A case of tophaceous gout in the lumbar spine: a review of the literature and treatment recommendations.

Study Design Case report. Objective The objective of this study is to report the occurrence of tophaceous gout in the lumbar spine. Methods Using a case report to illustrate the key points of gout in the spine, we provide a brief review of gout in the literature as it relates to its orthopedic and spinal manifestations as well as guidelines for management. Results This case report details the occurrence of a large and clinically significant finding of tophaceous gout in the lumbar spine in a 24-year-old man with a known history of gout and a 3-year history of progressive back pain. Conclusion A high index of suspicion can assist in diagnosis of patients presenting with back pain or neurologic findings with a history of gout. A previous history of gout (especially the presence of tophi), hyperuricemia, and the radiological characteristics presented here should aid the clinician in making the diagnosis of spinal gout. Early diagnosis has the potential to prevent the need for surgical intervention.

Introduction

Gout is a common inflammatory arthritis that is characterized by the deposition of monosodium urate crystals in the synovium. An estimated 6.1 million adults in the United States have gout.1 Monosodium urate crystals have decreased solubility at lower temperatures, and consequently, the most commonly affected sites are peripheral joints. Other crystalline arthropathies include pseudogout. Pseudogout is the deposition of calcium pyrophosphate dihydrate crystals in the joints or periarticular structures, which leads to inflammation in joints. Pseudogout shows similar clinical findings to gouty arthritis although tophi are exclusive to gout.

Occurrence of gout in the spine is rare, with little over 70 cases reported in the literature. Not all levels of the spine are equally likely to be affected. One review of the literature found that the lumbar spine was most commonly affected (56% of cases), followed by the cervical and thoracic spine, which both occurred in 22% of cases.2 Out of these cases, the most common presenting symptoms were nonspecific paraparesis (39.0%), radiculopathy (27.0%), and back pain (18.0%).3 Given the rare incidence and nonspecific presentation, an inclusion of gout in the differential diagnosis of atypical neurocompressive pathologies is necessary for diagnosis. In the spine, gout may affect the epidural space, ligamentum flavum, intervertebral disc, pedicles, facet joint capsule, and neural foramen.4 This may present as spinal stenosis, lumbar radiculopathy, spondylolisthesis, or cauda equina syndrome.

Biopsy is the gold standard in confirming the diagnosis. Histologic findings show a granulomatous infiltrate of multinucleated giant cells, histiocytes, and fibroblasts. In addition, specimens examined under polarized light microscopy demonstrate the characteristic needle-shaped crystals with negative birefringence of gout. High serum urate levels, a concomitant history of advanced renal disease, previous gout attacks (podagra), and the cutaneous manifestation of tophi all point to the diagnosis.

Report of a Case

A 24-year-old man with a 4-year history of tophaceous gout and chronic kidney disease presented with a 3-year history of lower back pain that acutely worsened over the course of a week before hospital admission. He had developed shooting pain down the lateral aspect of his thigh with the right worse than the left. Of note, the patient had not been taking any of his gout medication for the six months before admission. He has had several acute flares of gout since his diagnosis and has disabling tophi in his hands.

Physical exam was notable for weakness of the right lower extremity, with 4/5 strength in ankle dorsiflexion, extension of the big toe, and ankle plantarflexion. His creatinine on admission was 4.80 mg/dL and serum uric acid was 14.6 mg/dL.

Imaging initially obtained for abdominal pain and fever was suspicious for tumor (Fig. 1), demonstrating a large, heterogeneous, infiltrating calcified soft tissue mass in the lumbosacral region, expanding the neural foramen, and scalloping the vertebral body, with erosion of the facet joints. Bone scintigraphy showed mild increased uptake in the right L4-S1 region. Magnetic resonance imaging (MRI) revealed an isointense mass surrounding the L5 nerve root on T1-weighted images (Fig. 2), with extensive cystic component on T2-weighted images (Fig. 3). Postcontrast sequences were not performed due to poor renal function. Tissue diagnosis was then indicated although the concordance of imaging with the patient's history and physical exam suggested gout. The patient underwent ultrasound-guided fluid aspiration, which revealed negatively birefringent crystals on polarized light microscopy, confirming the diagnosis of gout (Fig. 4).

Fig. 1

Axial noncontrast CT at the L5-S1 level shows a hyperattenuating, partially calcified soft tissue mass scalloping the posterior vertebral body, widening the right neural foramen, and eroding the right facet joint. CT, computed tomography.

