Gout involved the cervical disc and adjacent vertebral endplates misdiagnosed infectious spondylodiscitis on imaging: case report and literature review

Gout is a metabolic disorder characterized by hyperuricemia and abnormal depositions of urate around a variety of tissues, more frequently including peripheral joints of the upper and lower extremities, typically in the first metatarsophalangeal joint [1]. Gouty involvement in the axial skeleton is a seemingly uncommon manifestation.

Any segment of the spine and its components (vertebral bodies, pedicles, lamina, ligaments, interapophyseal cartilage, and epidural and intradural spaces) may be involved, with lumbar involvement being the most common [2, 3]. It has been reported by Michael et al. that most cases (80.6%) only involved one region of the spine and 24.8% affected only the cervical spine [1]. Gout involving the endplates of two contiguous vertebral bodies and intervertebral disc is rare, which frequently mimics some degenerative changes and infectious spondylodiscitis on imaging, leading to delayed diagnosis and treatments. Therefore, the main imaging differentiation factors between these conditions should be further investigated. Up to now, there have only been 10 cervical gout cases with images reported in the English-language literature searched in PubMed [3‐11]; most of them showed the incomplete image sequence and poor image quality which were insufficient to understand the imaging manifestations of this condition for improving diagnostic accuracy. In this article, we report a case about a spinal gout affected the cervical disc and adjacent endplates with a complete and continuous image data with higher image quality and resolution than previous published cases, whose etiology was initially not completely determined and suspected as infectious spondylodiscitis, and provide a brief literature review concerning cervical gout. In addition, the case report is prepared and reported in accordance with CARE-checklist [12].

In our case, gout-related cervical spine lesions were confirmed and a series of complete and continuous high-resolution images including multiplanar reconstruction (MPR), volume rendering (VR) CT images, plain and contrast-enhanced MR images together with exhaustive description were fully displayed. To the best of our knowledge, there have only been 10 such cases with images reported in the English-language literature searched in PubMed (Table 1) [3‐11]; most of them just show incomplete and indistinct images. Due to that there were also reports that spinal gout had similar image appearance to infection [4, 5, 16, 17], the main imaging differentiation factors between these conditions should be further discussed.

Gouty involvement in intervertebral disc may be rarer than facet joint, which mostly mimics pyogenic discitis [5, 11, 16, 18], but it showed the opposite outcome in the reports reviewed in our article. Considering these 10 reports and including our case, 7 patients’ lesions involved discs and only 2 involved facet joints. As for sites of cervical involvement, spinal lesions of 7 patients were seen in the middle cervical segment; 3 of them located in the middle and lower cervical segment, and only 1 patient’s lesion located in the upper cervical segment. The lesions can occur in any segment of cervical spine, but are commonly seen in the middle cervical spine C3–6.

The imaging findings of our patient were initially difficult to tell if it was gout or infection. However, looking back on the images, we found that radiological abnormalities for spinal gout may have some difference with common infectious spondylosis according to literature report. Plain films sometimes appear false negative especially in the early stages and subsequent bone changes are advantageous but nonspecific feature of spinal gout [4, 6, 7, 11]. CT can help visualize the bone and soft tissue changes caused by tophi which appear as low-density area [6, 7, 9, 10]. The typical appearance related to these changes is characterized by punched-out erosion and well-defined margins without surrounding infiltrative changes; structures of vertebrae and endplates can remain unaffected and wedging changes of vertebral bodies are hardly seen [6‐10]. MRI appears to be sensitive but nonspecific for the diagnosis of spinal gout, but MRI has an obvious advantage in manifesting abundant information of soft tissue in or around the gouty lesion [19‐21]. In the literature review, 5 cases involving the cervical intervertebral discs with MR images was mainly low signal intensity on T1 and T2 weighted images [4, 5, 7, 9]. In 2 cases with enhanced MR images, the involved discs were enhanced significantly [4, 9]. And MR characteristics of 4 patients with tophus were intermediate-to-low signal intensity on T1-weighted images, and on T2-weighted images, the signal intensity varied from low to high [4, 7, 9, 10], which mostly coincided with previous studies [1, 19, 20]. After gadolinium enhancement, the tophi shows homogeneous or heterogeneous enhancement, mainly depending on volumes and distribution of calcification [16]. In the previous studies, the MRI findings have ranged from well-defined punched-out endplate erosive change and narrowing of intervertebral space to severe destructive and proliferative discovertebral changes. And no significant edema was found in the trabecular bone and soft tissue adjacent to the lesions. However, spinal cord edema can sometimes be seen resulting from the cord compression by lesions [5, 7, 10, 11].

