Septic Arthritis of Cervical Spine Facet Joints: A Case Report and Review of Imaging

Background

Septic arthritis of the facet joint (SAFJ) historically accounted for about 4% of all pyogenic spinal infections and has been considered a rare condition [1]. However, with the aging of the population, the increase in compromised hosts, and the increase in use of MRI in recent years, there have been an increasing number of reports of SAFJ, which now make up about 20% of pyogenic spinal infections [2]. However, SAFJ is generally not well known and is difficult to diagnose. SAFJ can be associated with severe sepsis and residual neuropathy; early diagnosis and appropriate treatment are essential [2,3].

Of these SAFJ infections, 86% to 97% are located in the lumbar region [2,3]. To the best of our knowledge, there have been only 15 reported cases of septic arthritis of the cervical facet joint (SACFJ) [4–16]. Here, we report a case of SACFJ that was diagnosed early by MRI, in which a favorable clinical course was achieved by conservative treatment with antibiotics. In addition, we evaluated SAFJ over time by CT and MRI.

Case Report

A 73-year-old Japanese woman’s chief concerns were numbness on the right forearm (ulnar side) and upper arm (extension side), and difficulty in moving the right finger. Her medical history was unremarkable. She did not smoke or drink. The patient had a fever of 37.5°C, hyposensitivity in the right C7 and C8 regions, muscular weakness in triceps brachii MMT4/5, wrist flexion MMT4/5, wrist extension MMT4/5, finger extension MMT2/5,and finger flexion MMT4/5 (Figure 1, Table 1). Laboratory tests showed WBC count 9600/µL, CRP count 7.58 mg/d, and elevated inflammatory markers. Simple X-ray and CT of the cervical spine showed only deformation in the cervical spine, but MRI of the cervical spine revealed a high signal change in the right facet joint and paraspinal muscle of C7/Th1 in the sagittal section of the STIR image. In the same horizontal section, epidural mass lesions were observed extending from the C6/7 and C7/Th1 intervertebral foramen to the spinal canal (Figure 2). Based on the above, the patient was diagnosed with C7/Th1 right SACFJ and cervical epidural abscess. Treatment with Cephem antibiotics was initiated in accordance with the treatment of pyogenic spondylitis. In this case, cefotiam 3 g/day, which is effective against gram-positive cocci and, to some extent, gram-negative rods, was used for initial intravenous antibiotic treatment. The dose of antimicrobials was adjusted according to renal function. Methicillin-sensitive Staphylococcus aureus (MSSA) was detected in 2 sets of venous blood cultures. Microbiological examination showed good susceptibility of cefotiam to this MSSA. Five days after initiation of treatment, the fever went down, and upper-limb muscle weakness and sensory weakness began to gradually improve. CRP was negative for blood data about 3 weeks after initiation of treatment. On day 30, a cervical spine MRI showed that the epidural abscess had disappeared, although the signal change in the facet joint remained (Figure 3). After 5 weeks of intravenous antibacterial therapy, we switched to the oral antibiotic cefaclor 750 mg/day and continued treatment for an additional 3 weeks. The patient was discharged from the hospital after 6 weeks of treatment. Although MRI on day 93 after initiation of treatment showed a slight residual signal change in the facet joint (Figure 4), symptoms had not recurred by the sixth month after hospital discharge.

Discussion

For our patient, we performed CT and MRI over time for SACFJ and monitored progress. Reportedly, SALFJ-related bone destruction takes about one month to appear on simple X-rays, and bone destruction and epidural abscess take about 2 weeks to appear on CT [17,18], but signal change in soft tissues can be detected as early as 2 days after onset by MRI [19,20]. We found it difficult to make a diagnosis from clinical symptoms, laboratory tests, simple X-ray, and CT, but were able to reach a rapid diagnosis with the addition of MRI. We thus consider MRI useful for diagnosing early-stage SACFJ. However, on day 30 and day 93 after initiation of treatment, although symptoms and blood data had been normalized, the MRI signal change at the facet joint remained (Figures 3, 4). Residual MRI enhancement has also been reported even after normalization of laboratory tests and symptoms in pyogenic spondylitis, suggesting that MRI may be less useful for determining the effects of treatment [21]. MRI may not also be useful in determining treatment efficacy in SACFJ. In contrast, bone erosions and joint destruction that were not visible on CT at admission were confirmed by CT on the 10th day. The cervical spine CT on the 41st day showed no progression of bone destruction. Fusion of the facet joint was confirmed by CT on day 191, with no sign of cervical spine instability (Figure 5). We found that if sufficient quenching of the infection is achieved, destruction of the facet joints will also result in bony fusion.

We summarized the 15 cases of SACFJ that we found documented in the literature (Table 2) [4–16]. Most patients were male, and the average age was 61.2 years. Most of the infections were unilateral, with no notable skewing to either the right or left side. These results were similar to those reported for septic arthritis of the lumbar facet joint (SALFJ) [18]. The most common site of onset was at C1/C2, with 6 cases. Symptoms were similar to those for pyogenic spondylitis, including neck pain, fever, and neurological symptoms, with fever and unilateral neck pain particularly common at the start of SAFJ [5]. Similar to pyogenic spondylitis, the pathogenesis of SAFJ includes direct infiltration from surrounding reservoirs of infection [7] and hematogenous [5] and iatrogenic causes [7]. In about 30% of patients, SACFJ was associated with underlying diseases such as diabetes or cirrhosis. Similar to the reports for SALFJ, the most common causative organism was Staphylococcus aureus (11/15 cases, 73%), including 1 case of methicillin-resistant Staphylococcus aureus (MRSA) [15].

Treatment included surgical treatment, but conservative treatment with antibiotics was selected in 7/15 cases (46%) reported for the cervical spine. Conservative treatment used antibiotics for more than 6 weeks, and most patients improved without dysfunction. In most reports, antimicrobials are selected to target MSSA and MRSA. Also, initially, they are more often empirically treated. In any case, using susceptible and appropriate antimicrobials is considered essential. However, epidural abscess of SACFJ accounted for up to 13 of the 15 cases (86%), and if spinal cord symptoms or paralytic symptoms progressed after conservative treatment, drainage techniques include surgical treatment were to be considered. Since the spinal canal of the cervical spine is narrower than that of the lumbar spine, symptoms related to the cervical spine tend to become more severe with neurological symptoms related to an epidural abscess [7]. In addition to draining the abscess, common surgical treatments are fusion surgery, including the Brooks procedure14, the Harms technique [7], and occipitocervical fusion [6] for C1/ C2, and laminectomy [3,10,13,16] for other parts of the spine.

Conclusions

SACFJ is associated with a high risk of septic shock, residual severe neurological symptoms, and cervical spine instability, so early diagnosis by MRI and treatment with antibiotic therapy are important. Epidural abscesses are extremely common with SACFJ, and surgical treatment, including drainage, is required if there is a progression of paralysis or other spinal cord symptoms. Our patient showed no signs of progression of paralysis or other spinal cord symptoms, and a good outcome was achieved through conservative treatment with antibiotics. For SACFJ, as well as pyogenic spondylitis, MRI may not be useful in determining treatment efficacy.