Differentiation Between Tuberculous and Pyogenic Spinal Infection

Introduction: Spinal tuberculosis is the most common form of skeletal tuberculosis. The radiological features of spinal tuberculosis are similar to those of pyogenic spinal infection, and a definitive differential diagnosis often cannot be made on the basis of roentgenographic evidence. We investigated clinical manifestations of spinal tuberculosis and pyogenic spinal infection, and imaging modalities for differential diagnosis.

Methods: One hundred and thirty-six affected regions in 121 patients with spinal infections were investigated. There were 66 females and 55 males, and the mean age was 61.1 years. The mean duration of symptoms from onset to the time of diagnosis was 5.8 months. The affected spinal regions were cervical in 9 cases, thoracic in 45, thoracolumbar in 13, lumbar in 58, and lumbosacral in 11. All regions were investigated using conventional radiography, computed tomography (CT) scan, and magnetic resonance imaging (MRI). For MRI studies, all patients were evaluated on T1-weighted images (T1WI), T2-weighted images (T2WI), and gadolinium(Gd)-enhanced images. Laboratory tests included white blood cell count, erythrocyte sedimentation rate, C-reactive protein, and interleukin-6. Diagnosis was confirmed by culture or histologic examination of tissue removed using transpedicular needle biopsy.

Results: Among the 136 regions examined, there were 55 regions of pyogenic spinal infection and 81 regions of spinal tuberculosis. Table 1 shows characteristics that were significantly different between pyogenic spinal infection and spinal tuberculosis. There were no significant differences in laboratory values observed between the two conditions. We defined each patient’s Chiba-Higashi Score (CHS) as the total number of characteristics from Table 1 observed in that patient. The mean CHS in patients with pyogenic spinal infection and spinal tuberculosis was 3.5 and 8.0, respectively. Forty-three of 48 (90%) patients with CHS <6 were diagnosed with pyogenic spinal infection; and 76 of 82 (93%) patients CHS e”6 tuberculosis.

Conclusions: MRI is useful for evaluation of spinal infections. In particular, Gd-enhanced MRI provides definitive differentiation between pyogenic and tuberculous infection. The CHS system is useful for aiding corrective diagnosis of spinal infection.

Differential characteristics of pyogenic spinal infection and spinal tuberculosis
Characteristics	Pyogenic	Tuberculosis	P value
No. of affected vertebrae >/=3 on T1WI	19%	42%	0.005
Vertebral collapse	21%	67%	<0.0001
Preserved height of disc	44%	68%	0.007
Bony fragments on CT scan	42%	73%	<0.0001
Absence of spur formation	81%	98%	0.001
Mixed signal intensity on T2WI	33%	72%	<0.0001
Mixed signal intensity on Gd-enhanced MRI	16%	49%	<0.001
Rim enhancement on Gd-enhanced MRI	9%	74%	<0.0001
Absence of Gd-enhancement within disc	43%	64%	0.02
Paraspinal abscess	30%	60%	<0.001
Duration to the time of diagnosis >/= 4 months	24%	69%	<0.001
Presence of active pulmonary tuberculosis	0%	59%	<0.0001