Comparative analysis of tuberculous and brucellar spondylodiscitis

Introduction

Spondylodiscitis is a serious disease accounting for 2–7% of all cases of pyogenic osteomyelitis, with incidence varying from 1 per 100,000/year to 1 per 250,000/year. ¹ Subacute and chronic spondylodiscitis are caused by a wide spectrum of pathogens, of which Mycobacterium tuberculosis is considered the most common and other organisms include Brucella spp. in endemic areas. ²

There are few studies which compare spontaneous tuberculous (TS) and brucellar spondylodiscitis (BS). ³ The aim of this prospective study was to compare the clinical – laboratory investigations as well as management – follow-up and outcome of the TS and BS patients.

Materials and methods

This prospective study included patients with spontaneous TS and BS who were admitted to the Van Education and Research Hospital, Turkey, over a two-year period (from January 2008 to June 2010). Patients with known predisposing factors for spondylodiscitis (e.g. spinal surgery, penetrating trauma to the vertebrae, accompanying diabetes mellitus, chronic renal failure or immunosuppression) were excluded.

The diagnosis of TS was based on clinical, laboratory and radiological signs combined with tuberculin skin test with positive results (values of 10 mm or over) and/or history of TB to diagnose spinal infections.

The diagnosis of BS was based on clinical signs of brucellosis and the serum agglutination test (SAT) results of ≥1/160 combined with radiological signs.

Blood cultures were taken from all patients and analysed with automated systems (BACTEC 9050, Bectone Dickinson, NJ, USA). A Vectra 1.5-T scanner (General Electric Medical Systems, Buckinghamshire, UK) was used to perform magnetic resonance imaging (MRI).

TS patients were treated with standard doses of isoniazid, rifampicine, ethambutol and pirazinamid for two months, followed by isoniazid combined with rifampicine for 7–10 additional months. BS patients were treated with either intramuscular streptomycine 1 g/daily for 21 days and oral doxycyline 100 mg twice daily for six months or oral doxycyline 100 mg twice daily and oral rifampicine 900 mg once daily for six months.

Statistical analyses

The Student's t test was applied for the comparison of means and the Pearson chi-square test was used for comparison of proportions; a P value <0.05 was considered to be statistically significant.

Results

The study included 41 patients (mean age: 47.49 ± 14.38 years, range: 24 to 80 years). Eighteen patients were in group BS and 23 were in group TS. The demographical, clinical and laboratory data for the patients are shown in Table 1.

Purified protein derivative (PPD) tests were positive with a minimum 15 mm diameter in group TS. None of the TS patients had a previous history of tuberculous infection and had not been vaccinated against Mycobacterium tuberculosis. Chest radiographs in three patients showed healed pulmonary lesions.

SAT was positive >1/640 in 11(61.1%), >1/320 in four (22.2%) and >1/160 in three (16.7%) patients of group BS. Blood culture was positive just in one BS patient in all groups.

The mean number of vertebrae involved was 2.3 ± 0.5. In the TS patients the lesion was more frequently seen in the posterior parts of vertebrae than BS (P < 0.001). Although paravertebral or epidural masses were also present more frequently in the TS group, psoas abscesses were only statistically significant. The involvement of sacral vertebrae was found simultaneously together with lower lumbar involvement in two BS patients (11.1%) and four TS patients (17.4%; Table 2).

After starting medical treatment all patients, except one in the TS group, showed definite clinical response within a month. This patient showed neurological deterioration and required surgical intervention. Relapses were only found in two BS patients after a six-month follow-up (an overall 4.9% relapse rate) and they received a new course of the treatment they had previously received. All patients recovered without sequelae.

Discussion

In endemic areas like the Eastern Anatolia region, TB or brucella infection of the spine can be confused. Thus, the present study was designed in order to compare spontaneous spondylodiscitis caused by these agents.

The mean age of TS patients was greater and this finding is consistent with previously reported sudies. ³

The clinical picture of spondylodiscitis is insidious. In our study, the most frequently seen symptom was back pain. For this reason we recommend that the clinicians who encountered patients with refractory back pain to bear in mind the probability of spondylodiscitis.

Fever was more frequently seen in BS patients. In fact, in 11 patients the diagnosis of brucellosis was first made at the time of the onset of the spondylodiscitis which was contrary to previous reports that stated that BS was a late complication, not usually accompanied by general symptoms. ⁴ Constitutional symptoms were more frequently seen in TS which is consistent with previous reports. ^3,5,6 Several studies have reported 20–75% rates for neurological involvement in TS patients. ^3,7 We observed objective sensory loss, impaired tendinous reflexes or lower limb weakness in 56.5% of the TS patients and 22.2% of the BS patients. Laboratory findings have shown that leucocytes and C-reactive protein (CRP) levels in the BS group were higher than in the TS group. It may have been due to the fact that most of the patients were suffering from acute BS. The erythrocyte sedimentation rate (ESR) was significantly higher in the TS patients and this finding was in accordance with the literature. ³

Magnetic resonance imaging (MRI) findings have noted that sacroiliitis were frequently seen in both groups which is in agreement with previous reports. ^5,8 The involvement of sacral vertebrae coinciding with the lumbar part has not been commonly reported to date. However, we observed it in both groups. Spinal TB is a rare form and mostly occurs with a preferential involvement of the mid thoracic and upper lumbar parts ^2,3,9 However, in our study none of the TS patients had thoracic vertebrae involvement. Soft tissue abscesses and the involvement of posterior parts of vertebrae were frequently in the TS group which were consistent with the published literature. ^3,4,9

There are studies which report up to a 45% need for surgical treatment and 35% the presence of functional sequelae. ^3,10 However, none of our cases, except one in the TS group, underwent surgical intervention and all responded excellently.

Conclusion

Although clinical data alone do not distinguish exactly between TS and BS, involvement of the posterior parts of the vertebrae, accompanying constitutional symptoms and high levels of ESR can be helpful in differentiation of TB.

Authors' contributions

AKÇ and AA designed the study and collected the clinical data. CA participated in the design of the study, drafted the manuscript and contributed significantly to the interpretation of data. All authors read and approved the final manuscript.

Competing interests

The authors have no conflicts of interest regarding the work reported in this paper.