Fig. 2

Axial T1-weighted MRI at the L5-S1 level demonstrates a heterogeneous soft tissue mass mostly isointense to muscle surrounding the exiting right L5 nerve root and extending anteriorly into the retroperitoneum, with an epidural component causing dural compression and displacement. MRI, magnetic resonance imaging.

Fig. 3

Sagittal T2-weighted MRI scan shows the heterogeneous mass with soft tissue and cystic components. The solid components fill the right L5-S1 and S1-2 neural foramina, with scalloping of the vertebral bodies. There is facet joint erosive change at both L4–5 and L5-S1. MRI, magnetic resonance imaging.

Fig. 4

Polarized light microscopy of ultrasound-guided fluid aspirate of paraspinal mass reveals numerous needle-like negatively birefringent monosodium urate crystals.

The patient was taken to the operating room for lumbar decompression. Intraoperatively, there was significant marginal sclerosis in areas of the sacrum, especially the right sacral ala and S1 foramen. The mass had also grown into the paraspinal muscles and into the retroperitoneum along the L5 nerve root. A decompressive laminectomy of L4-S1 and resection of intraspinal canal lesion and perineural lesion was performed (Fig. 5). The right L4 pedicle extending to the vertebral body was completely destroyed. Large aggregates of chalky tophi and a cystic collection of milky white fluid were intralesionally resected. Postoperatively, the patient was restarted on colchicine and allopurinol and given a brief burst of prednisone. By the 6-week clinic visit, he had regained his strength in his right lower extremity and had interval resolution of his lower back pain.

Fig. 5

Surgical pathology specimen: en bloc resection of a nodular, chalky soft tissue mass.

Discussion

This case describes the uncommon presentation of tophaceous deposits in the spine. As mentioned, gout rarely affects the spine and even more rarely evolves in such an aggressive fashion. Initially, it was felt that imaging and clinical symptoms favored malignancy given the progressive neurologic deficit and imaging characteristics. Physical exam and plain films revealed the presence of multiple gouty tophi in other small joints, which increased suspicion for gouty arthropathy of the spine (Fig. 6). In the absence of such remarkable physical findings, isolated spinal gout can be extremely difficult to diagnose and as such a tissue diagnosis before intervention is highly encouraged except in the most urgent/emergent scenarios.

Fig. 6

Oblique radiograph of the right wrist obtained 3 years prior shows classic features of gout, including juxta-articular “punched out” erosions without osteoporosis at the second metacarpophalangeal joint and large calcific soft tissue tophus at the ulnar side of the wrist.

Although crystal deposition disease of the spine is rare, the diagnosis can be made by the patient's history, the results of computed tomography (CT) or MRI of the spine, and tissue samples. Gouty tophi normally appear as a hypointense, homogenous mass associated with a joint on T1- and T2-weighted MR images, which enhances with gadolinium because of vascularized reactive tissue in the tophus.5 6 Imaging characteristics of spinal gout are nonspecific, however, and the use of an image-guided fine needle aspiration or biopsy is recommended. The imaging characteristics in our case were somewhat unique given the heterogeneity of the mass demonstrating discrete areas of soft tissue, calcification, and cyst formation, raising the initial concern of a nerve sheath tumor with possible malignant degeneration. The mass was noted to extend along the right-sided L5 and S1 nerve roots. Also, we believe this massive spinal tophus to be the largest reported, measuring 7.5 cm × 2.8 cm × 10.3 cm, and extending from the level of L3 to S1 in the sagittal plane. In most cases, diagnosis can only be confirmed by histological examination of biopsy material. This minimally invasive diagnostic test allows differentiation from other important imitators such as neoplastic disease or infection and avoids unnecessary exploration. Conversely obtaining a tissue diagnosis before formal intervention can avoid “unintended” intralesional resection of sarcoma. Dual-energy CT may have a future role in differentiating spinal gout from infection or tumor and obviating biopsy by identifying the presence of uric acid in tissues. Although some controversy exists, most presentations of axial pain caused by spinal gout can be medically managed.3

Patients without concomitant neurological deficits can be treated medically after spinal infection is excluded. Medical treatment with nonsteroidal anti-inflammatory agents, such as naproxen and ibuprofen, and steroids, such as prednisolone, are effective to control pain acutely. This is followed by administration of a urate-reducing agent for long-term control such as probenecid, allopurinol, or rasburicase. Maintaining adequate hydration and alkalization of urine is required to prevent recurrent episodes.3 5 It is important for the clinician to realize that surgery is only warranted for relief of neurologic symptoms and that long-term management hinges on adequate medical therapy. Given the long duration of this patient's axial skeletal pain, aggressive medical management may have rendered surgery unnecessary; however, a cautious approach is warranted when neurological deficits are present.