INFECTIOUS SPONDYLITIS - MRI CHARACTERISTICS

Magnetic resonance imaging (MRI) scans of 24 patients with clinically proven infectious spondylitis were retrospectively evaluated. Evaluati on was made of abnormal signal and enhancement patterns within vertebr al bodies, interventing disks, and epidural and paraspinal abscesses. The causative organisms included Mycobacterium tuberculosis, fungi and pyogenic bacteria. Staphylococcus aureus was the predominant causativ e organism among pyogentic bacteria. Decreased signal intensity of ver tebral marrow on Tl-weighted images tvas more extensive in pyogenic in fections. Multilevel involvement (more than two) was observed in six o f the 24 patients. Contiguous multilevel involvement was observed only in patients with tuberculous spondylitis. Noninvolvement of the inter vertebral disk space was observed in two patients with pyogenic spondy litis. Epidural abscess was found in lj patients, most of whom had den se, homogeneous enhancement. Paraspinal abscess was found in 18 patien ts. Diffuse patchy enhancement without obvious abscess formation in th e paraspinal compartment was found in those patients with pyogenic inf ections. ''Rice bodies'' were found in paraspinal abscesses in only th ree patients with tuberculous spondylitis. It was difficult to differe ntiate candidal from tuberculous spondylitis on MRI. Compared dth pyog enic infection, tuberculous spondylitis had a predilection for spinal deformity, subligamentous spread, contiguous multilevel involvement, p resence of signal voids in paraspinal abscesses on T2WI and a lesser e xtent of marrow edema.