Imaging manifestations of spinal gout is not specific and can resemble that of degenerative changes and infectious spondylodiscitis [4, 5, 18, 22, 23]. Therefore, it is necessary to exclude other probable etiologies. In patients with Modic type 1 vertebral disc changes, reactive sclerosis accompanied by marrow edema usually appears as hypointense on T1-weighted images and hyperintense on T2-weighted and STIR images in acute conditions, and its lesions generally show well defined boundary [24]. For pyogenic spinal infection, disc changes appear as invariably reduced height, non-anatomic T2 hyperintense and enhanced significantly; irregularity, destruction and enhancement of endplates and adjacent vertebral bodies can be seen as well. Inhomogeneous paraspinal inflammatory swelling is common and small abscesses with a limited area can also be formed in some cases [25]. However, vertebral lesions in spinal tuberculosis are usually extensive, causing collapse and malformation in the late stage. Bone destruction, dead bone, narrowing of intervertebral space, angulate deformity and cold abscess are the hallmarks of the disease and can help differentiate it from other conditions, and paraspinal collection occurs more commonly than in pyogenic infection and may be bilateral and disproportionately larger than the degree of bone destruction [26, 27]. In the cases of spinal brucellosis, the principal features in the sclerotic period are vertebral body hyperplasia, osteophyte proliferation, bony spines resembling “bird beaks” (that sometimes forms bony bridges) and endplate sclerosis; paraspinal soft tissue shadows and predural granulomas are more common than usual, and paravertebral abscesses are less common [27]. The main radiological differentiation factors between these conditions is the characteristics of the osteolytic lesions and changes of paravertebral tissues.

In recent years, a newer method, dual-energy CT (DECT), has been more commonly applied in the differential diagnosis of gout [3, 28, 29]. The sensitivity of DECT in identifying monosodium urate crystals up to 78–100% makes it more competitive than other methods of imaging. The urate depositions can be clearly seen on DECT, which is able to directly measure the size and volume of depositions [1]. Therefore, DECT apparently has diagnostic potential for patients with an unclear diagnosis or atypical clinical manifestations [22].

Clinically, it is necessary for physicians to break the boundary of the reasoning mechanism that local lesions in the intervertebral discs and adjacent vertebral endplates are just degenerative changes, infectious disease or tuberculosis; henceforth, gout should be higher on the list of differentials especially for the patients not responding to conservative measures. In laboratory tests, hyperuricemia and the elevated level of C-reactive protein were also uncertain that they were caused by gout of limbs or the new lesions, and the new lesions were gout or infection. Blood culture should be supplemented to exclude the possibility of infection when the lesion was difficult to define. Definite diagnosis of gout was most commonly made during surgery. In the 10 clinical cases, surgery was performed in 6 cases. An additional 1 case was diagnosed via needle aspiration. In 3 cases, the patients were diagnosed on the basis of blood culture, other clinical data, a history of gout and a rapid response to colchicine. Similar to the majority, etiology of our case was completely confirmed during surgery.

Treatment for spinal gout commonly includes conservative medication and surgery. Owing to the fact that data in most literature suggests that spinal gout may contribute to paraplegia, early intervention is needed after a definite diagnosis. Decompression surgery followed by pharmacological treatment of lowering serum uric acid may be the first treatment for the majority of patients [1]. If necessary, individual prophylaxis and therapeutic strategies can be provided as well.

Cervical spinal gout involving the disc and adjacent vertebral endplates is uncommon and may misunderstand degenerative changes and infectious spondylodiscitis. When such this condition with atypical symptoms and low specific imaging studies is encountered clinically, physician and radiologist should take the gouty spondylitis into account with a combination with previous history and clinical manifestations.