imaging images show no recurrence of the nidus.

Discussion

Osteoid osteoma is the third most common benign bone tumor, and predilection sites of the osteoid osteoma are long bones.¹⁰ The spine is involved in just 10% of the cases and the lumbar spine is the most commonly affected, whereas the tumor is rarely seen in the cervical spine.¹¹ Histologically, this tumor consists of a centrally located vascularized nidus, typically surrounded by a variable amount of new bone formation.¹² The most common clinical presentation of an osteoid osteoma is a sharp local pain, which typically predominates at night. Patients with osteoid osteoma in the cervical vertebra often present with resistant localized neck pain and stiffness in the spine.¹³ The diagnosis of osteoid osteoma in our patient was stated by means of typical clinical and imaging data. Histopathological examination was not necessary.¹⁴

There are currently three therapy options available for treatment of osteoid osteoma: conservative treatment with NSAIDs, surgical resection, and percutaneous ablation (e.g. RFA, cryoablation). Conservative treatment with NSAIDs is usually the first choice in newly diagnosed cases, but it often needs to be suspended because of inadequate pain relief and severe adverse effects. Traditionally, surgical resection has been the next step and was the definitive treatment for a long time.¹⁵ But open surgery may result in procedure-related complications and a long hospital stay.¹⁶ Recently, RFA has been applied more diffusely in the treatment of osteoid osteoma owing to fewer complications and shorter length of hospital stay.¹⁷

Rosenthal et al. first reported RFA as a minimally invasive therapeutic option for the treatment of osteoid osteoma.¹⁸ Since then, a lot of studies have confirmed its effectiveness and safety.^19–21 However, many physicians do not perform RFA on patients with cervical osteoid osteoma because of the risk of spinal cord and nerve root damage from heat. There are a few reported cases of RFA-treated osteoid osteoma in cervical vertebra. Animal studies by Dupuy and colleagues have shown that RFA can be safely applied to the vertebral column so long as there is an intact cortex and/or cerebrospinal fluid acting as an insulator between the lesion and the spinal cord or nerve roots.²² Vanderschueren et al. suggest that if the tumor margin is within 2 mm of the intraspinal structures, it might be dangerous using RFA and surgical resection is indicated.²³ RFA should be the treatment of choice in lesions 2 mm away from the nerve root, and surgery should be reserved for lesions adjacent (2 mm) to the nerve root causing nerve root compression.

Our experience confirmed this aspect. In our case, the distance from dangerous structures (spinal cord) was 8 mm. So we think RFA is executable. To our knowledge, this represents the first case of osteoid osteoma of the C1 treated successfully by CT-guided RFA. Prior to our case, the highest spinal segment treated with RFA was C2, reported by Liu and colleagues.²⁴ They used a 13G bone biopsy needle into the center of the nidus, and a 1 cm electrode was introduced into the nidus through the cannula. Our technique is very similar to theirs although we used a 16G biopsy needle, which reduced the damage from puncturing and improved safety.

Conclusion

The clinical case that we have presented shows that CT-guided percutaneous RFA of C1 vertebral osteoid osteoma is an alternative method. The technique might be contraindicated when the nidus is less than 2 mm away from the neural structures. Larger series are needed to evaluate the safety and efficacy of this method and to support its use in the management of osteoid osteomas located in the atlas.

Declaration of conflicting interests

The authors declared no potential conflict of interest with respect to the research, authorship, and/or publication of this article.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.