Intramedullary spinal cord abscess and subsequent granuloma formation: a rare complication of vertebral osteomyelitis detected by diffusion-weighted magnetic resonance imaging.

An intramedullary spinal cord abscess, which is usually associated with discitis, is an uncommon but potentially important complication of vertebral osteomyelitis. The authors describe a rare case of an intramedullary conus medullaris abscess and lumbar osteomyelitis sparing the intervertebral discs and without discitis. The patient also developed a granuloma in the cauda equina during treatment. Diffusion-weighted MRI was useful for differentiating the granulomatous lesion from the relapse of infection. A 65-year-old immunocompetent man with moderately controlled diabetes presented with progressive lowerextremity numbness and weakness with urinary dysfunction. He had progressive paraparesis, bilateral leg paresthesia, and sphincter compromise. Magnetic resonance imaging revealed an intramedullary ring-enhanced lesion, which was hyperintense on diffusion-weighted images. The lesion, an intramedullary spinal cord abscess, was surgically drained. During antibiotic treatment, serial MRI showed an enlarging enhanced lesion in the cauda equina, and a recurrent infection was suspected. A second-look surgery confirmed the formation of a granuloma and the absence of a relapse of the abscess. Although the enhanced lesion increased in size, its intensity on diffusion-weighted images remained unchanged. After 3 months of antibiotic treatment, all enhanced lesions were diminished. An intramedullary spinal cord abscess is a rare but important complication of vertebral osteomyelitis, and it requires immediate treatment. Diffusion-weighted MRI was useful for the initial diagnosis as well as for monitoring treatment efficacy.