Pyogenic spondyilitis and tuberculous spondylitis are responsible for most cases of infectious spondylitis. If appropriate treatment is not given, infectious spondylitis can cause irreversible neural symptoms or a deformity of the spine; thus, it is important to carry out diagnosis and treatment in an early stage of the disease
3,
4. The prevalence of pyogenic and tuberculous spondylitis are reported as 1% and 0.15 to 3%, respectfully. In Korea, tuberculous spondylitis, which appears in a relatively high percentage of cases, is responsible for most of the cases of infectious spondylitis. However, with the recent development of anti-tubercular drugs and a decreasing endemic rate, the incidence of tuberculous spondylitis is decreasing. In contrast, frequent spinal surgery, invasive manipulation, urinary and digestive system and misuse or overuse of antibiotics has caused an increase of pyogenic spondylitis
2. There have been several reports about clinical, hematological, pathological and radiological finding to differentiate pyogenic and tuberculous spondylitis. Recently, there have been reports of spondylitis from two different roots of fungi detected on CT, a needle biopsy and MRI, which have emphasized the importance of accurate diagnosis and appropriate treatment
1,
2,
5-
8. The symptoms of tuberculous spondylitis have distinguishable clinical features. Normally, pyogenic spondylitis rarely affects people aged between 50 and 70 years, but often affects people aged between 30 and 50 years, which suggests that younger people are more likely to be affected. Tuberculous spondylitis often involves the thoraco-lumbar junction area and more than one column is invaded
9. However, pyogenic spondylitis is found more often in the lumbar and cervical regions. Specific features found in pyogenic spondylitis are that is that it does not involve the vertebrae, posterior arch and spinous process. Therefore, if the spondylitis involves the former mentioned structures, it is likely to be tuberculous spondylitis
10,
11. The ratio of pyogenic spondilitis between men and women is 1.5~3:1, which indicates that men are more easily affected. The early stage symptoms of pyogenic spondylitis are lower back pain, fever, loss of appetite, dullness, tenderness and stiffness. It shows a faster clinical course than tuberculous spondylitis. Symptoms of tuberculous spondylitis are back pain, partial tenderness and nighttime diaphoresis. In a hematological study, pyogenic spondylitis shows an increased or normal erythrocyte sedimentation rate, leukocyte count and CRP level. In tuberculous spondylitis, 80% of the cases showed an increased erythrocyte sedimentation rate than an increase in the level of CRP. With plain X-rays, erosion of the column end plate can be seen, but sensitivity and specificity are very low. MR imaging has a reported sensitivity of 96%, a specificity of 92%, and an accuracy of 94% for the diagnosis of vertebral osteomyelitis
12. Fatma et al.
13 mentioned that MRI evidence of disc space involvement was apparent in only 46% of lesions. A study of the signal intensity on T1- and T2-weighted images revealed a pattern that may be dissimilar to that commonly reported. Post-contrast enhancement adds more certainty to the diagnosis of tuberculous spondylitis. Liu et al.
14 studied 29 cases of tuberculous spondylitis. Continuous two vertebral involvement, subligamental spread of paraspinal abscesses and cord indentation were observed in 93% of the cases. Destruction of the vertebral body occurred in 76% of the cases. These investrigators also concluded that Gd-DTPA administration did not facilitate diagnosis. Eugene
15 performed a retrospective study on 103 cases of pyogenic spondylitis. In less than two weeks of symptoms, MRI appeared to give the correct diagnosis or suggest pyogenic vertebral osteomyelitis as a possible diagnosis in 55% and 36% of cases, respectively. After two weeks, the percentage of correct and possible diagnoses of pyogenic vertebral osteomyelitis increased to 76% and 20%, respectively. A diagnosis was made within one month in most cases. Martin et al.
16 observed in a retrospective study on 122 cases of pyogenic and tuberculous spondylitis that the result of a biopsy provided a clear distinction between tuberculous and pyogenic spondylitis in 62.2% of cases, either by means of histology or by culture. Pain, gibbus formation and bony fusion gave no significant clues for the differential diagnosis. The combination of several unspecific findings such as patient history, erythrocyte sedimentation rate and radiographic assessment can lead to a correct diagnosis.
As in the previous studies, differentiation between pyogenic and tuberculous spondylitis has been made by clinical, hematological, radiological and pathological studies. In the present study of seven atypical cases, among the hematological, radiological and pathological evaluations, a pathological study is the most helpful. If the general condition of the patient is poor and the result of a biopsy is negative, starting treatment for the most likely diagnosis with periodic watching of the clinical, hematological and radiological changes is important for a precise diagnosis.